28. eolian deposition on the ontong java plateau …€¦ · vary if changes in atmospheric...

Berger, W.H., Kroenke, L.W., Mayer, L.A., et al., 1993Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 130

28. EOLIAN DEPOSITION ON THE ONTONG JAVA PLATEAU SINCE THE OLIGOCENE:UNMIXING A RECORD OF MULTIPLE DUST SOURCES1

Lawrence A. Krissek2 and Thomas R. Janecek3

ABSTRACT

The record of eolian deposition on the Ontong Java Plateau (OJP) since the Oligocene (approximately 33 Ma) has beeninvestigated using dust grain size, dust flux, and dust mineralogy, with the goal of interpreting the paleoclimatology andpaleometeorology of the western equatorial Pacific. Studies of modern dust dispersal in the Pacific have indicated that theequatorial regions receive contributions from both the Northern Hemisphere westerly winds and the equatorial easterlies; limitedmeteorological data suggest that low-altitude westerlies could also transport dust to OJP from proximal sources in the westernPacific. Previous studies have established the characteristics of the grain-size, flux, and mineralogy records of dust deposited inthe North Pacific by the mid-latitude westerlies and in the eastern equatorial Pacific by the low-latitude easterlies since theOligocene. By comparing the OJP records with the well-defined records of the mid-latitude westerlies and the low-latitudeeasterlies, the importance of multiple sources of dust to OJP can be recognized.

OJP dust is composed of quartz, illite, kaolinite/chlorite, plagioclase feldspar, smectite, and heulandite. Mineral abundanceprofiles and principal components analysis (PCA) of the mineral abundance data have been used to identify assemblages ofminerals that covary through all or part of the OJP record. Abundances of quartz, illite, and kaolinite/chlorite covary throughoutthe interval studied, defining a mineralogical assemblage supplied from Asia. Some plagioclase and smectite were also suppliedas part of this assemblage during the late Miocene and Pliocene/Pleistocene, but other source areas have supplied significantamounts of plagioclase, smectite, and heulandite to OJP since the Oligocene. OJP dust is generally coarser than dust depositedby the Northern Hemisphere westerlies or the equatorial easterlies, and it accumulates more rapidly by 1-2 orders of magnitude.These relationships indicate the importance of the local sources on dust deposition at OJP. The grain-size and flux records of OJPdust do not exhibit most of the events observed in the corresponding records of the Northern Hemisphere westerlies or theequatorial easterlies, because these features are masked by the mixing of dust from several sources at OJP. The abundance recordof the Asian dust assemblage at OJP, however, does contain most of the features characteristic of dust flux by means of the NorthernHemisphere westerlies, indicating that the paleoclimatic and paleometeorologic signal of a particular source area and wind systemcan be preserved in areas well beyond the region dominated by that source and those winds. Identifying such a signal requires"unmixing" the various dust assemblages, which can be accomplished by combining grain-size, flux, and mineralogic data.

INTRODUCTION

One of the major objectives of drilling on the Ontong Java Plateau(OJP) during Ocean Drilling Program (ODP) Leg 130 was to recoverand investigate long-term and detailed short-term records of paleocli-mate and paleoenvironments from an area that has remained in anear-equatorial setting through much of the Cenozoic (Kroenke, 1984;Kroenke, Berger, Janecek, et al., 1991). In pelagic depositional settingsof the oceans, especially those similar to OJP that are located onbathymetric highs, far from major land masses, and in low to midlatitudes (Fig. 1), eolian processes are the dominant supplier of ter-rigenous particles to the underlying sediments (Pewe, 1981; Prospero,1981; Pye, 1987; Chamley, 1989). These physical characteristics mini-mize the supply of terrigenous particles to OJP sediments by fluvialprocesses, ice rafting, and turbidity flows, leaving eolian processes asthe dominant source of terrigenous input. The recovery of a relativelycomplete post-Oligocene record on OJP provides the opportunity toinvestigate long-term changes in the records of dust grain size, massaccumulation rate (MAR), and mineralogy, and to interpret those datain terms of the paleoclimatology and paleometeorology of OJP and thesurrounding areas. This study examines the dust record from theOligocene (approximately 33 Ma) to the present; a companion study(L.A. Krissek and T.R. Janecek, unpubl. data, 1992) examines atemporally detailed Pliocene and Quaternary dust record.

1 Berger, W.H., Kroenke, L.W., Mayer, L.A., et al., 1993. Proc. ODP, Sci. Results,130: College Station, TX (Ocean Drilling Program).

2 Department of Geological Sciences, Ohio State University, Columbus, OH 43210,U.S.A.

3 Ocean Drilling Program, Texas A&M University, 1000 Discovery Drive, CollegeStation, TX 77845-9547, U.S.A.

The Oceanic Dust Record and Its Implications

Over the past several decades, three major characteristics of eoliancomponents in marine sediments have been examined in a number ofstudies: the mean dust grain size, the dust mass accumulation rate(MAR), and the dust mineralogy. Each of these characteristics re-sponds to a distinct set of geologic, climatic, and meteorologiccontrols; the potential importance of each control on a particularcharacteristic depends upon the temporal and spatial scales of therecord under study. For example, tectonically driven lithosphericplate motions have little effect on Quaternary dust records, but theybecome very important in understanding dust records that extendthrough the Cenozoic (Rea, 1989).

Because dust grain size, MAR, and mineralogy respond to anumber of environmental and climatic conditions that exist at the timeof dust formation, transport, and deposition, these characteristics ofancient dust components in marine sediments have been widely usedto infer paleoclimatologic and paleometeorologic histories. For ex-ample, the mean grain size has been used as a proxy for wind intensity,with an increase in grain size interpreted to record a general increasein wind strength (Parkin, 1974; Parkin and Padgham, 1975; Janecekand Rea, 1985; Clemens and Prell, 1990). A quantitative relationshipbetween wind intensity and dust grain size has not been well resolved,however. Wind intensity can change on short time scales (10-100 k.y.)in response to hemispheric or global climate (e.g., glacial/interglacialcycles), and on longer time scales (>500 k.y.) in response to changesin global climate and global paleogeography (e.g., opening or closingof oceanic "gateways"; Kennett, 1982).

Dust MAR is generally used as a proxy for aridity in the continen-tal source area of the dust (see discussion in Rea [1989] and referencestherein), with an increase in the MAR interpreted to record increased

471

L.A. KRISSEK, T.R. JANECEK

,v Ontong Java'--V.' V x \ ' x \ N x ! ' ! / } \ I \ ' ^ v \

\ Hess Rise —

Ontong Java\ Plateau M a g e l l a n R l s e

Manihiki p\Plateau i )

155° 160°

Figure 1. Location map of the Ontong Java Plateau and the Leg 130 sites.

aridity. More recently, however, Pye (1989) has demonstrated that dustwill become more available in a source area as the climate changeseither from semiarid to arid (increasing aridity) or from hyperarid toarid (decreasing aridity). The dust flux at a particular location can alsovary if changes in atmospheric circulation patterns result in a differentsource area supplying dust to that site. On short time scales (10-100k.y.), atmospheric circulation patterns may respond to changes inhemispheric or global climate (e.g., glacial/interglacial cycles),whereas circulation patterns respond on longer time scales (>500 k.y.)to tectonic events such as mountain building (Rea, 1989). An additionalcomplication in interpreting a long time-scale record of dust MAR isthat lithospheric plate motions can move a site from the influence ofone major wind belt into the influence of a second major wind belt; ifthe climates are significantly different in the upwind continental sourceregions for the two wind belts, then a change in dust MAR will reflectthe migration history of the site, as well as changing climate within asource region or changing wind patterns.

The mineralogy of the total dust component is determined by thelithologies and weathering conditions present in the continentalsource regions (a response to source characteristics), the grain size ofthe dust (a response to wind strength), and the relative importance ofdust contributed from each potential continental source (a responseto source aridity and wind patterns). Most studies of dust mineralogyto date have minimized the effect of grain size by examining only thefinest fraction (grains with diameter <2 µm), although Krissek andClemens (1991) examined the mineralogy of the total dust componentat ODP Site 722 in the Arabian Sea. Studies of the total dust compo-nent (Krissek and Clemens, 1991) and the fine dust (<2 µm; Debra-bant et al., 1991) in Arabian Sea sediments identified similar dustsources, although the presence of tectosilicates and carbonates in thetotal dust provided additional information about lithologies and loca-tions of the source areas. Changes in dust mineralogy on short timescales (10-100 k.y.) have generally been interpreted to record gla-cial/interglacial effects on either weathering conditions or source-areaimportance (aridity changes or wind pattern shifts; Leinen, 1989;Krissek and Clemens, 1991). Mineralogic changes on longer timescales (>500 k.y.) have generally been interpreted to record changesin one or more of the following: outcrop geology of the source areascaused by erosion, volcanism, or orogeny; source-area importancecaused by global shifts in climate or atmospheric circulation; andsource-area importance caused by migration of a site out of the

140° 160° 180° 160°

influence of one wind belt and into the influence of another (e.g.,Schramm, 1989).

The Ontong Java Plateau and Its Geologic Setting

The OJPpresently extends from approximately 5°N to 9°S latitude(Kroenke, Berger, Janecek, et al., 1991), thereby lying under theinfluence of the northeasterly and southeasterly trade winds (Teradaand Hanzawa, 1984). Sites occupied during ODP Leg 130 wereconcentrated on the northern edge of OJP, at latitudes of F ^ ° N . Thegeologic history of OJP and the surrounding areas is summarized byKroenke (1984); of particular concern here is its history of litho-spheric plate migrations, because those migrations may have placedOJP under the influence of several different wind regimes during thepast 30 m.y. Hammond et al. (1975) used paleomagnetic data fromDSDP Site 289 to demonstrate that OJP migrated northward at a rateof approximately 2.5 cm/yr between 70 and 30 Ma, moving fromapproximately 10°36'S at 70 Ma to an equatorial position at 30 Ma.The data from Site 289 do not provide information about OJP migra-tion history since 30 Ma, but other studies (van Andel et al., 1975)have established a similar migration rate for the central Pacific since30 Ma. Tectonic reconstructions by Yan and Kroenke (this volume)show that OJP has been located north of 10°S since 30 Ma (Fig. 2).Although the exact details of OJP migration over the past 30 m.y. arenot clear, OJP does appear to have remained within the realm of themodern-day trade winds throughout the time interval considered inthis study.

Modern Meteorology and Dust Characteristicsof the Pacific

The grain-size, MAR, and mineral/chemical compositions ofmodern aerosols and ancient dust of the Pacific, Atlantic, and Indianoceans have been examined in a number of studies; recent summariesof this work include Pewe (1981), Prospero (1981), Pye (1987),Chamley (1989), and Leinen and Sarnthein (1989). Of particularinterest here is information about dust in the Pacific Ocean that canbe used to interpret the dust records from OJP. The composition andflux of modern dust and its effect on the underlying sediments are bestknown from studies of material collected in the North Pacific andequatorial Pacific regions (Rex and Goldberg, 1958; Prospero and

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EOLIAN DEPOSITION ON ONTONG JAVA PLATEAU

Bonatti, 1969; Rex et al., 1969; Windom, 1969; Duce et al., 1980;Blanket al., 1985;Uematsuetal., 1985; Arimotoetal., 1987;Prosperoet al., 1989). The dispersal trajectories of the dust have been mappedfrom satellite observations and meteorological data (Merrill, 1989;Merrill et al., 1989). Taken together, these studies have demonstratedthat dust derived from central Asia and transported within the tropo-sphere by the prevailing westerlies is the predominant terrigenouscomponent in surface sediments of the North Pacific; this dust ispredominantly supplied during the spring, when storms most activelyraise dust in the arid regions of central Asia. Dust trajectory studiesby Merrill (1989) and Merrill et al. (1989) have demonstrated that theinfluence of Asian dust can extend southward into the zone of thenortheast trade winds, and that low concentrations of Asian dust mayeven cross into the Southern Hemisphere. This distribution developsas Asian dust, initially carried eastward by strong flow in the tropo-sphere, is entrained around subtropical anticyclones and descendsinto the surface trade winds. The implication of this transport path forour studies of OJP dust is that material derived from Asia can besupplied to the western equatorial Pacific, as demonstrated by thepredominance of Asian dust in aerosols collected at Enewetak (11 °N,162°E;DuceetaL, 1980).

Less information is available about dust transported solely withinthe equatorial easterlies, although Prospero and Bonatti (1969) re-ported spring dust concentrations over the eastern equatorial Pacificapproximately equal to those from the equatorial mid-Pacific(Prospero, 1979). The sources for this dust were interpreted to be thedeserts of northern Chile and Peru (for the southeast trades) andsouthwest Mexico (for the northeast trades). Arimoto et al. (1987)reported that the dust concentrations at American Samoa (14°S,170°W) were between 1% and 10% of the Asian-dominated dustconcentrations at Enewetak, and that they exhibited little seasonalvariability. These data suggest that only a small amount of dust istransported from the Americas to the vicinity of OJP by the equato-rial easterlies.

Direct studies of atmospheric aerosols and their dispersal pathshave not been conducted on OJP, but additional dust may be suppliedto OJP from nearby sources by variable near-surface winds. Forexample, Terada and Hanzawa (1984) state that equatorial westerliesare sometimes observed at elevations below 5 km, and provide windroses for surface winds in the tropics during January, May, andSeptember. In the vicinity of OJP, the wind roses for January and Mayare dominated by flow from the east and northeast; the wind rose forSeptember, however, also shows components of flow from the southand west. These winds could be responsible for transporting dust toOJP from the volcanic arc rocks exposed in New Guinea and theSolomon Islands.

The Geologic Record of Dust Deposition in the Pacific

Several good long-term records of atmospheric circulation areavailable from the North Pacific, including those from LL44-GPC3(JanecekandRea, 1983;Schramm, 1989) and DSDP Sites 576 and 578(Janecek, 1985; Schoonmaker et al., 1985; Leinen, 1985; LeNotre etal., 1985; Rea et al., 1985; Schramm, 1989); these findings have beensummarized by Rea (1989). Leinen (1989) has also presented usefulinformation about the composition of dust supplied to the North Pacificfrom three different source areas during the late Quaternary. From thesestudies, the dust record of the Northern Hemisphere westerlies sinceapproximately 33 Ma can be characterized as follows:

1. Dust MAR increases gradually through much of the Neogene,with well-defined increases at LL44-GPC3 and Site 576 at approxi-mately 21-23, 15-16, 8, and 5 Ma. All records of the NorthernHemisphere westerlies exhibit a significant increase (as much as 1order of magnitude) in MAR at approximately 2.4 Ma, which isattributed to the onset of Northern Hemisphere glaciation. This over-

all pattern is explained as recording the general increase in Neogenearidity that accompanied polar cooling (Rea, 1989).

2. Dust grain size increases gradually from the Oligocene to theHolocene, with well-defined increases at LL44-GPC3 and Site 576at approximately 30-37, 10-20, and 5 Ma. Grain size increases onlyslightly at the onset of Northern Hemisphere glaciation. This overallpattern is explained as recording a general increase in wind intensityaccompanying the development of steeper thermal gradients throughthe Neogene.

3. Dust mineralogy includes quartz, illite, smectite, chlorite, pla-gioclase feldspar, and kaolinite. Within upper Quaternary sediments(Leinen, 1989), an illite-smectite-quartz assemblage was derivedfrom loess in central Asia, a plagioclase-quartz-smectite-chloriteassemblage contains material derived from Asia and mixed with soilmaterial from Japan, and an illite-chlorite-plagioclase assemblagewas derived from northern Asia. Older sediments in the North Pacificgenerally have mineralogies much like that of the upper Quaternarydeposits, although clay-sized material carried by the westerlies ap-pears to have changed from relatively kaolinite/quartz-rich in thePaleogene to relatively plagioclase/chlorite/illite-rich in the Neogene(Schramm, 1989).

The record of dust transported by the northeasterly trades duringthe Cenozoic has not been examined in much detail. Clays andassociated minerals in sediments at DSDP Site 462 in the Nauru Basininclude mixed-layer clays, chlorite, and some kaolinite, quartz, andfeldspar; the influence of nearby volcanism is recorded by the pres-ence of volcaniclastic grains, Fe-rich smectite, and clinoptilolite(Kurnosov and Shevchenko, 1981). Older sediments recovered atsites further to the north record activity of the easterlies before theMiocene and indicate that the easterlies consistently supplied less dustthan the westerlies (Janecek and Rea, 1983; Janecek, 1985). On thebasis of limited data, Schoonmaker et al. (1985) conclude that dustsupplied by the easterlies to sediments at DSDP Site 576 beforeapproximately 20 Ma was relatively quartz-poor and smectite-rich.

Long-term records of the activity of the southeast trade winds wereexamined at DSDP Sites 597-602, located on the flank of the EastPacific Rise (Bloomstine and Rea, 1986), and at Site 595 in the centralSouth Pacific (Schramm and Leinen, 1987). Dust MARs in both areasare much lower than those in the North Pacific and are relativelyuniform from the Oligocene to the present. Dust grain size at Site 598increases in sediments younger than approximately 10.5 Ma, a changeattributed to wind intensification that accompanied formation ofAntarctic ice. None of these records from the Southern Hemisphereexhibit the marked changes in MAR or grain size found in Pliocene-Pleistocene sediments of the North Pacific.

METHODS

The samples for this study were taken from Holes 803D, 805B,and 8O5C at an interval of approximately 4.5 m (two samples percore). Several studies (Gillette, 1974; Gillette et al., 1974; Gillette andWalker, 1977; Johnson, 1976, 1979) have demonstrated that the dustpopulation in transport reaches equilibrium at a distance of approxi-mately 1000 km from the dust source; because OJP lies beyond thatdistance from potential sources, the effects of differential dust trans-port to these two sites on OJP are considered to be minimal, and therecords from these three holes were combined for this study. Thesamples from Hole 803D provided material with ages of approxi-mately 0-14.8 and 19.4-34.1 Ma; samples from Hole 805B were usedto examine the record at 14.1-22.7 Ma; and the samples from Hole8O5C supplemented the Hole 8O3D samples over the age range from23.1 to 29.4 Ma (Appendix A). The samples were taken from thenannofossil ooze/chalk to foraminifer nannofossil ooze/chalk thatforms lithologic Unit I at each of the respective holes (Kroenke,Berger, Janecek, et al., 1991).

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140 150 160 180 -170 -160 -150 -140

Figure 2. Tectonic reconstructions of the western equatorial Pacific at 30 Ma (A) and 0 Ma (B) (from Yan and Kroenke, this volume). The Ontong Java Plateauwas located near the equator throughout the past 30 m.y., in the region influenced by the modern equatorial easterlies.

Terrigenous Abundance

The abundance of terrigenous material was determined by isolat-ing the detrital mineral component through a series of chemicalextractions and weighing it. The eolian component is isolated bytreating the samples successively with buffered acetic acid to removecalcium carbonate; with buffered sodium dithionite-sodium citrate toremove iron oxides and hydroxides; with sodium hypochlorite toremove organic material; and with sodium carbonate to removebiogenic opal. The procedure is outlined in detail in Rea and Janecek(1981). These extractions, however, do not remove volcano-genie components.

Eolian Grain Size

Grain-size analysis of the eolian component was conducted on the1-28 µm size fraction using an eight-channel Laser Sensor Technol-ogy, Inc., Lab-Tec 100ME particle-size analyzer. The Lab-Tec 100MEsweeps a focused laser beam at a constant velocity across particlessuspended in a solution. The "transit time" of the beam across a

particle is measured and is a function of the size of the particle.Complete information about the unit and the methodology used in thisstudy are provided in Mazzullo and Graham (1988).

Mineralogy

The mineralogy of the eolian component was analyzed by powderx-ray diffractometry (XRD), using the general procedures outlinedby Krissek (1989). Approximately 100 mg of the bulk residue thatremained after the chemical extractions were weighed and mixedwith 10% by weight boehmite (A1OOH), which serves as an internalstandard. The mixtures were back-loaded as powders into randommounts for XRD analysis. All slides were solvated with warmethylene-glycol vapor for 8-12 hr immediately preceding analysison a Philips diffractometer. Slides were scanned at a rate of 1 ° 2θ/minwith Ni-filtered CuK-alpha radiation. Data were plotted on a strip-chart recorder.

The 15-18 Å smectite (001), 10 Å illite (001), 7 Å chlorite/kaolin-ite (002/001), 6.11 Å boehmite (020), 4.26 Å quartz (100), 4.02 Åplagioclase (201), and 3.04 Å calcite (104) peaks were measured with

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140 150

Figure 2 (continued).

160 170 180 -170 -160 -140

a digitizing polar planimeter. The generally low intensity of thekaolinite/chlorite peak precluded further distinction of individualkaolinite and chlorite abundances. In addition to these peaks, whichhave been used successfully to indicate mineral abundances inprevious studies (Krissek, 1984,1989; Krissek and Clemens, 1991),three other peaks were also measured on these diffractograms. Thefirst, a broad peak located at 4.66^4.13 Å, ranged from dominant topoorly defined on the diffractograms. When well defined, this peakwas centered at approximately 4.38 Å and tentatively identified asthe (401) diffraction of the zeolite heulandite. This identificationmust be considered tentative, however, because other heulanditepeaks that are generally more intense than this peak were not presenton the diffractograms.

Two other peaks were also measured because the broad heulanditepeak sometimes interfered with the 4.26 Å quartz and 4.02 Å plagio-clase peaks. These are the 3.34 Å quartz (101) and 3.18-3.20 Åplagioclase (002) peaks, which are not commonly used as indicatorsof mineral abundance because of interference with diffraction peaksof illite and potassium feldspar (K-feldspar), respectively. In thissample set, however, the low average intensity of the 10 Å illite peakand the general correlation between higher intensity values of the two

quartz peaks (Fig. 3A) indicate that the intensity of the 3.34 Å peakis a valid indicator of quartz abundance. In a similar manner, theabsence of other K-feldspar peaks and the general correlation betweenhigher intensity values of the two plagioclase peaks (Fig. 3B) indicatethat the intensity of the 3.18-3.20 Å peak is a valid indicator ofplagioclase abundance.

By adding a uniform concentration of boehmite to all samples, theratio of mineral peak area to boehmite peak area can be used tocompare the abundance of a particular mineral between samples.These mineral/boehmite peak area ratios cannot be converted toabsolute mineral abundances, however, so that the absolute abun-dances of two or more minerals cannot be compared. Analyticalprecision was evaluated by analyzing replicate slides of ten samples,and estimated uncertainties are presented in Table 1.

Definition of Mineral Assemblages

Previous mineralogical studies of the fine-grained terrigenousfraction of marine sediments have demonstrated the usefulness ofprincipal components analysis (PCA, or "factor," analysis) for defin-ing assemblages of minerals that covary through all or part of the

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Quartz 1/boehmite Plagioclasβ 1/Boβhmitβ

Figure 3. Scatter plots of XRD peak intensities. A. 4.26 quartz peak (Ql) vs. 3.34 quartz peak (Q2). B. 4.02 plagioclase (PI) vs. 3.18-3.20 plagioclase peak (P2).

interval under study (Leinen, 1989; Krissek and Clemens, 1991). Theadvantage of defining such assemblages is that the provenance of apolymineralic assemblage is generally more distinctive than theprovenance of a single mineral (e.g., quartz). In this study, the PCAprocedure available on "Data Desk" (Velleman and Velleman, 1988)was used to define assemblages of covarying minerals. This proce-dure extracts principal components ("factors") from the matrix ofcorrelations between variables, thereby giving equal weight to eachvariable in the analysis. The factor matrix generated by a PCA iscomposed of coefficients whose magnitudes indicate the relativeimportance of each variable (mineral) within that factor (mineralassemblage). Differences in sign (positive vs. negative) of the factormatrix coefficients for two variables within a factor indicate a patternof inverse correlation for those two variables. The PCA procedure on"Data Desk" does not provide coefficients that indicate the impor-tance of each factor on individual samples; for this reason, strati-graphic profiles showing the importance of each factor downhole arenot presented here.

Factor analysis was conducted on the entire OJP data set to defineassemblages of minerals that covary throughout the time intervalstudied. Factor analysis was also conducted on mineral data fromthree subdivisions of the OJP record to investigate potential changesin the mineral assemblages through time. The boundaries of the timeintervals chosen (0-5, 7-17, and 17-34 Ma) were selected to (1)correspond with changes in the patterns of variation in the OJPmineral abundance profiles, (2) correspond with times of majorchange defined previously in studies of dust grain size and MARelsewhere in the Pacific, and (3) avoid covariations that are artificiallyinduced by an interval of incomplete calcite removal in OJP sediments5-7 m.y. old. To prevent analytically questionable data points fromstrongly affecting the factor analysis results, all mineral/boehmiteratios >5 standard deviations from the mean for that mineral wereremoved before the factor analysis was performed.

Linear Sedimentation Rates

Linear sedimentation rates at Sites 803 and 805 were calculatedfrom paleomagnetic and biostratigraphic datums reported in Kroenke,Berger, Janecek, et al. (1991). The datums, their positions in each hole,and the resulting sedimentation rates are listed in Table 2 and illustratedin Figures 4 and 5. At Hole 803D, these include 2 paleomagneticdatums and 11 biostratigraphic datums; the resulting sedimentationrates range from a minimum of 1.6 m/m.y. at 14.9-19.5 Ma to amaximum of 30.3 m/m.y. at 21.8-23.7 Ma. At Site 805, datums fromthe depth intervals of interest in Holes 805B and 8O5C were combined;

the resulting data set consisted of four biostratigraphic datums, whichgave sedimentation rates ranging from 13 to 21.3 m/m.y. for the periodfrom 13.6 to 28.2 Ma. Sample ages (Appendix A) were calculated bylinear interpolation of the appropriate sedimentation rates.

Mass Accumulation Rates

To calculate the mass accumulation rate (MAR) of the sediment,the actual dry mass of sediment per unit volume was multiplied bythe linear sedimentation rate. Dry-bulk density values for this sampleset were interpolated from shipboard physical properties data forSites 803 and 805 (Kroenke, Berger, Janecek, et al., 1991), and theresulting MARs are plotted in Figure 5 and listed in Appendix A.

RESULTS

Eolian Mass Accumulation Rates

The abundance of terrigenous material ranges from 2% to 14%in sediments deposited since 34 Ma at Sites 803 and 805, with anaverage value between 4% and 5% (Fig. 5). The mineralogic datapresented below, however, indicate that sample pretreatment did notremove all of the calcite in the youngest sediments, especially those4.85-7.6 m.y. in age. As a result, the peak in terrigenous abundanceat 5-8 Ma is an artifact and does not indicate a real increase interrigenous content.

Most of the terrigenous abundance values range from 4% to 8%,whereas the bulk MAR values respond directly to changes in thesedimentation rate and range from essentially 0 to almost 4 g/cm2/k.y.(Fig. 5). The terrigenous MAR is the product of the bulk MAR and theterrigenous abundance; because the bulk MAR varies by more than afactor of 10 whereas the terrigenous abundance varies by much less,the terrigenous MAR closely follows the trend of the bulk MAR plot.Terrigenous MARs were generally between 100 and 300 mg/cm2/k.y.in the Oligocene to early Miocene, with highest values at approxi-mately 31-28 and 24-22.5 Ma. Terrigenous MARs decreased duringthe early Miocene, particularly from 24 to 21 Ma, and they haveremained generally <IOO mg/cm2/k.y. since 20 Ma. The apparent peakin terrigenous MAR centered at approximately 6 Ma is an artifact ofincomplete calcite removal during sample processing.

Eolian Grain Size

The average grain size of the eolian component ranges from 5 to13 µm at Sites 803 and 805 (Fig. 5). Grain size averages between 8and 9 µm in Oligocene and lower Miocene sediments (34-21 Ma),

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Table 1. Estimates of analytical uncertainty inmineral abundance ratios.

Table 2. Age datums, their depths, and resultantsedimentation rates at Holes 803D, 805B, and 805C.

Mineral

SmectiteIffiteKaolinite/ChloriteHeulanditeQuartzPlagioclaseQuartzPlagioclaseCalcite

Diffractionpeak(Å)

14-171074.384.264.023.34

3.18-3.203.04

Uncertainty

±0.9±0.02±0.15±1.2±0.16±0.13±0.17±0.25±0.04

Note: Values average absolute uncertainties in the mineral/boehmite peak area ratios, based on replicate analyses often samples.

decreases to approximately 7 µm in the lower to middle Miocene(21-10 Ma), and increases to an average of approximately 10 µm inupper Miocene and younger sediments (10-0 Ma). The incompleteremoval of calcite during pretreatment of the 5-8 Ma samples doesnot have an obvious effect on the grain-size signal for that interval.

Mineralogy of the Eolian Component

Mineral/boehmite peak area ratios are plotted in Figure 6 and listedin Appendix B. High calcite/boehmite ratios (Fig. 6A) are concentratedin the interval 5-8 Ma, reflecting incomplete calcite removal duringsample pretreatment. Other non-zero values are scattered throughoutthe remainder of the profile, but calcite abundances significantly diluteabundances of the other minerals only in the interval 5-8 Ma.

Smectite has the largest average mineral/boehmite peak area ratioof the minerals identified in this study (Fig. 6B); the smectite/boehmite ratio is consistently larger than 2 and averages between 4and 5 for the entire data set. The smectite record shows no long-termtrend, but it does exhibit several shorter term excursions in the lowerto middle Miocene that are larger than the analytical uncertainty. Themost obvious of these excursions is the short-lived increase in smec-tite content in the middle Miocene, centered at approximately 14 Ma.

The record of heulandite (zeolite) abundance (Fig. 6C) exhibits arelatively uniform baseline value, with higher abundances scatteredthroughout the interval studied. The higher abundances appear to clus-ter in the lower Oligocene (32-29 Ma), the lower to middle Miocene(23-14 Ma), and the upper Miocene to upper Pliocene (7-2 Ma).

The two records of plagioclase/boehmite peak area ratios (Figs.6D-6E) are similar through most of the section studied but exhibitslightly different patterns in the youngest sediments. Both plagioclaserecords are high in the Oligocene and decrease into the lower Miocene(approximately 20 Ma). In both records, however, this general de-crease is interrupted by significantly increased plagioclase content inthe upper Oligocene (approximately 27 Ma). Plagioclase abundancesremain consistently low from the lower Miocene to at least the lowerPliocene. In sediments younger than the lower Pliocene, the 3.18 Åplagioclase contents increase significantly, whereas the 4.02 Å pla-gioclase record shows no significant change over the same interval.Because of the greater intensity of the 3.18-3.20 Å plagioclase peakand reduced interference effects on it relative to the 4.02 Å peak, theincrease in plagioclase content since the early Pliocene is consideredto be real.

The two records of quartz/boehmite peak area ratios (Figs. 6F-6G)are very similar throughout the section studied. Quartz abundance islow in the Oligocene and increases gradually through the upperOligocene and lower Miocene to a maximum in the middle Miocene(approximately 15 Ma). Quartz abundances then decrease through theremainder of the middle Miocene and part of the upper Miocene,before increasing dramatically (by a factor of approximately 4)

Event

Hole 803D:Top sectionOlduvai (0)Mammoth (O)LO D. quinqueramus (N)LO D. hamatus (N)FO G. peripheroacuta (F)LO T. carinatus (N)FO 5. Belemnos (N)LO G. kugleri (F)FO G. kugler (F)LO G. opima (F)LO E. formosus (N)FO D. hesslandii (N)

Holes 805B and 805C:LO S. heteromorphus (N)LO S. belemnos (N)LO G. Kugleri (F)LO G. opima (F)

Depth(mbsf)

0.0017.6036.5069.85

174.35239.15246.60255.50260.30317.85346.80519.95606.70

325.00393.00441.00577.00

Age(Ma)

0.01.93.25.08.7

14.919.520.021.823.728.240.042.9

14.019.022.028.0

LSR(cm/k.y.)

9.414.518.328.210.51.6

17.82.7

30.36.4

12.97.2

1.31.62.1

through the Pliocene and Quaternary. The dilution effect of abundantcalcite in the samples from the interval 5-8 Ma obscures the exactposition of the quartz minimum in the upper Miocene, but bothrecords clearly indicate a change in that time from decreasing toincreasing quartz abundances.

The record of kaolinite-chlorite/boehmite peak area ratios (Fig. 6H)is rather noisy, with the section older than approximately 5 Ma char-acterized by single-point peaks rising above a background value ofzero. Kaolinite/chlorite abundances are generally higher in the Plio-cene and Quaternary section (younger than 5 Ma), although the effectsof dilution by calcite in slightly older sediments may obscure anincrease in kaolinite/chlorite abundance defined in the upper Miocene.The only other significant increase in kaolinite/chlorite abundance bymultiple data points is a maximum at 13-15 Ma, which may result fromanomalously small boehmite peaks on those diffractograms.

Illite was not identifiable on the majority of diffractograms, al-though samples that contain illite are scattered throughout the intervalstudied (Fig. 61). Illite-bearing samples cluster near the lower/upperOligocene boundary (approximately 31 Ma) and in the lower Miocene(21-18 Ma); illite abundances are consistently high in Pliocene andQuaternary samples (younger than 5 Ma), with a marked increase inillite abundance over the past 1.5 m.y. As with the records of quartzand kaolinite/chlorite, illite contents may actually begin to increaseduring the upper Miocene, but calcite dilution in the interval from 5to 8 Ma obscures any potential signal of that age.

DISCUSSION

Mineralogy of Eolian Componentsat Ontong Java Plateau

The eolian component in sediments of Oligocene to Quaternaryage on the OJP consists of smectite, irlite, kaolinite/chlorite, quartz,plagioclase, and heulandite (zeolite). This mineral assemblage isconsistent with terrigenous assemblages reported previously in mod-ern and ancient sediments of the North Pacific and the equatorialPacific. As discussed in the "Introduction" section (this chapter),previous studies have attributed the transport of these various com-ponents to the Northern Hemisphere westerlies, the northeasterlytrades, the southeasterly trades, and variable local winds, all of whichcan supply dust to OJP. For this reason, the presence/absence of anindividual mineral cannot be used a unique indicator of both dustsource and transport path; instead, OJP dust provenance is interpretedfrom two separate lines of evidence:

477


600 -

10 20 30Age (Ma)

40

B o

100 -

200 -

300 -

C 250

300 -

350 -

400 "

I.

I.

-

-

I1 '

DD

' 1 ' 1 ' 1

%

• i

®(D

i ' i

CD

i • i •

-

-

(Dm. I . I .

450 "

500 "

550 -

6008 10 12 14 16 18 20 22 24 26 28 30

Age (Ma)

Figure 4. Age/depth plots for Holes 803D (A), 805B (B), and 805C (C). Datumsare from Kroenke, Berger, Janecek, et al. (1991). Circles = nannofossils, squares= foraminifers, diamonds = diatoms, triangles = radiolarians, and crosses =magnetostratigraphic reversal boundary. Symbol size approximates sampleinterval uncertainty. Selected subsets of these datums were used to determinethe sedimentation rates shown in Table 2, Appendix B, and Figure 5.

1. Assemblages of minerals that covary on O JP are identified, bothby examining the abundance records of individual minerals and byconducting factor analysis of the mineral abundances (Table 3). Theseassemblages are then compared with assemblages that have beenclearly linked to known source regions and wind transport paths byother studies, to identify potential source regions.

2. Temporal variations in the abundances of the OJP mineralassemblages are compared with well-established temporal records ofdust MARs deposited beneath the various major wind belts. A windregime is interpreted to have transported the OJP mineral assemblageif the mineral assemblage and dust MAR exhibit correlative tem-poral variations.

Definition of Dust Assemblages at Ontong Java Plateau

The mineral abundance data presented in Figure 6 and discussedin the "Results" section (this chapter), as well as Fl of PCA1 (Ta-ble 3), suggest that quartz, illite, and kaolinite/chlorite covary throughthe entire interval examined on OJP. This pattern of covariation isclearly expressed in the smoothed profiles of generalized abundancesshown in Figure 7. Each of these minerals has relatively low abun-dances in the Oligocene and lowest Miocene, and each exhibits a peakin the lower-mid Miocene. For illite, this peak is located at 21-18 Ma,whereas the major Miocene peak for quartz is located at 13-16 Ma.Each of these minerals has low abundances for the remainder of themiddle and upper Miocene, and then increases to maximum values inthe Pliocene and Quaternary. Calcite dilution in the interval 5-8 Mamay obscure the time when each mineral abundance first began toincrease but should not affect the general pattern described here, sincemaximum abundances of each mineral are clearly located in sedi-ments younger than 5 Ma.

Plagioclase and smectite abundances also covary with the abun-dance of quartz/illite/kaolinite/chlorite, although the patterns of co-variation change significantly through the interval considered (Fig. 7and Table 3). The marked increase in plagioclase abundance duringthe Pliocene and Quaternary closely resembles the correlative in-creases in quartz/illite/kaolinite/chlorite abundances, suggesting theinput of a quartz/illite/chlorite/kaolinite/plagioclase assemblage dur-ing the Pliocene and Quaternary (and possibly the latest Miocene).Fl of PCA2 also reflects this association, identifying an importantsmectite/illite/quartz/plagioclase assemblage that is not distinguishedin older sediments. Plagioclase abundances continue to covary withquartz/illite abundances to approximately 17 Ma (Fl of PC A3), andcorrelate with quartz to some extent in sediments older than 17 Ma(Fl of PCA4). A significant proportion of the plagioclase and quartzvariations are inversely correlated in sediments older than 17 Ma,however, as indicated by F2 of PCA4. This change is obvious inFigure 7, where plagioclase abundances generally decrease from theOligocene to the Miocene whereas quartz abundances increase. Thischange from strong covariation to a combination of positive andinverse covariation supports three conclusions:

1. Additional plagioclase was supplied to OJP independent of thequartz/illite/chlorite/kaolinite/plagioclase assemblage before themiddle Miocene.

2. The independent source of plagioclase was an important sup-plier of plagioclase to OJP during the Oligocene and earliest Miocene.

3. The importance of the independent source of plagioclase gradu-ally decreased relative to the source of the quartz/illite/chlo-rite/kaolinite/plagioclase assemblage from the Oligocene through theearly to middle Miocene.

Smectite's consistently high background abundance suggests theeffect of a significant independent source of smectite throughout theinterval studied. This interpretation is supported by the results ofPCA1 (Table 3), which identifies a monomineralic F3 as the majorsource of variations in smectite abundance. The strongest association

478


A Sedimentation rate (cm/k.y.) Terrigenous material (%)

2 4 6 8 10 12 14

Terrigenous MAR (mg/cm2/k.y.)

0 100 200 300 400 500

Terrigenous size (µm)4 6 β 10 12 14

1 2 3 4

Bulk MAR (g/cm=/k.y.)

BSedimentation rate (cm/k.y.)

1.0 1.5 2.0 2.5 3.0

"Sriigenous material (%)

0 2 4 6 β 10

2 3

Bulk MAR (g/cm2/k.y.)

Terrigenous MAR (mg/cm2/k.y.)

100 200 300

Terrigenous size (µm)

Figure 5. Linear sedimentation rates, bulk mass accumulation rates, terrigenous mass accumulation rates, and terrigenous grain size datafor Sites 803 (A) and 805 (B). Control points for sedimentation rates are presented in Table 2. The data used to construct these figures arepresented in Appendix A.

479


A Calcium/Boehmitθ (803) B

0 5 10 15

Smβctitθ/Boθhmitθ (803)

0 5 10 15

Zθolitθ/Boehmitθ (803)

0 5 10 15

5 10 15

Calcium/Boehmitβ (805)

20 4 8 12 16

Smectite/Boehmite (805)

5 10 15

Zeolite/Boehmite (805)

Figure 6. Mineral/boehmite peak area ratios (data presented in Appendix B). Solid circles = Site 803, open square = Site 805. Note that the x-axis scales for the

two sites are offset to facilitate plotting but the range of the scales is equivalent. A. Calcite/boehmite. B. Smectite/boehmite. C. Heulandite/boehmite. D. 4.02

plagioclase (Pl)/boehmite. E. 3.18-3.20 plagioclase (P2)/boehmite. F. 4.26 quartz (Ql)/boehmite. G. 3.34 quartz (Q2)/boehmite. H. Kaolinite-chlorite/boehmite.

I. Illite/boehmite.

between smectite and other minerals is in the interval younger than5 Ma, where abundances of both smectite and the quartz/illite/kaolinite/chlorite assemblage fluctuate rapidly; this pattern of co-variation is clearly identified by Fl of PCA2. Another similarity inthe mineral abundance records is the presence of a major abundancepeak in smectite and in quartz/illite/kaolinite/chlorite in the middleMiocene (approximately 13-15 Ma; Fig. 7); this feature is recordedby the association of smectite and kaolinite + chlorite in F2 of PC A3.

In summary, covariations in mineral abundance patterns suggestthat four distinct minerals/mineral assemblages have been suppliedindependently to OJP since the Oligocene:

1. Aquartz/illite/kaolinite/chlorite assemblage, modified to includeplagioclase and minor smectite since the middle Miocene. The impor-

tance of this assemblage increased gradually from the Oligocene to amaximum in the middle Miocene, decreased into the late Miocene,and increased significantly through the Pliocene and Quaternary.

2. Smectite, supplied to produce a relatively high and consistentbackground abundance from the Oligocene to the Quaternary.

3. Plagioclase, supplied from a source whose importance de-creased through the early Oligocene, increased significantly in theearly late Oligocene, and decreased from the late Oligocene to theearly Miocene. The importance of this plagioclase source appears tohave remained low since the early Miocene.

4. A zeolite, probably heulandite, supplied to produce a relativelylow and consistent background abundance. The importance of theheulandite source increased episodically in the early Oligocene, theearly to middle Miocene, and the late Miocene to late Pliocene.

480


D Plagioclase(P1)/Boθhmit^(803) E Plagioclasβ (P2)/Bθθhtnitθ (803) F

-0.5 0.0 0.5 1.0 1.5 0.0 1.0 2.0 3.0 4.00 l • • • i • •. • • . i '•-i n . • • • • i i •. • • •-• 0

Quartz (Q1)/Boβhmitβ (803)

0.0 0.5 1.0

5- 5-

0 0.5 1 1.5 2

Plagioclasβ (P1)/Boehmitβ (805)

0 1 2 3 4 5Plagioclasβ (P2)/Boehmite (805)

0.5 1

Quartz (Q1)/Boβhmitβ (805)


Dust Sources and Transport Paths

Potential sources for these four minerals/mineral assemblages canbe identified by comparing the compositions of the four minerals/as-semblages to the compositions of Pacific dust derived from modernand well-constrained ancient source regions. The wind regime re-sponsible for transporting each mineral/assemblage can be interpretedfrom two lines of evidence: the geographic position of the inferredsource region relative to OJP, and the similarity in temporal variationsof the dust importance and the dust MAR record for that wind pattern.These interpretations are presented below for each of the four miner-als/assemblages.

The quartz/illite/kaolinite + chlorite/(±plagioclase and ±smectite)assemblage contains minerals that develop from a range of subaerialweathering conditions and a range of rock types (Chamley, 1989).This assemblage closely resembles the bulk composition of modernaerosols derived from Asia and collected in the northwest Pacific(Blank et al., 1985), and of Recent, Quaternary, and Cenozoic dust

derived from Asia and transported to the northwest Pacific by theprevailing westerlies (Blank et al., 1985; Leinen, 1989; Schramm,1989; Schoonmaker et al., 1985; LeNotre et al., 1985). On the basisof this compositional similarity, we infer that dust derived from Asiahas been supplied to OJP since the Oligocene (recorded as Fl ofPCA1, Table 3), with greatest relative importance in the middleMiocene (Fl of PC A3) and the Pliocene through Quaternary (Fl ofPCA2). The trajectory by which modern Asian dust is carried to theequatorial central and western Pacific involves transport at highelevation by the westerlies and at lower elevation by the easterlies(Duce et al., 1980; Merrill, 1989; Merrill et al., 1989). The abundanceof this mineral assemblage at OJP correlates well with the mass fluxrecord of Asian dust transport to the northwestern Pacific by thewesterlies since the Oligocene, exhibiting a similar general increasethroughout the Neogene and well-defined increases in the middleMiocene and latest Miocene through Quaternary (Janecek and Rea,1983; Janecek, 1985; Leinen, 1985; Rea et al., 1985; Rea, 1989).These similarities suggest that source areas beneath the westerlies

481


Quartz (Q2)/Boβhmitβ (803) H Kaolinite+Chlorite/Boehmite (803) I

1.0 3.0 5.0 0.0 0.5 1.0 1.5

Illitθ/Boθhmite (803)

0.0 0.5 1.0

2 4

Quartz (Q2)/Boehmite (805)

0 0.5 1 1.5 2

Kaolinitβ+Chlorite/Boehmitθ (805)

0.5 1 1.5

Illitθ/Boθhmite (805)


have exerted a stronger influence than source areas beneath theeasterlies on the composition of the mineral assemblage brought toOJP by the easterlies since the Oligocene.

A separate source supplied plagioclase to OJP from the Oligoceneto at least the early Miocene (F2 of PCA4). The importance of thissource gradually decreased through that time, with the exception ofa major increase during the late Oligocene. The area providing thisplagioclase-rich dust cannot be identified uniquely, but the two mostobvious alternatives are North and South America, with transport bythe easterlies, and local sources to the west, with transport by low-level equatorial westerlies. Schoonmaker et al. (1985) have arguedthat quartz-poor "basic" dust was supplied to DSDP Site 576 by theeasterlies before 20-25 Ma; the transport of similar material furtherwest could have supplied additional plagioclase to OJP at that time.The record of plagioclase abundance variations, however, does notexhibit features similar to those observed in MAR records of dustdeposited under the influence of the easterlies during the Oligoceneto early Miocene. Dust MARs at DSDP Sites 576 (Janecek, 1985),

595 (SchrammandLeinen, 1987), and 597-602 (Bloomstine and Rea,1986) are low and relatively uniform throughout the Oligocene andlower Miocene, unlike the pattern of decreasing plagioclase abun-dance at OJP. As a result, comparisons of the plagioclase abundancedata and these MAR records cannot be used to argue convincingly forplagioclase supply from the Americas by easterly winds.

No direct data can be used to argue for plagioclase supply to OJPfrom local sources to the west, but the geologic history of the areaduring the Oligocene and early Miocene provides a reasonable con-text for such an interpretation. Subduction-related arc volcanismduring the Oligocene extended from Guadalcanal northwestwardalong the "old North Solomon Arc" of Kroenke (1984), correlativewith the supply of abundant plagioclase to OJP. Volcanism endedthroughout the arc in the early Miocene, when the supply of plagio-clase-rich dust was also decreasing. In summary, the additional pla-gioclase supply during the Oligocene and early Miocene may haveoriginated from either the Americas or the island arcs to the west.Present data are insufficient to test these two alternatives rigorously,

482


but patterns of temporal variation suggest the importance of the morelocal sources.

Some smectite has been supplied to OJP by way of Asian dustsince the late Miocene, as discussed above. To maintain the relativelyhigh and consistent background level of smectite observed throughoutthe OJP sediments and indicated by F3 of PCA1, however, an addi-tional source must also have supplied a significant amount of smectite(F2 of PC A3 and F3 of PCA4). The potential sources for this materialare the same as those considered for plagioclase: the Americas, withtransport by means of the easterlies, and local sources to the west,with transport by means of the equatorial westerlies. The influence ofthe smectite source appears to have been relatively uniform from theOligocene into at least the late Miocene, as shown by the similaritybetween F3 of PCA4 and F2 of PC A3. For that reason, the mineralogy(Schoonmaker et al., 1985) and relatively uniform MARs (Bloom-stine and Rea, 1986; Schramm and Leinen, 1987) of dust carried bythe easterlies compare better to the smectite signal than they did tothe plagioclase record. The possibility of smectite supply from theadjacent island arcs cannot be eliminated, however. Smectite is acommon product of the subaerial weathering of volcanic source rocks,and can also be formed by early diagenesis of volcanic ash (Chamley,1989). The time at which pedogenic smectite is formed is controlledby the time at which the parent volcanic rocks enter the zone ofweathering, not by the age of initial eruption; as a result, a relativelyconsistent supply of detrital smectite to OJP from islands to the westwould only require the continuous exposure of volcanic source rocksto weathering, not continuous volcanic activity. If the dominantsource of smectite at OJP was from the alteration of volcanic ash,however, the relatively consistent abundance of smectite would re-quire a relatively uniform supply of volcanic ash through time.Subduction-related volcanism ceased in the early Miocene on islandswest of OJP (Kroenke, 1984), suggesting that the supply of volcanicash was not relatively uniform from the Oligocene to the Recent.Instead, appropriate volcanic rocks have apparently been exposed toweathering on those islands since the Oligocene and early Miocene,with the potential to supply detrital smectite by way of the equato-rial westerlies.

Heulandite, the final component of OJP dust, is a zeolite that iscommonly produced by in-situ alteration of volcanic ash, although itcan also form authigenically in the absence of ash (Mumpton, 1981).The various volcanic arcs of the western Pacific are the most obviouspotential suppliers of the volcanic ash now converted to heulandite inOJP sediments. Some of this ash probably originated from the islandsimmediately adjacent to OJP; for example, Oligocene volcanismalong the "old North Solomon Arc" (Kroenke, 1984) may have beenthe source of the ash now found in the cluster of heulandite-rich upperOligocene samples at OJP. That occurrence of heulandite is alsorecorded by the intermediate magnitude of the factor matrix coeffi-cients for heulandite (zeolite) in all factors identified by PCA4. Thecessation of volcanism in the "old North Solomon Arc" in the earlyMiocene, however, implies that other areas must have contributedvolcanic ash at other times, especially during the late early to middleMiocene (F4 of PCA3) and the late Miocene to late Pliocene (F4 ofPCA1). The sources of such ash are not easily identified, although theincrease in heulandite during the late Miocene to late Pliocene in-cludes a time of generally increased volcanism throughout the Pacific(Kennett et al., 1977; Rea and Scheidegger, 1979). Some of the ashmay have even originated from eruptions in the northwestern Pacificand followed a transport trajectory similar to that of Asian dustdeposited at OJP. Because the heulandite abundances at OJP mayreflect the combined input of ash from a number of sources that aregeographically widespread, the mineral abundance data alone cannotbe used to identify specific source regions for each major input of ash.Such correlations would require detailed geochemical data that arebeyond the scope of this study.

Table 3. Results of factor analysis of mineral abundance ratios, includingdistribution of variance among the four most important factors identifiedin each case, factor matrix, and interpreted source of each mineralassemblage.

PCAl:Interval analyzed: 0-34 MaN= 132 casesVariance (%)Factor matrix:

Smectite/BoehmIllite/BoehmKaol+Chl/BoehmZeolite/BoehmQuartz 1/BoehmPlagl/BoehmQuartz2/BoehmPlag2/Boehm

Source

PCA2:Interval analyzed: 0-5 MaN= 16 casesVariance (%)Factor matrix:

Smectite/BoehmIllite/BoehmKaol+Chl/BoehmZeol/BoehmQuartz 1/BoehmPlagl/BoehmQuartz2/BoehmPlag2/Boehm

Source

PCA3:Interval analyzed: 7-17 MaN= 27 casesVariance (%)Factor matrix:


Source

PCA4Interval analyzed: 17-34 MaN= 78 casesVariance (%)Factor matrix:


Source

Fl

29.7

-0.156*-0.565*-O.63O-0.137

*-0.775-0.290

*-0.856-0.446Asiandust

42.7

*-0.817*-0.737-0.162-0.350

*-0.782-0.356

*-0.802*-0.824Asiandust

38.6

-0.213*-0.729-0.194

*-0.522*-0.575*-0.793*-0.860*-O.7O7Asiandust

23.5

-0.1880.244

-0.173-0.445

*-0.570*-0.665*-0.641*-0.613?Asiandust?

F2

20.2

-0.2240.2720.471

-0.3990.057

*-0.8070.143

*-0.658?Unaltered

local volcanics?

17.2

-0.3050.033

*-0.835-0.459

0.108-0.3350.4330.253

?Changes withinAsian dust?

20.5

•0.820-0.444*0.757-0.2690.170

-0.2100.2180.034

?Americandust?

19.0

-0.096-0.182

*-0.654-0.354-0.259*0.542

*-0.499*0.566

?Unaltered vs.weathered local

volcanics?

F3

13.5

*-0.8640.4280.036

-0.042-0.154

0.234-0.180

0.182American

dust

15.8

0.302-0.201-0.039*0.579-0.359

*-0.7840.1390.187

Unaltered vs.altered local

volcanics

12.9

-0.143-0.305-0.164

*-0.439*0.669*0.451-0.116-0.183

777

15.1

*0.782-0.514-0.250-0.388

0.080-0.234

0.200-0.122

?Americandust?

F4

11.9

0.1810.0600.068

*0.8770.0850.0660.0130.356

?Alteredlocal

volcanics?

11.2

0.0880.3160.376

*0.5220.3440.2530.1490.372

?Alteredlocal

volcanics?

12.1

0.0850.1110.172

*0.6110.3630.0760.198

*0.607Altered vs.

unaltered localvolcanics

11.2

0.223*0.7550.1380.3810.2660.0200.1490.122

?Asiandust?

Notes: Table includes distribution of variance among the four most important factors identified in eachcase, the factor matrix, and the interpreted source of each mineral assemblage. An asterisk (*)indicates mineral with large factor matrix coefficients, judged to be important in determining thecomposition and provenance of a factor. N = number of cases.

Dust Flux, Dust Mineralogy, and Continental Aridity

In studies of dust records extracted from marine sediments, dustMAR has generally been used as an indicator of aridity in thecontinental source area of the dust (Pye, 1989; Rea, 1989). The dustMAR record at Sites 803 and 805, however, is dominated by vari-ations in bulk sedimentation rate, which are largely a function ofcarbonate production and dissolution. Because of this domination bycarbonate, paleoclimatic interpretations of the eolian MAR record aresuspect unless both the bulk MAR and the abundance of the eolian

483


Quart z/illite/Kaol+chl Plagioclasθ (P2) Smectite

Figure 7. Generalized mineral abundance profiles from OJP. Profiles were generated from the raw data by normalizing eachmineral/boehmite value by the greatest mineral/boehmite ratio for that mineral and then smoothing the data with a 9-point filter. A.Components derived from Asia: quartz (thick line), illite (thin solid line), kaolinite/chlorite (dashed line). B. Plagioclase, which wassupplied from Asia to the younger sediments and from an important independent source to the older sediments. C. Smectite,predominantly supplied independent of the Asian source, probably from a local source. D. Heulandite, probably supplied from anindependent local source.

component increase together. Despite this complication, the dustMAR record from OJP does reflect the effects of multiple dust sourcesin at least two ways:

1. Dust MARs at OJP are generally 100 mg/cm2/k.y. or more,whereas dust MARs at Sites 576 and 598 are lower by more than anorder of magnitude. Because Sites 576 and 598 lie upwind of OJP inthe westerlies and easterlies, respectively, the flux of dust at OJPcaused by those wind systems should be no greater than the fluxesobserved at Sites 576 and 598. As a result, the flux at OJP in excessof the fluxes at Sites 576 and 598 must be contributed from localsources that do not influence the sites farther north and east; and

2. Both total MAR and the abundance of the eolian componentincrease in the peak centered at approximately 22 Ma. This event issimilar to one observed at GPC-3 in the North Pacific, suggesting thatAsian dust temporarily dominated the total dust flux at OJP at thattime. Other features in the North Pacific dust MAR record are notobserved at OJP, probably because local dust diluted the supply ofAsian components.

Within the bulk OJP dust, changes in the importance of themineralogically defined Asian dust assemblage correlate well withchanges in the MAR of North Pacific dust that have generally beenascribed to aridity effects (Janecek and Rea, 1983; Janecek, 1985;Rea, 1989). These include the following: the general increase throughthe Neogene, attributed to a general increase in aridity accompanyingincreased polar ice volume; the major middle Miocene peak, attrib-uted to aridification that accompanied a major expansion of theAntarctic ice cap; and the major increase in the Pliocene-Pleistocene,

attributed to aridification during Northern Hemisphere glaciation.Similar changes are not observed in the abundance records of plagio-clase, smectite, or heulandite, probably because more localized geo-logic, tectonic, or climatic controls had a significant influence on thesupply of dust from these smaller, more proximal, lower latitudesource areas.

Grain Size, Dust Mineralogy, and Wind Intensity

The grain-size profile at OJP does not directly mirror the recordsof either the Northern Hemisphere westerlies (Rea et al., 1985; Rea,1989) or the easterlies (Bloomstine and Rea, 1986; Rea, 1989),probably because the dust deposited at OJP since the Oligocene is acomplex mixture of dust transported by the westerlies, the easterlies,and local winds, such as the equatorial westerlies. One generalsimilarity, however, is the increase in grain size since approximately20 Ma at both OJP and the North Pacific sites (DSDP Site 576 andGPC-3). This grain-size increase reflects the increasing importanceof Asian dust at OJP during this time, as was also indicated by themineralogical data. A significant difference between OJP and NorthPacific dust, however, is the larger average size of the dust at OJP(8-9 µm at OJP vs. 2 µm at Site 576). This difference may originatein two ways: differences in the instruments used to analyze the twosets of samples and/or supply of coarser grains to OJP from localsources. The grain sizes of the North Pacific dust were measured asthe average size within the 1-16 µm size interval, whereas the grainsizes of the OJP dust are the average size within the 1-28 µm fraction.Because particle volume increases geometrically with increasinggrain diameter, the inclusion of only a few larger grains will signifi-

484


cantly increase the average size calculated for a sample. The impor-tance of local dust sources, as indicated by the high dust MARs andthe abundance of plagioclase, smectite, and heulandite, makes itreasonable to expect that the dust supplied to OJP contains at least afew grains larger than those transported thousands of kilometers tothe North Pacific. Because OJP dust is a mixture of materials suppliedfrom multiple sources, by different wind systems, and with verydifferent mineralogies, dust grain size does not accurately reflect theintensity of any single wind regime.

CONCLUSIONS

On first observation, the records of dust MAR and dust grain sizein sediments deposited at OJP since the Oligocene bear little resem-blance to well-established records of dust flux and grain size due totransport by the Northern Hemisphere westerlies or equatorial east-erlies over that time. Dust mineralogy data, however, can be used toidentify distinct minerals or mineral assemblages in the OJP sedi-ments, each with a distinct supply history. One of these assemblages,composed predominantly of quartz, illite, kaolinite, and chlorite,originates in Asia. Variations in the abundance of this assemblagesince the Oligocene mirror known changes in the flux of dust trans-ported to the northwest Pacific by the westerlies. Such similaritiesidentify both the source area and the major transport control on thiscomponent of the total OJP dust. In contrast, other dust components(plagioclase, smectite) may be contributed from either local or distantsource areas, and their transport paths are poorly constrained. In allcases, the correlation of a particular mineral or mineral assemblageto its source region and/or transport pathway becomes mores difficultas the age of the sediment increases.

These results remind us that dust records extracted from marinesediments are most easily interpreted when the dust flux is dominatedby a single wind regime and, generally, a single source region; suchrecords can then be considered dust "type sections." In areas thatreceive dust from multiple sources by way of multiple wind regimes,mineralogic data can be used to subdivide the dust into individualcomponents. The origin and transport record of each dust componentcan then be examined individually. The insight gained by examiningeach dust component separately can subsequently be used to understanddust flux and grain-size records that do not agree with those from the"type sections," and thereby improve our understanding of paleocli-mate and its dynamics at the boundaries between major wind regimes.

ACKNOWLEDGMENTS

This work was supported by Leg 130 JOI-USSAC grants to bothauthors (L.A.K and T.R.J.). The manuscript was reviewed by oneanonymous reviewer, and we are grateful for the thoughtful remarks.

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Date of initial receipt: 2 April 1992Date of acceptance: 1 September 1992Ms 130B-004

486


APPENDIX A

Depth, age, bulk density (DBD), sedimentation rate (LSR), bulk mass accumulation rate(MAR), terrigenous abundance, terrigenous MAR, and terrigenous size data for each sample

from Hole 803D and Holes 805B and 805C

Core, section,interval (cm)

130-803D-lH-2,582H-2, 582H-5, 583H-2, 583H-5, 584H-3, 584H-5, 585H-2, 515H-5, 586H-2, 586H-5, 587H-2, 587H-5, 588H-2, 588H-5, 589H-2, 589H-5, 58

10H-2, 5810H-5, 5811H-2, 5811H-5, 5812H-2, 5812H-5, 5813H-2,5813H-5,5814H-2, 5814H-5, 5815H-2, 5815H-5.5816H-2.5816H-5.5817H-2.5817H-5,5818H-2.5818H-5, 5819H-2, 5819H-5, 5820H-2, 5820H-5, 5821H-2.6121H-2.9821H-5, 5822H-2, 5822H-5, 5823H-2, 5823H-5, 5824H-2, 5824H-4, 5825X-2, 5825X-4, 5826X-2, 5826X-5, 5827X-2, 5828X-K6228X-3, 5829X-2, 5829X-5, 5830X-2, 5530X-4,4831X-2, 5831X-4, 7032X-2, 6632X-5, 6233X-2, 5833X-5, 6634X-2, 5334X-5,4135X-2, 4335X-5, 3036X-2, 5836X-5, 5837X-2, 5837X-5, 5838X-2, 5838X-5, 5839X-2, 58

Depth(mbsf)

2.14.69.1

14.118.625.128.133.037.642.647.148.252.757.762.267.271.7

76.781.286.290.795.7

100.2105.2109.7114.7119.2124.2128.7133.7138.2143.2147.7152.7157.2162.2166.7171.7176.2181.2181.6185.7190.7195.2200.2204.7209.7212.7219.2222.2228.9233.4238.6246.5249.5257.6262.1267.2270.1276.8279.9286.5290.9296.2300.8305.3309.7314.9319.3324.8329.3334.4338.9344.1348.6353.7

Age(Ma)

0.220.490.971.501.952.392.602.943.243.513.763.824.064.344.584.855.075.245.405.585.745.926.076.256.416.596.756.927.087.267.427.607.767.938.098.278.438.618.88

9.399.78

10.2610.6911.1711.6012.0812.3712.9913.2813.9214.3514.8519.4519.6620.7821.8622.0322.1222.3422.4522.6622.81

23.2923.4323.6023.9324.7825.4826.2726.9727.7828.2728.47

DBD(g/cm3)

0.7340.7670.8220.8750.8970.8710.8720.9200.9180.9060.9110.9250.9760.9520.9440.9450.9540.9971.0101.0101.0101.0301.0601.0601.0101.0401.0501.0601.0701.0301.0001.0001.0600.9961.0101.0601.0801.0801.040

:

.020

.030

.120

.170

.1501.0901.0101.0501.070

:

•

:

:

:

.090

.120

.150

.140

.140

.210

.220

.330

.250

.280

.280

.250

.260

.250

.270

.280

.230

.290

.300

.280

.320

.320

.310

.300

.320

.350

.310

.290

LSR(cm/k.y.)

0.940.940.940.941.451.451.451.45.83

1.831.831.831.831.831.831.832.822.822.822.822.822.822.822.822.822.822.822.822.822.822.822.822.822.822.822.822.822.821.051.051.051.051.051.051.051.051.051.051.051.051.051.050.160.16

.780.273.033.033.033.033.033.033.033.033.033.033.033.030.640.640.640.640.640.642.58>.58

Bulk MAR(g/cm2/k.y.)

0.690.720.770.82

.30

.26

.26

.33

.68

.66

.67

.691.791.741.731.732.692.812.852.852.842.902.992.992.842.932 . %2.983.012.912.832.833.002.812.842.983.063.06

.09

.07

.08

.18

.22

.21

.14

.06

.10

.12

.15

.18

.21

.200.180.192.180.363.803.873.883.793.813.783.843.873.743.903.933.890.850.840.840.830.840.863.39;U 3

Terr.(%)

5.09.16.15.66.95.73.57.24.18.2

10.74.93.12.43.84.76.35.03.74.14.65.45.3

13.58.96.34.67.97.06.94.32.92.44.82.83.92.33.03.2

3.63.93.82.96.18.28.38.36.74.85.46.14.55.94.82.53.82.33.54.62.92.82.9

8.04.9

11.74.54.44.39.16.54.65.85.2

Terr. MAR(mg/cm2/k.y.)

34.565.647.146.089.772.044.396.068.9

136.0178.382.955.341.865.781.3

169.6140.6105.4117.0130.7156.6158.3403.1253.0184.7136.2235.3210.4200.7121.582.172.0

134.879.5

116.170.391.735.0

38.945.946.535.069.586.691.193.176.856.565.473.3

8.211.4

104.49.0

144.489.0

136.0174.4110.4105.9111.3

311.9192.3455.3

38.037.135.975.754.839.7

196.6173.2

Size(µm)

9.611.010.911.812.010.910.411.511.510.412.09.09.09.6

12.411.411.812.X12.811.413.113.112.89.0

10.510.310.210.210.310.310.88.98.05.87.98.98.87.78.5

11.510.16.28.77.28.96.78.88.06.4

11.312.410.912.212.111.911.012.811.510.311.911.811.5

6.711.310.210.19.7

10.410.37.4

11.510.312.5

487


APPENDIX A (continued).


130-803D-39X-5, 5840X-2, 5840X-5, 5841X-2, 5342X-2, 5842X-5, 5843X-2, 5843X-5, 5844X-2, 5844X-5, 5845X-2, 5845X-5, 5846X-2, 2946X-2, 5246X-5, 5347X-2, 5847X-5, 5848X-2,4850X-2, 5851X-2, 5852X-2, 5853X-2, 5854X-2, 55

13O-8O5B-36X-2, 7236X-4, 7237X-2, 7237X-4, 7238X-2, 7238X-4, 7239X-2, 7239X-4, 7240X-2, 6340X-4, 6241X-2.6941X-4, 7042X-2, 7242X-4, 7143X-2, 7243X-4, 7244X-2, 7244X-4, 7245X-2, 7245X-4, 7246X-2, 7246X-4, 7247X-1, 1248X-2, 7248X-4, 7249X-2, 7249X-4, 72

13O-8O5C-50X-2, 5050X-4, 5051X-2, 5051X-4.5052X-1,4352X-3, 4353X-2, 4253X-4, 6654X-1.7854X-4, 9455X-1.8655X-2, 8056X-1.2756X-0, 3957X-1.2257X-2, 10358X-I, 1860X-1.2061X-2, 7061X-4, 7062X-1.7562X-3, 7563X-I.3864X-I.70

Depth(mbsf)

358.2363.4367.9373.0382.8387.3392.5397.0402.1406.6411.8416.3

421.3425.8431.1435.6440.6459.6469.3479.0488.7498.4

332.22335.22341.92344.92351.62354.62361.22364.22370.83373.82380.49383.50390.22393.21399.92402.92409.52412.52419.22422.22428.72431.72436.12447.72450.72457.32460.32

469.00472.00477.50480.50485.63488.63496.82500.06505.38510.04515.06516.50524.17524.60533.72

543.38562.80574.50577.50582.75585.75592.08602.00

Age(Ma)

28.6428.8429.0229.2129.5929.7729.9730.1430.3430.5130.7130.8931.0731.0831.2631.4631.6431.8332.5632.9433.3133.6934.06

14.1414.3714.8815.1115.6315.8616.3716.6017.1117.3417.8518.0818.6018.8219.2419.4319.8420.0320.4520.6421.0521.2321.5122.1322.2722.5822.72

23.1323.2723.5223.6723.9124.0524.4324.5824.8325.0525.2925.3525.7125.7326.1626.2726.6227.5328.0828.2228.4628.6028.9029.37

DBD(g/cm3)

1.3401.3501.3701.3701.2901.3501.4001.4101.3801.3801.3701.360

1.3701.3601.3501.3401.3801.3601.3201.4401.3901.450

1.2231.1851.2031.1721.2381.2311.2641.2311.1961.2411.2481.2941.3881.3601.3111.3891.4141.4131.2961.4101.3871.3891.4841.3451.3411.5181.527

:

.366

.350

.416

.349

.407

.382

.297

.370

.334

.398

.437

.479

.650

.653

.486

.489

.433

.508

.426

.488

.528

.505

.563

LSR(cm/k.y.)

2.582.582.582.582.582.582.582.582.582.582.582.582.582.582.582.582.582.582.582.582.582.582.58

1.301.301.301.301.301.301.301.301.301.301.301.301.301.601.601.601.601.601.601.601.601.601.602.132.13

2.132.13

2 .13

2.132.132.132.132.132.132.13

2.132.132.132.132.132.132 .13

2.132.132.132.132.132.132.132.132.13

Bulk MAR(g/cm2/k.y.)

3.453.493.543.533.333.473.623.653.563.553.543.52

3.533.523.473.463.563.503.403.723.593.75

1.59.54

1.561.521.611.601.641.601.551.611.621.681.802.182.102.222.262.262.072.262.222.222.372.872.863.233.25

2.912.873.022.873.002.942.762.922.842.983.063.153.523.523.16

3.173.053.213.043.173.263.213.33

Terr.

(%)

8.97.27.28.66.35.67.52.94.25.16.34.36.98.18.13.43.64.33.85.54.25.82.1

4.24.63.84.12.52.43.13.97.38.13.57.25.54.13.45.64.85.81.24.53.34.84.24.54.33.52.2

1.82.43.73.16.33.52.85.45.53.33.93.41.37.21.42.53.33.81.85.28.44.63.12.7

Terr. MAR(mg/cm2/k.y.)

306.9251.5255.1303.8209.8194.4271.4105.8149.4181.0222.8151.2

286.3284.8118.1124.5153.2133.0187.1156.3208.1

78.8

66.870.959.462.540.238.450.962.4

113.5130.656.8

121.199.289.271.3

124.4108.6131.124.9

101.573.2

106.799.7

129.0122.9113.171.5

52.469.0

II 1.689.1

188.8103.077.3

157.5156.398.2

119.4107.145.7

253.544.3

104.7116.057.8

158.0266.2149.799.489.9

Size(µm)

11.212.211.86.6

11.712.39.0

10.010.89.28.9

10.19.77.66.96.86.66.26.4

10.97.38.7

10.0

10.09.26.78.57.27.06.55.8

12.17.17.58.16.58.76.28.08.28.56.36.88.2

12.012.811.39.66.67.8

10.97.76.8

12.19.8

11.710.09.3

10.26.86.3

10.26.39.28.37.3

12.011.510.110.79.3

10.912.612.5


APPENDIX B

Mineral abundance data (mineral/boehmite ratios) for samples from Hole 803D and Holes 805B and 805C


130-803 D-1H-2, 58lH-2,582H-2, 582H-5, 583H-2, 583H-5, 584H-3, 584H-5, 585H-2, 515H-2, 515H-5, 586H-2, 586H-5, 587H-2, 587H-5, 588H-2, 588H-5, 589H-2, 589H-5, 58

10H-2, 5810H-5, 58HH-2,5811H-5, 5812H-2, 5812H-5, 5813H-2, 5813H-5.5814H-2, 5814H-5, 5815H-2, 5815H-5, 5816H-2, 5816H-5, 5816H-5, 5817H-2,5817H-5, 5818H-2, 5818H-5, 5819H-2, 5819H-2, 5819H-5, 5820H-2, 5820H-5, 5821H-2,9821H-5, 5822H-2, 5822H-5, 5823H-2, 5823H-5, 5824H-2, 5824H-4, 5825X-2, 5825X-4, 5826X-2, 5826X-5, 5827X-2, 5828X-1,6228X-3, 5829X-2, 5829X-5, 5830X-2, 5530X-4, 4831X-2.5831X-4, 7032X-2, 6632X-5, 6234X-2, 5334X-5.4134X-5,4135X-2, 4335X-2, 4435X-5, 3036X-2, 5836X-2, 5836X-5, 5837X-2, 58

Depth(mbsf)

2.12.14.69.1

14.118.625.128.133.033.037.642.647.148.252.757.762.267.271.776.781.286.290.795.7

100.2105.2109.7114.7119.2124.2128.7133.7138.2138.2143.2147.7152.7157.2162.2162.2166.7171.7176.2181.6185.7190.7195.2200.2204.7209.7212.7219.2222.2228.9233.4238.6246.5249.5257.6262.1267.2270.1276.8279.9286.5290.9305.3309.7309.7314.9314.9319.3324.8324.8329.3334.4

Age(Ma)

0.220.220.490.971.501.952.392.602.942.943.243.513.763.824.064.344.584.855.075.245.405.585.745.926.076.256.416.596.756.927.087.267.427.427.607.767.938.098.278.278.428.618.889.399.78

10.2610.6911.1711.6012.0812.3712.9913.2813.9214.3514.8519.4519.6620.7821.8622.0322.1222.3422.4522.6622.8123.2923.4323.4323.6023.6023.9324.7824.7825.4826.27

Sm/B

3.9465.1973.2735.0154.1830.0002.7791.9263.0962.9242.8994.2165.3445.0653.7244.4946.4293.1563.7214.9595.0914.1296.5453.1364.1223.1843.3813.4292.1373.8943.6272.9512.6982.7786.1834.7005.8004.0304.4714.0514.4384.3846.1724.3814.3124.3105.0983.6384.8945.5773.6134.8946.4118.365

57.8006.3134.3864.4842.1163.7107.2276.8486.4684.2254.6996.6156.1186.7783.9466.6082.3813.5826.0163.1733.3251.975

Ill/B

0.2570.4090.5300.2920.1830.0000.0000.1820.0960.1770.0000.0000.5250.0000.0000.1080.4290.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.1460.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0002.8000.0000.0700.2740.2090.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.1820.0000.0000.0000.123

K+Chl/B

0.6760.0300.9390.6920.4150.0000.6100.5455.2870.6585.0220.7571.0000.0000.3290.6029.1960.2810.3930.0000.0000.3230.0000.0000.5120.0000.0000.0000.0000.4680.0000.0000.0000.0000.5070.5130.0000.0000.0000.2040.2920.0000.6550.0000.0000.0000.3900.0000.0000.0000.0000.0000.3040.3656.2000.6570.6490.3550.0000.0000.1820.2730.0000.4930.2600.0000.0000.0000.0000.0000.0000.5820.2700.0000.2380.210

Zeol/B

1.0002.0610.5611.7381.159

17.2112.4680.6361.1811.4811.1461.7841.541

30.1610.9341.6872.1430.8911.443

17.0001.4550.9192.5000.0001.0980.0000.0003.476

18.0200.0005.7062.7560.6790.0001.1971.3252.8220.1521.5411.2553.2501.7262.7411.3931.3331.0562.8055.3192.1672.1152.4671.7421.8212.808

20.4001.8962.2281.2588.6742.7422.3482.3181.9873.1413.7532.2881.912

12.2002.2161.8432.6901.6181.9841.3081.8501.370

Qtzl/B

0.8650.7420.5610.7230.1950.0000.5450.3720.3620.3920.3710.0810.5410.8390.5390.5660.6070.2660.4590.0000.2050.4840.3180.0000.3900.0000.0000.0000.1570.0000.1570.2930.0000.0000.2390.4380.0000.4240.1410.2760.2710.3150.1550.2860.3660.0990.4630.4260.3330.0000.3330.4390.4820.5194.4000.5070.4390.1130.0000.5320.2270.2880.3800.4650.3970.3080.2060.2220.0000.1960.0000.0000.2220.0960.2000.185

Plagl/B

0.2300.4700.4240.4310.1950.0000.3120.3800.2550.1650.4270.0000.3280.8710.5130.3980.5000.4060.3440.0000.3640.3710.4090.0000.0000.0000.2140.0000.4710.0000.3530.2680.0000.0000.1130.3130.0000.4550.2240.2760.6460.3560.2410.2020.3120.2540.2930.4040.1970.0000.0000.4700.1960.2883.0000.2690.0880.2581.1860.4520.1670.2420.3290.8870.4660.4230.1620.6670.0000.4120.1900.6550.3170.4230.2000.296

Qtz2/B

4.1354.1522.7422.7691.9152.684.974.248.447.658.404

2.4861.8693.1942.0662.1332.500

.969

.459

.020

.114

.387

.7730.8310.8780.3670.3570.5240.8630.5530.6860.3900.5470.3891.0561.438.422

1.6060.6000.7552.8750.822

.1031.0950.882

.4232.3411.0210.7271.1920.800

-1.5611.643.769

24.2001.7311.9471.0321.581.387

0.9091.4090.911.127

1.0820.7310.618

.3110.8380.7650.9520.800

.143

.1920.8750.444

Plag2/B

2.9052.2271.4241.5541.2202.4740.1820.8181.0851.1270.9661.7842.0492.0001.3551.3862.1791.2191.2300.6121.0230.9521.7731.0341.1950.6120.9521.0000.7841.0431.0000.9020.6600.6391.2961.0501.4001.3940.3290.8472.3131.2331.0691.5600,8921.0701.6100.8511.0761.0770.0001.2421.3751.154

10.4000.6121.1230.9841.6281.2261.0611.1061.4561.3381.8491.3651.5291.6000.7301.3923.0951.4731.7781.9811.5631.309

Calc/B

0.0000.0000.5304.1380.0000.0000.0000.0000.6060.5570.0000.8920.7380.0000.0000.0000.0001.9694.3116.4495.4554.016

14.0007.169

11.85410.89811.09512.7868.1579.1708.392

11.3176.1894.7500.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.4550.0000.0000.0000.0000.404

11.2000.4480.3330.0000.0000.0000.0000.0000.0000.0000.0000.0000.8530.0000.0001.4711.6900.0000.0000.0000.0002.111


APPENDIX B (continued).


130-803D-37X-5, 5838X-5, 5839X-2, 5840X-2, 5840X-5, 5841X-2, 5342X-2, 5842X-5, 5843X-2, 5844X-2, 5846X-2, 2946X-2, 5246X-5, 5346X-5, 5347X-2, 5847X-5, 5848X-2, 4850X-2, 5851X-2, 5852X-2, 5853X-2, 58

130-805B-36X-2, 7236X-4, 7237X-2, 7237X-4, 7238X-2, 7239X-4, 7240X-2, 6340X-4, 6241X-2,6941X-4, 7041X-4, 7042X-2, 7242X-4, 7143X-2, 7243X-3, 7244X-2, 7244X-4, 7245X-2, 7245X-4, 7245X-4, 7246X-2, 7246X-4, 7247X-1, 1248X-2, 7248X-2, 7248X-4, 7249X-2, 72

13O-8O5C-5OX-2, 5050X-4, 5051X-2, 5051X-4, 5052X-1.4352X-1.4352X-3, 4353X-2, 4253X-4, 6654X-1.7854X-4, 9455X-1,8655X-2, 8056X-1.2757X-2, 10358X-1, 1860X-l,2061X-4, 706IX-4, 7062X-I.7562X-3, 7563X-1.3864X-1.70

Depth(mbsf)

338.9348.6353.7363.4367.9373.0382.8387.3392.5402.1421.1421.3425.8425.8431.1435.6440.6459.6469.3479.0488.7

332.2335.2341.9344.9351.6364.2370.8373.8380.5383.5383.5390.2393.2399.9402.9409.5412.5419.2422.2422.2428.7431.7436.1447.7447.7450.7457.3

469.0472.0477.5480.5485.6485.6488.6496.8500.1505.4510.0515.1516.5524.2

543.4562.8577.5577.5582.8585.8592.1602.0

Age(Ma)

26.9728.2728.4728.8429.0229.2129.5929.7729.9730.3431.0731.0831.2631.2631.4631.6431.8332.5632.9433.3133.69

14.1414.3714.8815.1115.6316.6017.1117.3417.8518.0818.0818.6018.8219.2419.4319.8420.0320.4520.6420.6421.0521.2321.5122.1322.1322.2722.58

23.1323.2723.5223.6723.9123.9124.0524.4324.5824.8325.0525.2925.3525.7126.2726.6227.5328.2228.2228.4628.6028.9029.37

Sm/B

4.8735.0136.5893.9012.8041.6333.2053.0125.4593.9154.2003.2082.9764.0006.0244.3908.6473.5005.4235.3334.083

6.7355.7805.3184.4366.8783.5222.3802.0274.9874.0157.3086.4496.0855.0006.0000.0005.1904.3712.1883.0005.0394.5815.5365.3406.9344.6495.520

5.9623.3704.5475.8543.3333.0917.2904.0635.9503.4484.5125.092

10.4475.6324.0855.2614.9856.3613.0555.6133.3494.1047.451

Ill/B

0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.4910.0000.1830.0000.0000.0000.0000.0000.0000.0000.000

0.0000.0000.0000.2180.0000.0000.0000.0000.2530.0000.1730.0000.0000.1300.0240.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000

0.0000.0000.0000.0000.6000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000

K+Chl/B

0.0000.2530.2680.2390.0000.1140.0000.0006.3290.0000.0000.0000.0000.0000.0000.1300.0000.2810.0000.0000.250

0.0000.2710.0000.0000.0000.0000.0000.2700.0000.4260.3080.0000.0000.2590.0000.0000.0000.0000.0000.0000.1430.1290.0950.3770.0000.0000.000

0.0000.1740.0000.0000.0000.0000.1610.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.3820.0000.3020.0000.000

Zeol/B

1.5271.4672.1432.479

26.0871.2661.0640.6051.5061.0341.3454.5852.3410.000

25.8331.312

20.8240.0001.2821.5612.617

2.4292.7801.6825.5091.8371.075

13.3601.4592.0276.6912.2312.9591.5082.6671.6594.7692.0480.0000.6981.3511.6231.1940.9769.5281.3553.4211.900

1.6671.5546.4931.6711.4671.5272.5651.9171.3131.1042.3172.3555.4471.5442.3290.6521.9393.2783.6910.9131.8371.7762.961

Qtzl/B

0.1640.1470.2500.4370.0000.0000.0900.0000.3410.1860.2000.1130.2320.0000.4760.1690.0000.0000.1410.0000.283

0.2650.3220.2950.5450.6940.2390.0000.2700.4800.0000.2120.2450.0000.4440.2200.7690.1270.1770.0000.2210.1300.1400.1900.0000.1320.2630.200

0.1540.2610.2000.1710.0000.1090.2420.2500.1630.0000.4390.3290.6050.1400.0000.0000.3180.1670.2180.1130.2790.5820.255

Plagl/B

0.8180.4400.6610.6340.0000.5190.2950.3260.7650.4240.2910.6040.4510.6720.6430.7530.0000.0000.8460.5150.750

0.2860.2710.2950.5450.6120.2090.0000.2430.5470.3090.2500.5510.0000.3520.2930.6150.2860.2740.1560.4030.1690.3760.2620.0000.2370.5090.140

0.4230.2170.2670.3780.0000.2550.3710.1670.5380.4030.5370.4470.7110.5090.8900.6810.9700.9170.5270.4000.7210.7910.902

Qtz2/B

1.0910.6530.9110.9151.1300.5820.5640.5470.4590.3730.3820.5470.4020.1311.0480.5321.1470.5160.5510.5150.583

1.6531.9831.3642.0361.959.164.340.405.360.074.212.653

0.9321.0931.0490.9491.0791.1770.3230.4030.8440.6340.7620.5660.5921.0001.180

1.0640.5870.7730.9020.3560.3641.3060.5830.5880.8511.3900.8950.9471.1930.5850.6090.8181.3330.8550.4880.5120.6420.804

Plag2/B

2.4361.453

(

(

.446

.366

.717

.899).359.547.282

).983.873.415.171.689

2.2382.3122.5291.4691.9741.4852.433

.163

.051

.000

.455

.4291.0901.4400.9591.2800.9711.2501.6730.0001.3151.4151.5900.9521.2100.8231.0131.2080.8600.8330.7920.7371.6841.160

1.6921.0981.3331.1590.8220.8361.3550.8751.7501.2241.7801.5131.8681.9121.5851.8992.2734.0561.3821.1381.8601.2692.020

Calc/B

0.0000.0000.0001.1270.0000.2781.0770.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000

0.0000.0000.0000.0000.0000.0001.8200.0000.0000.3680.5770.0000.0000.0001.0980.0000.0000.0000.0000.0000.0000.4410.3570.0000.0000.0000.000

0.0000.0000.1870.0008.7568.7270.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000

490

28. eolian deposition on the ontong java plateau …€¦ · vary if changes in atmospheric...

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