Joseph D. Ortiz

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A detailed (ca. 100 yr resolution) and well-dated (18 AMS 14C dates to 23 cal. ka BP) record of latest Pleistocene}Holocene variations in terrigenous (eolian) sediment deposition at ODP Site 658C o! Cap Blanc, Mauritania documents very abrupt, large-scale changes in subtropical North African climate. The terrigenous record exhibits a well-de"ned period of(More)
We reconstructed the radiocarbon activity of intermediate waters in the eastern North Pacific over the past 38,000 years. Radiocarbon activity paralleled that of the atmosphere, except during deglaciation, when intermediate-water values fell by more than 300 per mil. Such a large decrease requires a deglacial injection of very old waters from a deep-ocean(More)
We present a high-resolution magnesium/calcium proxy record of Holocene sea surface temperature (SST) from off the west coast of Baja California Sur, Mexico, a region where interannual SST variability is dominated today by the influence of the El Niño-Southern Oscillation (ENSO). Temperatures were lowest during the early to middle Holocene, consistent with(More)
In this study five different molecular markers were used to: (1) infer the phylogeographic differentiation of Thalassiosira weissflogii in the Atlantic and Pacific Oceans; and (2) address the biological species status of the inferred geographic lineages. The results of the ribosomal RNA data analyses suggested that the Hawaiian isolate evolved first after(More)
This paper describes a GC-MS method for the analysis of the carboxylic acid metabolite (SR26334, II) of methyl (+)-(S)-alpha-(o-chlorophenyl)-6,7-dihydrothieno[3,2-c]pyridine-5( 4H)-acetate hydrogensulfate (clopidogrel, SR 25990, I) in plasma and serum. The analytical procedure involves a robotic liquid-liquid extraction with diethyl ether followed by a(More)
Ž Ž . . Ž Ž .y. Dissolved boron in seawater occurs mainly in the form of boric acid B OH and borate B OH . While the 3 4 equilibrium properties of the dissociation of boric acid have been studied in detail, very little work has focused on the kinetics of the boric acid–borate equilibrium in seawater. Here, we present a theoretical study of the relaxation of(More)
We present a 6,000-yr record of changing water balance in the Pacific Northwest inferred from measurements of carbonate δ(18)O and grayscale on a sediment core collected from Castor Lake, Washington. This subdecadally resolved drought record tracks the 1,500-yr tree-ring-based Palmer Drought Severity Index reconstructions of Cook et al. [Cook ER, Woodhouse(More)
a Department of Geology, Kent State Univ., Kent, OH 44242, USA b Byrd Polar Research Center, Ohio State Univ., 1090 Carmack Rd, Columbus, OH 43210, USA c Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, PO Box 38, Solomons, MD 20688, USA d Department of Ocean, Earth, and Atmospheric Sciences, Old Dominion(More)
The Western Basin of Lake Erie (WBLE) is heavily influenced by the surrounding terrestrial ecosystem via rivers such as the Sandusky River and the Maumee River. As a result, the optical properties of the WBLE are influenced by multiple color producing agents (phytoplankton, colored dissolved organic matter (CDOM), organic detritus, and terrigenous inorganic(More)
Multiple paleoceanographic proxies in a zonal transect across the California Current near 42øN record modern and last glacial maximum (LGM) thermal and nutrient gradients. The offshore thermal gradient, derived from foraminiferal slx•ies assemblages and oxygen isotope data, was similar at the LGM to that at present (warmer offshore), but average(More)