2. sedimentological and geochemical characteristics of …

Larson, R. L., Lancelot, Y., et al., 1992Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 129

2. SEDIMENTOLOGICAL AND GEOCHEMICAL CHARACTERISTICS OFLEG 129 SILICEOUS DEPOSITS1

S. M. Karl,2 G. A. Wandless,3 and A. M. Karpoff4

ABSTRACT

Siliceous deposits drilled on Ocean Drilling Program Leg 129 accumulated within a few degrees of the equator during theJurassic through early Tertiary, as constrained by paleomagnetic data. During the Jurassic and Early Cretaceous, radiolarian ooze,mixed with a minor amount of pelagic clay, was deposited near the equator, and overall accumulation rates were moderate to low.At a smaller scale, in more detail, periods of relatively higher accumulation rates alternated with periods of very low accumulationrates. Higher rates are represented by radiolarite and limestone; lower rates are represented by radiolarian claystone. Our limiteddata from Leg 129 suggests that accumulation of biogenic deposits was not symmetrical about the equator or consistent over time.In the Jurassic, sedimentation was siliceous; in the Cretaceous there was significant calcareous deposition; in the Tertiary claystoneindicates significantly lower accumulation rates at least the northern part of the equatorial zone. Accumulation rates for Leg 129deposits in the Cretaceous were higher in the southern part of the equatorial zone than in the northern part, and the southern sideof this high productivity zone extended to approximately 15°S, while the northern side extended only to about 5°N.

Accumulation rates are influenced by relative contributions from various sediment sources. Several elements and elementratios are useful for discriminating sedimentary sources for the equatorial depositional environments. Silica partitioningcalculations indicate that silica is dominantly of biogenic origin, with a detrital component in the volcaniclastic turbidite units,and a small hydrothermal component in the basal sediments on spreading ridge basement of Jurassic age at Site 801. Iron in Leg 129sediments is dominantly of detrital origin, highest in the volcaniclastic units, with a minor hydrothermal component in the basalsediments at Site 801. Manganese concentrations are highest in the units with the lowest accumulation rates. Fe/Mn ratios are >3in all units, indicating negligible hydrothermal influence. Magnesium and aluminum concentrations are highest in the volcani-clastic units and in the basal sediments at Site 801. Phosphorous is very low in abundance and may be detrital, derived from fishparts. Boron is virtually absent, as is typical of deep-water deposits. Rare earth element concentrations are slightly higher in thevolcaniclastic deposits, suggesting a detrital source, and lower in the rest of the lithologic units. Rare earth element abundancesare also low relative to "average shale." Rare earth element patterns indicate all samples are light rare earth element enriched.Siliceous deposits in the volcaniclastic units have patterns which lack a cerium anomaly, suggesting some input of rare earthelements from a detrital source; most other units have a distinct negative Ce anomaly similar to seawater, suggesting a seawatersource, through adsorption either onto biogenic tests or incorporation into authigenic minerals for Ce in these units.

The A1/(A1 + Fe + Mn) ratio indicates that there is some detrital component in all the units sampled. This ratio plotted againstFe/Ti shows that all samples plot near the detrital and basalt end-members, except for the basal samples from Site 801, whichshow a clear trend toward the hydrothermal end-member. The results of these plots and the association of high Fe with high Mgand Al indicate the detrital component is dominantly volcaniclastic, but the presence of potassium in some samples suggests someterrigenous material may also be present, most likely in the form of eolian clay. On Al-Fe-Mn ternary plots, samples from allthree sites show a trend from biogenic ooze at the top of the section downhole to oceanic basalt. On Si-Fe-Mn ternary plots, thesamples from all three sites fall on a trend between equatorial mid-ocean spreading ridges and north Pacific red clay.Copper-barium ratios show units that have low accumulation rates plot in the authigenic field, and radiolarite and limestonesamples that have high accumulation rates fall in the biogenic field.

INTRODUCTION

Siliceous deposits are enigmatic indicators of high-productivity sedi-mentary environments. They accumulate in several marine environ-ments, which are generally distinguished with the aid of lithologiesassociated with the siliceous deposits. Sedimentary and geochemicalcharacteristics of siliceous deposits are used to discriminate betweendepositional environments and define paleoceanographic conditions forthese deposits.

On Leg 129, several types of siliceous deposits were cored. Theresults of detailed sedimentological studies are presented in Ogg etal. (this volume), and diagenetic studies are presented in Behl andSmith (this volume). The known environmental conditions include

Larson, R. L., Lancelot, Y., et al, 1992. Proc. ODP, Sci. Results, 129: CollegeStation, TX (Ocean Drilling Program).

2 U.S. Geological Survey, Branch of Alaskan Geology, 4200 University Drive,Anchorage, AK 99508-4667, U.S.A.

3 U.S. Geological Survey, National Center, MS 990,12201 Sunrise Valley Dr., Reston,VA 22092, U.S.A.

4 Centre de Géochimie de la Surface—CNRS, Institut de Géologie, 1 rue Blessig,67084 Strasbourg Cedex, France.

initial deposition on a mid-ocean spreading ridge at moderate accu-mulation rates averaging 700 g/cm2/m.y. (Ogg et al , this volume),near the equator in the middle of the Mesozoic Pacific Ocean(Lancelot, Larson, et al, 1990). The sites drilled during Leg 129initially migrated southward from the equator, and subsequentlymoved northward across the equator and into the north Pacific basin(Lancelot, Larson, et al., 1990). Accumulation rates for siliceousdeposits in excess of 1000 g/cm2/m.y. characterize these equatorialcrossings (Ogg et al., this volume). Although we know the generaltectonic, paleoceanographic, and biologic setting of these siliceousdeposits, sedimentary, diagenetic, and chemical characteristics canhelp us define these environments more precisely and gain insightsinto circulation patterns and productivity cycles in the MesozoicPacific Ocean.

In this paper we focus only on the siliceous deposits. Our purposeis to examine changes in siliceous deposition at Leg 129 sites throughtime, and to identify significant factors affecting siliceous deposi-tion. We do not address general sedimentation at these sites becauseabundant turbidite deposition masks other paleoceanographic proc-esses, and because poor recovery limits our ability to assess therepresentativeness and relative proportions of lithologies cored at Leg129 sites.

31

S. M. KARL. G. A. WANDLESS, A. M. KARPOFF

TERMINOLOGY

The classification of siliceous sediments and rocks in this paperfollows the definitions provided in the Initial Reports for Leg 129(Lancelot, Larson, et al., 1990). The term biogenic is applied when30% or more of the sediment is carbonate or silica from a biogenicsource. Pelagic biogenic ooze consists of 60% or more organisms.Transitional pelagic ooze contains 30% to 60% organisms, and at least40% silt or clay. Pelagic clay has less than 30% organisms.

There are several types of pelagic clay. Eolian pelagic clay con-tains detrital clay minerals and quartz crystals. Authigenic pelagicclay contains authigenic clay minerals, zeolites, iron oxides, andferromanganese micronodules. Volcanogenic pelagic clay containsglass, mafic minerals, feldspar, volcanic rock fragments, palagonite,and clay minerals derived from alteration of volcanic material. Pelagicclay in general may also contain fish parts and cosmic particles.Sediment samples were analyzed for clay mineralogy by X-ray dif-fraction (XRD) aboard ship and on the microprobe at the Universityof Strasbourg, France. The preliminary interpretations used for thisstudy did not discriminate species of smectite; Karpoff (this volume)identified dioctahedral smectite (d{060}=1.50Å), possible illite, andinterlayered illite-smectite.

The siliceous deposits studied include biogenic siliceous materialin various stages of preservation and recrystallization. Terms for silicaphases of samples used in this study are "field terms" based onproperties observed in core samples. Silica phases were not analyzedfor this study, but some samples correspond to samples analyzed byBehl and Smith (this volume). The term chert is used for siliceousdeposits recrystallized to opal C/T (cristobalite/tridymite) and cryp-tocrystalline, microcrystalline, or chalcedonic quartz. Chert has aglassy to waxy luster, smooth conchoidal fracture, and a hardness of6.3-7.0. Porcellanite has the same silica mineralogy plus more than10% clay. Porcellanite has a dull luster, matte surface, blocky fracture,and a hardness of 4.0-5.5. Radiolarite has less than 10% clay, a rough,sandy texture, granular fracture, and is soft to friable. Modifiers tothese terms are used to reflect the presence of components in excessof 25%. A clayey radiolarite has more than 25% clay. A "radiolaritewith clay" contains 10% to 25% clay.

Accumulation rates were calculated using fossil age determina-tions and stratigraphic thickness. Original rates of deposition orsedimentation are not known, because volume changes resulting fromdiagenetic processes have not been quantitatively determined. In thisstudy, high or low sedimentation rates are thus relative terms only.Accumulation rates less than 3 m/m.y. are considered low. Accumu-lation rates in excess of 10 m/m.y. are considered high. Because theocean is greatly undersaturated with respect to silica and dissolutiontakes place at the sediment-water interface, it is generally inferred thatlow accumulation rates reflect low sedimentation rates, and the con-verse is also true.

SAMPLE DESCRIPTION

Site 800

Unit I brown pelagic clay from the top of the sequence was notsampled for this study.

Unit II (Fig. 1) is late Campanian to Turonian in age, and consistsof 40 m of porcellanite and radiolarian chert (Lancelot, Larson, et al.,1990; Behl and Smith, this volume). Both phases are brown. The chertis patchy, cuts across sedimentary laminations, and increases inabundance downsection. All samples studied from this unit (Table 1)are composed of mottled brown and pale brown chert; the samplefrom Core 129-800A-7R has black Mn-oxide coatings on the surfaceof some bedding laminations.

Unit III is Turonian to early Albian in age and consists of 150 mof olive gray to gray radiolarian chert and finely laminated siliceouslimestone, with subordinate nannofossil chalk (Lancelot, Larson, etal., 1990). The silicification of the chalk and limestone is patchy and

discontinuous. Locally laminations are disrupted by burrows, andsome laminations are deformed. The chert contains up to 45% radio-larians, many of which are filled with opal C/T, chalcedony, and rarebarite crystals. The limestone contains up to 25% radiolarians as wellas foraminifers and locally abundant nannofossils. Limestone increasesdownsection. Replacement chert in the limestone forms bedding-parallel laminations and nodules with bedding-discordant, cuspate,convex-outward silicification fronts that grade from chert to calcare-ous porcellanite, which in turn grades to the host limestone. FromCore 129-800A-22R downward, volcanic clasts were observed andsmectite was identified by shipboard XRD analyses (Lancelot, Larson,et al., 1990). In Core 129-800A-23R clinoptilolite and smectite wereidentified in clayey radiolarite. These minerals are characteristic ofthe underlying volcaniclastic turbidite unit and indicate a gradationaltransition to that unit.

Samples from Unit III are composed of chert, radiolarian porcel-lanite, and porcelaneous radiolarite. Most samples are pinkish tobrownish green or gray, indicating transitional redox conditions.Samples from Cores 129-800A-13R and -24R contain black man-ganiferous streaks.

Unit IV is Aptian in age and consists of 221 m of volcaniclasticsand-silt-clay turbidites with intervals of pelagic radiolarian clay-stone. The turbidites are predominantly green, and the radiolarianclaystone intervals are typically brown. Turbidite sandstone is com-posed mainly of volcanic detritus, with minor, variable amounts ofcalcareous shallow-water biogenic debris or calcareous cement.Detrital claystone within turbidite beds contains volcanic glass,plagioclase, pyroxene, iron oxides, smectites, montmorillonite, cli-noptilolite, up to 25% radiolarians and up to 15% nannofossils. Thepelagic claystone, calcareous claystone, radiolarian claystone, andclayey radiolarite between turbidite beds are finely laminated andcontain up to 50% radiolarians, with subordinate volcanic glass, clayminerals, iron oxides, and rare plagioclase, pyroxene and volcanicrock fragments. Fractures in Core 129-800A-38R are coated withMn-oxide dendrites.

Samples studied from Unit IV are all from pelagic intervals exceptfor Samples 129-8OOA-26R-1, 135-139 cm, 129-800A-27R-1, 61-64cm, 129-8OOA-41R-1, 87-93 cm, and 129-800A-44R-1, 92-94 cm,which are claystones from the tops of turbidites sampled for compara-tive purposes.

Unit V is Barremian to Berriasian and consists of 48.5 m ofmassive to microlaminated clayey radiolarite and radiolarian clay-stone (Lancelot, Larson, et al., 1990). The unit is dominantly red orbrown, with rare green reduced zones. The radiolarite alternates withclaystone on a centimeter scale but radiolarite is the dominant lithol-ogy (60% to 80% of each core). Radiolarite layers contain up to 85%radiolarians. Some layers are bioturbated. Shipboard XRD analysesindicate the presence of smectite, zeolites, and feldspar. Manganeseoxides occur as lenses, as laminations, as accumulations aroundburrows or along redox fronts, as micronodules, as radiolarian fill-ings, and as fracture coatings. Fractures are also commonly filled withsilica. Samples studied from this unit are all from radiolarite layersexcept Sample 129-800A-52R-1,16-20 cm, which is a claystone withMn-oxide streaks.

Unit VI is Berriasian(?) in age and consists dominantly of doleritesills with minor amounts of recrystallized siliceous sediment trappedbetween sills (Lancelot, Larson, et al., 1990). The sample from thelowest sedimentary rock cored at Site 800 is from a chert lens betweendolerite sills. This chert is brown, red or bleached pink, and microlami-nated similar to the radiolarite of overlying Unit V. The sample studiedis massive brown chert with approximately 5% ghosts of radiolariansand 1 % opaque minerals. Iron staining is patchy in thin section.

Site 801

Unit I brown pelagic clay from the top of the sequence was notsampled for this study.

32

LEG 129 SILICEOUS DEPOSITS

Unit Lithostratigraphy "Trends"

2 >S ESi

38.0

38.0

Pelagic brown clays• clays (smectites)• iron oxides• zeolites (phillipsite)

•deep-sea deposits <0.5

(mbsf)

40.2Brown cherts and porcellanites

• opal-CT;diagenetic quartz

•silica diagenesis <3

150.4

Gray radiolarian cherts and limestones

• discordant diageneticboundaries

• opal-CT & quartz• calcite• clays• clinoptilolite

•changes in pelagicinput, Ca -> Si

•diagenetic processes

Q .CD

Q

300 —

221.0

400 —

Redeposited volcaniclastics

- Turbidites- Debrites- Interturbidite pelagic sedimentation- Fluidized / grain flow deposits

volcanic glass; alteredplagioclasepyroxenegreen clay mineralszeolites: clinoptilolite

fractures- calcite-filled- green clay minerals- manganite

fine-grainedthinly beddedthin sequences

alteration ofvolcaniclastics

resedimentation

coarse-grainedmassive bedsbrecciasdebrites

<35

48.5Clays and radiolarites

• clays• opal-CT / diagenetic quartz

finely laminated(Milankovitch cycles?)

<4>2

500 —

46.4

Dolerite sills with minor chert• 3 intrusive units• aphyric and holocrystalline• smectite-dominated alteration

sediment bakedmetamorphismof sills

Figure 1. Core ages, lithologies, and units for Site 800, Leg 129 (Lancelot, Larson, et al., 1990).

33

S. M. KARL, G. A. WANDLESS, A. M. KARPOFF

Table 1. Sample descriptions for Site 800, Leg 129.

Sample (cm)

129-800A-

6R-1, 67-697R-1, 2-58R-1,48-509R-1,30-33

10R-1, 13-1711R-1,7-1O12R-1, 30-3213R-1, 12-1414R-1, 110-11517R-1,68-7118R-1, 127-13023R-1,69-7024R-1,92-9524R-1, 68-7126R-1, 22-2626R-1, 135-13927R-1, 61-6427R-1, 110-11428R-3, 106-11030R-1, 125-12930R-2, 114-11831R-1, 12-1432R-CC, 10-1333R-7, 14-1834R-2, 139-14235R-3, 84-8836R-1, 110-11436R-4, 28-3241R-1,87-9342R-1, 41-4344R-1,92-9451R-1, 106-10852R-1, 16-2053R-1,32-3455R-1,76-8155R-2, 25-3056R-1, 8-1358R-1,37^2

Depth(mbsf)

40.249.259.468.878.387.997.6

106.9117.3144.9155.0201.2210.6210.8228.8230.0238.6239.1251.3267.2268.5272.1280.8296.6299.9310.2317.0320.7363.4369.0384.6450.7459.0465.2479.9480.9488.6507.2

Unit

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVVVVVVVVI

Age

late Campanianearly Campanianearly Campanian

early Campanian/TuronianTuronian

CenomanianCenomanianCenomanianCenomanianlate Albianlate Albian

early Albianearly Albianearly Albianlate Aptianlate Aptian

middle(?) Aptianmiddle(?) Aptian

early Aptianearly Aptianearly Aptianearly Aptianearly Aptianearly Aptianearly Aptianearly Aptianearly Aptianearly Aptian

Aptian(?) Barremian(?)Aptian(?) Barremian(?)Aptian(?) Barremian(?)Hauterivian/BarremianHauterivian/BarremianHauterivian/Barremian

BerriasianBerriasianBerriasian

• >

Samplelithology

ChertChertChertChertChert

PorcellanitePorcellanitePorcellaniteRadiolaritePorcellanitePorcellaniteRadiolariteRadiolariteRadiolariteClaystoneSiltstoneSiltstone

RadiolariteClaystone

PorcellaniteRadiolaritePorcellaniteClaystoneClaystoneClaystoneSiltstone

ClaystoneClaystoneClaystoneClaystoneSiltstone

RadiolariteClaystoneRadiolariteRadiolariteRadiolarite

ChertChert

Compactedthickness/time

(m/m.y.)

<3<3<3<36666666666

12<ct<3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 3512 < et < 352 < et < 42 < et < 42 < et < 42 < et < 42 < et < 42 < et < 42 < et < 4

Accumulationrate (g/cm2/m.y.)

6006306486601290133213801380143413681422147013621362

3192 <AR< 93103192<AR<93103240 < AR < 94503120 <AR< 91003168 <AR< 92402964 < AR < 86453060 < AR < 89253072 < AR < 89603216 <AR< 93803192 <AR< 93103240 < AR < 94503228 <AR< 94153240 < AR < 94503000 < AR < 87503300 < AR < 96253300 < AR < 96253120 <AR< 9100

532 <AR< 1064536 <AR< 1072518 <AR< 1036530 <AR< 1060530 < AR < 1060492 < AR < 984500 <AR< 1000

Unit II (Fig. 2) is Campanian to Cenomanian in age and 62 m thick.Poor recovery for this unit suggests a strong hardness contrast betweenlithologies recovered and not recovered. Recovered rocks were domi-nantly chert and porcellanite very similar to that of Unit II at Site 800.Minor recovered claystone suggests that much of the missing core mayhave been soft clay or claystone. The chert is pale to dark brown, andfinely laminated to banded, with alternating bands of pale brown chertand dark brown porcellanite. Some chert is bioturbated. Fractures arecommonly filled with Mn-oxide grains or dendrites. The chert containsup to 35% radiolarians and variable amounts of clay minerals. The unitis noncalcareous, except at its lower boundary, which is gradational tothe underlying turbidite unit: Core 129-801 A-13R contains calcareousradiolarian porcellanite; Cores 129-801A-14R and -15R contain tuf-faceous nannofossil claystone and chalk. The samples from Unit II(Table 2) are brown chert except samples from Cores 129-801 A- 12Rand -13R which are cherty porcellanite.

Unit III is Cenomanian to Albian in age, 92 m thick, and consists ofvolcaniclastic turbidites very similar to those of Unit IV at Site 800.Pelagic intervals are represented by radiolarian claystone, radiolarianporcellanite, radiolarite, chert, nannofossil claystone, and chalk. Theturbidites are dark greenish to bluish gray with beds up to 5 m thick, someof which contain shallow-water carbonate debris. The pelagic interbedsare mostly olive green to gray, and have discontinuous laminations orsparse bioturbation. The base of the unit consists of thin-bedded distal-facies turbidites with brown radiolarian claystone or radiolarite intervalsup to 1 cm thick, which is transitional to the underlying radiolarite unit.Samples studied from Unit III consist of pelagic gray to brown radiolarian

porcellanite and chert. For purposes of comparison, claystone fromthe tops of turbidite beds in Sections 129-801A-18R-2 and 129-801B-8R-2 were sampled, and a calcareous porcellanite from Sec-tion 129-801B-1 OR-1 was sampled. This latter sample contained10% limestone, 30% chert, and 60% porcellanite.

Unit IV is Valanginian to Oxfordian in age, 125 m thick, andconsists mainly of brown radiolarite with subordinate dark brownchert and porcellanite bands and nodules. The unit is subdivided intoan upper, chert-rich radiolarite with 10% or less clay, and a lowerradiolarite with 20% or more clay. Radiolarians comprise up to 90%of the radiolarite and up to 70% of the chert. Foraminifers are rare.Sedimentary structures include rare fine laminations, flasers, lamina-tions that grade to radiolarian clay, and rare bioturbation. Porcellaniteand chert zones crosscut these features. Black Mn oxides occur asgrains, microlaminations, and coatings on fractures. Interstitial Fe-Mn-oxide grains may comprise as much as 20% of some radiolarite.Shipboard XRD analyses indicate that hematite and smectite arepresent in addition to various phases of silica in cores from Unit IV.Samples studied from this unit are all radiolarite and chert. The samplefrom Section 129-801B-26R-CC contains Mn-oxide grains.

Unit V is Callovian in age, 18m thick, and consists of interbeddedred radiolarite and claystone. There is a distinct color change frombrown to red at the upper unit boundary. The layers of radiolarite andclaystone alternate on a centimeter scale, and average about 5 cm inthickness. Layer boundaries are gradational on a millimeter scale, asobserved in thin section, suggesting fluctuating depositional condi-tions. Radiolarite layers contain up to 25% clay minerals and rare

34


8begin ^Hole 801A

Depth(mbsf)

I ?Lithostratigraphy i«

100 —

200begin ^Hole 801B

Q.

Q

300

400 —

500begin ^ -Hole 801C

63.8

Pelagic brown clayA = Dark reddish-brownB = Brown with light streaks• Clays (smectites)• Iron oxides/hydroxides• Zeolites (phillipsite)

< 1

Brown chert and po reel Ian ite

• Opal-CT; diagenetic quartz

126.5

Volcaniclastic turbiditesand minor pelagic intervals

Glass and altered glassPlagioclaseBackground radiolarian sedimentation

< 12>5

318.3

IV

442.9

Brown radiolarite

A = Brown radiolariteB = Brown clayey radiolarite(both with dark brown chert)

Fine-scale sub-horizontal bioturbationDecreasing clay content up-sectionAbundant Mn oxides (and micronodules)

<5

V461.6

Alternation of red radiolarite and claystone

VI

Basalt

Interbedded silicified claystone at 453 mbsfIntrusive and pillow unitsAphyric and holocrystallineHydrothermal deposit at 512 mbsf

590.9


35



Sample (cm)

129-801A-

8R-9R-

10R-12R-80-1C13R-14R-15R-16R-

, 1-3,0-3,0-5, 22-250M, 21-26, 26-28, 24-26, 135-138

17R-1,28-3018R-2, 14-1719R-CC, 12-1620R-1.8-12

129-801B-

8R-2, 60-6310R-11R-12R-14R-15R-16R-

, 70-73,31-36, 64-70, 52-57, 19-20,40-43

17R-1, 34-3618R-1,37^019R-1,24-2620R-21R-24R-25R-26R-I27R-29R-31R-33R-33R-35R-35R-37R-

, 23-26, 12-13, 69-73, 49-53

:c.o^i, 104-107. 17-19, 18-20, 10-14,126-129,51-55, 123-127,7-10

39R-1,4-7

129-801C-

4R-1, 11-165R-4, 11-166R-1,31-34

Depth(mbsf)

60.670.279.599.0

100.0108.7118.5128.1139.0147.5158.6176.3176.5

254.8272.7282.0292.0310.8319.9329.6338.9348.2357.5366.7375.8393.3397.7407.0407.7416.4425.8434.9436.1444.8445.5453.6462.7

521.8535.8540.8

Unit

11II11II11IIIIIIIIIIIIIIIIIIIIII

IIIIIIIIIIII

IVAIVAIVAIVAIVAIVAIVAIVAIVBIVRIVBIVBIVBIVBIVBIVBVVVVI

VIVIVI

Age

CampanianConiacian-Santonian

ConiacianCenomanian/Coniacian

9

CenomanianCenomanianCenomanianlate Albianlate Albianlate Albianlate Albian

middle Albian

middle AlbianPre-middle Albian, post-Valanginian

Pre-middle AlbianPre-middle Albian

ValanginianValanginian

Berriasian/ValanginianBerriasianBerriasianBerriasian

late Tithonianlate Tithonianlate Tithonian

early Tithonianearly TithonianKimmeridgianKimmeridgian

OxfordianCallovianCallovianCallovianCallovianBathonianBathonian

> Bathonian> Bathonian

Bathonian

Samplelithology

ChertChertChert

PorcellaniteChert

PorcellaniteChertChert

PorcellanitePorcellaniteClaystoneClaystone

Chert

ClayPorcellanitePorcellanite

ChertRadiolarite

ChertChertChertChertChertChertChert

RadiolariteRadiolariteRadiolarite

ChertChertChert

RadiolariteRadiolarite

ClayClaystoneClaystone

Chert

QuartzQuartzQuartz


(m/m.y.)

33337

35 <ct< 125 < c t < 125 <ct< 125 <ct< 125 <c t< 125 <ct< 125 <ct< 12

5 <ct< 125 <ct< 125 <ct< 125 <ct< 12

444444444444441.31.31.31.39?

?9

9


687645669699

9

6571150 <AR< 27601145 <AR< 27491220 <AR< 29281145 <AR< 27491360 <AR< 32641360 <AR< 32641190 <AR< 2856

1385 <AR< 33241285 <AR< 30841285 <AR< 30841285 <AR< 3084

1112101610521064106410401032988101610921072101610161040354354358358?7

777

burrows. Color mottling, anastomosing clay seams, and patchy silici-fication within layers are diagenetic features. Mn oxides on fracturesare rare relative to the overlying radiolarite unit. Claystone beds aredarker red than the radiolarite beds, contain rare burrows, and lessthan 25% radiolarians. The red color indicates oxic conditionsthroughout the section despite high productivity. Shipboard XRDanalyses indicate the presence of hematite and smectite in addition tovarious phases of quartz. Samples studied from this unit include twosamples of radiolarite, one of claystone, and one of soft, unlithifiedCallovian clay (Sample 129-801B-35R-1, 51-55 cm, Table 2).

Unit VI is Bathonian in age, and consists of basalt flows withinterpülow sedimentary rocks. The basalt is interpreted to representbasement (Lancelot, Larson, et al., 1990). InterpiHow lithologies includechert, claystone, carbonate, tuff, and hydrothermal quartz. These sedi-mentary rocks are thermally recrystallized and some are laced with veinsof drusy quartz. The chert contains quartz-filled radiolarians. Samplesstudied from this unit include radiolarian claystone, chert, and threesamples from Cores 129-801 C-4R,-5R, and -6R of hydrothermal quartzand goethite (Karpoff, this volume).

Site 802

Unit I consists of brown pelagic clay (Fig. 3). Unit II consists ofMiocene volcaniclastic turbidites with intervals of brown pelagicclaystone, nannofossil claystone, and nannofossil chalk. No sampleswere collected from these units for this study.

Unit III is early Miocene to Paleocene in age, 75 m thick, andconsists of nannofossil chalk with minor amounts of claystone, por-cellanite, and nodular chert (Lancelot, Larson, et al., 1990). The chalkis thick-bedded, commonly graded, laminated and cross-laminated,and bioturbated. Clasts of claystone are common in the chalk, andmixed assemblages of Cretaceous through Oligocene nannofossilsindicate that this chalk is redeposited carbonate ooze. The brownclaystone contains clay minerals, zeolites, volcanic glass, iron oxides,radiolarians, and nannofossils. The claystone is extensively biotur-bated. Chert occurs as scattered nodules, comprising less than 3% ofthe recovered core. The chert has sharp, irregular contacts with thechalk, and often contains carbonate inclusions. The chert is clearly adiagenetic product derived from dissolution of siliceous plankton in


Q.Φ

Cl

0

100

200 —

300 —

400 —

500

Co

re

in2R3R

4R5R

6R7R

9R10R

12R

14R15R16R

17R18R19R20R21R22R

23 R24R

25R

27R28R29R30R

31R

32R33R34R35R36R37R38R39R40R41R42R43R44 R45R46R47R48R49R

son5-lR52R53R54R55R56R

57R58R59R

Re

co

very

• • M

=

a

iP

60R 1blH ^™

Age

— , late Pliocene - Quaternary _

late Miocene - middle Pliocene

?

middle Miocene

early Miocene

? late Oligocene

early Eocene

Paleocene

late Campanian

Santonian

Coniacian

Cenomanian

? late Aptian

Lit

ho

log

y

_ _ _ _ _y v v v v

y v v v vV V V V VV V V V V

y v v v vy v V V V

y v v v vV V V V V

y v v v v

y v v v vV V V V V

y v v v v

1/ V V V V

' V V V V

' V V V V

' V V V VV V V V V

V V V V V

V V V V V^ V V V V/ V V V VV V V V Vif V V V V

f V V V VV V V V V

V V V V V' V V V VV V V V V' V V V V

' V V V V

i' V V V VV V V V Vf V V V VV V V V Vi' V V V V

^ V V V VV V V V V^ V V V V

lass*/ V V V V

>i \ S X \y y y y y

\ \ \ \ \y y y y y

\ x \ \ \

^ \ \ \ \y y y y /

\ \ \ \ \y y y y y

s x x •y. \y y y y y

\ X X X X

Un

it

1 14.6

II

160 6

B

237.4

III

329.9IV

349.2

V

460.0VI

469.9VII

497.1

V I I I - I X509.2

x

559.8

Ic LithostratigraphyojcCD

^ Pelagic brown clay

TuffVolcaniclastic turbidites

O

cb A : Tuff with pelagic clay

B : Tuff with calcareous claystone

oo and chalk

i n

en

CO

σ> Claystone

° Volcaniclastic turbidites

Claystone and radiolarite

<N Calcareous claystoneCM and radiolarian limestone

Claystone-volcanic turbidites

BasaltCO

o Pillow units• Sparsely microphyric and

hypocrystalline

Se

dim

en

tati

on

rate

(m

/m.y

.)

low

11

15

12

7

2-4

9

2

1.5


37



Sample (cm)

129-802A-

33R-1, 116-12034R-1, 128-13235R-CC, 0-437R-1, 11-1538R-CC, 12-1539R-1, 10-1543 R-1,75-7852R-2, 125-13055R-1, 138-14156R-1,43^756R-2, 88-92

Depth(mbsf)

294.0303.6320.5330.0348.6348.8382.9462.6489.3497.5499.5

Unit

IIIIIIIIIIVIVIVVVIVIIVIIIVIII

Age

early Eoceneearly Eocenelate Paleocenelate Paleocene

late Campanianlate Campanian

SantonianConiacian/Cenomanian(?)

Cenomanianlate Aptian(?)late Aptian(?)

Samplelithology

LimestoneChertChertChert

MudstonePorcellanitePorcellaniteRadiolariteRadiolariteRadiolariteMudstone


(m/m.y.)

7779

1775.55.55.55.51


189717851785

9

9

18691869139113971397452

the chalk. Samples studied from Unit III (Table 3) include radiolarianlimestone with Mn-oxide micronodules and red chert nodules withminor chalk inclusions.

Unit IV is Paleocene to late Campanian in age, 19 m thick, andconsists of zeolitic pelagic claystone with subordinate nannofossilclaystone, porcellanite, chert, and calcareous siltstone and sandstone(Lancelot, Larson, et al., 1990). The claystone contains 15%-40%zeolites, 3%—10% radiolarians, and scattered Fe-Mn oxyhydroxides.The Fe-Mn oxyhydroxides are indicators of deep-water depositionand slow accumulation rates; they are not found in continental margindeposits or areas with high accumulation rates. The claystone is thinlylaminated and commonly bioturbated. Some beds are graded orcross-laminated, and some have convolute layers or flame structures,indicating that they were deposited as turbidites. The samples studiedfrom Unit IV include a millimeter-laminated chert nodule from chalk,calcareous radiolarian mudstone, and massive brown porcellanite.

Unit V is late Campanian to Cenomanian in age, 111m thick, andconsists dominantly of volcaniclastic turbidites up to 1 m thick.Pelagic intervals are represented by claystone containing up to 20%radiolarians and/or nannofossils, which gradationally overlies tuf-faceous claystone. The sample studied from this unit is a greenishgray, slightly calcareous porcellanite from the top of a turbidite bed.

Unit VI is Cenomanian in age, 10 m thick, and consists ofinterbedded brown claystone and radiolarite (Lancelot, Larson, et al.,1990). The claystone contains clay minerals, Fe-Mn oxides, zeolites,and radiolarians in layers up to 125 cm thick. Radiolarite occurs inbeds less than 4 cm thick and ranges from green to gray to brown.Contacts between layers are gradational in some places and sharp inothers. The sample studied from Unit VI is a centimeter-scale beddedbuff-colored radiolarite and reddish brown clay. Bedding contactswithin the sample are sharp, not graded, suggesting alternating depo-sitional conditions.

Unit VII is Cenomanian to late Aptian in age and consists of 27 mof radiolarian limestone, nannofossil chalk, calcareous claystone,clayey sandstone, radiolarite, porcellanite, and chert (Lancelot, Larson,et al., 1990). Beds are laminated to massive and vary from a millimeterto more than a meter thick. The unit boundaries are defined by theoccurrence of carbonate rocks at the top and the base. The samplestudied from this unit is a laminated radiolarite with rare Fe-Mnmicronodules, which is similar to radiolarite from Unit VI.

Unit VIII is late Aptian(?) in age and consists of 2 m of claystonewith thin interbeds of radiolarite (Lancelot, Larson, et al., 1990). Theclaystone is yellowish-brown, thinly laminated, contains Fe oxides,zeolites, Fe-Mn micronodules, and pyritized burrows. Sharp, dis-crete, plane-laminated beds suggest current deposition, whereasscour and grading in some beds suggest turbidite deposition. Radio-larite beds are 1-4 cm thick, comprising approximately 10% ofrecovered core. Some radiolarite beds are graded, with sharp contacts,suggesting turbidite deposition. Samples studied from Unit VIII

include millimeter-laminated radiolarite with radiolarian claystone,and radiolarian claystone.

PALEOMAGNETIC CONSTRAINTS ON LEG 129SITES

The Mesozoic Pacific Ocean, as reconstructed from magneticdata, was larger than the modern Pacific Ocean (Larson and Pittman,1973) but had a strong equatorial current and wind patterns thatapproximately resembled modern patterns (Kennett, 1982). Magneticdata were used to determine paleolatitudes for Sites 800,801, and 802(Lancelot, Larson, et al., 1990; Steiner and Wallick, this volume; Ogget al., this volume), providing geographic constraints for depositionof various lithologic units.

Site 800

The oldest sediments and sedimentary rocks recovered from Site 800are Berriasian, at which time the site was located at approximately2°S and moving southward on the Pacific plate (Ogg et al., thisvolume). This location would have been in the equatorial zone of highproductivity (Bostrom, 1976), during accumulation of the radiolariteof Unit V. The site migrated to approximately 13°S, and startedmoving northward during the Aptian. During the Albian when sili-ceous limestone of Unit III was deposited, the site was still south ofthe equator. Accumulation of the radiolarian chert of Unit II corre-sponds to subsequent transition of the site to north of the equator, andbrown pelagic clay of Unit I marks passage into the northern Pacificprovince of low accumulation.

Site 801

Site 801 was situated approximately 9° south of the equator duringdeposition of radiolarite and claystone of Unit V in the Callovian, andmigrated as far north as 1°S of the equator during deposition of theradiolarite of Unit IV in the Tithonian (Ogg et al., this volume). Thesite moved southward during deposition of the volcaniclastic tur-bidites of Unit III. During the Aptian, Site 801 reached 16° S beforemigrating northward. At this maximum southern latitude for thissite, radiolarite, radiolarian claystone, and calcareous claystone weredeposited between turbidite events as background sedimentation. Thesite crossed the equator during deposition of brown chert and porcel-lanite of Unit II in the Late Cretaceous. In the Maestrichtian, the sitemigrated north of 5°N, into the North Pacific Basin, where Unit Ibrown pelagic clay was deposited.

Site 802

Site 802 was situated slightly south of the equator during deposi-tion of radiolarite, claystone, and turbidites of Units V through VIII

38


in the middle to Late Cretaceous (Lancelot, Larson, et al., 1990).Moving northward, it crossed the equator during accumulation of LateCretaceous to early Paleocene radiolarian claystone of Unit IV, andchalk of Unit III accumulated within a few degrees of the equator.Clay and turbidites of Units I and II were deposited north of theequatorial zone in the late Tertiary to Quaternary.

PALEOCEANOGRAPHIC CONDITIONS

The sequence of deposition at Sites 800, 801, and 802 indicatesthat the conditions of deposition were not symmetrical about theequator or homogenous in the equatorial province, nor were theyconsistent over time. Upwelling of nutrients caused by current shearbetween the northern and southern gyres in the Mesozoic Pacificresulted in high productivity in this zone of divergence at the equator(Heath and Moberly, 1971). Higher productivity results in higheraccumulation rates because biogenic material is exposed for less timeat the seafloor, and consequently less dissolves in corrosive, Si andCa undersaturated bottom waters (Berger, 1976). As a result of theseconditions, in deep water, higher accumulation rates are representedby radiolarite and limestone; lower accumulation rates are repre-sented by claystone. In the Jurassic, radiolarite was deposited betweenan unknown north latitude and at least 9°S, with slightly higheraccumulation rates closer to the equator; no evidence of calcareousdeposition remains, although calculated subsidence curves suggestSite 801 may have been near the carbonate compensation depth(CCD) (Ogg et al., this volume). In the Cretaceous, radiolarite wasdeposited between approximately 5°N and 16°S; calcareous biogenicmaterial was deposited between about 2°S to 10°S. Although sedi-mentary structures indicative of turbidite deposition were not ob-served in Cretaceous calcareous deposits cored, faunal evidence(Erba, this volume; Matsuoka, this volume) suggests at least some ofthe calcareous sediments were redeposited. These calcareous depos-its, recorded at Site 800 and in rare pelagic intervals between volcani-clastic turbidites at Sites 801 and 802, accumulated below the inferredCCD for the Cretaceous (see Ogg et al., this volume). Even if all ofthe Cretaceous calcareous sediments were redeposited, it is signifi-cant that calcareous material was available, since none was depositedor redeposited at shallower depths in the Jurassic. The distribution ofthis calcareous sedimentation (observed only for time intervals whenthese sites were located south of the equator) also suggests thatproductivity was higher on the southern flank of the equatorial zonethan on the northern flank. Accumulation rates for background sedi-ments in the volcaniclastic turbidite units could not be calculated, butthe presence of radiolarite in Cores 129-800A-42R and -43R, andCores 129-801B-8R through -12R, and calcareous claystone in Core129-800A-36R, during which time these sites were at their farthestsouth latitudes, suggests relatively high accumulation rates based onthe criteria mentioned above. In addition, accumulation rates werelower for the brown chert and porcellanite units (Units II), whichrepresent the equator crossings at Sites 800 and 801, than accumula-tion rates for radiolarite or limestone deposited south of the equatorduring the Late Jurassic and Early Cretaceous. Leg 129 data indicatesthat accumulation rates decline rapidly north of the equator (Figs. 1,2, and 3; Tables 4, 5, and 6; Ogg et al., this volume). This observationis in conflict with the curve of accumulation rates for other Pacificsites representing equatorial paleolatitudes plotted in Ogg et al. (thisvolume, fig. 11), and may reflect local variations in sedimentation oraccumulation rate, or differences in productivity and accumulationbetween Early and Late Cretaceous. The combination of factorscontrolling the presence of laminated, current-laid, bioturbated,pelagic, or turbiditic deposits of biogenic material at Leg 129 sites ispoorly understood in detail.

In the Tertiary background sedimentation north of the equator wasclay with less than 10% siliceous or calcareous biogenic material atvery low accumulation rates; we do not have data for this area of thePacific south of the equator during the Tertiary. The low accumulation

rates and low proportion of biogenic material for this claystone alsosuggest lower productivity in the Tertiary than for the same latitudesin the Late Cretaceous.

In the Late Jurassic to Early Cretaceous, the accumulation rate forbiogenic material in the equatorial divergence zone, which apparentlyextended several degrees south of the equator, was approximately1000 g/cm2/m.y. for Leg 129 sites; during the Late Cretaceous the ratefor the same calculated latitude was in the range of 1400 g/cm2/m.y.Immediately north of the equator, accumulation rates for non-redepos-ited biogenic material in the Late Cretaceous were less than700 g/cm2/m.y., and less than 200 g/cm2/m.y. in the Tertiary for Leg 129sites. North of the equatorial divergence zone, accumulation rates wereless than 300 g/cm2/m.y. in the Late Cretaceous and less than 200g/cm2/m.y. in the Tertiary.

Accumulation rates for background sedimentation may havechanged with respect to time and location during the Mesozoic andCenozoic for various reasons. Nonsymmetrical equatorial depositioninterpreted from Leg 129 stratigraphy may have been a function of(1) differences in relative vigor between the northern and southernPacific current gyres, (2) continent configurations and wind patterns,and (3) nutrient input differences between the arctic and antarctic.Factors affecting sedimentation of Leg 129 deposits over time includethe following: (1) small- and large-scale climatic changes that affectedthe width and productivity of the equatorial province (see Ogg et al.,this volume), (2) oceanographic changes in carbonate budget andrelative productivity of calcareous and siliceous organisms, (3) sub-sidence and heat flow on the flanks of the mid-Pacific spreadingridges, (4) local vs. regional intensity of the Cretaceous volcanicevents, and (5) frequency of turbidites that mask local depositionalconditions. Factors affecting accumulation, such as productivity, rateof deposition and burial, and corrosivity of bottom waters alsostrongly influenced the depositional sequence at these sites.

Pelagic clay minerals throughout the stratigraphic section at allthree sites are dominantly smectites (shipboard data and Karpoff,this volume) and may be dominantly authigenic clay minerals, asdescribed by Heath et al. (1974), or they may signify redistributionof volcanogenic material through time. Although the main episodesof volcanic activity in the vicinity of Leg 129 deposits occurredduring the mid- to Late Cretaceous and Miocene, as indicated by thevolcanic sills and volcaniclastic deposits, reworking of the volcani-clastic sediments by turbidites and bottom currents, as described byKelts and Arthur (1981), may have been an important process.

Jurassic

Homogenous radiolarite of Unit IV at Site 801 accumulated atapproximately 1000 g/cm2/m.y. under oxic conditions during the LateJurassic. Deposition was sufficiently rapid to prevent complete dis-solution of radiolarians but slow enough to maintain oxic conditionssouth of the equator. The diagenetic growth of manganese mi-cronodules, some of which are found inside radiolarian tests, suggeststhere was some period of exposure at the seafloor.

Cretaceous

Alternating pelagic claystone and radiolarite of Unit V deposited 2°Sto 10°S during the Early Cretaceous at Site 800 reflect changes inproductivity. This might be a consequence of changes in nutrient avail-ability, which can be enhanced during cooler global climates which forcestronger circulation between the poles and equator (Arthur et al., 1984).When these conditions are cyclic, they correspond to Milankovich cycles,and may contribute to depositional alternations such as were recorded atSites 800 and 801 (Ogg andMolinie, this volume; Ogg et al., this volume).Conditions apparently changed by the time Site 800 returned to the samelatitudes in the Late Cretaceous, at which time more homogenous radio-larian chert and limestone of Unit III were deposited at a greater accumu-lation rate than the alternating radiolarite and claystone of Unit V.

39


Table 4. Silica contents (in percent) of samples from Site 800, Leg 129.

Sample (cm)

129-800A-

6R-1,76R-6R-7R-7R-8R-8R-8R-9R-

10R-10R-11R-12R-12R-13R-13R-14R-14R-17R-17R-18R-

1,37, 67-69,2-5,66

1,01,22,48-50,30-33,13, 13-17,7-10,30-32,37, 12-14,46, 101, 110-115,25,68-71,70

18R-1, 12118R-1, 127-13019R-1, 119R-1,3721R-2, 822R-1, 1923R-1,69-7024R-1.3024R-1,68-7124R-1,92-9526R-1,22-2626R-1, 135-13927R-1, 61-6427R-1, 110-11428R-3, 106-11030R-1, 125-12930R-2,114-11831R-1, 12-1432R-CC, 10-1333R-7, 14-1834R-2, 139-14235R-3, 84-8836R-1,110-11436R-4, 28-3241R-42R-44R-51R-52R-53R-

,87-93,41^3, 92-94,106-108, 16-20, 32-34

55R-1, 76-8155R-2, 25-3056R-1, 8-1358R- ,37-42

Depth(mbsf)

39.740.040.249.249.858.959.159.468.878.378.387.997.697.7

106.9107.2117.2117.3144.4144.9154.4154.9155.0162.9163.3182.9191.2201.2210.2210.6210.8228.8230.0238.6239.1251.3267.2268.5272.1280.8296.6299.9310.2317.0320.7363.4369.0384.6450.7459.0465.2479.9480.9488.6507.6

Unit

IIIIIIIIIIII11IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVVVVVVVVI

TotalSiO2

85.580.887.389.392.087.589.087.686.692.889.682.885.690.689.869.193.078.262.285.283.692.088.985.580.148.733.683.985.379.490.446.255.055.072.848.675.685.774.070.042.642.367.140.642.343.357.044.580.273.381.083.179.887.095.7

Percentage of sample

BiogenicSiO2

71.063.379.683.487.177.980.880.879.386.983.975.776.582.784.166.888.163.759.676.170.787.182.774.061.547.111.274.174.164.285.236.231.327.059.911.356.675.854.446.7

5.713.441.3

6.05.39.3

24.56.1

62.849.466.771.162.276.893.8

HydrothermalSiO2

0.00.00.00.00.00.00.00.00.11.00.40.00.00.00.10.00.00.00.00.00.00.00.00.00.50.00.30.60.40.00.00.41.41.71.12.31.00.80.00.64.12.72.83.03.35.93.27.80.00.00.40.00.00.00.0

DetritalSiO2

14.517.57.75.95.09.68.36.87.25.05.37.19.17.95.62.35.0

14.52.69.1

12.95.06.2

11.618.21.7

22.19.2

10.915.25.29.6

22.326.311.835.017.99.1

19.622.732.826.223.031.633.728.129.330.617.423.913.912.017.610.2

1.9

Percentage of total silica

BiogenicSiO2

83.078.491.293.394.689.190.792.391.593.693.791.489.491.393.796.794.781.495.889.384.694.693.086.576.896.633.488.386.880.894.378.456.849.082.223.374.988.573.666.713.431.661.614.812.621.442.913.778.367.482.385.578.088.398.0

HydrothermalSiO2

0.00.00.00.00.00.00.00.00.11.10.50.00.00.00.10.00.00.00.00.00.00.00.00.00.60.00.80.70.40.00.00.92.53.11.64.71.40.90.00.99.76.44.17.37.8

13.75.6

17.50.00.00.50.00.00.00.0

DetritalSiO2

17.021.6

8.86.75.4

10.99.37.78.35.35.98.6

10.68.76.23.35.3

18.64.2

10.715.45.47.0

13.522.73.4

65.811.012.819.25.7

20.740.647.816.272.023.710.626.432.476.962.034.377.979.664.951.568.821.732.617.214.522.011.72.0

Notes: Ratios and equations from Heath and Dymond (1977) and Bishoff et al. (1979). Detrital SiO2% = 3.3 (A12O3

= 1.74 [(Fe2O3 - 0.75 A12O3) - 0.32 MnO]; biogenic SiO2% = total SiO2% - hydrothermal SiO2%.); hydrothermal SiO2

In the Early Cretaceous, when Site 801 was 5° to 10° south of theequator, finely laminated to massive radiolarite of Unit IV wasdeposited. By the middle Cretaceous, when Site 801 was as much as16°S, pelagic and biogenic accumulation patterns were masked by theinflux of volcaniclastic turbidites, however relatively high accumu-lation rates are inferred from pelagic radiolarite beds preserved be-tween turbidite beds. When Site 801 migrated north of the equatorduring the Late Cretaceous, alternating pelagic clay and radiolaritemay have accumulated, but poor drilling recovery prevents verifica-tion of this hypothesis. Although the nature of bedding is not certain,

accumulation rates were low and the unit contains more clay than unitsdeposited at similar latitudes south of the equator. The Cretaceousdeposits from Leg 129 suggest that productivity was higher in thesouthern part of equatorial divergence zone than the northern part; alsothe southern part of the zone was apparently greater in breadth.

Tertiary

When Site 802 was in the northern part of the equatorial zone inthe early Tertiary, chalk turbidites of Unit III were deposited. These

40



Sample (cm)

129-801A-

7R-CC, 18R,1, 1-39R-1,0-3

lOR-1,0-510R-1, 1112R-1,22-2580-100M13R-1, 21-2614R-1,26-2815R-1,24-2616R-1, 135-13817R-1, 28-3018R-2, 14-1719R-CC, 12-1620R-l,8-12

129-801B-

8R-2, 60-631 OR-1,70-7311R-1, 31-3612R-1,64-70HR-1,2414R-1,52-5715R-1, 19-2016R-1, 40-4317R-1,34-3618R-1.2418R-1,37-4019R-1,24-2620R-1,23-2621R-1, 12-1324R-1.5424R-1,69-7325R-1, 125R-1,49-5327R-1.3027R-1, 104-10729R-1, 17-1931R-1, 18-2033R-1, 10-1433R-1.4333R-1, 126-12933R-2, 4835R-1,51-5535R-1, 123-12735R-2, 12035R-2, 14035R-3, 135R-3, 1937R-1.7-1039R-1,4-7

129-801C-

4R-1, 11-165R-4, 11-16

Depth(mbsf)

60.460.670.279.579.699.0

100.0108.7118.5128.1139.0147.5158.6176.3176.5

254.8272.7282.0292.0310.5310.8319.9329.6338.9348.0348.2357.5366.7375.8393.1393.3397.2397.7407.0407.7416.4425.8434.9435.2436.1436.8444.8445.5447.0447.2447.3447.5453.6462.7

521.8535.8

Unit

IIIIIIII11IIIIIIIIIIIIIIIIIIIIIIIIII

IIIIIIIIIIIIIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVIVVVVVVVVVI

VIVI

TotalSiO2

90.896.783.989.890.576.382.884.186.079.675.478.976.982.988.6

89.558.077.177.482.585.282.993.192.485.491.095.591.892.885.390.785.984.796.893.792.792.868.781.483.783.764.674.556.364.866.769.891.894.8

81.111.4


BiogenicSiO2

84.595.472.784.583.658.371.272.977.264.958.864.460.973.182.4

83.625.858.959.166.774.569.189.187.773.285.293.786.786.874.684.274.672.695.690.388.288.338.364.269.370.730.549.812.330.434.240.184.990.4

53.63.9

HydrothermalSiO2

0.00.00.00.00.00.00.00.00.01.81.10.90.91.10.6

0.15.30.76.00.00.00.00.00.00.00.00.00.01.50.10.00.10.00.20.00.00.09.72.31.13.16.27.56.77.04.83.94.81.9

27.25.9

DetritalSiO2

6.31.3

11.25.36.9

18.011.611.28.8

12.815.513.515.18.75.7

5.826.917.612.315.810.713.84.04.7

12.25.81.85.14.5

10.66.5

11.212.1

1.03.44.54.5

20.614.913.39.9

27.917.237.327.427.725.72.02.4

0.31.5


BiogenicSiO2

93.198.786.694.092.376.586.086.789.781.677.981.779.288.193.0

93.444.576.376.380.887.583.495.794.985.793.698.194.493.587.592.986.885.798.796.395.295.155.878.982.884.447.366.921.946.951.357.592.595.4

66.134.6

HydrothermalSiO2

0.00.00.00.00.00.00.00.00.02.31.41.21.21.40.6

0.19.20.97.80.00.00.00.00.00.00.00.00.01.60.20.00.10.00.30.00.00.0

14.22.81.33.79.6

10.111.910.87.15.65.32.0

33.552.1

DetritalSiO2

6.91.3

13.46.07.7

23.514.013.310.316.120.617.114.610.56.4

6.546.322.815.919.212.516.64.35.1

14.36.41.95.64.8

12.47.1

13.114.3

1.03.64.84.9

30.018.215.811.843.123.066.242.341.636.92.22.6

0.413.3

Notes: Ratios and equations from Heath and Dymond (1977) and Bishoff et al. (1979). Detrital SiO2% = 3.3 (A12O3%); hydrothermalSiO2% = 1.74 [(Fe2O3 - 0.75 A12O3) - 0.32 MnO]; biogenic SiO2% = total SiO2% - detrital SiO2% - hydrothermal SiO2%.

voluminous deposits have masked clues to depositional conditionsat this location in the Tertiary. Background sedimentation at theequator consisted of pelagic clay with less than 10% siliceous orcalcareous fauna and low accumulation rates. Sites 800 and 801 werenorth of the equatorial zone during the Tertiary, where sedimentationand accumulation rates were both extremely low, and pelagic claywas deposited.

GEOCHEMISTRY OF LEG 129 SILICEOUSDEPOSITS

Leg 129 sedimentary rocks were analyzed geochemically in orderto characterize various types of siliceous deposits. Trends in elementabundance were consistent between the three sites. Elements testedas key environmental indicators include Si, Fe, Mn, Mg, Al, B, P, Ba,

41



Sample (cm)

129-802 A-

33R-1, 116-12034R-1, 128-13235R-CC, 0-437R-1, 11-1538R-CC, 12-1539R-1, 10-1543R-1, 75-7852R-2, 125-13055R-1, 138-14156R-1,43^756R-2, 88-92

Depth(mbsf)

294.0303.6320.5330.0348.6348.8382.9462.6489.3497.5499.5

Unit

IIIIIIIIIIVIVIVVVIVIIVIIIVIII

TotalSiO2

45.595.894.888.965.470.077.873.276.370.778.8


BiogenicSiO2

42.195.293.286.343.653.862.249.856.944.561.9

HydrothermalSiO2

0.00.00.00.00.51.20.00.00.00.04.6

DetritalSiO2

3.40.61.62.6

21.315.015.623.419.426.212.2


BiogenicSiO2

92.599.398.497.066.676.880.068.174.563.078.6

HydrothermalSiO2

0.00.00.00.00.81.70.00.00.00.05.9

DetritalSiO2

7.50.71.63.0

32.521.520.031.925.537.015.5

Notes: Ratios and equations from Heath and Dymond (1977) and Bishoff et al. (1979). Detrital SiO2% = 3.3 (A12O3%); hydrothermalSiO2% = 1.74 [(Fe2O3 - 0.75 A12O3) - 0.32 MnO]; biogenic SiO2% = total SiO2% - detrital SiO2% - hydrothermal SiO2%.

Cu, La, and Ce. Because some elements are characteristic of morethan one depositional environment, element ratios and partitioningequations have been derived to discriminate between environments(Bishoff et al., 1979, Leinen and Stakes, 1979; Leinen, 1981; Leinenand Pisias, 1982). Aluminum to metal ratios plotted according todefined fields in various diagrams (Bostrom, 1973, Karpoff et al.,1988; Karpoff, 1989) help to determine detrital and metalliferoussources of the sediments. A copper-barium plot discriminates betweenbiogenic and authigenic sources (Karl, 1982). Finally, rare earthelement (REE) patterns are compared in order to identify sedimentarysources and depositional trends.

Methods of Analysis

One hundred and one samples of siliceous rocks were chosen fromSites 800, 801, and 802. These samples were selected to representbackground sedimentation as well as depositional episodes, such ashigh productivity events or turbidite events. For example, in theturbidite units, both the fine-grained tops of turbidites and the pelagicinterval between turbidites were sampled for purposes of comparison.In the alternating chert/shale units, both lithologies were sampled.Statistically, however, each unit is represented overwhelmingly bypelagic deposits in this study. Poor recovery in general at Leg 129sites, and in particular for siliceous lithologies, limited our ability toadequately sample every unit.

Samples studied each weighed approximately 15 g and wereground to -100 mesh in a tungsten carbide mill. Tungsten carbidemills are known to contaminate samples in Co, Nb, Ta, and W; thiscrushing equipment was chosen because these elements were consid-ered less important than contaminating elements from other means ofcrushing. After crushing the samples were divided into three splits.One split was analyzed nondestructively for minor elements by X-rayspectroscopy, and by X-ray fluorescence for major elements (Appen-dix Tables A1-A3 and B1-B3). The precision of the minor elementanalyses is approximately 10%, and of the major elements is l%-2%.The second split was analyzed for Boron by quantitative emissionspectroscopy. Rare earth element compositions were determined onthe third split by induced neutron activation analysis (AppendixTables C1-C3). The samples were irradiated for 7 hr in the TRIGAreactor at the U.S. Geological Survey in Denver, and counted 4 timesover 8 weeks.

Thirty additional samples of siliceous rocks were analyzed formajor and minor elements by microprobe at the University of Stras-bourg, France (Appendix Tables Dl and D2). The precision of theseanalyses is about 2% for major elements and 10% for minor elements,

which is comparable to the analyses performed in the U.S. GeologicalSurvey laboratories. Consequently these data were plotted togetherwhere appropriate.

Results

Silica

The two main sources of silica in the ocean are detrital aluminosili-cates (both terrigenous and volcaniclastic) and biogenic tests (Bostromet al., 1974; Heath, 1974; Berger, 1976). Alteration of clays and volcanicglass, and hydrothermal emanations also contribute minor amounts ofsilica (Rona et al., 1980). Since the ocean is 98% undersaturated withrespect to silica (Berger, 1976), biogenic siliceous deposits only accumu-late under areas with high rates of deposition. High rates of depositionare controlled by the availability of nutrients, which are brought up to thephotic zone in regions of current shear, such as the equatorial divergence,or where winds and currents impinge on continental margins (Kennett,1982). Siliceous deposits in the modern Pacific Ocean accumulate nearthe equator, at high latitudes, and along the continental margins (Ber-ger, 1976; Keene, 1976; Jenkyns, 1978). At the equator, productivityis ultimately controlled mainly by climate, because temperature con-trast between the poles and equator during cool climates drives strongerwinds and currents. During times of low productivity, only pelagic clayaccumulates. The cyclicity of pelagic clay and siliceous deposits on acentimeter scale has been attributed cyclic climatic variations, orMilankovitch cycles (RCCG, 1986; Rea et al., 1991).

The siliceous deposits at Sites 800, 801, and 802 were depositedbetween 5°N and 15° S of the equator, and are dominantly biogenic.The central Pacific low-latitude paleo-location of these sites, withwinds from the east, resulted in a negligible contribution of terrige-nous material to this area during deposition of the sediments sampledfor this study. Illite and quartz grains signify terrigenous contributionsto siliceous deposits; the scarcity of illite and the lack of quartz grainsin Leg 129 deposits suggests most of the detrital sediments arevolcaniclastic. Interbedded volcaniclastic turbidites indicate an inter-mittent volcanic source. Reworking of volcanic detritus by bottomcurrents between volcanic episodes may have intercalated volcanicmaterial with the pelagic deposits. There was probably some contri-bution of silica from alteration of volcanic-derived clay minerals andglass in the volcaniclastic turbidite sections. At the base of Site 801,there is hydrothermal silica.

Partitioning ratios for elements representing the above sedimentsources were used to calculate relative proportions of these sources.Partitioning of silica, based on ratios and equations from Heath andDymond (1977) and Bishoff et al. (1979) (Tables 4, 5, and 6), shows

ODP SITE 800 (Fe% (XRF AND MICROPROBE))


ODP SITE 801 (Fe% (XRF AND MICROPROBE))

-20

-60

-100

-140

-180

-220

-260

-300

-340

-380

-420

-460

-500

-540

-

- •— •

•

• •- •

•

•

-•

_

-

—

m

• ••

•

•

••

• •

••

• •

•

• • "•

•

• •

1

••

• •

• "•

1

1

II

IV

V

VI

0

-50

-100

-150

-200

-250

-300

-350

-400

-450

-500

-550

-

•••

•••

-

• •

•

-

•••

— • ••

••

_ • . 1••

•

—

•

••

•

•

• mm

m

m

i

•

•

• # •

•

•

•

1

1

II

IM

IV

V

VI

6

Fθ%

10 12 6

Fβ%

10 12

ODP SITE 802 (Fe% (XRF))

-250

-300 i-

-350

-400

-450

-500

-550

•

•

•

•

•

— • •

-

I I I I I

III

IV

V

VI

VII

VIII-IX

X

0 2 4 6

Fθ%

10 12

Figure 4. Iron contents of samples from Leg 129.

43


ODP SITE 800 (Mn% (XRF AND MICROPROBE))

-20

-60

-100

-140

-180

_ -220CO

£ -260

Φ -300Q

-340

-380

-420

-460

-500

-540

0.0

ODP SITE 801 (Mn% (XRF AND MICROPROBE))

-

• • •• •

— • • ••

•

X •

— ••

a• •

• ••

•

- ••

" ••

• •~ •

• •

•

1

II

III

IV

V

VI

0

-50

-100

-150

-200

-250

-300 f•

-350

-400

-450

-500

-550

-

•• •

• ••

•

••

•

X•

••

••

•— • •

••

•

• • •• •

••

•i•

-• ta•

m

1 , f , •

1

II

III

IV

V

VI

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Mn%

ODP SITE 802 (Mn% (XRF))

-250

-300

-350

-400

-450 -

-500

-550

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 O.f

Mn%

Figure 5. Manganese contents of samples from Leg 129.

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.J

Mn%

••

•

•

•

•

—• •

I I

III

IV

V

VI

VM

VIII-IX

X

44

ODP SITE 800 (Mg% (XRF AND MICROPROBE))


ODP SITE 801 (Mg% (XRF AND MICROPROBE))

-20

-60

-100

-140

-180

_ -220CO

£ -260

S• -300

-340

-380

-420

-460

-500

-540

0

-50

-100

-150

-200

| -250

JS

g• -300Q

-350

-400

-450

-500

-550

1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8

Mg% Mg%

ODP SITE 802 (Mg% (XRF))

-

- • • •

••

_ •• •_ • •

• •• •

~• ••• •

- • ••

•• •

•

. •

- • •• •

I

1 1 1

1

II

III

IV

V

VI

-

•l•

•""

• •• •- • •

••

••

•••-• •1•

•• • •

• rt •

I

1 1 1

1

II

III

IV

V

VI

-300

-350

-400

•450

-500

.sen

•V

m

—

—

•

•

1 1 1 1 1

III

IV

V

VI

VII

V I I I -IX

X

0 1 2 3 4 5 6 7 8

Mg%

Figure 6. Magnesium contents of samples from Leg 129.


ODP SITE 800 (Al% (XRF AND MICROPROBE))

-20 -

• ••60 h • • •

-140

-180

_ -220m

1 -260

g• -300Q

-340

•380

-420

-460

-500

-540

IV

VI

ODP SITE 801 (Al% (XRF AND MICROPROBE))

-50

-100

-150

-200

-250

-300 \

-350

-400

-450

-500

-550

-

•• •

— • ••

••

••

• •

••

•

•••

— • ••

••

• • • •• •

••

• • • •

I

1 1

1

II

III

IV

V

VI

ODP SITE 802 (Al% (XRF))

-250

-300 =-

-350

-400

-450 -

-500

-550

•

•

•

•

•

— • •

1 1 1 1

III

IV

V

VI

VII

VIII-IX

X

Figure 7. Aluminum contents of samples from Leg 129.

46

ODP SITE 800 (P% (XRF))



-20

-60

-100

-140

-180

-220

-260

-300

-340

-380

-420

-460

-500

-540

-

-—

••

-

••

•

•--

-

—

••

•-

1

•

•

••

•

••

•

•

1

••

•

••

•1

• ••

1

II

III

IV

V

VI

0

-50

-100

-150

-200

-250

-300

-350

-400

-450

-500

-550

a

-

—

-

—

•

••

•_ 1

•

-••

••

•

•

•

••

••

•

•

••

• ••

••

••

••

•

••

•

1 1

1

II

III

IV

V

VI

0.00 0.05 0.10

P%

0.15 0.20 0.00 0.05


-250

-300

-350

-400 -

-450

-500

-550

•

•

•

•

•

— • •

I I

III

IV

V

VI

VII

VIII-IX

X

0.00 0.05 0.10

P%

0.15 0.20

0.10

P%

0.15 0.20

Figure 8. Phosphorous contents of samples from Leg 129.

47

Figure 9. Boron contents of samples from Leg 129.

ODP SITE 800 (B ppm (MASS SPEC.))

-20 - I- i

-60 - • B 'I

-100 - m ••

• 1 4 0 : . in

-180 -

_ -220 - _

t -260 . . .c •S -300 - • •

* IV

-340 -

-380 - .

-420 -

-460 - ~~m • •~~

V-500 = —"

I I I I I I I V l

.540 I I I I I I I I I I I I I I I I I I

0 10 20 30 40 50 60 70 80

B ppm


o I 1 1

i

-50 -•

•

-100 - • • • "•

-150 - a •

• •

-200 -_ III

| -250 - .•

JZ •

I" -300 - •Q •

•

-350 - • " u

• " IV

-400 - u • ••

• •-450 - . m r ~ V

—Ü

-500 - vi•

. 5 5 0 F I I I I I I I I I 1 I 1 I I I I I0 10 20 30 40 50 60 70 80

B ppm


-250 | 1 1

-300 - a

m•

IV-350 . •

"5 _.Q •E~ -400 - Va.Φ

a

-450 -

• ~~vi~

VII

-500 — " i VNT

! ×_

X

-550 I—!—I—I I ! I I I—!—I I I I I I L J0 10 20 30 40 50 60 70 80

B ppm

Figure 10. Lanthanum contents of samples from Leg 129.

ODP SITE 800 (La ppm (INAA))

-20 - I_ B

-60 - jj• "_ m

-100 - m ••

-180 -

c • W = ' • ' * .•» • •

i -260 - . - ".£ •

I" -300 - %IV

-340 -

• .

-380 - •

-420 -

-460 - ~~" B ~ •• • • V

.500 =iI I I I I V l

. 5 4 0 I I I I I I 1 I I I I I I I 1 I I I I 1

0 5 10 15 20 25 30 35 40 45

La ppm


o | i

i

-50 = _ B

••

-100 - •• "• •

-150 - •

• •

-200 -III

1 -250 -•

J= m

g• -300 - •

•

-350 -u " •

- " • IV

-400 - m • ••

•• •

-450 - . ~~•~ *~ V•

-500 ~ v|

. 5 5 0 1 * 1 I I I I I I I I I I I I I I I I i

0 5 10 15 20 25 30 35 40 45

La ppm


-250 | 1 1

111

-300 - m

m

•

IV

-350 • •

^ •E"2 -400 - Vo.ΦQ

-450 -

• VI

VII

-500 = i • vüT[x_

X

-550 I — I — I — L J I—I I I I I | | I I | | L J

0 5 10 15 20 25 30 35 40 45

La ppm


that the silica at all three sites is predominantly biogenic, with a high(volcaniclastic) detrital component in the samples from the turbiditeunits. Thin section observations, microprobe, and XRD analysesindicate that the clay minerals at Sites 800, 801, and 802 are domi-nantly undifferentiated smectites, including rare montmorillonite,that are most likely volcanogenic. The apparent hydrothermal silicathat shows up in the turbidite units may in part be due to inadequaciesof the partitioning ratios, and to unaccounted-for excess iron that mayhave been concentrated and mobilized by diagenetic processes. Smallamounts of Fe and Al in biogenic material (Bostrom, 1976) are alsounaccounted for in these partitioning calculations.

Iron

In the modern Pacific Ocean iron is most concentrated in sedimentson the East Pacific rise and in areas of volcanic arcs (Bostrom et al., 1973).The accumulation of Fe in sediments near spreading ridges appears to beproportional to spreading rates, and probably has a magmatic source(Bostrom, 1973; Bishoff et al., 1980; Dean et al., 1989). Iron is carried inslightly reduced CO2-rich fluids, and is the first element to precipitate asamorphous oxides with amorphous silica, as the chemical environmentbecomes more oxidized at the seafloor, followed by Mn, Cu, and Ni(Bostrom et al., 1973; Lonsdale et al., 1980).

At Site 800, Fe is the most abundant in the volcaniclastic unit(Fig. 4), suggesting a predominantly volcanic detrital source. It de-creases upward in the overlying unit, possibly indicating a gradation-ally decreasing volcaniclastic contribution. The tops of Unit III andUnit II are apparently free of volcaniclastic detritus. The slight Feenrichment in Unit V may result in part from hydrothermal or diage-netic mobilization of Fe from the underlying dolerite sills.

Thin sections from hydrothermal deposits at the base of Site 801contain coarsely-crystalline quartz and iron oxides that are apparentlychemically precipitated. The sediments immediately overlying thebasalt contain amorphous iron and silica in addition to abundantradiolarian tests. At Site 801, Fe concentrations (Fig. 4) are generallycomparable to those at Site 800, especially in the turbidite unit, butthey are remarkably high in the basal and interpiU°w sediments. Thesevalues are consistent with moderate to fast spreading rates for thismid-ocean ridge (Lancelot, Larson, et al., 1990).

At Site 802, Fe concentrations are low in the chalk unit, and similarto Sites 800 and 801 in the volcaniclastic turbidite units (Fig. 4).

Manganese

The distribution of Mn in sediments in the modern Pacific Ocean ismainly associated with spreading ridges and seamounts, suggesting asource similar to that of Fe. However, the diagenetic behavior of Mn isdifferent from that of Fe. Manganese is very mobile in reducing environ-ments, and requires a more oxidizing environment than Fe to precipitate.At Sites 800 and 801, Mn may have been preferentially mobilized bydiagenetic processes and migrated up the section. Since bottom waters inthe central paleo-Pacific apparently were oxidizing, but since organicmatter could have reduced buried sediments, Mn may have movedupward through reduced sediments in the sedimentary column, andaccumulated at a redox boundary, which commonly occurs where thereis a change to slow depositional and accumulation rates (Drever, 1982).

At Site 800, Mn concentrations are highest in Units II and V(Fig. 5), the units with the lowest accumulation rates. Moderate Mnabundances in Unit IV may reflect a volcaniclastic source, or repre-sent pelagic intervals of low accumulation.

At Site 801, Mn is also high in the units with low accumulationrates (Fig. 5). The increase of Mn in Unit IV relative to underlyingUnit V may be due to diagenetic remobilization, since Mn is lowrelative to Fe in Unit V, but may be partly hydrothermal.

Manganese is very low in all units at Site 802 (Fig. 5) relative tounits at Sites 800 and 801, but is highest in the pelagic sedimentsoverlying the pillow basalt at the base of the hole.

The Fe/Mn ratios of ridge crest hydrothermal sediments is ap-proximately 3 (Bostrom, 1973; Bishoff et al, 1979). Fe/Mn ratios areconsiderably higher than 3 for all units at all three sites, suggesting,as did the silica calculations, that detrital Fe is a more significantsource of Fe than hydrothermal Fe, but also that remobilization of Mnmay be an important diagenetic process.

Magnesium

A major source of magnesium in marine sediments is maficdetritus from weathering of basalt or volcaniclastic material (Bishoffet al., 1979). A detrital source for Mg at all three sites is indicated bythe highest Mg values in the turbidite units (Fig. 6). Mg values arealso high in the basal units at Site 801, which could be authigenic Mgderived from seawater or detrital Mg derived from weathering ofbasalt at the seafloor. Carbonate rocks are another source of Mg, butMg values are similarly low in the limestone and radiolarite units atall three sites.

Aluminum

Aluminum in marine sediments is derived dominantly from detri-tal sources. This is supported by high Al values in the turbidite unitsat all three sites (Fig. 7). As with Mg, the high Al values in the basalsediments at Site 801 strongly suggest weathering of basement as onesource for these sediments. This hypothesis is supported by highFe/Mn values for Unit V at Site 801.

Phosphorous

Phosphorous is carried in some hydrothermal fluids (Bostrom,1973), but is mainly associated with biogenic debris in marine sedi-ments (Berger, 1976). Under more alkaline conditions, phosphate ismore mobile than iron, and thus tends to be enriched in more reducedsediments (Price, 1976).

At Sites 800, 801, and 802 the abundance of P is consistently low,but is highest at the base of the turbidite units (Fig. 8), which are morereduced than the other units. P is also relatively abundant in theradiolarite/claystone units at Site 801. Fish parts were observed in thinsections of chert, claystone, and volcaniclastic rocks from several units,and thus the likely source of P at all three sites is fish debris.

Boron

Boron is considered to be a biogenic indicator and is found mainlyin sponge spicules, which are associated with shallow-water deposits(Hein et al, 1981, 1982; Truscott and Shaw, 1983). No shallow-watersediments were drilled on Leg 129, and sponge spicules are extremelyrare, only observed in sandstone and chalk turbidites that were rede-posited from shallow water.

Boron concentrations are low in all units, and there are no strati-graphic trends (Fig. 9). Special effort was made to measure boronquantitatively. Results indicate that boron is not important in deep-water deposits. In fact, the lack of boron may be useful as a deep-waterenvironmental indicator.

Lanthanum

Lanthanum abundances in sedimentary rocks reflect total REEabundances because REE have very similar physical and chemicalproperties (Henderson, 1984). The source of REE in deep marinesediments is controversial, but generally assumed to be seawater, fromwhich it is adsorbed mainly onto authigenic or biogenic phases (Piper,1974). Eolian or other detritral sources are volumetrically less important.

La abundances in siliceous samples from Leg 129 are generallyhighest in the samples from pelagic units with the lowest accumula-tion rates, and higher in the pelagic samples with clay than in pelagic

50

Figure 11. Cerium contents of samples from Leg 129.

ODP SITE 802 (Ce ppm (INAA))

- 2 5 0 | •

III-300 - .

••

IV-350 — • •

M

-α •E~ -400 - VQ.ΦQ

-450 -

• ~~vT~

. v "-500 - — l • virT

. ix_

X

-550 ' 1 1 I I I I I 1 I 1 I L . _

0 10 20 30 40 50 60

CΘ ppm


-20 - I- •

-60 - • a "= •—

-100 - m " ••

-140 7 . • III

-180•

C - 2 2 0 = . — ' .2 m •E -260 - . . .JS - .

g" -300 *

" • • ,v

-340 -

-380 - .

-420 -

-460 - -

-500 = . "I V l

.540 I 1 1 1 1 1 1 1 1 1 1 1 1 1

0 10 20 30 40 50 60

Ce ppm


o | 1

i

-50 = β

••

-100 - • m • ".

.-150 ~ •

-200 -III

1 -250 - .

j= •

S" -300 = •

m

-350 - m " •

- . " IV

-400 - " ••

•. •

-450 - . ~~÷~~ ~~*~ V— a

-500 — vi

i

-550 L^J 1 1 1 1 1 1 1 1 1 1 1

0 10 20 30 40 50 60

CΘ ppm


ODP SITE 800 (Ce ppm/AI%)

-20

-60

-100

-140

-180

._. -220n

& -260

g• -300 rα

-340

-380

-420

-460

-500

-540

0 2 4 6 8 10 12 14 16 18 20 22 0 2 4

(Cβ ppm)/(AI%)


-250

-300

-350

-400 -

-450 -

-500


-

-

_

—

-

•

•

••

•

1

•

1 1 1

•

•

•

•

•

• •

1•

•

•

••

1 1

••

••

••

1 1

1

II

III

IV

V

VI

u

-50

-100

-150

-200

-250

-300

-350

-400

-450

-500

-550

•

— •••

•_ •

•

••

••

•_ •

••

•

• ••

•• •

•

•

I I ^ I I I I I

•

I I

I

II

III

IV

V

VI

8 10 12 14 16 18 20 22

Cβ ppm/AI%

-550

-

•

•

•

-

•

•

•J i •

I I I

III

IV

V

VI

VII

V I I I -IX

X

8 10 12 14 16 18 20 22

Cθ ppm/AI%

Figure 12. Cerium/aluminum ratios for samples from Leg 129.

52

ODP SITE 800 (AI/(AI+Fe+Mn) (XRF AND MICROPROBE))


ODP SITE 801 (AI/(AI+Fe+Mn)(XRF AND MICROPROBE))

-20

-60

-100

-140

-180

_ -220

B. -260

I" -300Q

-340

-380

-420

-460

-500

-540

III

IV

VI

-50

-100

-150

-200

-250

-300 r

-350

-400

-450

-500

-550

-

-

—

-

-

-

•

-

1

•

•

•

• •

•

1

•

••••

••••

•••

•

•

•

•

•I

•• •

••

••

• ••

•

1

1

II

IV

V

VI

0.0 0.1 0.2 0.3 0.4 0.5 0.6

AI/(AI+Fθ+Mn)

ODP SITE 802 (AI/(AI+Fe+Mn) (XRF))

-250

-300 -

-350

-400 -

-450

-500

0.0 0.1 0.2 0.3 0.4 0.5 0.6

AI/(AI+Fβ+Mn)

••

•

•

•

•

— • •

-

I I I

III

IV

V

VI

VII

VIII-IX

X

0.0 0.1 0.2 0.3 0.4 0.5 0.6

AI/(AI+Fβ+Mn)

Figure 13. Aluminum/metal ratios for samples from Leg 129.

53


ODP SITE 800 (Fe/Ti VERSUS AI/(AI+Fe+Mn)) ODP SITE 801 (Fe/Ti VERSUS AI/(AI+Fe+Mn))

1000

100 -

10 -

1

1000

100 -

10 -

1

•,H

\λ \

Ii

i i

i i

i i

1

\

\ X\ A +

o \ .

X

s

0

+

•

"i 0

^ Δ B

1 \

UnitUnitUnitUnitUnit

B-T

1

IIII!IVVVI

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

AI/(AI+Fθ+Mn)

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

AI/(AI+Fβ+Mn)

ODP SITE 802 (Fe/Ti VERSUS AI/(AI+Fe+Mn))

1000

100 -

10 -

- H

j\i\\\

i i

i i

i i

MI

i

E Unit III

* Unit IV

o Unit V

* Unit VI

• Unit VII

D Unit VII

D

1

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

AI/(AI+Fβ+Mn)

Figure 14. Plot of Fe/Ti vs. A1/(A1 + Fe + Mn) (after Bostrom, 1973). H = hydrothermal compositional end-member, T = terrigenous compositional end-member,

B = basaltic compositional end-member.


samples without clay. There is also a subtle increase in the La contentsof samples upsection at each site. At Site 800, the lowest concentra-tions of La are in radiolarian chert and limestone of Unit III (Fig. 10).The highest concentrations of La are in claystone samples from thetops of turbidite beds, but high La concentrations are not restricted tothese beds. At Site 801, REE are virtually absent in the hydrothermaldeposits within the pillow basalt section at the base of the hole (Fig. 10).La concentrations in the rest of the section are lowest in biogenicsamples in Unit VI, deposited on basement, and highest in a claysample from Unit V near basement. La abundances are higher in thepelagic samples with clay than in the clay-poor radiolarite of Unit IV.At Site 802, La concentrations are lowest in the nannofossil chalk unitand the highest La "concentrations of all three sites are in pelagicclaystone of Unit VI (Fig. 10).

The relative abundances of La in the samples studied suggest thathigh La (and REE) concentrations correspond to high clay contents,and that clay from units with low accumulation rates have generallyhigher La abundances than clay associated with the volcaniclasticturbidites. There appears to be a possible detrital source of REEdeposited on basement at Site 801, and in the volcaniclastic depositsat all three sites, but an authigenic source for La and the REE seems tobe dominant in all units. A biogenic source for REE is also indicated,but appears to be subordinate to authigenic sources.

Cerium

Cerium is typically depleted with respect to the other REE indeep-water pelagic sediments. It is not depleted in shallow-waterterrigenous sediments (Shimizu and Masuda, 1977; Murray et al.,1990), and it is not depleted in eolian pelagic sediments in the Pacific(Olivarez et al., 1991). Toyoda et al. (1990) found that the negativecerium anomaly is mainly associated with sediments deposited atspreading ridges and equatorial divergence zones, in sediments withlow accumulation rates and relatively high REE contents. The deple-tion of cerium in deep-water sediments is thought to reflect thenegative Ce anomaly that characterizes seawater, which is conse-quently thought to be the source of REE in deep marine pelagicsediments (Bostrom et al., 1973; Piper, 1974; Henderson, 1984).Cerium is depleted in many pelagic constituents, including fora-minifers, pteropods, fish bones, diatoms, and radiolarians, and also inauthigenic minerals such as barite, phosphorite, phillipsite, and thevarious smectites (Piper, 1974; Toyoda et al, 1990). Cerium is notdepleted with respect to the other REE in illite or other terrigenousclay minerals, nor is there a cerium anomaly in volcanogenic clayminerals. Cerium is enriched in ferromanganese nodules, whichadsorb Ce from seawater, and may be responsible for the depletion ofCe in seawater (Piper, 1974). Ce is preferentially extracted (relativeto La and Nd) from seawater because it is the only REE that oxidizeseasily in seawater, and oxidized Ce is highly insoluble (Piper, 1974).

Ce concentrations for Leg 129 siliceous deposits (Fig. 11) aregenerally very similar to La concentrations, with the exception ofsamples rich in Mn and Fe-Mn oxides. This observation is consistentwith high Ce contents in Fe-Mn oxyhydroxides observed elsewherein the deep Pacific (Piper, 1974). The distribution of high Ce concen-trations supports a dominant authigenic source, ultimately derivedfrom seawater, for Ce. The negative Ce anomalies for sediments fromthe pelagic units also supports a seawater source.

Ce/Al

Since La and Ce abundances suggest a detrital source for some ofthe REE in units with detrital constituents, the Ce/Al ratio was plottedin order to test the proportion of Ce that is detrital relative to theproportion that is authigenic or biogenic. In general the ratio for allthree sites has a similar range. At Site 800 the Ce/Al ratio is higher inthe pelagic units and lower in the volcaniclastic units, suggesting

detrital sources of Ce are subordinate to pelagic sources (Fig. 12). AtSite 801, the Ce/Al ratio is highest in the brown chert and porcellaniteof Unit II, and the lowest of all three sites in basal Units V and VI,distinctly suggesting a detrital source for those sediments, and that Ceis not derived from this source (Fig. 12). The volcaniclastic depositsalso have a relatively low Ce/Al ratio. The Ce/Al ratios for samplesfrom Site 802 are highest in the dominantly biogenic units, andrelatively high for the pelagic interval sampled in the turbidite unit(Fig. 12). The ratio is lowest in the claystone sample from Unit VIII,which may include tuffaceous clay similar to the subjacent unit.

The variation in the Ce/Al ratio, and the trend of high values forsediments in pelagic units and low values for sediments in detritalunits suggests independent sources for these two elements, and sup-ports an authigenic or seawater source rather than a detrital source forCe and the other REE.

MULTIELEMENT PLOTS

Multielement plots are another method of visually partitioningsource components in sedimentary rocks. A few of these plots showinteresting trends.

Al-Fe-Mn

The ratio A1/(A1 + Fe + Mn) is an index of detrital claycomponent, and generally a ratio greater than 0.4 is considered toindicate a detrital source in marine sediments (Bostrom and Peter-son, 1969; Bostrom, 1973). All samples studied from Site 800 havevalues at or above 0.4 for this ratio (Fig. 13). At Site 801, only thelower part of the Unit IV radiolarite, and Units V and VI havevalues less than 0.4 (Fig. 13), suggesting the lack of a detritalsource. At Site 802, only one sample from Unit VIII has a valueless than 0.4 (Fig. 13). Because XRD and microprobe analyseshave detected only traces of possible illite in these units (Karpoff,this volume), and because of wind and current patterns in thePacific Ocean (Kennett, 1982) a terrigenous (eolian) source islikely to be a very small contributor to the high aluminum to metalratios for these sites. A plot of Fe/Ti to A1/(A1 + Fe + Mn)(Bostrom, 1973) better clarifies source components for Leg 129sediments. All of the samples from Site 800 fall in a general areabetween terrigenous and basaltic compositions (Fig. 14). At Site801, however, there is a distinct downsection trend toward thehydrothermal end-member as the position of the samples ap-proaches mid-ocean ridge basalt (MORB) basement, a reflectionof the high Fe contents of these sediments (Fig. 14). At Sites 800and 801, another discernible trend is that sediments with higheraccumulation rates fall closer to the basaltic end-member. Thesamples from Site 802 tend to plot closer to the basalt end-member(Fig. 14), which also coincides with higher accumulation rates.Samples studied from Unit VIII at Site 802 reflect a slight hy-drothermal signature, in support of previous observations of Mnabundance in that unit.

On a triangular plot of Al-Fe-Mn (Fig. 15), with fields defined byclay deposits from specific oceanic environments (Karpoff, 1989),the samples from Sites 801 and 802 fall on a trend from biogenic oozefor the upper units, to oceanic basalts for the lower units in each hole.This is consistent with indications from the single-element plots thatvolcanic detritus from the seafloor is mixed in with biogenic materialnear basement. The trend is not so pronounced for Site 800 where thehole bottoms in intrusive rocks rather than basement.

On an Si-Fe-Mn plot (Fig. 16) Leg 129 samples are compared withother types of oceanic clay deposits (Karpoff et al., 1988). TheLeg 129 samples fall on a well-defined trend between equatorialmid-ocean ridge sediment and north Pacific red clay, even thoughmany of these samples were deposited south of the equator. Appar-ently, sediments deposited in the vicinity of the equator and equatorial

55


divergence zones have distinctly less Mn than clay deposited in thesouthern or central Pacific.

Cu-Ba

Copper and barium in marine sediments are mainly derived fromdetrital, hydrothermal, and biogenic sources. In biogenic deposits,when detrital and hydrothermal sources can be shown to be negligible,the ratio Cu/B a can be instructive with respect to authigenic, biogenic,and biogenic dissolution residue source components (Karl, 1982).The authigenic contribution should reflect accumulation rates. Theboundary between the authigenic and biogenic fields is based on aCu/Ba ratio of 0.15, and the boundary between the biogenic anddissolution residue fields is defined by a ratio of 0.02.

At Site 800, brown chert and porcellanite of Unit II and pelagicclay from between the volcaniclastic turbidite beds of Unit IV fall inthe authigenic field (Fig. 17). Alow accumulation rate was calculatedfor Unit II (Table 1), but the authigenic signature of the pelagic claysfrom Unit IV indicates a slow rate of accumulation for backgrounddeposits which is masked by thick turbidite deposits. Samples fromthe limestone-chert and radiolarite units fall in the biogenic field aswell as the authigenic field. Only one sample from the siliceouslimestone suggests a high rate of biogenic dissolution, or poor pres-ervation of biogenic ooze.

At Site 801, samples from the radiolarite units fall mainly in thebiogenic field; most other samples fall in the authigenic field (Fig. 17),indicating low accumulation rates, as with similar units from Site 800.Samples from the basal sedimentary unit plot in both fields, support-ing possible alternations in depositional rate, as suggested by Ogg etal. (this volume).

At Site 802, all of the samples except one from the calcareous unitfall in the authigenic field (Fig. 17).

RARE EARTH ELEMENT PATTERNS

REE patterns provide another means of testing for source compo-nents of marine sediments. Characteristic REE abundances and pat-terns have been determined for terrigenous clay deposits (Fig. 18) andfor pelagic clay deposits, umbers (spreading ridge sediments), ferro-manganese nodules, and seawater (Fig. 19). REE patterns and abun-dances for various types of basalt cored at Sites 800,801, and 802 areavailable for comparison in Floyd and Castillo (this volume).

Comparison of REE patterns of Leg 129 samples studied (Fig. 20)with those of terrigenous shale and pelagic clay (Figs. 18 and 19)shows a distinct difference, based on both REE abundances and onthe presence or absence of a Ce anomaly. Patterns and abundancesindicate the source of REE in Leg 129 samples is seawater. The highbiogenic source component in Leg 129 samples supports this conclu-sion because REE are adsorbed from seawater onto planktonic tests(Bostrom et al., 1973; Piper, 1974). REE may also be incorporated inprimary and authigenic minerals from pore waters during early andlate diagenesis (German and Elderfield, 1990), and La and Ce abun-dances for Leg 129 samples suggest this is a more important processthan biogenic adsorption. Alternatively, REE adsorbed onto biogenictests could subsequently be incorporated into authigenic mineralsduring diagenetic processes. REE patterns, especially the Ce anomaly,also reflect redox conditions of deposition and diagenesis.

Marine clay deposits are commonly normalized to "average shale"using one of the sources in Figure 18, but for several reasons, "averageshale" is considered inappropriate for Leg 129 samples: (1) the lack ofeolian quartz grains, the scarcity of illite, and chemical element abun-dances and ratios argue against a terrigenous source, (2) a negativecerium anomaly suggests a dominant seawater source for REE for mostLeg 129 samples studied, and (3) REE patterns for some units suggestthe source is mixed. Normalization to seawater would not allow readycomparison to other sediments or sources since this approach has notbeen taken by other workers. Normalization to chondrite is a com-

monly used standard of comparison, and has the additional advantageof comparability to basalt REE patterns from Leg 129, since volcanicmaterial derived from basement or local volcanic activity has beentargeted as an important sedimentary source.

REE patterns for the different units from Leg 129 are generally lightrare earth element (LREE) enriched with negative cerium and europiumanomalies. Seawater is not LREE enriched (Fig. 19). The basalt samplesfrom Leg 129 include several units with different chemical charac-teristics. Site 801 basement has an upper sequence of LREE-enrichedalkali basalt and a lower sequence of LREE-depleted tholeiitic basalt(Floyd and Castillo, this volume). Site 802 basalt is homogenous,undepleted tholeiite (Floyd et al., this volume). The basalt has nocerium anomaly, and only the lower tholeiite at Hole 801C has asmall negative europium anomaly. The only basalt that has an REEpattern similar to the sedimentary rocks studied is the LREE-enrichedupper alkali basalt at Site 801. Volcanic sources of the turbidites mayor may not have been LREE enriched. Terrigenous shales are LREEenriched (Fig. 18), but factors previously discussed argue against thissource. LREE enrichment can be a result of diagenetic low-oxygenconditions in biogenic sediments (German and Elderfield, 1990), butevidence cited above indicates these red sedimentary rocks weredeposited under oxidizing conditions and only show subtle signs ofreduction in some places.

At Site 800, chert and siliceous limestone of Units II and III areLREE enriched with pronounced negative Ce and Eu anomalies(Fig. 20A, B). The Ce anomaly is probably due to adsorption of REEfrom seawater by plankton and authigenic minerals. A negative Euanomaly in deep-water marine sediments may be derived from seawa-ter (Fig. 19). Negative Eu anomalies are also found in eolian materialor hydrothermal precipitates (Elderfield, 1988), neither of which iscommon in these Leg 129 deposits. However the negative Eu anoma-lies in most Leg 129 siliceous deposits may reflect an authigenicsource derived from some combination of these three potentialsources. Steinberg et al. (1983) suggested that positive Eu anomaliesin marine sediments probably reflect feldspar content. The lack of aCe anomaly for almost all of the samples from the volcaniclastic unit(Fig. 20C), and the Ce/Al ratio for this unit (Fig. 12), also suggestmixed sources. Samples from the radiolarite of Unit V for REE(Fig. 20D) have a slight negative Ce anomaly, much smaller than theCe anomalies of biogenic Units II and III. This may reflect somevolcaniclastic input for Unit V. The lowest sample from Site 800, frombetween the dolerite sills, has very low REE contents, and negativeCe and Eu anomalies (Fig. 20E). This sample is recrystallized chert,and its protolith may have been similar to the radiolarite of Unit V.The low REE contents may reflect a more dominant biogenic sourcefor this sample than for the radiolarite of Unit V.

At Site 801 the brown chert of Unit II has an identical REE patternto the chert of Unit II at Site 800 (Fig. 20A, F). The pelagic clay fromUnit III turbidites (Fig. 20G) has a very similar pattern to the turbiditesat Site 800 (Fig. 20C), virtually lacking a Ce anomaly. Unit IVradiolarite at Site 801 has low REE contents, and most samples havea negative Ce anomaly (Fig. 20H). This unit has common Fe-Mnmicronodules, which may have imparted additional Ce to the sampleswith no negative Ce anomaly, as described by Piper (1974). Thepronounced negative Eu anomaly may reflect seawater or authigenicsources. The radiolarite and claystone of Unit V at Site 801 havesimilar REE patterns and abundances (Fig. 20) to pelagic Units II ofSites 800 (Fig. 20A) and 801 (Fig. 20F), which may have accumulatedunder similar conditions near the equator. The interpülow chert at thebase of the Site 801 section has very low REE abundances (Fig. 20J),with a pattern similar to seawater (Fig. 19). The hydrothermal quartzhas even lower REE contents, also with a pattern that resemblesseawater (Fig. 20J).

Chert and limestone of Unit III at Site 802 have a strong negativeCe anomaly, a small negative Eu anomaly, and relatively low REEcontents (Fig. 20K). Unit IV brown claystone (Fig. 20L) is similar tothe brown chert of Units II at Sites 800 and 801. Unit V pelagic

56


claystone from between turbidite beds (Fig. 20M) has a similarsignature (with very small negative Ce anomaly and small negativeEu anomaly) to the pelagic claystone from the correlative Cretaceousturbidite units at Sites 800 and 801. Radiolarian claystone of UnitsVI, VII, and VIII have similar light REE-enriched patterns with subtleCe and Eu anomalies (Fig. 20N, O, P) that may reflect dilution byvolcaniclastic material.

SUMMARY AND CONCLUSIONS

The siliceous rocks studied from Leg 129 have complicated geo-chemical signatures reflecting multiple sedimentary sources. Abun-dant radiolarians, high silica concentrations, and major and minorelement partitioning equations and plots indicate a dominant biogenicsource for most of the samples studied. XRD and microprobe analysesof mineral contents, Fe and Al concentrations, and element partition-ing equations identified a significant volcaniclastic source for sam-ples from pelagic intervals in turbidite units, and for samples fromunits directly overlying volcanic rocks. Abundant siliceous microfos-sils and high Si and Ba signify high biogenic productivity as back-ground sedimentation during volcaniclastic turbidite deposition. HighFe concentrations in interpülow sediments and sediments overlyingspreading ridge basement at Site 801 signify hydrothermal input,which is only evident for these basal sediments. Mn distributionsindicate mobilization by diagenetic processes. Cu/Ba ratios indicateelement concentrations were also influenced by authigenic processesin lithol-ogies with low accumulation rates. The very low abundanceof B in these deep marine deposits reinforces its usefulness as ashallow-water indicator. The relative abundance and distribution ofREE, as well as REE patterns for samples studies, suggest seawater,through authigenic or biogenic processes, is the primary source ofREE in deep marine sediments, but a subordinate detrital source isindicated for some units. Volcanic episodes contributed detrital ma-terial to the sedimentary sequences at Leg 129 sites at slightlydifferent times during the Mesozoic and Tertiary, and reworking ofbottom sediments and redistribution of clay minerals beyond the mostdistal turbidite deposits by bottom currents may also have been animportant process.

Paleomagnetic evidence (Steiner and Wallick, this volume; Ogg et al.,this volume) indicates that all three sites were near the equator for mostof the time the samples studied represent. Accumulation rates andsediment compositions for Leg 129 deposits suggest that sedimenta-tion was not symmetrical about the equator, nor consistent withinrespective equatorial depositional zones through time. Accumulationrates in the late Mesozoic were much higher in the southern part ofthe equatorial divergence zone than in the northern part. The southernpart of the equatorial zone was also apparently broader than the partnorth of the equator. During the Jurassic, only siliceous depositsaccumulated in the equatorial zone, but during the Cretaceous siliceouslimestone accumulated. During the Tertiary accumulation rates werelower and considerably less biogenic material is preserved. Paleocean-ographic models (Berger, 1976; Kennett, 1982) suggest that theequatorial province was a zone of high productivity during this time,and that these sites were isolated from terrigenous influence. Leg 129stratigraphic data supports these models. The geochemistry of Leg 129siliceous rocks also supports these models, and provides additionalinformation regarding the oxic depositional conditions and variationsin biogenic, authigenic, and volcanogenic input near the equator duringthe late Mesozoic.

ACKNOWLEDGMENTS

We would like to express our gratitude to Floyd Brown of the U.S.Geological Survey for expediting chemical analyses; to analyticalchemists Zoe Ann Brown, Elizabeth Bailey, Dave Siems, Joe Taggert,and Paul Lamothe; to Jonathan Whitesides for sample preparation;and to Scott Bie for organizing and plotting data. We would like to

thank reviewers David Z. Piper, James R. Hein, and Peter Hempel.We also thank our fellow Leg 129 scientists, the drilling crew, and theship crew on the JOIDES Resolution for their help.

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Murray, R. W., Buchholtz ten Brink, M. R., Jones, D. L., Gerlach, D. C , andRuss, GP., Ill, 1990. Rare earth elements as indicators of different marinedepositional environments in chert and shale. Geology, 18:268-271.

Olivarez, A. M., Owen, R. M, and Rea, D. K., 1991. Geochemistry of eoliandust in Pacific pelagic sediments: implications for paleoclimactic interpre-tations. Geochim. Cosmochim. Acta, 55:2147-2158.

Piper, D. Z., 1974. Rare earth elements in the sedimentary cycle: a summary.Chem. Geol., 14:285-304.

Price, N. B., 1976. Chemical diagenesis in sediments. In Riley, J. P., andChester, R. (Eds.), Chemical Oceanography, San Francisco (AcademicPress), 6:1-59.

Rea, D. K., Pisias, N. G., and Newberry, T, 1991. Late Pleistocene paleocli-matology of the central equatorial Pacific: flux patterns of biogenic sedi-ments. Paleoceanography, 6:227-244.

Research on Cretaceous Cycles Group (RCCG), 1986. Rhythmic bedding inUpper Cretaceous pelagic carbonate sequences: varying sedimentary re-sponse to climate forcing. Geology, 14:153-156.

Robertson, A.H.F., and Fleet, A. J., 1976. The origins of rare earths inmetalliferous sediments of the Troodos Masif, Cyprus. Earth Planet. Sci.Lett, 28:385-394.

Rona, P. A., Bostrom, K., and Epstein, S., 1980. Hydrothermal quartz vug fromthe mid-Atlantic Ridge. Geology, 8:569-572.

Shimizu, H., and Masuda, A., 1977. Cerium in chert as an indication of marineenvironment of its formation. Nature, 266: 346-348.

Steinberg, M., Bonnot-Courtois, C, and Tlig, S., 1983. Geochemical contri-bution to the understanding of bedded chert. In Iijima, A., Hein, J. R., andSiever, R. (Eds.), Siliceous Deposits in the Pacific Region: Amsterdam(Elsevier), Dev. in Sedimentol. Ser., 36:193-210.

Toyoda, K., Nakamura, Y, and Masuda, A., 1990. Rare earth elements of Pacificpelagic sediments. Geochim. Cosmochim. Acta, 54:1093-1103.

Truscott, M. G., and Shaw, D. M., 1983. Boron in cherts. Progr. Abstracts,Geol. Assoc. Can., A70.

Date of initial receipt: 19 June 1991Date of acceptance: 24 March 1992Ms 129B-111

58

[BLANK PAGE]


Site 800 Explanation

1 Biogenic ooze2 Red clay

3 Metalliferous sediment4 Oceanic basalt5 Authigenic crust6 Manganese nodules7 Hydrothermal deposits

S Unit IIUnit III

O Unit IV+ Unit VH Unit VI


1 Biogenic ooze2 Red clay3 Metalliferous sediment4 Oceanic basalt5 Authigenic crust6 Manganese nodules7 Hydrothermal deposits

m Unit IIA Unit IIIO Unit IV+ Unit VE3 Unit VI

Mn

Figure 15. Plot of Al-Fe-Mn for samples from Leg 129. Fields from Karpoff (1989).

60



1 Biogenic ooze2 Red clay3 Metalliferous sediment4 Oceanic basalt5 Authigenic crust6 Manganese nodules7 Hydrothermal deposits

9 Unit IIIUnit IV

O Unit V+• Unit VIEH Unit VIID Unit VIII

Figure 15 (continued).

61


Site 800

Fe

Site 801

Explanation

1 Equatorial mid-ocean ridge (Oman)2 North Pacific red clay3 Central Pacific clay4 North Pacific clay5 South Pacific red clay6 Bauer Deep sediment7 East Pacific Rise sediment8 Bauer Deep nodules

ffi Unit IIA Unit IIIO Unit IV* Unit V03 Unit VI

Mn

Explanation

1 Equatorial mid-ocean ridge (Oman)2 North Pacific red clay3 Central Pacific clay4 North Pacific clay5 South Pacific red clay6 Bauer Deep sediment7 East Pacific Rise sediment8 Bauer Deep nodules

B Unit IIA Unit IIIO Unit IV+ Unit VEl Unit VI

Mn

Figure 16. Plot of Si-Fe-Mn for samples from Leg 129. Fields from Karpoff et al. (1988).



1 Equatorial mid-ocean ridge (Oman)

2 North Pacific red clay

3 Central Pacific clay

4 North Pacific clay

5 South Pacific red clay

6 Bauer Deep sediment

7 East Pacific Rise sediment

8 Bauer Deep nodules

B Unit III

A Unit IV

O Unit V

+ Unit VI

ED Unit VII

DUnit VIII

Mn


63


ODP SITE 800 (Cu ppm VERSUS Ba ppm)

250

225 -

200 -

175 -

150 -

500 1000 1500 2000 2500

Ba ppm


250

ü

225 -

200 -

175 -

150 -

125

100 -

75

50

25

a Unit IIA Unit IIIo Unit IV* Unit V• Unit VI

500 1000 1500 2000 2500

Ba ppm

Figure 17. Plot of copper vs. barium for samples from Leg 129. Fields from Karl (1982). A= authigenic, B = biogenic, R = biogenic dissolution residue.

64



250

o

225 -

200 -

175 -

150 -

125 -

100 -

75 -

50 -±

..... 1

1

1 1

1

_ A

i• /

-Δ /-j> /

/ a Unit III/ * Unit IV

/ o Unit V/ + Unit VI

/ • Unit VII/ a Unit VII!

/

B

S ^ ^ ^ ^ ^

R

I

500 1000 1500

Ba ppm

2000 2500


100

LU

cra

Oü

LLJ

<

CO

50

20

10

SHALES

A Russian Platform avg. Balashov et. al.,1964 '

• European composite Haskin and Haskin, 1966

• North American composite Gromet et. al.,1984

o Post-Archean Average AustraliaNance and Taylor, 1976

Ce Nd Sm Eu Gd Dy Er

RARE EARTH ELEMENTS

Yb

Figure 18. Distributions of REE for average shales, normalized to chondrite,from Gromet et al. (1984), sources of data in Gromet et al. (1984).

langanese nodules

-East Pacific Rise Crestmetalliferous sediment

"... ..••"^Seawater x 10*

La Ce Pr Nd Sm EuGd Dy Ho Er Tm Yb Lu

RARE EARTH ELEMENTS

Figure 19. Chondrite-normalized distributions of REE in seawater and oceanicsediments. Sources of data: EPR sediment from Bender et al. (1971); lowerMn nodule pattern from Bernat in Bonatti et al. (1976); higher Mn nodulepattern from Ehrlich in Robertson and Fleet (1976); clay and seawater patternsfrom Haskin et al. in Robertson and Fleet (1976); Cyprus umbers pattern fromRobertson and Fleet (1976).

65

Figure 20. Chondrite-normalized (chondrite values of Anders and Ebihara, 1982) rare earth element plots for Leg 129 samples. A. Site 800, Unit II. B. Site 800,Unit III. C. Site 800, Unit IV. D. Site 800, Unit V. E. Site 800, Unit VI. F. Site 801, Unit II. G. Site 801, Unit III. H. Site 801, Unit IV. I. Site 801, Unit V.J. Site 801, Unit VI. K. Site 802, Unit III. L. Site 802, Unit IV. M. Site 802, Unit V. N. Site 802, Unit VI. O. Site 802, Unit VII. P. Site 802, Unit VIII.


^ LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU Q LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU

ODP SITE 800 ODP SITE 800100 - 100 -

UNIT II ' * UNIT III :"^ 50 ^\ ', •— 50 Jk\\

I 2° ^ ^ ~ ^ ^ ^ ^ - * - £ 2° ^ ^

| 2 | 2

<σ TOCO ' • : CO 1 :

Q LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU D LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU

ODP SITE 800 ODP SITE 800inn - -

ioo-*v UNIT IV " V UNIT V ;

I ' ^ ^ ― ! ! ^ •& 2

<Λ ' ^ T

E LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU p LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU

ODP SITE 800 ODP SITE 80110°" UNIT VI "; 1 0 0 ' UNIT II "

CL 2 > r ^ ^ ^ ^ ^ - - ^ ^ ^ • "ö. 2

co ] " \ ^ ^ co 1 ;


LA CE PR N P P M S M E U G D T B D Y H O E R T M Y B L U

ODP SITE 801UNIT III

C

oo

ECD

CO

1 0 0

5 0

2 0

10

5

2

LA CE

-

%

PR ND PM SM EU GD TB

- - - - J \ ^

^ ^ ^ " ^

" • • - - . . . . ^ ^ ^ ^

* ^

DY HO ER

ODPUNIT

TM

SITEIV

-–—-.^ = = ^— • —

YB LU

801

\

LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU

ODP SITE 801UNIT V

• ^ 50

ODP SITE 801UNIT VI

V

LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU

ODP SITE 802UNIT III


67


M LA CE PR ND PM SM EU GO TB DY HO EB TM YB LU N LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU

ODP SITE 802 . ODP SITE 802

o

1 0 °•\ UNIT VII ~ o 1 0 ° \ _ U N ' T V "

•σ *^~* "σ ^ _c 10 - c 10 - ^ -O : O :0 5 ü 5

1 2 E 2TO <O

CO 1 : CO ' :

O LA CE PR ND PM SM EU GD TB DY HO ER TM YB LJU p LA CE PR ND PM SM BJ GD TB DY HO ER T M YB UJ

ODP SITE 802 \ ODP SITE 8021 0 0 > UNIT VIII " 1 O O r \ _ _ ^ UNIT VI I

c i o - * - c i o - -O : : O :o 5 o B

I , a ,CO 1 ; CO 1 ;

[BLANK PAGE]


APPENDIX A

Table Al. Major element oxide data (in percent) for samples from Site 800, Leg 129.

Sample (cm)

129-800A-

6R-1, 67-697R-1, 2-58R-1,48-509R-1, 30-33

10R-1, 13-1711R-1,7-1O12R-1,30-3213R-1, 12-1414R-1,110-11517R-1,68-7118R-1, 127-13023R-1,69-7024R-1,68-7124R-1,92-9526R-1,22-2626R-1, 135-13927R-1, 61-6427R-1,110-11428R-3, 106-11030R-1, 125-12930R-2, 114-11831R-1, 12-1432R-CC, 10-1333R-7, 14-1834R-2, 139-14235R-3, 84-8836R-1, 110-11436R-4, 28-3241R-1,87-9342R-1,41^344R-1,92-9451R-1, 106-10852R-1, 16-2053R-1,32-3455R-1,76-8155R-2, 25-3056R-1,8-1358R-1, 37-42

Depth(mbsf)

40.249.259.468.878.387.997.6

106.9117.3144.9155.0201.2210.6210.8228.8230.0238.6239.1251.3267.2268.5272.1280.8296.6299.9310.2317.0320.7363.4369.0384.6450.7459.0465.2479.9480.9488.6507.2

SiO2

87.3089.3087.6086.6089.6082.8085.6089.8078.2085.2088.9083.9079.4090.4046.2055.0055.0072.8048.6075.6085.7074.0070.0042.6042.3067.1040.6042.3043.3057.0044.5080.2073.3081.0083.1079.8087.0095.70

A12O3

2.341.802.052.191.602.162.761.694.402.771.882.804.611.572.906.777.973.58

10.605.432.765.936.889.937.956.979.59

10.208.528.899.285.277.254.223.655.333.080.57

FeTO3

1.020.841.541.861.441.341.591.343.271.691.192.433.241.182.515.937.023.379.314.692.534.095.539.877.576.868.979.629.878.53

11.503.334.833.542.713.261.930.35

MgO

0.580.520.640.780.410.680.800.641.440.830.590.981.330.491.863.557.611.65

10.101.770.921.802.077.31

12.503.346.99

10.609.786.93

10.801.551.871.371.041.360.750.14

CaO

0.410.350.290.240.113.480.230.110.490.250.170.501.080.27

22.508.912.544.504.710.910.460.941.337.557.331.239.695.096.551.412.850.580.660.590.930.540.370.05

Na2O

0.460.380.440.440.340.380.480.320.750.580.400.711.010.410.701.842.530.842.691.250.671.541.561.461.661.531.411.891.821.371.780.710.910.770.610.800.640.15

K2O

0.480.370.480.560.460.670.860.581.320.750.550.740.970.330.702.550.790.840.790.790.451.270.933.782.361.172.832.351.382.671.411.391.941.130.971.550.910.20

TiO2

0.090.070.110.130.100.130.170.100.350.220.130.250.450.160.311.031.570.391.510.640.290.510.801.540.900.861.481.701.490.951.770.340.440.270.210.280.150.02

P 2 O 5

0.260.230.180.150.070.060.100.070.210.090.060.160.120.080.130.190.220.090.230.120.070.140.170.180.300.140.250.250.320.330.410.150.150.160.100.150.100.05

MnO

0.160.140.290.490.020.020.020.020.020.020.020.020.060.020.310.150.150.110.150.060.030.050.080.170.150.140.250.230.240.100.200.090.970.470.270.340.180.04

LOI925C

5.775.045.465.634.587.445.634.098.496.594.886.506.873.96

22.0013.8014.4011.4010.908.134.959.049.86

15.6016.8010.1018.0015.7016.9011.7015.505.557.105.405.775.613.981.32

Oxidetotal

98.8799.0499.0899.0798.7399.1698.2498.7698.9498.9998.7798.9999.1498.87

100.1299.7299.8099.5799.5999.3998.8399.3199.2199.9999.8299.44

100.0699.93

100.1799.88

100.0099.1699.4298.9299.3699.0299.0998.59

Note: Analyses obtained by X-ray fluorescence, U.S. Geological Survey laboratories.

70


Table A2. Major element oxide data for (in percent) samples from Site 801, Leg 129.

Sample (cm)

129-801A-

8R-1, 1-39R-

10R-12R-80-1C13R-14R-15R-

,0-3,0-5,22-250M,21-26, 26-28, 24-26

16R-1, 135-13817R-1, 28-3018R-2, 14-1719R-CC, 12-1620R-1, 8-12

129-801B-

8R-2, 60-631 OR-1,70-7311R-1, 31-3612R-1, 64-7014R-1, 52-5715R-1, 19-2016R-1,40-4317R-1,34-3618R-1,37^019R-1,24-2620R-1,23-2621R-1, 12-1324R-1,69-7325R-1,49-5327R-1, 104-10729R-1, 17-1931R-1, 18-2033R-1, 10-1433R-1, 126-12935R-1,51-5535R-1, 123-12737R-1, 7-1039R-1,4-7

129-801C-

4R-1, 11-165R-4,11-166R-1, 31-34

Depth(mbsf)

60.670.279.599.0

100.0108.7118.5128.1139.0147.5158.6176.3176.5

254.8272.7282.0292.0310.8319.9329.6338.9348.2357.5366.7375.8393.3397.7407.7416.4425.8434.9436.1444.8445.5453.6462.7

521.8535.8540.8

SiO2

96.783.989.876.382.884.186.079.675.478.976.982.988.6

89.558.077.177.485.282.993.192.491.095.591.892.890.784.793.792.792.868.783.764.674.591.894.8

81.111.45.3

A12O3

0.43.41.65.43.53.42.73.94.74.14.62.61.7

1.88.15.33.73.24.21.21.41.80.51.61.42.03.71.01.41.46.34.08.45.20.60.7

0.10.50.9

FeTO3

0.31.50.93.81.92.01.94.04.23.64.02.61.6

1.49.24.46.32.22.30.70.90.90.21.22.01.42.20.91.11.0

10.33.79.98.33.31.7

15.73.97.5

MgO

0.100.800.431.300.900.970.921.291.821.712.181.220.74

0.615.421.092.300.840.990.240.250.320.100.270.270.430.850.160.260.271.450.962.061.380.270.15

0.106.325.88

CaO

0.050.370.220.460.420.360.470.600.940.500.541.230.36

0.271.340.580.490.290.270.100.120.230.050.110.110.100.200.070.150.150.370.180.360.260.050.12

0.0239.3039.90

Na2O

0.150.630.351.230.730.610.490.961.190.880.950.640.48

0.482.011.170.660.720.730.230.230.320.150.270.170.310.710.190.230.240.890.641.070.780.150.15

0.150.150.15

K2O

0.130.770.331.170.760.760.750.971.581.471.810.870.60

0.492.411.172.530.791.070.280.340.420.110.410.340.490.980.280.370.392.151.252.771.640.290.22

0.020.230.03

TiO2

0.020.150.100.620.240.250.180.670.890.450.530.400.27

0.201.690.560.390.180.230.050.070.070.020.060.050.090.180.040.060.070.390.260.600.360.030.04

0.020.020.02

P2O5

0.050.230.140.130.240.120.100.130.190.110.110.090.09

0.080.260.100.170.080.090.050.080.080.050.060.050.050.050.050.080.080.200.050.090.120.050.10

0.060.050.08

MnO

0.040.180.080.330.180.090.030.050.040.040.040.020.02

0.020.130.120.080.320.460.100.180.190.050.150.220.3 10.400.210.280.120.060.020.110.070.050.15

0.020.390.63

LOI 925C

0.846.744.798.457.006.435.566.958.476.777.216.214.38

3.9911.107.455.385.056.102.593.023.331.792.732.703.164.652.142.942.827.044.819.126.861.950.96

2.6638.4040.30

Oxidetotal

98.7498.7198.7199.2798.7299.0599.0399.0999.4098.5698.7998.8598.88

98.8099.7199.0899.4298.8899.3498.6499.0398.6698.6098.62

100.0498.9998.6298.7399.5499.3297.8099.5699.1599.4298.5199.13

99.95100.60100.62


Table A3. Major element oxide data (in percent) for samples from Site 802, Leg 129.

Sample (cm)

129-802 A-

33R-1,116-12034R-1, 128-13235R-CC, 0-437R-1,11-1538R-CC, 12-1539R-1, 10-1543R-1, 75-7852R-2, 125-13055R-1, 138-14156R-1,43-4756R-2, 88-92

Depth(mbsf)

294.0303.6320.5330.0348.6348.8382.9462.6489.3497.5499.5

SiO2

45.595.894.888.965.470.077.873.276.370.778.8

A12O3

1.030.190.470.806.454.554.727.085.897.933.71

FeTO3

0.480.070.200.395.184.133.223.833.954.845.46

MgO

0.670.100.100.181.721.071.711.801.691.661.45

CaO

27.300.250.102.933.774.820.921.040.911.230.78

Na2O

0.330.150.150.241.451.100.801.221.011.580.69

K2O

0.140.040.110.151.100.751.451.611.471.751.42

TiO2

0.050.020.020.071.160.960.310.450.440.760.24

P 2 O 5

0.150.070.060.100.290.180.360.360.270.220.24

MnO

0.140.020.020.020.090.060.040.190.230.240.05

LOI925C

24.301.902.235.25

13.0011.908.118.907.268.296.48

Oxidetotal

100.0998.6198.2699.0399.6199.5299.4499.6899.4299.2099.32


71


APPENDIX B

Table Bl. Minor element analyses (in parts per million) for samples from Site 800, Leg 129.

Sample (cm)

129-800A-

6R-1,67-69

7R-1,2-5

8R-1,48-50

9R-1,30-33

10R-1, 13-17

11R-1,7-1O

12R-1,30-32

13R-1, 12-14

14R-1, 110-115

17R-1,68-71

18R-1, 127-130

23R-1,69-70

24R-1,68-71

24R-1,92-95

26R-1,22-26

26R-1, 135-139

27R-1, 61-64

27R-1, 110-114

28R-3, 106-110

30R-1, 125-129

3OR-2,114-118

31R-1, 12-14

32R-CC, 10-13

33R-7, 14-1834R-2, 139-142

35R-3, 84-88

36R-1, 110-114

36R-4, 28-32

41R-1, 87-93

42R-1, 41-4344R-

51R-

52R-

53R-

55R-

55R-:

56R-

58R-

, 92-94

, 106-108

, 16-20

, 32-34

,76-81I, 25-30

,8-13,37-42

Depth

(mbsf)

40.2

49.2

59.4

68.8

78.3

87.9

97.6

106.9

117.3

144.9

155.0

201.2

210.6

210.8

228.8

230.0

238.6

239.1

251.3

267.2

268.5

272.1

280.8

296.6

299.9

310.2

317.0

320.7

363.4

369.0

384.6

450.7

459.0

465.2

479.9

480.9

488.6

507.2

Ba

61

51

93

500

331

162

292

54

277

72

58

45

250

35

396

103

4544

226

75

47

7794

69

42

70

29

31

22

85

20

91

615

493

516

754

429

164

Cr

20

20

20

20

20

20

20

2042

20

20

20

20

20

20

170

196

26

65841

20

3035

355

296

70

367

610

573

266

539

20

20

20

20

20

20

20

Cu

70

52

60

73

67

26

24

16

110

31

10

21

43

31

21

84

145

20

93

44

18

29

40

134

277

31

112122

56

49

21

113105

69

63

80

48

10

Ni

32

22

48

37

28

23

19

19

40

36

3923

3317

22

56

79

35326

5020

2654

150

322

65

174

241

242

144

260

44

79

45

3941

20

12

Rb

1711

15

18

13

22

30

17

43

25

13

19

31

10

20

48

22

22

18

22

10

3721

45

28

38

30

18

21

73

18

50

72

44

38

60

37

10

Sr

35

29

33

37

19

76

31

18

58

43

24

80

170

37

228

616

571

119

390

221

95

365

245

121

130

217

122

124

136

131

136

70

122

94

68

74

53

10

Zn

47

38

42

44

43

27

38

3042

40

25

22

58

26

25

49

73

32

84

69

32

37

82

81

67

73

81

87

77

94

93

76

12682

64

71

42

22

Zr

35

33

38

3932

37

43

33

7154

34

54

81

35

49

96

137

61

136

92

44

82

122

146

97

112

133

139

112

110

135

73

108

64

56

70

46

16

Y

35

29

24

22

9

13

20

14

31

18

9

20

20

15

16

11

15

15

18

14

9

17

15

1922

21

19

19

19

33

21

21

28

19

14

20

13

5

La

28

24

20

16

10

16

13

12

35

18

10

22

24

15

15

27

31

19

24

18

11

27

26

29

29

25

29

26

26

39

3117

25

18

11

17

14

10

Ce

20

16

15

19

15

16

11

1034

21

10

23

28

20

20

42

48

27

39

23

19

42

42

49

43

36

46

47

39

60

48

41

44

29

21

31

21

10

B

54

41

49

52

33

45

45

39

63

53

34

39

56

34

63

21

19

35

16

48

30

36

67

47

34

45

44

34

31

51

32

41

48

33

32

43

28

22

Note: Analyses obtained by X-ray spectroscopy, and by mass spectrometer for B, U.S. Geological Survey laboratories.

72


Table B2. Minor element analyses (in parts per million) for samples from Site 801, Leg 129.

Sample (cm)

129-801A-

8R-1, 1-39R-1,0-310R-l,0-512R-1,22-2580-100M13R-1,21-2614R-1, 26-2815R-1, 24-2616R-1, 135-13817R-1, 28-3018R-2, 14-1719R-CC, 12-1620R-1, 8-12

129-801B-

8R-2, 60-631 OR-1,70-7311R-1, 31-3612R-1, 64-7014R-1,52-5715R-1, 19-2016R-1,40-4317R-1, 34-3618R-1,37^019R-1,24-2620R-1,23-2621R-1, 12-1324R-1,69-7325R-1, 49-5326R-CC, 0 ^27R-1, 104-10729R-1, 17-1931R-1, 18-2033R-1, 10-1433R-1, 126-12935R-1,051-05535R-1, 123-12737R-1, 7-1039R-1,4-7

129-801C-

4R-1, 11-165R-4, 11-166R-1,31-34

Depth(mbsf)

60.670.279.599.0100.0108.7118.5128.1139.0147.5158.6176.3176.5

254.8272.7282.0292.0310.8319.9329.6338.9348.2357.5366.7375.8393.3397.7407.0407.7416.4425.8434.9436.1444.8445.5453.6462.7

521.8535.8540.8

Ba

13178381881091241479747717248417394

3685127411915341513252057850367260310201690251395369

40001010400097824279

182121

Cr

20202020202020416929472520

2030425232020202020202020202020202020403751302020

202020

Cu

10683246614930404444401817

2110654274038131727103453508012055584015455106872417

101010

Ni

10381438302737364035342415

1417537223334101515101114142218101010622569592014

203745

Rb

10331128293630355544662612

11413048284410I010101410214745101012734193591010

101010

Sr

1043241104754401332381101167438

42259170485813517222610272829595810161515937137481010

10120124

Zn

19493064584646513937382620

25123813458512632342129282737472327269845114853219

171233

Zr

1449351235763449612978835945

391568157496122252914312936535219262912460125942618

131615

Y

5352015292421221816161712

141816261313791258891310575235121156

5511

La

I0301121262720272320131713

162412141010101010101010101010101010101010131010

101010

Ce

10321043242912303027232316

164429222223101010101310161520101210131424201010

101010

B

8.4653169465237495650463626

20345536424223262129231224283716181758366163206.3

3511


Table B3. Minor element analyses (in parts per million) for samples from Site 802, Leg 129.

Sample (cm)

129-802A-

33R-1, 116-12034R-1, 128-13235R-CC, 0-437R-1, 11-1538R-CC, 12-1539R-1, 10-1543R-1,75-7852R-2, 125-13055R-1, 138-14156R-1,43-4756R-2, 88-92

Depth(mbsf)

294.0303.6320.5330.0348.6348.8382.9462.6489.3497.5499.5

Ba

1020193226111607911511613256

Cr

2020202561453030212420

Cu

37101118445326591047718

Ni

2214161688503254818246

Rb

1010101021174249434436

Si-

SOS1010562402458015310225439

Zn

25272825907237869810748

Zr

2810112013110261969212149

Y

16551431284449453340

La

1010101028233949322626

Ce

1010101032285557453334

B

2049357564555978364780


73

APPENDIX C

Table Cl. Rare earth element and minor element analyses (in parts per million) for samples from Site 800, Leg 129.

DepthSample (cm)

Rare earth element data

129-800 A-

6R-1,67-697R-1,2-58R-1,48-509R-1, 30-33

10R-1, 13-1711R-1,7-1O12R-1,30-3213R-1, 12-1414R-1,110-11517R-1,68-7118R-1, 127-13023 R-1,69-7024R-1,68-7124R-1,92-9526R-1,22-2626R-1, 135-13927R-1, 61-6427R-1,110-11428R-3, 106-11030R-1, 125-12930R-2,114-11831R-1, 12-1432R-CC, 10-1333R-7, 14-1834R-2, 139-14235R-3, 84-8836R-1,110-11436R-4, 28-3241R-1,87-9342R-1,41^344R-1,92-9451R-1, 106-10852R-1, 16-2053R-1,32-3455R-1,76-8155R-2, 25-3056R-1, 8-1358R-1,37-42

(mbsf)

40.249.259.468.878.387.997.6

106.9117.3144.9155.0201.2210.6210.8228.8230.0238.6239.1251.3267.2268.5272.1280.8296.6299.9310.2317.0320.7363.4369.0384.6450.7459.0465.2479.9480.9488.6507.2

La

21.7016.3017.0016.406.72

10.0014.008.55

27.4013.806.80

17.4019.1011.0016.720.424.313.919.615.79.3

21.320.720.621.318.021.122.218.732.025.516.127.919.713.118.511.42.0

Ce

20.0015.2015.6018.209.40

11.7016.008.70

29.4017.009.50

22.0026.0012.0021.138.744.021.338.024.015.332.038.039.639.034.041.644.036.457.544.835.644.627.819.830.116.73.2

Nd

21.0015.0015.0015.006.208.30

12.007.10

22.0013.006.80

15.0015.009.20

14.016.019.013.017.012.07.4

16.016.018.016.014.019.020.016.029.021.014.024.017.012.017.011.02.0

Sm

4.683.643.393.201.452.133.001.835.172.781.333.323.912.062.913.484.512.934.292.771.623.583.444.464.243.584.574.904.116.505.083.035.083.982.633.592.560.52

Eu

1.070.840.770.740.330.460.650.401.200.630.300.780.920.490.7521.0101.2000.6801.2600.6600.3900.8600.9281.2301.2000.9331.3401.4301.2301.6601.5100.6531.0700.8340.5380.7030.5120.120

Th

0.69 :0.560.510.49

Yb

.15

.80

.60

.500.25 0.710.30 0.770.43 .100.29 0.700.76 .700.41 0.930.21 0.540.490.52

.10

.400.31 0.820.4300.4500.5600.4100.6100.3800.240 (0.4800.4600.6000.5600.5000.6100.6500.5600.9230.6800.4410.7180.5400.3740.4700.3570.077

.30

.10

.40

.30

.60

.10).66.30.40.70.70.50.60.60.40

i.50.70.60

2.10.60.10.50

191).31

Lu

0.290.250.220.200.100.100.130.080.220.110.080.150.180.100.180.140.170.160.200.150.100.160.190.230.220.200.220.190.170.340.230.220.290.200.150.200.120.03

Ba Cr Cs

Minor element data

665989

49034214028049

26068694317

240393975842

2307050579987476324703285

11098

590470477725396140

7.05.19.4

11.020.012.016.011.036.016.014.020.09.0

24.028.8

167.0140.035.3

575.041.616.931.037.0

343.0200.064.0

335.0549.0604.0214.0565.0

20.424.913.011.016.18.92.5

1.100.831.000.971.100.951.200.741.901.100.900.960.591.400.930.450.221.000.230.890.551.000.880.780.521.200.600.460.282.200.402.093.332.222.013.251.940.36

Hf

0.560.480.600.640.510.560.690.441.200.860.560.820.531.400.851.872.641.002.681.570.741.402.393.001.902.102.802.942.402.252.921.332.011.210.991.390.830.17

Rb

19.012.017.020.018.023.030.019.044.023.018.020.011.028.023.043.011.023.015.019.013.028.023.043.026.030.032.024.022.067.026.045.063.040.035.454.233.0

8.5

Sb

0.290.250.450.581.090.190.260.370.330.240.330.210.210.210.150.140.190.160.570.120.150.150.180.160.090.160.210.190.120.220.240.220.550.300.270.350.260.12

Th

1.981.441.591.781.411.702.301.403.402.301.742.001.203.061.482.473.401.982.302.901.672.903.482.821.902.902.352.391.803.882.103.625.593.292.764.382.610.56

U

1.7001.1001.3000.4602.3400.2000.4000.2800.4801.2000.3100.4300.4000.5800.4500.4400.6200.3900.3700.4100.3900.5900.5201.2000.8000.4700.7800.6100.5300.5400.3500.7700.9800.9001.1001.2001.3001.300

Zn

35.027.034.036.032.021.026.022.036.027.021.016.016.047.022.345.064.025.075.058.024.030.069.078.056.056.069.076.064.080.276.059.997.762.649.255.833.013.0

Zr

423059609040

11050

120505060867280

160170160110946862

15015011096

130120140150230

52965961694424

Sc

4.634.204.474.223.143.614.402.937.194.752.904.312.446.304.64

16.0018.005.99

19.607.303.627.508.53

22.4014.0011.9019.5023.3023.1015.1023.20

6.938.905.754.926.684.090.84

Ni

292044322730182353703624183217626430

27041182952

14025047

15021020014021040613630322220

Sr

27402728308071404076907728

14024059050012038018010030024012015023012019014014017089

1408558775650

Note: Analyses obtained by induced neutron activation analysis (INAA), U.S. Geological Survey laboratories.

Table C2. Rare earth element and minor element analyses (in parts per million) for samples from Site 801, Leg 129.

Sample (cm)Depth(mbsf) La Ce Nd Sm Tb Yb Lu Ba Cr Cs Hf Rb Sb Th Zn Zr Ni


Sr


129-801A-

8R-1, 1-39R-1,0-3

1 OR-1,0-512R-1,22-2580-100M13R-1, 21-2614R-1,26-2815R-1,24-2616R-1, 135-13817R-1,28-3018R-2, 14-1719R-CC, 12-1620R-1,8-12

129-801B-

8R-2, 60-631 OR-1,70-7311R-1, 31-3612R-1,64-7014R-1,52-5715R-1, 19-2016R-1,40-4317R-1,34-3618R-1, 37-4019R-1,24-2620R-1,23-2621R-1, 12-1324R-1,69-7325R-1,49-5326R-CC, 0-427R-1, 104-10729R-1, 17-1931R-1, 18-2033R-1, 10-1433R-1, 126-12935R-1, 51-5535R-1, 123-12737R-1.7-1039R-1,4-7

129-801C-

4R-1,11-165R-4,11-166R-1,31-34

60.670.279.599.0

100.0108.7118.5128.1139.0147.5158.6176.3176.5

254.8272.7282.0292.0310.8319.9329.6338.9348.2357.5366.7375.8393.3397.7407.0407.7416.4425.8434.9436.1444.8445.5453.6462.7

521.8535.8540.8

2.722.210.516.718.116.914.218.718.314.414.112.09.8

12.017.712.0010.2010.5011.704.807.108.761.804.706.206.40

10.9010.503.607.345.00

19.608.09

25.6011.601.804.90

0.771.901.60

2.926.011.932.319.825.514.728.330.924.124.020.515.0

16.535.726.4020.2018.1025.30

6.558.319.943.308.737.19

11.5016.7015.906.019.606.68

28.0010.0029.9014.502.303.90

0.221.602.20

3.220.09.7

13.016.016.014.016.017.013.012.011.08.2

8.118.011.010.08.8

10.04.37.88.11.94.85.66.5

10.09.83.56.44.1

27.06.8

22.010.0

1.45.0

0.61.82.4

0.704.892.432.833.943.663.183.593.682.982.722.641.84

1.944.222.7602.8201.9802.1001.1401.8701.8000.4201.1501.3901.4502.1702.1500.7931.4801.0405.9401.4203.8302.3000.4401.110

0.1300.4600.868

0.1401.0600.5570.7040.8540.8010.6950.8760.9090.7270.6490.6500.449

0.4531.2100.6610.7560.3890.4080.2200.4030.3870.0960.2500.3000.2950.4360.4380.1700.3080.2101.3700.3000.7730.5160.1100.270

0.0470.1200.260

0.0980.7200.3600.3410.5530.5050.4740.5200.4730.4000.3700.3580.280

0.3010.5530.4120.5100.2800.2900.1400.2700.2880.0700.1700.2100.2100.3040.3070.1300.2100.1500.9150.2000.4600.3600.0650.200

0.0510.0830.230

0.402.151.100.901.681.301.301.200.920.960.980.810.66

0.791.301.202.020.871.100.410.660.790.290.570.830.711.061.000.370.770.502.240.661.301.200.230.65

0.280.281.10

0.020.290.160.120.220.170.180.170.120.120.130.110.08

0.100.170.1500.2860.1300.1400.0570.0870.0970.0210.0680.0900.1000.1510.1500.0460.0960.0740.3230.0950.2000.1700.0350.080

0.0220.0400.150

Minor element data

1805739

18097

11013081

43016044316089

2173

12035

200532130330200

67510684580958

1500240360330

6190917

400089420

250

179.9

12

2.009.885.70

15.4011.4012.2014.5037.1052.9029.4038.4028.3023.00

16.30213.00

29.633.311.512.73.93.95.92.55.24.46.0

11.911.13.54.04.5

27.228.939.322.9

2.95.3

3.63.4

21.6

0.21.60.720.971.231.171.110.971.11.31.530.840.49

0.580.672.121.101.772.160.730.870.930.281.200.861.642.582.570.771.101.074.813.055.303.380.560.31

0.090.160.07

0.170.770.452.050.890.930.661.451.951.211.320.920.69

0.592.981.5001.0600.8691.0700.3300.4200.4700.2000.4800.4300.6000.9520.9400.3200.4500.4903.0501.4003.2002.1700.6500.380

0.0960.1100.140

4.326.011.025.025.025.025.023.033.032.041.220.014.0

12.035.031.0048.2030.0033.0012.0014.0015.004.00

17.0014.0024.0043.0042.0012.0016.0018.0078.0046.8094.7059.0013.007.60

3.109.302.00

0.140.330.240.240.290.160.270.240.180.170.190.190.10

0.160.170.240.200.180.290.090.240.200.120.250.230.220.530.560.350.270.201.300.480.991.400.210.10

0.310.050.04

0.392.601.082.892.372.672.162.683.042.573.101.741.26

1.111.972.501.562.633.251.051.231.490.471.371.251.702.952.820.921.191.184.602.555.382.980.380.58

0.080.160.11

0.601.802.000.440.460.390.350.310.390.340.290.250.20

0.391.500.800.250.760.742.501.201.702.901.700.540.540.520.941.500.830.681.101.000.980.900.460.23

0.210.300.44

18.036.021.050.439.535.033.336.027.029.029.018.014.0

15.0103.064.026.043.337.015.017.022.011.017.019.020.029.432.08.8

15.015.077.934.492.163.517.07.5

13.07.3

34.0

40392880504350798149446057

501207043589050574040394837395542

425

10060

1101302927

401730

0.6085.2302.8406.3104.5704.4903.9205.4206.4505.3505.5603.4802.400

2.40015.1008.395.804.415.481.802.152.370.912.572.363.254.825.161.772.362.32

15.406.56

14.7010.502.762.11

0.500.987.32

11321127212531323324292011

1215033.016.029.034.011.022.012.012.018.016.08.9

15.015.08.0

12.08.3

65.024.061.052.017.022.0

22.015.032.0

4033199026363497

14095764039

34220150.044.051.0

100.022.028.030.030.032.028.025.055.060.023.030.022.0

180.039.0

150.040.00.0052

24.0

40.0130.0140.0


Table C3. Rare earth element and minor element analyses (in parts per million) for samplesfrom Site 802, Leg 129.

Sample (cm)


129-802A-

33R-1, 116-12034R-1, 128-13235R-CC, 0-437R-1, 11-1538R-CC, 12-1539R-1, 10-1543R-1, 75-7852R-2, 125-13055R-1, 138-14156R-1,43^756R-2, 88-92

Sample (cm)

Minor element data

129-802 A-

33R-1, 116-12034R-1, 128-13235R-CC, 0-437R-1, 11-1538R-CC, 12-1539R-1, 10-1543R-1,75-7852R-2, 125-13055R-1, 138-14156R-1,43-4-156R-2, 88-92

Depth(mbsf)

294.0303.6320.5330.0348.6348.8382.9462.6489.3497.5499.5

Depth(mbsf)

294.0303.6320.5330.0348.6348.8382.9462.6489.3497.5499.5

La

12.204.704.70

11.0029.1024.8034.3043.0032.0027.0020.70

Ba Cr

897 3.513 2.118 1.927 11.7

100 51.454 36.972 21.2

100 24.099 21.8

110 26.645 12.1

Ce

7.922.103.506.91

34.8024.2048.4052.8040.0035.0028.80

Cs

0.230.090.200.300.950.612.022.972.131.921.54

Nd

12.04.54.49.4

28.023.029.036.026.025.022.0

Hf

0.3300.1400.1900.2902.6001.7801.1401.8701.7202.3100.930

Sm

2.5901.0301.0602.1906.8005.6406.9708.7106.1405.8705.900

Rb

4.303.104.205.00

25.0015.0040.2047.8040.0039.0041.00

Eu

0.5980.2550.2300.4891.6701.3001.6501.9801.4301.4001.550

Sb

0.100.160.120.150.340.240.200.220.300.230.19

Tb

0.3850.1820.1700.3400.9770.7641.0701.2800.9830.8400.980

Th

0.560.190.300.763.232.143.144.764.084.012.29

Yb

1.230.540.510.952.592.152.643.513.182.433.12

U

0.190.541.901.600.620.470.830.930.660.820.48

Lu

0.1700.0670.0480.1300.3460.3030.3500.4800.4380.3440.429

Zn

17.07.4

21.013.068.155.330.065.572.386.637.0

Zr

25301840

12060529687

11033

Sc

2.480.671.121.778.737.086.31

10.108.61

11.406.90

Ni

19.012.011.08.0

71.039.026.047.069.074.034.0

Sr

480.040.040.041.0

230.0200.071.0

160.0100.0230.050.0


76

[BLANK PAGE]


APPENDIX D

Table Dl. Major element oxide data (in percent) for additional samples from Leg 129.

Sample (cm)

129-800 A-

6R-1,76R-1,377R-1,668R-1, 18R-1, 22

10R-1, 1312R-1, 3713R-1,4614R-1, 10117R-1.2518R-1, 7018R-1, 12119R-1, 119R-1, 3721R-2, 822R-1, 1924R-l,30

129-801A-

7R-CC, 110R-1,11

129-801B-

14R-1, 2418R-1.2424R-1.5425R-1, 127R-l,3033R-1,4333R-2, 4835R-2, 12035R-2, 14035R-3, 135R-3, 19

Depth(mbsf)

39.740.049.858.959.178.397.7

107.2117.2144.4154.4154.9162.9163.3182.9191.2210.2

60.479.6

310.5348.0393.1397.2407.0435.2436.8447.0447.2447.3447.5

Unit

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

11II

IVIVIVIVIVVVVVVV

SiO2

85.5080.8092.0087.5089.0092.8090.6069.1093.0062.2083.6092.0085.5080.1048.7033.6085.30

90.890.5

82.585.485.385.996.881.483.756.364.866.769.8

A12O3

4.405.301.502.902.501.502.400.701.500.803.901.503.505.500.506.703.30

1.92.1

4.83.73.23.40.34.53.0

11.38.38.47.8

FeTO3

2.002.501.001.501.301.701.300.501.100.502.901.102.504.400.305.202.70

1.11.2

3.42.42.72.80.55.75.4

15.313.311.19.8

MgO

1.041.360.420.900.830.330.750.250.540.361.280.511.241.900.312.271.20

0.530.54

1.420.900.970.880.061.110.772.841.962.141.76

CaO

0.400.700.200.900.200.200.30

14.400.30

18.700.700.300.400.50

26.2025.000.50

0.500.30

0.600.500.400.600.300.500.401.400.800.700.60

Na2O

1.001.140.390.700.700.370.510.220.440.240.920.500.690.970.171.270.73

0.420.55

1.190.800.800.880.190.880.681.431.411.371.13

K2O

1.071.380.440.660.690.480.880.260.570.281.140.501.131.680.110.840.93

0.490.51

1.361.150.940.990.131.631.223.672.783.062.70

TiO2

0.200.230.130.150.140.160.160.100.130.100.370.150.280.460.081.080.31

0.100.16

0.300.210.170.210.050.310.200.850.560.590.54

Mn3O4

0.270.440.200.220.110.010.010.030.010.080.020.010.010.030.090.070.07

0.1350.118

0.5610.3030.5280.4280.1100.0400.0390.4020.1570.1490.070

LOI925C

4.305.542.743.903.502.852.62

13.332.52

16.523.632.333.595.00

23.1024.203.28

2.502.68

4.513.773.213.721.604.013.556.856.175.835.19

Oxidetotal

100.1899.3999.0299.3398.97

100.4099.5398.89

100.1199.7898.4698.9098.84

100.5499.56

100.2398.32

98.47598.658

100.64199.13398.21899.808

100.04100.0898.959

100.342100.237100.03999.39

Note: Analyses obtained by microprobe at the University of Strasbourg, France.

78


Table D2. Minor element data (in parts per million) for additionalsamples from Leg 129.

Sample (cm)

129-800A-

6R-1.76R-1.377R-1.668R-1, 18R-1.2210R-1, 1312R-1.3713R-1.4614R-1, 10117R-1.2518R-l,7018R-1, 12119R-1, 119R-1,3721R-2, 822R-1, 1924R-l,30

129-801A-

7R-CC, 110R-1, 11

129-801B-

14R-1, 2418R-1.2424R-1,5425R-1, 127R-1.3033R-1.4333R-2, 4835R-2, 12035R-2, 14035R-3, 135R-3, 19

Depth(mbsf)

39.740.049.858.959.178.397.7107.2117.2144.4154.4154.9162.9163.3182.9191.2210.2

60.479.6

310.5348.0393.1397.2407.0435.2436.8447.0447.2447.3447.5

Ba

851505962572142918412732449416056871419952282

43100

23610592629154488

18499231227256024492036

Cr

191912161431301152135031254378229

129

11161481

201654394313

Cu

8713832854842201620123721598164229

7742

626473693259941371198762

Ni

38447231526132816356634372211446

3423

4630291812929142827660

Sr

40591757191625195191946622447120454257

2826

8256777211754210811411292

Zn

819838572544230161516542032562010355

1632

7851476646639159124109104

Zr

54602744362937152919692945768

11848

2314

68534649108673148155140112

Note: Analyses obtained by microprobe at the University of Strasbourg, France.

79

2. sedimentological and geochemical characteristics of …

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