Patterson, D. B. and Farley, K. A. and Norman, M. D. (1999) ^4He as a tracer of continental dust: A 1.9 million year record of aeolian flux to the west equatorial Pacific Ocean. Geochimica et Cosmochimica Acta, 63 (5). pp. 615-625. ISSN 0016-7037 http://resolver.caltech.edu/CaltechAUTHORS:20121120-150916146
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The mass accumulation rates (MARs) of aeolian dust in the ocean basins provide an important record of climate in the continental source regions of atmospheric dust and of the prevailing wind patterns responsible for dust transport in the geologic past. The incorporation of other terrigenous components such as volcanic ashes in seafloor sediments, however, often obscures the aeolian dust record. We describe a new approach which uses the delivery rate of crustal ^4He to seafloor sediments as a proxy for the mass accumulation rate of old continental dust which is unaffected by the addition of other terrigenous components. We have determined the flux of crustal ^4He delivered to the seafloor of the Ontong Java Plateau (OJP) in the western equatorial Pacific over the last 1.9 Myrs. Crustal ^4He fluxes vary between 7.7 and 30 ncc cm^(−2) kyr^(−1) and show excellent correlation with global climate as recorded by oxygen isotopes, with high crustal ^4He fluxes associated with glacial periods over the entire interval studied. Furthermore, the onset of strong 100 kyr glacial–interglacial climate cycling is clearly seen in the ^4He flux record about 700 kyrs ago. These data record variations in the supply of Asian dust in response to climate driven changes in the aridity of the Asian dust sources, consistent with earlier work on Asian dust flux to the northern Pacific Ocean. However, in contrast to previous studies of sites in the central and eastern equatorial Pacific Ocean, there is no evidence that the Inter Tropical Convergence Zone (an effective rainfall barrier to the southward transport of northern hemisphere dust across the equator in the central and eastern Pacific) has influenced the delivery of Asian dust to the OJP. The most likely carrier phase for crustal helium in these sediments is zircon, which can reasonably account for all the ^4He observed in the samples. As a first order estimate, these results suggest that the mass accumulation rate of Asian dust on the OJP over the last 1.9 Myrs varied from about 4 to 15 mg cm^(−2) kyr^(−1). In contrast, previous studies show that over the same interval the total MAR of terrigenous dust (i.e. Asian dust plus local volcanics) on OJP varied between about 34 and 90 mg cm^(−2) kyr^(−1).
|Additional Information:||© 1999 Elsevier Science Ltd. Received June 10, 1998; accepted in revised form November 18, 1998. This work was supported by the David and Lucille Packard Foundation and the Australian Research Council. We thank Dr. David Rea and two anonymous referees for their comments. Special thanks to Dr. R. Muller for providing the Fourier Transform spectral analysis. DBP wishes to also thank Mr. John Miller of ODP for help and hospitality during sample retrieval. This is GEMOC Contribution 142.|
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|Official Citation:||D.B Patterson, K.A Farley, M.D Norman, ^4He as a tracer of continental dust: a 1.9 million year record of aeolian flux to the west equatorial Pacific Ocean, Geochimica et Cosmochimica Acta, Volume 63, Issue 5, March 1999, Pages 615-625, ISSN 0016-7037, 10.1016/S0016-7037(99)00077-0. (http://www.sciencedirect.com/science/article/pii/S0016703799000770)|
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|Deposited By:||Ruth Sustaita|
|Deposited On:||20 Nov 2012 23:28|
|Last Modified:||20 Nov 2012 23:28|
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