13. cretaceous interactions between volcanism and ... · 13. cretaceous interactions between...

13. CRETACEOUS INTERACTIONS BETWEEN VOLCANISM AND SEDIMENTATION IN THEEAST MARIANA BASIN, FROM MINERALOGICAL, MICROMORPHOLOGICAL, AND

GEOCHEMICAL INVESTIGATIONS (SITE 585, DEEP SEA DRILLING PROJECT)1

Hervé Chamley, Hervé Coulon, Pierre Debrabant, and Thierry Holtzapffel, Sédimentologie et Géochimie,Université de Lille I2

ABSTRACT

At Site 585 of Deep Sea Drilling Project Leg 89 more than 500 m of volcaniclastic to argillaceous middle-Late Cre-taceous sediments were recovered. Analyses by X-ray diffraction (bulk sediment and clay fraction), transmission elec-tron microscopy, molecular and atomic absorption, and electron microprobe were done on Site 585 samples. We iden-tify four successive stages and interpret them as the expression of environments evolving under successive influences:

Stage 1, late Aptian to early Albian—subaerial and proximal volcanism, chiefly expressed by the presence of augite,analcite, olivine, celadonite, small and well-shaped transparent trioctahedral saponite, Al hydroxides, Na, Fe, Mg, andvarious trace elements (Mn, Ni, Cr, Co, Pb, V, Zn, Ti).

Stage 2, early to middle Albian—submarine and less proximal volcanic influence, characterized by dioctahedral andhairy Mg-beidellites, a paucity of analcite and pyroxenes, the presence of Mg and K, and local alteration of Mg-smec-tites to Mg-chlorites.

Stage 3, middle Albian to middle Campanian—early marine diagenesis, marked by the development of recrystalliza-tion from fleecy smectites to lathed ones (all of alkaline Si-rich Fe-beidellite types), by the development of opal CT andclinoptilolite, and by proximal to distal volcanic influences (Na parallel to Ti, K). Local events consist of the supply ofreworked palygorskite during the Albian-Cenomanian, and the recurrence of proximal volcanic activity during the ear-ly Campanian.

Stage 4, late Campanian to Maestrichtian—development of terrigenous supply resulting from the submersion oftopographic barriers; this terrigenous supply is associated with minor diagenetic effects and is marked by a clay diversi-fication (beidellite, illite, kaolinite, palygorskite), the rareness of clay recrystallizations, and the disappearance of vol-canic markers.

INTRODUCTION

Deep Sea Drilling Project Holes 585 and 585A, drilledduring Leg 89 in the Mariana Basin (northwestern tropi-cal Pacific, Fig. 1), permitted the recovery of over 500 mof volcaniclastic to argillaceous middle-Late Cretaceoussediments. Site 585 is located north of Ita Maitai Guyot(13°29.00'N, 156°48.91 'E; water depth 6109 m; penetra-tion 763.7 m at Hole 585, 892.8 m at Hole 585A). Thesedimentary section at this site is divided into six litho-logic units (Moberly, Schlanger et al., 1983, and this vol-ume): I—nannofossil ooze and brown clay (Pleistocene,0-7 m,); washing followed recovery of Unit I to Unit II;II—nannofossil chalk, siliceous limestone, chert, zeolit-ic claystone (middle Eocene-Maestrichtian, 256-399 m);III—zeolitic claystone with nannofossils, chalk, and chert(Maestrichtian-late Campanian, 399-426 m); IV— chertand zeolitic claystone (Campanian, 426-485 m); V—clay-stone, locally with zeolites, graded radiolarian fine sand,organic-rich laminae, and carbonate (Campanian-mid-dle Albian, 485-590 m); VI—volcanogenic sandstones,mudstones, and breccias with shallow-water debris (mid-dle Albian-late Aptian, 590-892.8 m).

Our objective was to describe and interpret the condi-tions of Cretaceous sedimentation in the Mariana Basin

Moberly, R., Schlanger, S. O., et al., Init. Repts. DSDP, 89: Washington (U.S. Govt.Printing Office).

2 Address: Sédimentologie et Géochimie, ERA 764, Université de Lille I, 59655 Ville-neuve d'Ascq Cedex France.

140°

30°

20°

13°30'

10°

10°

20°150° 160°

156°50'170°

Figure 1. Location of Site 585, DSDP Leg 89.

from mineralogical, micromorphological, and geochemi-cal investigations of Site 585 materials. Fifty samplesfrom the Aptian to Maestrichtian section were analyzedusing X-ray diffraction (bulk material and clay fraction)and molecular and atomic absorption (bulk material);21 samples were studied by transmission electron micros-copy on particles smaller than 4 or 2 µm. The techniquesused in these analyses are those described by Chamley et

413

H. CHAMLEY, H. COULON, P. DEBRABANT, T. HOLTZAPFFEL

al. (1983) and Chamley and Debrabant (1984). Addi-tional geochemical data on clay minerals were providedby studying the [060] peaks on X-ray diffraction dia-grams of nonoriented powders, using the methods sum-marized by Desprairies (1983b).

Microchemical analyses of the clay fraction (< 2 µm)of six samples (585-27-1, 13-15 cm; 585-31-3, 29-31 cm;585-44-3, 17-19 cm; 585-46-2, 40-42 cm; 585-48-2, 4-6 cm; and 585A-17-1, 15-17 cm) were made using a CA-MEBAX electron microprobe apparatus, consisting ofthree spectrometers working simultaneously and auto-matically. The following elements were measured semi-quantitatively: Na, Si, Al (reference to albite), Fe, Ca(reference to andradite), K (reference to orthoclase), Mg,Ti, Mn, Cr, Ni, Zn (reference to different pure substanc-es). The results are expressed in mass concentrations ofoxides and reported in weight percentages after correc-tion of the absorption and fluorescence effects.

We present the mineralogy, micromorphological, andgeochemical results before discussing the data in termsof evolutionary environments. As the changes recordedfrom the different technical approaches are generally syn-chronous, we use the same stratigraphic zonation for eachmethod (Table 1). Four zones are identified and consid-ered in stratigraphic order.

MINERALOGY

The main clay mineralogical results, combined withgeneral lithologic and geochemical data, are presentedin Figure 2. Semiquantitative data of the bulk mineralo-gy are summarized in Table 2.

Zone 1 comprises the lower part of lithologic volcani-clastic Unit VI (Cores 585-55 to -48, and Cores 585A-19to -11, 892.8-686.1 m); the bulk mineralogy of this zone(late Aptian-early Albian) is characterized by the occur-rence of abundant analcite, fairly abundant celadonite,titaniferous augite, and clay minerals. The absence ofquartz and the occasional presence of common olivineand of rare feldspars typically characterize this mineral-ogical zone. Calcite is absent or very rare. The clay min-eralogy (less than 2 µm noncalcareous particles) showshighly variable assemblages dominated either by smec-tite or by smectite and a micaceous mineral. Highly crys-tallized smectite is the exclusive mineral occurring in theclay fraction of the lowermost volcaniclastic sedimentsof Site 585 (Cores 585A-17 to -19), consisting of variousgraded sandstones to unorganized breccias, with abun-dant ooids, benthic foraminifers, rudist fragments, andother shallow-water carbonate debris. In overlying Cores585A-16 to -11 and Cores 585-55 to -49, well-crystallizedsmectite (35-85% of the clay fraction, except in Core 49

Table 1. Stratigraphic zonation used in this chapter.

Mineralogical, micromorphological,(age range) and geochemical zones

Hole 585cores

Hole 585Acores

4 (late Campanian to Paleocene) 20 to 17 —3 (middle Albian to middle Campanian) 39 to 26 10 to 52 (early to middle Albian) 47 to 43 —1 (late Aptian to early Albian) 55 to 48 19 to 11

where smectite is exclusive) is mainly accompanied byvariable amounts of a glauconitic mineral, determinedby detailed X-ray analyses as typical celadonite (5-55%).Associated minerals include ordinary chlorite (0-10%),irregular mixed layers of illite-smectite, chlorite-smec-tite, and rarely illite-vermiculite types, and rare feldspars.

Zone 2. This mineralogical zone (Cores 585-47 to -43,686.1-636.1 m) corresponds to the upper part of litho-logic Unit VI (Cores 585-42 to -40 have not been stud-ied). The mineralogy of this early to middle Albian se-ries is little different from that determined in the lowerpart of Unit VI (Zone 1), which corresponds to the con-tinuing volcaniclastic character of the sedimentation.

The main differences in the bulk mineralogy consistof the appearance of rare quartz and true illite, the mod-erate augmentation of feldspars, the great increase in theabundance of clay minerals, the ubiquity of calcite insmall amounts, and the disappearance of olivine. Anal-cite and augite remain present in significant amounts,and decrease in concentration upsection. The clay min-eralogy shows the occasional occurrence of poorly crys-tallized chlorite associated with expandable layers andsome chlorite-smectite irregular mixed layers (585-46-2,40-42 cm especially), as well as traces of kaolinite (585-45-1, 8-10 cm) and of rare but rather ubiquitous quartzand feldspars. The uppermost part of the zone (fromCore 585-45 upward) is characterized by the disappear-ance of chlorite and irregular mixed layers, and the strongaugmentation of highly crystallized smectite, which be-comes nearly exclusive in Cores 585-44 and -43.

Zone 3. The third mineralogical zone (middle Albi-an-middle Campanian) extends from Cores 585-39 to -26and 585A-10 to -5 in the uppermost part of lithologicUnit VI as well as to Units V and IV (636.1-476.3 m).This interval is characterized by the ubiquity of argillites(i.e., claystones). The argillites are often laminated andgraded in the lower part (distal turbidites, with radiolar-ians and carbonates), associated with radiolarians, car-bonates, zeolites, or organic matter in the middle part,and rich in zeolites and cherts in the upper part (Fig. 2).A break in the bulk mineralogy (Table 2) separates thismineralogical zone from the underlying one. Quartz be-comes ubiquitous and sometimes abundant, opal CT iscommonly present and generally abundant, clinoptilo-lite is ubiquitous but low in abundance. The typical vol-canogenic minerals such as analcite, celadonite, and ti-taniferous augite are absent. Clay minerals occur abun-dantly; feldspars and calcite are present in various levelsand amounts. The clay mineralogy (Fig. 2) shows thelarge abundance (more than 95%) of well-crystallizedsmectite (of lesser average crystallinity, however, than inZones 1 and 2), and the minor presence of true illite(less than 5%). Associate minerals in the less than 2-µmfraction include rare to abundant quartz, abundant opalCT, rare to common feldspars, and clinoptilolite. Origi-nal levels occur in Cores 37 to 34 of Hole 585, wheremedium-crystallized palygorskite occurs in significantamounts, accompanied or not by kaolinite, quartz, feld-spars, opal, or clinoptilolite. The same mineralogicalpattern occurs in Cores 585A-10 to -9, suggesting theuse of clay mineralogical assemblages for stratigraphic

414

Site 585

Age LithologySample

(core-section,cm level)

Clay minerals (%)

20 40 60 80

Associatedminerals

Al

Al + Fe + Mn

0.4 0.5 0.6

Mn*Mn sample/Fe sample

Mn shale/Fe shale

Paleoc.

4 0 0 - Maestr. Z-z-2-i i i i i i i

17-2, ‰18-1, 50

— 19-1,1520-2, 101

tI. Camp

5 0 0 -

A A •

Turon.

I. and m.Cenom

I. Alb.

S 600 —

|34-2,85135-1, 1

—P137-1.3138-1,939-1, 132

7 0 0 - e. Albian

8 0 0 -

Aptian

I •Chert, radiolaritic ....,,......,,,,,,.Chalk, limestone | A A |ç|aystoπe J C n l o r i t e

, claystone ^ ^ c o n g l o m e r a t e UH HU Smectite::::::|Sand, sandstone,

••- •Uiit s i l tstone

Kaolinite Rare

^Mixed-layers O Common

|-z-Z-|Zeolitic clay |:::::;|^ " | |Illite s.l. ^ ^ P a l y g o r s k i t e #Abundant

Figure 2. Site 585—main clay mineralogical and geochemical data. (In Sample column, prefix A indicates Hole 585A samples.)


Table 2. Site 585 bulk mineralogy.

Sample(core-section,

cm level)

Hole 585

17-2, 14618-1, 5019-1, 1520-2, 10126-1, 2626-1, 6327-1, 1327-4, 5727-4, 7428-4, 3029-2, 6330-1, 5031-3, 2934-2, 8535-37-38-39-43-

, 1, 31, 9, 132, 13

44-3, 1745-1, 846-2, 4048-2, 449-5, 11754-3, 1155-1, 11

Hole 585A

5-1, 795-3, 137-1, 927-3, 708-1, 79-1, 6710-1, 111-1, 11312-4, 6112.CC15-5, 13716-1, 617-1, 1518-2, 1

Quartz

VRVRA

ARR—

RR

ARARARARVAARVAAA

VRRRRR———

VRARARA—A

VA——

——_—

Feldspars

VR_——AAR——R—R—R—

ARVRR

ARR

ARARAR——

RRRRA

ARVR———RRRR

Clays

ARRAAAAA

ARARAAA

VAARARA

VAVAA

VAA

ARA

ARAR

ARAAAA

ARARR

ARARR

ARAA

Pyrite

_RR————

—

—

——_——————————

—————————_———

Calcite

VAVA——

——

RVRARR

ARAR——RRRR

ARAR—R—

R———RR——

R—R—

OpalCT

RVA—

VA

VAVAAAA

—RA———

——————

VAAR

ARRA———

————

Clinoptilolite

VRVRARARRR

VRARARR

VRVRR————R—————R——

VRVR—RR———_———_—

Analcite

—_—————

————————————

ARA—A—

———_——AAAAAAA

Celadonite

——————————————————_——

AR—

ARAR

——————RR

AR—

ARRR

Augite

—————_—————————_—R

AR—

ARARARRR

——————ARARA

ARARR

AR

Olivine

————__—————————————————

AR—

———————

AR—————

Note: The abundance of each mineral is given by the height of the major peak (I 100) above the background of the powder X-ray diffraction dia-grams, according to a conventional scale: very abundant (VA = > 150 mm), abundant (A = 40-150 mm), common (AR = 10-40 mm), rare(R = 4-10 mm), very rare (VR = < 4 mm) (half values in mm for the poorly crystallized minerals); — = mineral is absent.

correlations. Core 585-34 (20% palygorskite in the clayfraction) corresponds particularly to Core 585A-1O (20%palygorskite), which fits very well with the Cenomanianage given by the biostratigraphy (Premoli Silva and Sli-ter, this volume). Mineralogical correspondences betweenboth holes in late Albian to Coniacian-Santonian sam-ples are presented in Table 3. Note that the uppermostpart of mineralogical Zone 3 (especially Samples 585-27-1, 13-15 cm and 585-26-1, 63-65 cm) shows a fewcharacters evoking some aspects of Zones 1 or 2 (Fig.2): smectite nearly exclusive and very well crystallized,and the absence of quartz and opal.

Zone 4. The last mineralogical zone occurring in theCretaceous section (late Campanian, Maestrichtian) cor-responds to lithologic Unit III (zeolitic and nannofossilclaystone) and overlaps the base of Unit II (chalk). Onlysampled in Cores 585-20 to -17, the sediments are char-acterized by a mineralogical diversification, especially

in the clay fraction. Still dominant, smectite is fairlywell crystallized and associated with illite (15-20% ofthe clay fraction), chlorite-smectite irregular mixed lay-ers (traces), kaolinite (0-5%), palygorskite (0-5%), rarequartz, common to abundant clinoptilolite, rare feld-spars, and abundant opal CT. The bulk mineralogyshows abundant clay minerals and variable amounts ofquartz and clinoptilolite, and the local presence of feld-spars, pyrite, calcite, and opal.

MICROMORPHOLOGY

Clay Morphological TypesTransmission electron microscope investigations of the

less than 4- or 2-µm fractions from Holes 585 and 585Asamples show the presence of many morphological typesof clay particles. The most characteristic are the follow-ing (Fig. 3; Plates 1-3).

416

CRETACEOUS INTERACTIONS

Table 3. Clay mineralogical correspondences in Cores 585-35 to -28 and 585A-1O to -5.

Sample(hole-core-section, cm

level) IlliteMixedlayers Smectite Kaolinite Palygorskite Quartz Feldspars Opal CT Clinoptilolite

585-28-4, 30585-29-2, 63585A-5-1, 79585A-5-3, 13585-30-1, 50585-31-3, 29585A-7-1, 92585A-7-3, 70585A-8-1, 7585A-9-1, 67585-34-2, 85585A-1O-1, 1585-35-1, 1

tracestracestraces

tracestraces

5tracestraces555

traces5

traces

1001001001001001009510010095757090

traces20205

+ = rare; + + = common; + + + = abundant; + + + + = very abundant; — = absent.

Smectites Illites (s.l.) Chlorites

Type 1Transparent smectites

Type 2Hairy smectites

Type 3Folded smectites

Type 1Celadonites

Type 1Hexagonal chlorites

<ö0.2 µm

See Plate 1, Fig. 1

1µm

See Plate 1, Fig. 2

1µm

See Plate 1, Fig. 3

0.2 µm

See Plate 2, Fig. 1

1µm

See Plate 2, Fig. 3

Type 4Fleecy smectites

Type 5Intermediate smectites

Type 6Lathed smectites

Type 2True illites

Type 2Irregular chlorites(?)

1µm

See Plate 1, Fig. 4

1µ.m

See Plate 1, Fig. 5

0.5 µm

See Plate 1, Fig. 6

1µm

See Plate 2, Fig. 2

1µITI

See Plate 2, Fig. 4

Figure 3. Main clay micromorphological types.

Smectites

Type 1, transparent smectites. These are very smallsheets with well-defined but nonpolygonal outlines, near-ly transparent to the penetration of electrons. They ap-pear homogeneous, and locally constitute aggregates oflarger size (about 2 µm).

Type 2, hairy smectites. These appear as finely foldedlayers, giving to the particle a hairy shape.

Type 3, folded smectites. This type of clay particleappears in large and flat layers, more or less folded,rather similar to the "opaque smectites" described byHoffert (1980).

Type 4, fleecy smectites. These are poorly definedsheets with cloudy outlines, sometimes slightly folded,showing various sizes, and commonly described in manyAtlantic and Pacific Mesozoic to Cenozoic sediments (e.g.,Chamley, 1981; Chamley et al., 1983).

417


Type 5, intermediate smectites. These resemble fleecyType 4 smectites, with some outlines consisting of Type 6lathed sheets.

Type 6, lathed smectites. This assemblage is made upof small and thin lathed sheets at 60° or 120°.

All intermediate stages exist between pure fleecy andpure lathed smectites. This continuous series of parti-cles is very similar to the morphological series describedin Albian-Aptian and Paleogene sediments of the NorthAtlantic Ocean by Holtzapffel et al. (1985); it is inter-preted as the result of an early diagenetic evolution fromfleecy to lathed smectites.

Micaceous Clays—Mites (s.l.)

Type 1, celadonites. These are very small and slightlyelongated chips (0.2-0.5 µm), rather transparent on mi-crographs when isolated, with well-shaped outlines. Theycommonly constitute aggregates of larger size.

Type 2, true illites. These are typical micalike sheets,with well-defined and nonpolygonal outlines, fairly largesize, and commonly with a watered-looking surface (e.g.,Beutelspacher and Van der Marel, 1968).

Chlorites

Type 1, hexagonal chlorites. These form large darksheets with hexagonal to pseudohexagonal outlines, sug-gesting an ordered growth.

Type 2, irregular chloritesf?). These are large darksheets with poorly defined shape (often sharp but non-polygonal and irregular outlines, locally finely foldedsheets, locally transitional shape with cloudy structures).

Palygorskite

These clay particles take the form of typical elongatedfibers, forming bundles, or isolated and more or lessbroken particles.

Kaolinite

Typical hexagonal, isolated, and fairly small sheetscharacterize this type of particle.

Stratigraphic Distribution

The four zones identified from the mineralogical da-ta show specific micromorphological features.

Zone 1. From Cores 585-55 to -48 and from Cores585A-19 to -11, this volcaniclastic assemblage is charac-terized by the presence of transparent smectites (Type 1)and celadonite chips (Plate 2, Fig. 1). Their abundance,estimated by counting on micrographs, corresponds tothe relative abundance of each mineral deduced fromX-ray diffraction analyses (Fig. 2). Fleecy smectites (Type4) locally occur in very low amounts. Small quantitiesof hexagonal chlorite are recognized at some levels (585-54-3, 11 cm; 585-48-2, 4 cm) (Plate 3, Fig. 1). At thebase of the zone (585A-15-5, 137 cm; 585A-17-1, 15 cm)small dark particles with with spiral shape occur, consti-tuting in some cases large aggregates (about 2 µm) (Plate2, Fig. 6). The shape of these particles resembles Fe orAl oxides (Beutelspacher and Van der Marel, 1968).

Zone 2. Ranging from Cores 585-47 to -43), this zonestrongly differs from the underlying one. Transparent

smectite (Type 1) and celadonite are still present in verysmall amounts at the base of the zone (e.g., Sample 585-47-1, 9 cm) but disappear upwards. The main differ-ences consist of the appearance of fleecy, intermediate,and lathed smectites (Types 4, 5, 6) showing highly vari-able relative abundances (e.g., fleecy smectites predomi-nate in 585-44-3, 17 cm; Plate 3, Fig. 4). In some cases(Cores 585-44 and -45), hairy smectites (Type 2) occur inlow amounts (Plate 1, Fig. 3). Micaceous clay particles,poorly represented in this zone, generally consist of trueillite.

Zone 3. Between Cores 585-39 and -26 and Cores585A-10 and -5, fleecy, intermediate, and lathed smec-tites (Types 4, 5, 6) are still present, but the fleecy type isalways predominant (Plate 3, Fig. 3). True illite occursin small quantities. Two peculiar levels, also recognizedby X-ray mineralogy, exist in this zone. The first level(585-34-2, 85 cm and 585A-10-1, 1 cm) corresponds tothe presence of palygorskite, characterized by numerousindependent to bundled fibers associated with fleecy tolathed smectites (Plate 2, Fig. 5). The second level (585-27-1, 13 cm to 585-26-1, 63 cm), particularly well char-acterized by micromorphology, is located in the upper-most part of Zone 3 and shows the presence of easily rec-ognizable folded smectites (Type 3) in significant amounts(Plate 3, Fig. 5). This type of smectite does not occurbelow (e.g., 585-27-4, 57 cm); it seems to appear sud-denly but to disappear progressively at the top of Zone 3(585-26-1, 27 cm).

Zone 4. From Cores 585-20 to -17), the mineralogicaldiversification identified by X-ray diffraction (smectite,illite, palygorskite, and/or kaolinite, irregular mixed lay-ers) is corroborated by electron microscope data (Plate3, Fig. 6). The smectite morphology is fairly homoge-neous and characterized by the large abundance of thefleecy Type 4. Intermediate and lathed smectites (Types5 and 6) are very rare, which suggests little or no diage-netic effects on clay mineralogy (Holtzapffel and Cham-ley, 1983).

GEOCHEMISTRY

The geochemical data obtained by molecular and atom-ic absorption analyses and by microprobe investigationssupport the distinction of the same four stratigraphiczones previously outlined. The rough geochemical dataare given in Tables 4 and 5. Some samples have beensubdivided in two or three distinct parts, because of dif-ferent lithologies (585-26-1, 27 cm; 585-34-2, 85 cm; 585A-10-1, 1 cm). Figure 2 summarizes the main geochemicaltrends at Site 585 from different ratios defined by De-brabant and Foulon (1979) and Debrabant and Chamley(1982).

Zone 1From Cores 585-55 to -48, and Cores 585A-19 to -11),

the lower part of Site 585 is characterized by the relativeabundances of Fe, Mg, and Na (e.g., MgO/Al2O3,K2O/MgO, Na2O/TiO2), associated with relatively highamounts of transition trace elements (Mn, Ni, Cr, Co,Pb, V, Ti) and sometimes of Zn. The low and constantvalues of the SiO2/Al2O3 ratio point to the lack of free

418


Table 4. Hole 585 geochemical data.


interval in cm)

1-1, 85-8717-2, 66-6717-2, 146-14818-1, 50-5519-1, 15-1720-2, 101-10426-1, 27-29W26-1, 27-29B26-1, 63-6527-1, 13-1927-4, 57-6027-4, 74-7628-4, 30-3229-2, 63-6530-1, 50-5231-3, 29-3034-2, 85-87W34-2, 85-87B35-1, 1-337-1, 31-3338-1, 9-1139-1, 132-13343-1, 13-1544-3, 17-1945-1, 8-1046-2, 40-4247-1, 9-1248-2, 4-849-5, 117-11953-2, 77-7854-3, 11-1355-1, 11-15

SiO2

(wt.%)

48.6076.3014.4047.7057.3052.9069.7060.2051.4050.4070.3071.4061.2069.3061.8053.8041.5070.5058.2081.6067.9061.3050.1048.5053.3038.5045.4043.1051.7039.5039.4045.60

A12O3

(wt.%)

16.138.252.952.68

13.9313.907.62

10.1614.6714.917.588.39

10.358.928.91

11.193.068.75

10.945.23

10.409.64

12.4514.2312.7013.2814.4813.9013.6814.3915.7814.05

Fe2O3

(wt.%)

9.853.320.961.495.926.964.687.95

10.7410.612.704.026.714.775.989.581.955.208.193.48

10.028.60

11.9410.2811.5112.0812.9910.8912.7110.5513.9213.67

CaO(wt.%)

2.531.58

41.0922.59

2.551.621.522.313.402.361.361.513.752.285.423.55

24.761.705.521.442.484.394.425.303.709.684.139.595.28

10.416.235.18

MgO(wt.%)

3.451.800.790.673.042.721.992.952.542.311.291.552.672.452.353.530.872.353.011.442.532.525.103.885.296.854.683.173.453.322.934.62

Na2O(wt.%)

5.081.420.800.782.082.501.551.873.163.202.072.032.091.861.882.320.440.912.160.841.561.301.941.271.662.341.343.842.505.056.161.26

K2O(wt.%)

2.341.680.790.733.273.391.361.812.722.821.581.731.801.341.472.170.621.702.291.091.750.731.764.683.133.114.265.762.692.273.004.42

TiO2

(wt.%)

1.040.340.150.190.220.220.811.001.371.461.040.860.920.860.921.130.200.471.140.370.881.442.171.871.401.771.701.912.341.732.271.67

P2O5(wt.%)

0.600.20n.d.0.300.501.900.400.60n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.0.20n.d.0.20n.d.0.500.300.300.30n.d.0.300.300.20n.d.0.20

Sr(ppm)

26811667945221634718422135835823723723116321622133795

21611617926827914215816313795

72613284

137

Mn(ppm)

8337957

2562563

10051473389626973920415447679757

117317941326537

1499600747

13781215129413832146133612151073111012881341

Zn(ppm)

484337111205279179116216316190100

984219042099436166111121121105142126189121132153142132

n.d.174184452

Li(ppm)

6634141166422136201710122017234212262322233235293548401526141438

Ni(ppm)

336584027

15215865

1053431373745304255286398555599

12010612515412284959374

107

Cr(ppm)

1215627245167

12412236429589436030652054435024

1491231041171551147283

14414877

Co(ppm)

12314176

38391930171358

161414196

195715213452342744322847244244

Cu(ppm)

3821664129

149183486719105

116832271414381943122390745535

n.d.6710323716

Pb(ppm)

7650492846484934323529212630203527643624521633234538163428263729

V(ppm)

1702030106050806050607030

1307050302050802050

10017013010019060

120140130200150

Note: B = black and W = white parts of sediment; n.d. = not determined.

Table 5. Hole 585A geochemical data.


interval in cm)

5-1, 79-805-3, 13-147-1, 92-947-3, 70-728-1, 7-99-1, 67-71

10-1, 1-3B10-1, 1-3S10-1, 1-3W11-1, 113-11512-4, 61-6312.CC13-3, 72-7315-5, 137-13916-1, 6-1017-1, 15-1818-2, 1-319-3, 1-4

SiO2

(wt.<Co)

77.7064.9060.9061.9057.3068.3073.9081.9070.2045.0045.3047.3040.3046.3046.3044.3045.7045.70

A12O3

(wt.%)

5.438.72

10.4210.0415.535.667.634.625.71

15.6317.2415.6611.9911.3910.9813.5913.8513.45

Fe2O3

(wt.%)

2.534.468.714.937.572.484.953.003.48

10.8311.7313.1511.218.819.009.309.38

10.10

CaO(wt.%)

2.323.031.552.492.107.541.371.195.446.523.854.60

12.1311.3711.1410.058.538.89

MgO(wt.%)

1.452.123.632.701.941.452.231.471.612.923.533.567.132.712.776.376.467.91

Na2O(wt.%)

1.531.952.001.753.881.511.000.700.796.687.525.803.723.703.786.366.483.98

K2O(wt.%)

0.88.50.87.74.24.24.81.20.47.90.15.85

1.923.522.770.250.240.36

TiO2

(wt.%)

0.560.781.071.061.710.420.580.780.771.962.102.501.861.291.291.521.540.88

P2O5(wt.%)

n.d.n.d.n.d.n.d.n.d.n.d.0.500.501.70n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.

Sr(ppm)

1321951791633521529553

1261007474

11011411094105126389

Mn(ppm)

127818351535569710732078

631479831

11411404436

1457842842

106810731120

Zn(ppm)

1265563137168147121142258126163490205237205142137899

3124

Li(ppm)

9173935111927202315201629

8879

20

Ni(ppm)

112087773035785275656390

1609894

119130178

Cr(ppm)

3331946748287359387992

151147106113127126176

Co(ppm)

n.d.7

3112169

218

26363553492626353642

Cu(ppm)

9473660

10139674042272269856056515055

Pb(ppm)

182228303325252317413030372829393037

V(ppm)

205030808030402020

1702002201808090

150150

16

Note: B = black and W = white parts of sediment; n.d. = not determined.

silica. Potassium is little represented, except toward thetop of the zone and seems to be locally associated withSr (Cores 585A-16 and -17, more than 1000 ppm). P isnot detectable until Core 585-55.

The microprobe analysis of 34 particles of Sample585A-17-1, 15 cm shows the presence of three dominantminerals:

The first of these is Na-rich magnesian smectite, whichis abundant (70% of the studied particles) and chemi-cally homogeneous (Table 6). The trioctahedral charac-ter of the mineral, devoid of Al within the octahedra,and marked by significant amounts of Fe in the tetrahe-dra and of Na in the interlayers, is corroborated by the[060] X-ray diffraction peak located close to 1.540 Å

(Fig. 4). The mineral probably consists of a iron sapo-nite (Millot, 1964), typically generated in volcanic envi-ronments (Desprairies, 1981 and 1983a).

The second dominant mineral is titaniferous augitewith abundant adsorbed Na.

Na2O

11.29

K2O

2.33

CaO(%)

10.39

SiO2(%)

38.27

A12O3

(%)

8.97

Fe2O3

(%)

7.53

MgO

12.83

TiO2

7.80

M11O2(%)

0.18

The third is aluminum hydroxide, not identified byX-ray diffraction, possibly subamorphous, and corre-sponding to the peculiar spiral particles detected by elec-

419


Table 6. Microchemical analyses (%) of smectites (average values).

Sample(hole-core-section,

cm level) Age Na2O K2O CaO SiO2 A12O3 Fe2O3 MgO TiO2 MnO2 Types of smectites

585-27-1,585-31-3,585-44-3,585-46-2,585-46-2,585A-17-1

1329174040, 15

CampanianTuronian

m. Albian

e.-m. AlbianAptian

0.231.871.091.401.049.00

1.407.142.851.400.863.09

0.920.511.090.800.881.68

60.7860.0353.2446.9343.1937.90

15.3211.0817.8921.5615.4110.70

15.4712.5511.809.61

10.6111.83

4.915.539.19

17.6927.1224.42

0.520.841.280.530.690.93

0.250.230.100.070.170.20

Fe-beidelhtesAlkaline smectitesMg-beidellitesEvolving Mg smectites

(transition to Mg-chlorites)Saponite


cm level)

585-26-1, 27

585-26-1,63

585-27-1, 13

585-27-4, 57

585-27-4, 74

585-39-1, 132

585-44-3, 1 7

585-44-3, 40

585-47-1,9

585A-11-1, 113

585A-17-1, 15

Zone

3

2

1

Mineralogy

Smectites

Smectites

Smectites

Smectites

Smectites

Smectites

Smectites

SmectitesChlorites

SmectitesChlorites

CeladonitesSmectites

Smectites

Morphology

Sm

. 1

Sm

. 2

Sm

.3

i0

l

5 Cela

do.

Ch

lor. 1

Ch

lor.

2

I

X-ray data: d[060] reflection

Results (Å)

1.502

1.502 1.533

1.504 1533

1.502

1.502

1.502

1.501 1526

1.480-1.540

1.505

1.509-1.538

1502 1.537

Interpretations

Fe or Mg-beidellites

Fe or Mg-beidellites(+ saponites?)

Fe or Mg-beidellites(+ saponites?)




Fe or Mg-beidellites(+ nontronites?)

Smectites to chloriteseries


CeladoniteSaponite

Saponite(+ beidellites?)

Microprobedata

OnlyFe-beidellites

OnlyMg-beidellites

Evolving Mg-Sm.to Mg-Chlo.

Saponite

Figure 4. Location of the [060] X-ray reflection of selected samples and relationships with the micromorphological zonation (see textfor morphological types). The size of d-spacing values is proportional to the height of the X-ray diffraction corresponding peak.Sm. 1 = smectite of Type 1, and so on.

tron microscopy (Plate 2, Fig. 6). These particles occurin significant amounts (15%) and are associated withabundant Na.

Na2O K2O CaO SiO2 A12O3 Fe2O3 MgO TiO2

12.05 1.70 1.49 2.35 78.94 1.13 1.95 0.80 0.06

Note that feldspars identified in Sample 585-48-2, 4 cmconsist of albite and orthoclase types (Table 7).

Zone 2

In Cores 585-47 to -43, the K abundance tends to in-crease and the Na abundance to decrease (e.g., Na2O/K2O < 1, Fig. 2), whereas Mg, Ti, Fe, and Mn remainfairly abundant. The increase in concentration of potas-sium corresponds to relatively high amounts of feldsparsin the bulk sediments.

Microchemical analyses were done on two samples,the first of which—Sample 585-46-2, 40 cm (36 parti-cles)—contains the following minerals:

• Alkaline feldspars of K, Na, and K-Na types, form-ing about 35% of the particles identified and correspond-ing to different minerals from orthoclase to albite (Ta-ble 7).

• Pyroxenes (15% of particles) more Si- and Mg-richand less alkaline than in underlying Zone 1 (diopside-hedenbergite types, Deer et al., 1963a).

Na2O

1.11

K2O

0.23

CaO(ft)

11.15

SiO2

(ft)

50.09

A12O3

(ft)

6.10

Fe2O3

(*)

4.63

MgO(ft)

24.23

TiO2

(ft)

1.00

(ft)

0.10

• Smectitelike minerals (35%), constituting an inho-mogeneous group marked by the abundance of Mg andgradually ranging from an Al-Si type to a Mg-rich type

420


Table 7. Microchemical analyses (°/o) of feldspars (average values).


cm level)

585-27-1, 13

585-31-3, 29

585-44-3, 17585-46-2, 40

585-48-2, 4

585A-17-1, 15

Age

Campanian

Turonian

m. Albiane.-m. Albian

e. Albian

1. Aptian

Na2O

6.214.469.015.841.268.338.560.50

11.170.35

K2O

0.907.942.198.59

11.180.936.16

10.131.60

13.76

CaO

6.220.912.820.700.251.870.670.210.740.44

SiO2

55.6262.8662.1161.8861.3562.3357.6061.0961.9663.01

A12O3

23.8818.9720.7117.7722.0217.4321.1121.3319.2016.96

Fe2O3

5.453.372.133.191.642.322.211.932.873.69

MgO

1.180.910.871.431.936.773.374.650.971.17

TiO2

0.320.290.140.310.300.130.260.050.500.38

MnO2

0.090.130.030.200.060.020.020.050.080.08

Types of feldspars

Andesine-oligoclaseAlkaline-feldsparAlbiteAlkaline-feldsparOrthoclaseAlbiteAlkaline-feldsparOrthoclaseAlbiteOrthoclaseNo feldspars

but aluminumhydroxides

(Table 6) (Weaver and Pollard, 1973). The structural for-mulas can be calculated as exclusive smectites (Table 8),and in this case the magnesium of the Mg-rich type isabundant in both octahedra and inter layers:

The Mg-rich type could also be a transition mineral be-tween a Mg-smectite and a Mg-chlorite. Such a Si-de-pleted intermediate structure suggests a pseudochlorite,partly expandable, consisting of a transitional mixtureof beidellite and of a neutral brucitic interlayer (Caillèreet al., 1982):

(Si3.57Alo.43) ( A I i .07F4^5Mg 0 . 3 4 Ti 0 0 4 )Na 0 . 1 7 K 0 . 1 0 Ca 0 . 0 8 O, 0 (OH) 2

Mg 3 (OH) 6

This second hypothesis appears more likely, because thepresence of the Mg-rich mineral corresponds to poorlycrystallized chlorite, associated with expandable layers,and to poorly defined 1.48-1.54 Å reflections (X-ray da-ta, Figs. 2 and 4), and to irregular dark sheets identifiedon electron micrographs (Plate 2, Fig. 4). The accumula-tion of Mg in the smectite interlayers progressively wouldpermit the growth of a typical magnesian chlorite, also

identified in few amounts by microprobe analysis (seebelow).

• Magnesian chlorite, characterized by a very high pro-portion of Mg and low proportions of Si:

Na2O

0.95

K2O

0.52

CaO

0.61

SiO2

36.89

A12O3

16.21

Fe 2 O 3a

9.76

MgO

33.07

TiO2

1.66

(%)

0.24

a (FeO = 8.78 %)

The structural formula of this trioctahedric chlorite isof the following type, in which the tetrahedric substitu-tions are compensated in the brucitic layer and all the Alis located in tetrahedra:

(Si3.i6Alo.84) I (Mg2Fe02+3Ti0 10)Na0 16K0

(Mg2.2Al080)(OH)6

The second Zone 2 sample microchemically analyzedis 585-44-3, 17 cm (35 particles). Most of the clay-sizedparticles investigated (65%) are homogeneous magne-sian and iron-rich smectites, distinct from those of un-derlying levels because of higher amounts of Fe2O3 than

Table 8. Structural formulas of smectites in Holes 585 and 585A (from microprobe analyses).

Sample(age) Structural formula o a Total Al Total Mg Types of smectites

585-27-1, 13(Campanian)

585-31-3, 29(Turonian)

585-44-3, 17(m. Albian)

585-46-2, 40(e.-m. Albian)

(Si3.96A10.04)(A11.05Fe0.52Mg0.47Ti0.02)K0.10Ca0.09Na0.03°10(°H)2

( S i 3.79 A 1 0.2lK A 1 0.92 F e 0.73 M g0.46 T i 0.02) K 0.11 C a 0.06 N a 0.03°lθ(° H )2

( S i 3.66 A 1 0.34K F e 0.97 A 1 0.71 M g0.44 T i 0.02) K 0.15 C a 0.06 N a 0.03 M g0.02 O 10< O H )2

S i 4 + > 4, smectites with free SiO 2 (Grim and Kulbicki, 1961)

( S i 3.88 A 1 0.12)( A 1 0.72 F e 0.61 M gθ.53 T i 0.04) K 0.59 N a 0.24 C a 0.04°lθ( O H )2

( S i 3.68 A 1 0.32)( A 1 0.62 F e 0.68 M gθ.58 T i 0.03) K 0.69 N a 0.31 C a 0.07°lθ( O H )2

( S i 3.42 A 1 0.58X M g0.87 A 1 0.78 F e 0.56 T i 0.06) K 0.23 N a 0.15 C a 0.09 M g0.01 O 10(° H )2

( S i 2.98 A h.02)( M gl .35 A 1 0.60 F e 0.46 T i 0.03) M g0.32 N a 0.32 N a 0.17 K 0.11 C a 0.05 O 10( O H )2

( S i 2.80 A 1 1.18 F e 0.02)( M g2.19 F e 0.50 T i 0.03) M g0.44 N a 0.13 K 0.07 C a 0.06 O 10(° H )2

(l^Aptiail) ^ (S i2.66A 10.87F e0.47)(Mg2.52F e0.t7T i0.O4)N a1.21KO.27C aO.12°10(°H)2

0.27

0.05

0

0.79

0.82

0

0

0

0.25

1.09

1.13

1.28

0.84

0.94

1.36

1.62

1.18

0.87 2.52

Fe-beidellites

Alkaline smectites

Mg-beidellites

EvolvingMg-smectitestransition toMg-chlorite

Saponite

o = octahedral charge deficit.

421


MgO, and identified as a mixture of Mg-beidellites (Ta-bles 6 and 8).

The other particles studied in this sample include po-tassic feldspars (25%) of orthoclase type (Table 7), andcommon micaceous minerals of the following composi-tion, probably corresponding to the "true illite" identi-fied by X-ray diffraction and electron microscopy (Deeret al., 1983b):

K 2O CaO SiO2 A12O3 Fe 2 O 3 MgO TiO 2 MnO 2

2.33 7.61 0.29 52.19 23.69 8.31 4.62 0.83 0.12

Zone 3

This zone ranges from Cores 585-39 to -26, and fromCores 585A-10 to -5. A major break marked by a strongincrease of free silica (SiO2/Al2O3, Fig. 2) occurs be-tween Cores 43 and 39 of Hole 585. The relative de-crease of metallic elements is determined by the silicaaugmentation, as shown by the persistence of noticeableamounts of transition elements in the most argillaceoussamples. Zone 3 is also characterized by a strong corre-lation between Na2O and TiO2. The correlation factorr(Na2O, TiO2) = 0.96 and the corresponding regressionline are characteristic of the late Albian to Campanianperiod: Na2O = 2.15 TiO2 (Fig. 5).

The lower part of Hole 585 Zone 3 (Cores 38-34)shows an excess of K compared to Na (Na2O/K2O < 1,Figs. 2 and 5), whereas the upper part (Cores 31-26)shows a reverse trend (Na2O/K2O > 1). The same geo-chemical zonation occurs at Hole 585A, and points togood correlations between both holes. For example, Sam-ple 585A-10-1, 1 cm (black) correlates to Sample 585-

34-2, 85 cm (black). Cores 585A-9 to -5 strongly resem-ble Cores 585-31 to -29 in relative abundance of Na2Ocompared to K2O, development of some transition met-als (Mn, etc.), and in Cores 585-29 and 585A-5, parallelincrease of SiO2 and Zn (Tables 4 and 5).

The uppermost part of Zone 3 (585-27-1, 13 cm and585-26-1, 63 cm) is characterized by a small but suddenincrease in Fe and Mn, and in a smaller proportion ofNa, K, Ti, and locally P. This particular level correspondsto the presence of folded smectites, which are especiallyabundant (Plate 3, Fig. 5).

Microprobe analyses were done on two samples. Inthe first sample, 585-31-3, 29 cm (23 particles), mostparticles identified (80%) correspond to Si-rich alkalinesmectites (Tables 6 and 8), fairly rich in iron, and proba-bly ranging from a type-fixing free silica (Grim and Kul-bicki, 1961) to a more aluminous type. The octahedralsubstitutions are abundant, and compensated by alka-line cations. The other particles chiefly consist of Na-Kfeldspars, often more calcic than in underlying sediments(Table 7). In the second sample, 585-27-1, 13 cm (36particles), 70% of the particles identified are Si-rich smec-tites (Table 6), constituting a group characterized by an-tagonistic contents of Fe and Si [r(SiO2, Fe2O3) = - 0.81],and by moderate octahedric substitutions. Different struc-tural formulas can be calculated, ranging from a beidel-lite s.s. to a Fe-beidellite (Table 8). Other minerals arechiefly feldspars, either potassic or calcic (Table 7).

Zone 4

From Cores 585-20 to 17, the latest Cretaceous sedi-ments show a strong increase of aluminum (see index D,detrital index, in Fig. 2), manganese (see index Mn*,Fig. 2), and phosphorus (P 2O 5, Table 4). The variabilityof the sedimentation is reflected by variable amounts of

6-

<N 4

• Cores 55-39, Hole 585 j A ptian-Albian® Cores 19-11, Hole 585Af+ Cores 38—26, Hole 585 \ late Albian —©Cores 10—5, Hole 585A J CampanianA Cores 10—17, Hole 585 Maestrichtian —

Paleocene

A A

A

Θr^<r

0.5 1.0 1.5 2.0 2.5TiO2(%)

Figure 5. Relationships between Na2O and TiO2 at Holes 585 and 585A.

422


Si and Ca. The mineralogical diversification identified byX-ray diffraction corresponds to common contents of Ti,Fe, and to the predominance of K over Na, frequent innonvolcanogenic environments (Debrabant and Cham-ley, 1982).

DISCUSSION AND CONCLUSION

The combined study of mineralogical, micromorpho-logical, geochemical, and microchemical characters ofSite 585 sediments, considered in a general lithologic con-text, gives insight into a paleoenvironmental reconstruc-tion of Mariana Basin history during the Cretaceous (Figs.6 and 7). Four successive stages are identified.

Stage 1, late Aptian to early AlbianCores 585-55-48; Cores 585A-19-11)

The association of highly crystallized Mg-smectite (Na-saponite), celadonite, analcite, titaniferous augite, oliv-ine, Na- to K-feldspars, and the abundance of Fe, Mg,Na, K, and different trace elements (Mn, Ni, Cr, Co,Pb, V, Zn, Ti) indicate the importance of volcanic influ-ence on the mineralogy and geochemistry of the sedi-ments. This close relationship between inorganic sedi-mentation and volcanism is corroborated by the litholo-gy, which is characterized by a heterogeneous mixture ofvolcanic sandstones, mudstones, and breccias (Site 585report, this volume). As a probable consequence, thesmall, well-shaped, transparent smectites (apparently notpreviously described in the literature), the celadonite chips,and the hexagonal chlorites characterize the micromorpho-logy of clay minerals resulting from the evolution of theSite 585 heterogeneous volcanogenic materials. The vol-canogenic origin of Cretaceous smectites in Aptian sedi-ments of the Mid-Pacific Mountains has already beensuggested by Mélières et al. (1981).

The large amount of numerous volcanogenic parti-cles points to the proximity of Site 585 to volcanoes.Only sparse fleecy smectites could indicate a minor con-

tribution of a more distant supply. The presence of shal-low-water calcareous debris (Site 585 report, this vol-ume) suggests the presence of volcanic islands and thesubaerial eruption of a large portion of volcanic materi-als. This interpretation is substantiated by the abundanceof Na fixed or adsorbed by most of the minerals; in Me-sozoic sediments of the Atlantic sodium has been pro-posed as a marker of subaerial volcanism (Debrabantand Chamley, 1982). Additional arguments are providedby the presence of aluminum hydroxides of a possiblepedogenic origin. Thiede et al. (1982) indicate the im-portance of terrestrial organic matter in mid-Cretaceoussediments of the tropical and subtropical Pacific Ocean.As a consequence, the transparent and small smectitescould be characteristic of alteration products of volcanicmaterials produced in a Na-rich subaerial environment.

Note that toward the end of Stage 1 (from Cores585A-16 and -15 upward), the more potassic characterof the sediment geochemistry could be related to the abun-dance of celadonite. Such an interpretation does not fitwith the relative abundance of strontium. The associa-tion of K and Sr, and locally of P, more likely indicates achange in the geochemical character of volcanism, prob-ably of a trachybasaltic or a trachyandesitic type (Faure,1978; Stueber, 1978). Feldspar-rich trachytes are describedat Site 585 between 850 and 700 m water depth (Site 585report, this volume). Celadonite could proceed from thealteration of these rocks.

In summary, Stage 1 at Site 585 indicates the stronginfluence of a local and subaerial volcanism on the sedi-mentation.

Stage 2, early to middle Albian TransitionCores 585-47-43

The bulk and clay minerals continue to include volca-nogenic species such as analcite and titaniferous augite,which corresponds to the persistence of the volcanogen-ic supply shown by lithological observations. The geo-

Feo0,

MgO

Figure 6. Microchemical correlations of clay minerals from selected samples.

Legendπ 585-27-1, 13 cmo 585-31-3, 29 cm• 585-44-3, 1 7 cm* 585-46-2, 40 cm• 585-17-1, 15 cm

423

Age

CO

CO

c

pani

c

bCOO

3

eno.

ü

c

m.-

l. A

lbi<

CO

<

Φ

CCO

Ap

t

Φ

ro

</>c

Lit

ho

log

'I

4

c

6


cm level)

17-2, 6617-2, 14618-1 50

19-1, 1520-2, 101

26-1, 2726-1, 63

27-1, 1327-4, 5727-4, 7428-4, 30

29-2, 6330-1, 5031-3, 2934-2, 8535-1 137-1, 31

38-1, 939-1, 132

43-1, 1344-3, 17

45-1, 8

46-2, 4047-1 9

48-2, 449-5, 117

53-2, 7754-3, 11

55-1, 11A11-1,113A12-4, 6A12.CCA13-2, 72

A15-5, 137A16-1.6

A17-1, 15A18-2, 1A19-3, 1

ths

*•o•σ

Zo

ne

s a

in m

ete

r

390

A

4 7 6

3

6 3 6

2

6 8 6

1

8 9 2

Clay m

CO — j -.

Sm

ect

ite

Illit

es

(s.l

Ch

lori

tes

Φ

—T

rue

ill

ite

oCO

O

Mineralogy

n. Other min.

r>a

Ka

olin

ite

An

alc

ite

Au

git

e

Oliv

ine

Qu

artz

- -

Φ

Op

al C

T

Clin

op

tik

J I.. .

• *

CO

Mai

n re

nra

lc

min

eje

ne

t

CO

CO

itic

"α>

CO

Typ

i

CO

3ra

boc

o

>CO

"ypi

-–

-–

Morphology

Smectites

Φ

Tra

nsp

arH

airy

Φ

at

Fold

ed

Flee

cy

Inte

rmed

Lath

ed

I:

III. Chlo

coQ . _

Ce

lad

. cl

"

Tru

e i

llitt

He

xag

on

Irre

αu

lar

CO> ,cσ

Fib

rou

s c

CO

•σX

Fe o

r A

l

(0

Mai

n r

err

rals

cr

Fo

zΦ

n

CO

3ra

cz

b

ΦN

to

ee

ry

CO

itic

Det

ral

s

Φ

'F

c:ou

t

Φ>

-–

— -

Geochemistry

Mainelements

CO D) ΦLL

fI

i- 00

-

Microprobedata

(smectite)

7// Fe~ 7/?C/ beidellite 22

yy Alkaline %7< ^ smectite /×^•

Z9 M 9 - Z>9//u. beidellite o^

Evolving7λ Mg- T/}u<• smectite £/-

to

Mai

n r

eπlic

are

e s

ΦCJcd)

res

Q_

CD

ocΦ

OC

>

c

CO

- –

-–

Interpretations

Stage 4

Detrital inputMinor diagenetic modifications

(silica-rich minerals)

Stage 3

Recurrence of proximal ,volcanic influence

Marine diagenesis(clay and silica-rich minerals)

Local volcanic events

1

Reworking from neritic 'basins or wind transport'

Stage 2

Transition from volcanicto diagenetic processes

(clay minerals)

Detrital input

Proximal andsubaerial volcanic

influence

Figure 7. Site 585: main data and interpretations. (In Sample column, prefix A indicates Hole 585A samples.) In Interpretations column, bold-faced lettering indicates major phenomena; minorevents are represented by regular lettering.


chemistry confirms the continuing influence of volcan-ism by the relative abundance of magnesium (Fig. 7),Ti, Fe, and Mn (Table 4); by the parallelism betweenNa2O and TiO2, constant during most of the Late Cre-taceous (Fig. 5); and by the abundance of Na- to K-feld-spars.

Nevertheless, the volcanic influences appear to be lessproximal than during Stage 1, because smectites com-prise dioctahedral types with aluminum in the octahedra(Mg-beidellites) (Fig. 6), increased amounts of SiO2, anddecreased amounts of MgO. Volcanogenic micromorpho-logies, consisting of hairy smectites and of a few trans-parent smectites (i.e., Stage 1), are largely associated withfleecy to lathed smectites, probably indicative of in siturecrystallizations without specific volcanic influence (Holt-zapffel et al., 1985). Volcanogenic olivine and celadon-ite have disappeared, and are superceded by some trueillites of a detrital origin. The sodium content decreases,and suggests a lesser contribution of subaerial volcan-ism. To summarize, Stage 2, identified by inorganic in-vestigations, appears as a transition period character-ized by continuously marked but less proximal and lessaerial volcanic influence.

A singular episode occurred during this stage, espe-cially represented in Core 585-46. A continuous series ofclay minerals ranging from Mg-beidellite to Mg-chlorite,including chlorite-smectite irregular mixed layers and ex-pandable chlorite, indicates a change in the depositionalconditions, permitting the accumulation of magnesiumand the existence of prediagenetic transformations (Mil-lot, 1964). This mineralogical series suggests the tempo-rary development of a confined environment, in whichthe fixation of abundant magnesium on beidellites de-termined the progressive passage to pseudochloritic andchloritic minerals. Similar diagenetic modifications arebelieved to have occurred on the northwestern Africanmargin during the lower Mesozoic (Chamley and Debra-bant, 1983).

Stage 3, middle Albian to middle CampanianCores 585-40-26; Cores 585A-10-15

The Stage 2/Stage 3 boundary corresponds to the firststrong break recorded in the Site 585 bulk mineralogy,which correlates with the passage of volcanogenic heter-ogeneous sediments to claystones. The minerals typicalof a volcanic influence (augite, analcite) disappear, andare replaced by quartz, opal CT, and clinoptilolite. Smec-tites associated with minor amounts of true illite remainvery abundant, but are commonly not as well crystal-lized as in volcanogenic deposits and correspond to Si-rich alkaline types (Fig. 6). These data suggest a moredistant influence of volcanism, nevertheless still markedby the Na- to K-feldspars and by the Na2O-TiO2 corre-lation (Fig. 5).

The development of opal CT and of clinoptilolite in-dicates the importance of early diagenetic processes af-fecting the silica. Other in situ changes characterize thesmectites, which show a continuous series between fleecy,partly lathed, and completely lathed types. This evolu-tion has been recorded and interpreted in Cretaceous andPaleogene sediments of the North Atlantic (Holtzapffel

et al., 1985), and probably corresponds to an in situ re-crystallization of fleecy smectite to lathed smectite, with-out significant geochemical or mineralogical quantita-tive modifications. As a result, the third period identi-fied during the Cretaceous at Site 585 is characterized bya decrease of volcanic influence and an increase of earlydiagenetic processes, which chiefly affect silica-rich min-erals and smectites of distant origins.

Two recognizable periods occurred during Stage 3. Thefirst period (Cores 585-37-34, and 585A-10 to -9, lateAlbian to Cenomanian) is marked by fairly abundantpalygorskite and quartz, and by little kaolinite and trueillite. Palygorskite fibers are quite independent and mixedwith other minerals, and do not correspond to any spe-cific lithology. This level could reflect the reworking ofneritic basins undergoing a basic chemical sedimenta-tion (Millot, 1964; Weaver and Beck, 1977; Chamley,1979), perhaps contemporaneous with the tectonic sub-sidence of volcanic archipelagoes. It could also reflectthe supply of distant minerals by wind and marine trans-port, as recently shown in the Shatsky Rise area duringthe latest Cretaceous-earliest Paleogene (Lenötre et al.,in press). A third explanation could be the migration ofthe Mariana Basin across an arid climatic latitudinal zoneduring the northward movement of the Pacific Plate.Such a reworking points to a diversification of mineral-ogical sources and perhaps to the diminution of mor-phological barriers for distant supply.

The second period is evident at the top of Zone 3, inCores 27 and 26 (Campanian). The local increase of Fe,Mn, Na, K, and Ti as well as the temporary appearanceof some folded-smectites, probably of a dioctahedral type(Fe-beidellite) and highly crystallized, suggest a possiblerecurrence of a proximal volcanic influence. Such anevent, possibly having occurred elsewhere in the under-lying series and not recorded because of sparse recovery(Fig. 2), is also suggested by the Na2O-K2O association(Table 4). This association could indicate the presence ofNa-Ti amphiboles, well-known in West Pacific trachy-basalts or trachyandesites (Aoki, 1959). In spite of that,the sedimentation is marked by a more continental de-trital character than in the Aptian-Albian volcanogenicsediments, as shown by its more aluminous and less mag-nesian chemical composition (Fig. 6, Table 8).

Stage 4, late Campanian to MaestrichtianCores 585-20-17

The mineralogical diversification occurring during theuppermost Cretaceous (smectite, illite, palygorskite, ka-olinite, irregular mixed layers) correlates to a more alu-minous character of the geochemistry (D, Fig. 2) and tothe strong decrease of clay diagenetic modifications (abun-dance of fleecy smectites, rarity of partly lathed smec-tites). These data, together with the strong diminutionof volcanogenic markers (Ti, Fe, K, Na), point to thedevelopment of the terrestrial detrital character of sedi-mentation of very distant supply, broadly of pedogenicorigin, derived from Asiatic landmasses (e.g., Chamleyet al., in press). This major change in environmentalconditions probably resulted chiefly from the develop-ment of circulation, suggested by the oxidizing precipi-

425


tation of Mn (Mn*, Fig. 2; Debrabant and Foulon, 1979)and of Ti and Cu, and by the relative abundance of P ofbiogenic origin. Diagenetic effects persist locally only(opal CT, clinoptilolite), especially in the relatively morepermeable carbonate-rich levels. To summarize, the lastCretaceous stage corresponds to the development of de-trital input associated with developing circulation, dis-tant supply, and minor diagenetic modifications.

To conclude, the mineralogical, micromorphologicalstudy of DSDP Site 585 shows that from late Aptian toMaestrichtian a series of sedimentary regimes were suc-cessively dominated by volcanogenic, diagenetic, and ter-rigenous influences. The Mariana Basin first dependedon local supply, then progressively received more distantand diversified sedimentary contributions as a result ofthe submersion of volcanic archipelagoes, the subsidenceof submarine barriers, and the development of circulation.

ACKNOWLEDGMENTS

We gratefully acknowledge the U.S. National Science Foundation,the shipboard party of DSDP Leg 89, and especially S. O. Schlanger,M. Baltuck, and A. Schaaf for enabling us to work with Site 585cores. M. Bocquet, J. Carpentier, J.-C. Deremaux, F. Dujardin, A. LeMaguer, and P. Récourt provided very efficient technical assistance.Very pertinent and useful scientific comments were made by M. Bal-tuck, A. Desprairies, E. Suess, and J. Schoonmaker. Financial sup-port was provided by A. T. P. 1983 "Géologie et Géophysique desOceans" of C.N.R.S. (France).

REFERENCES

Aoki, K., 1959. Petrology of alkali rocks of the Iki Island and Hi-gashi-Matsuura district, Japan. Sci. Rept. Tohoki Univ., Ser. 3, 3:261.

Beutelspacher, M., and Van der Marel, M. W., 1968. Atlas of ElectronMicroscopy of Clay Minerals and Their Admixtures: Amsterdam(Elsevier).

Caillère, S., Henin, S., and Rautureau, M., 1982. Minéralogie desArgiles: Classification des Argues, (Vol. II): Paris (Masson).

Chamley, H., 1979. North Atlantic clay sedimentation and paleoenvi-ronment since the Late Jurassic. In Talwani, M., Hay, W., and Ry-an, W. B. F. (Eds.), Deep Drilling Research in the Atlantic Ocean:Continental Margins and Paleoenvironment. Maurice Ewing Ser.,Am. Geophys. Union, 3:342-361.

, 1981. Clay sedimentation and paleoenvironment in the Shi-koku Basin since the middle Miocene (Deep Sea Drilling ProjectLeg 58, North Philippine Sea). In Klein, G. deV., Kobayashi, K., etal., Init. Repts. DSDP, 58: Washington (U.S. Govt. Printing Of-fice), 669-681.

Chamley, H., Cadet, J.-P., and Charvet, J., in press. Nankai Troughand Japan Trench late Cenozoic paleoenvironments deduced fromclay mineralogical data. In Kagami, H., Karig, D. E., Coulbourn,W. T, et al., Init. Repts. DSDP, 87: Washington (U.S. Govt. Print-ing Office).

Chamley, H., and Debrabant, P., 1983. Heritage de minéraux méta-morphiques et diagenèse dans le Mésozoique inférieur de la margeAtlantique du Maroc. C. R. Acad. Sci., 296:651-656.

, 1984. Mineralogical and geochemical investigations of sed-iments on the Mazagan Plateau, northwestern African Margin,(Leg 79, Deep Sea Drilling Project). In Hinz, K., Winterer, E. L.,et al., Init. Repts. DSDP, 79: Washington (U.S. Govt. Printing Of-fice), 497-508.

Chamley, H., Debrabant, P., Candillier, A.-M., and Foulon, J., 1983.Clay mineralogical and inorganic geochemical stratigraphy ofBlake-Bahama Basin since the Callovian, Site 534, Deep Sea Drill-ing Project Leg 76. In Sheridan, R. E., Gradstein, F. M., et al., In-it Repts. DSDP, 76: Washington (U.S. Govt. Printing Office), 437-451.

Debrabant, P., and Chamley, H., 1982. Influences océaniques et con-tinentales dans les premiers depots de 1'Atlantique Nord. Bull. Soc.Geol. France, 7, XXIV, 3:473-486.

Debrabant, P., and Foulon, J., 1979. Expression géochimique des var-iations du paléoenvironnement depuis le Jurassique supérieur surles marges Nord-Atlantiques. Oceanologica Acta, 2, 4:469-475.

Deer, W. A., Howie, R. A., and Zussmann, J., 1963a. Rock-FormingMinerals: Chain Silicates (Vol. II): London (Longmans).

, 1963b. Rock-Forming Minerals: Sheet Silicates (Vol. Ill):London (Longmans).

Desprairies, A., 1981. Authigenic minerals in volcanogenic sedimentsarea during Deep Sea Drilling Project Leg 60. In Hussong, D. M.,Uyeda, S., et al., Init. Repts. DSDP, 60: Washington (U.S. Govt.Printing Office), 455-466.

, 1983a. Metamorphic processes in sediments in contact withyoung oceanic crust—East Pacific Rise, Leg 65. In Lewis, B. T. R.,Robinson, P. T., et al., Init. Repts. DSDP, 65: Washington (U.S.Govt. Printing Office), 375-389.

., 1983b. Relation entre le paramètre b des smectites et leurcontenu en fer et en magnesium. Application à Pétude des sedi-ments. Clay Minerals, 18:165-175.

Desprairies, A., Bonnot-Courtois, C , Jehanno, C , Vernhet, S., andJoron, J.-L., 1984. Mineralogy and geochemistry of alteration prod-ucts in Leg 81 basalts. In Roberts, D. G., Schnitker, D., et al., Init.Repts. DSDP, 81: Washington (U.S. Govt. Printing Office), 733-742.

Faure, G., 1978. Strontium abundance in common igneous rock types.In Wedepohl, K. H. (Ed.), Handbook of Geochemistry (Vol. II,4): Berlin (Springer-Verlag).

Grim, R. E., and Kulbicki, G., 1961. Montmorillonite high-tempera-ture reactions and classification. Am. Mineral., 46:1329-1369.

Hoffert, M., 1980. Les "argues rouges des grands fonds" dans le Paci-fique centre—Est. Authigenèse, transport, diagenèse. Sciences Géo-logiques, Mém., 61.

Holtzapffel, T., Bonnot-Courtois, C , Chamley, H., and Clauer, N.,1985. Heritage et diagenèse dans la constitution des smectitesNord-Atlantiques (Crétacé-Paléogène). Bull. Soc. Geol. France,l(8):25-33.

Holtzapffel, T., and Chamley, H., 1983. Morphologie et genèse desmectites albo-aptiennes et paléogènes de 1'Atlantique Nord: heri-tage et recristallisation. C. R. Acad. Sci., 296:1599-1602.

Lenötre, N., Chamley, H., and Hoffert, M., in press. Nature and sig-nificance of Sites 576 and 578 clay stratigraphy (Leg 86 DSDP,Northwestern Pacific). In Heath, G. R., Burckle, L. H., et al., In-it. Repts. DSDP, 86: Washington (U.S. Govt. Printing Office).

Mélières, F , Deroo, G., and Herbin, J.-P., 1981. Organic-rich and hy-persiliceous Aptian sediments from western Mid-Pacific Mountains,Deep Sea Drilling Project Leg 62. In Thiede, J., Valuer, T. L., etal., Init. Repts. DSDP, 62: Washington (U.S. Govt. Printing Of-fice), 903-921.

Millot, G., 1964. Géologie des Argiles: Paris (Masson).Moberly, R., Schlanger, S. O., et al., 1983. The Mesozoic superocean.

Nature, 302:381.Stueber, A. M., 1978. Strontium abundance in rock-forming minerals;

strontium minerals. In Wedepohl, K. H. (Ed.), Handbook of Geo-chemistry (Vol. II, 4): Berlin (Springer-Verlag).

Thiede, J., Dean, W. E., and Claypool, G. E., 1982. Oxygen-deficientdepositional paleoenvironments in the mid-Cretaceous tropical andsubtropical Pacific Ocean. In Schlanger, S. O., and Cita, M. B.(Eds.), Nature and Origin of Cretaceous Carbon-Rich Fades: Lon-don (Academic Press), pp. 79-100.

Weaver, C. E., and Beck, K. C , 1977. Miocene of the southeasternUnited Stages: a model for chemical sedimentation in a perimarineenvironment. Sediment. Geol., 17# Spec. Issue.

Weaver, C. E., and Pollard, L. D., 1973. The Chemistry of Clay Min-erals: Amsterdam (Elsevier).

Date of Initial Receipt: 11 May 1984Date of Acceptance: 7 November 1984

426


µ.m

'

1 µm

1 µm

Plate 1. Micromorphologic types of smectites. 1. Type 1: transparent smectites (Sample 585A-17-1, 15 cm, Zone 1, Aptian). 2. Type 2: hairysmectites (Sample 585-44-3, 17 cm, Zone 2, Albian). 3. Type 3: large folded smectites, probably indicative of a recurrent volcanic influence(Sample 585-26-1, 63 cm, Zone 3, Campanian). 4. Type 4: fleecy smectites (Sample 585-46-2, 40 cm, Zone 2, Albian). 5. Type 5: intermediatesmectite with fleecy and lathed outlines (Sample 585-44-3, 17 cm, Zone 2, Albian; detail from Plate 3, Fig. 4). 6. Type 6: isolated lathed smec-tites (Sample 585-44-3, 17 cm, Zone 2, Albian; detail from Plate 3, Fig. 4).

427


1 µm

0.5 µm

•

1 µm 1 µm

Plate 2. Other morphologic types. 1. Illite, Type 1: small celadonite chips (Sample 585A-15-5, 137 cm, Zone 1, Aptian). 2. Ilite, Type 2: typicalmicalike sheet (Sample 585-47-1, 9 cm, Zone 2, Albian). 3. Chlorite, Type 1: hexagonal sheet (with celadonite chips) (Sample 585-48-2, 4 cm,Zone 2, Albian). 4. Chlorite, Type 2: irregular dark and large sheet (ic) with fleecy smectite (fs) (Sample 585-46-2, 40 cm, Zone 2, Albian; detailfrom Plate 3, Fig. 2). 5. Palygorskite fibers, more or less broken (Sample 585-34-2, 85 cm, Zone 3, Cenomanian). 6. Small dark particles,with spiral shape, sometimes isolated, and sometimes constituting large aggregates (Al or Fe oxides?) (Sample 585A-17-1, 15 cm, Zone 2, Aptian).

428


1 µm

Plate 3. Examples of different morphologic clay assemblages. 1. Zone 1 assemblage: transparent smectites, celadonite chips (c), and hexagonalchlorites (he) (Sample 585-48-2, 4 cm, Zone 1, early Albian). 2. Zone 2 assemblage: fleecy and intermediate smectites (fs; is), true illites (i), andirregular chlorite (c) (Sample 585-46-2, 40 cm, Zone 2, early Albian; see detail on Plate 2, Fig. 4). 3, 4. Two assemblages with fleecy intermedi-ate and lathed smectites (Zones 2 and 3). 3. Sample 585-27-4, 57 cm, Zone 3, Campanian: fleecy smectites (fs) are more abundant than intermedi-ate ones (is); presence of opal (o). 4. Sample 585-44-3, 17 cm, Zone 2, Albian: lathed (Is) and intermediate smectites (is) are dominant. 5. Pecu-liar assemblage of Zone 3 with folded smectites: recurrence of volcanic influence (Sample 585-27-1, 13 cm, Campanian). 6. Zone 4, typical de-trital assemblage: fleecy smectites, true illites, and rare palygorskite fibers (Sample 585-17-2, 146 cm, Maestrichtian).

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