Deglacial dust provenance changes in the eastern Equatorial Pacific and implications for ITCZ movement

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doi: 10.1016/j.epsl.2011.11.014
Author(s): Xie, Ruifang C.; Marcantonio, Franco
Author Affiliation(s): Primary:
Texas A&M University, Department of Geology and Geophysics, College Station, TX, United States
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, Vol.317-318, p.386-395. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. Supplementary data available in online version. 60 refs.; illus., incl. sketch map
Summary: The provenance of eolian dust supplied to deep-sea sediments has the potential to offer insights into changes in past atmospheric circulation. Specifically, measuring temporal changes in dust provenance can shed light on changes in the mean position of the Intertropical Convergence Zone (ITCZ), a region acting as a barrier separating wind-blown material derived from northern versus southern hemisphere sources. Here we have analyzed Nd, Sr, and Pb isotope ratios in the operationally-defined detrital component extracted from deep-sea sediments in the eastern equatorial Pacific (EEP) along a meridional transect at 110°W from 3°S to 7°N (ODP Leg 138, sites 848-853). Sr isotope results show that barite Sr has a significant influence on 87Sr/86Sr isotope ratios of samples in the upwelling zone of the EEP. However, sites located >3° or more away from the equator (sites 852 and 853) are believed to not be affected by barite Sr and provide useful detrital Sr signals. 208Pb/206Pb and 207Pb/206Pb ratios in all cores fall into the Pb-isotope space of five potential dust sources (Asia, North and Central/South America, Sahara, and Australia), with no distinct isotopic fingerprinting of the dominant source(s). εNd values were most valuable for discerning detrital source provenance, and their values at all sites, ranging from -5.46 to -3.25, were more unradiogenic for sediments deposited during the last glacial than for those deposited during the Holocene. There are distinct latitudinal trends in the εNd values, with more radiogenic values further south and less radiogenic values further north, excluding site 848. This distinction holds true for both Holocene and last glacial periods. For the most southerly site, 848, we invoke, for the first time, a distinct southern hemisphere Australian source as being responsible for the unradiogenic Nd isotope ratios. Both average last glacial and Holocene εNd values show similar sharp gradients along the transect between 5.29°N and 2.77°N, suggesting little movement of the glacial ITCZ in the EEP. However, during the deglacial, this gradient is stronger and shifted further north between 5.29°N and 7.21°N, suggesting a more northerly, possibly stronger, deglacial ITCZ. Abstract Copyright (2012) Elsevier, B.V.
Year of Publication: 2012
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 24 Surficial Geology, Quaternary Geology; Alkaline earth metals; Atmospheric circulation; Australasia; Australia; Cenozoic; Clastic sediments; Deglaciation; Dust; East Pacific; Equatorial Pacific; Holocene; Intertropical convergence zone; Isotopes; Lead; Leg 138; Marine sediments; Metals; Neodymium; North Pacific; Northeast Pacific; ODP Site 848; ODP Site 849; ODP Site 850; ODP Site 851; ODP Site 852; ODP Site 853; Ocean Drilling Program; Pacific Ocean; Provenance; Quaternary; Rare earths; Sediment transport; Sediments; South Pacific; Southeast Pacific; Strontium; Temporal distribution; Transport; Upwelling
Coordinates: N001058 N001100 W1103110 W1103111
S025940 S025938 W1102847 W1102849
N071239 N071240 W1094504 W1094506
N051733 N051734 W1100432 W1100435
Record ID: 2012051995
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands