Provenance of Pelagic clay in the Eastern Pacific: Dating the downcore Cenozoic dust record.

Pacific pelagic sediments provide a temporal and spatial context for mapping changing continental sources of eolian dust during the Cenozoic Era. To "fingerprint" sources of terrigenous sediment, we have examined the 0-5Ma record for ODP and piston core sites using Pb, Sr, and Nd isotopes on pelagic and hemipelagic clay extracts. Q-mode factor analysis revealed three factors accounting for 98.4% of the total isotopic variance. Contour plots of factor loadings indicate these three factors represent: 1) the well-known Asian-derived dust province in the central North Pacific; 2) a North American source (easternmost North Pacific); and 3) South American source (south of the Intertropical Convergence Zone). From this analysis, it appears that the late Cenozoic Asian dust source can be quantitatively differentiated downcore from both North American and South American continental sources in the Pacific realm. Extending the downcore record into the mid-Cenozoic has required fish teeth 87Sr/86Sr isotope dating of pelagic clays. Piston cores raised by the R/V Ewing in 1997 - EW9709 PC-01, PC-02, PC-04, PC-05, PC-07, PC-11 and PC-14 between 30 degrees North and the equator have been dated by this technique. Combined, these cores cover an age range of 28Ma to present. Isotope analysis of Nd, Sr and Pb in the dust fraction from these cores can be combined with the published records from LL44 GPC-3 and ODP 885/886 to generate a more comprehensive down core record of dust accumulation during the mid-late Cenozoic in the East-Central Pacific. This approach has promise for evaluating changes in long-term atmospheric circulation across major Cenozoic global climate transitions and the paleolatitude of the Intertropical Convergence Zone.