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R. Randall Schumann

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In areas of low uplift rate on the Pacific Coast of North America, reoccupation of emergent marine terraces by later high-sea stands has been hypothesized to explain the existence of thermally anomalous faunas (mixtures of warm and cool species) of last interglacial age. If uplift rates have been low for much of the Quaternary, it follows that higher (older) terraces should also show evidence of reoccupation. Strontium isotope analyses of fossils from a high-elevation marine terrace on Anacapa Island, California yield a suite of ages ranging from ~2.4-2.3 Ma to ~1.4-1.5 Ma. These results indicate that terrace reoccupation and fossil mixing on Anacapa Island could have taken place over several interglacial periods...
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This data release contains the data tables for the USGS North American Packrat Midden Database (version 5.0). This version of the Midden Database contains data for 3,331 packrat midden samples obtained from published sources (journal articles, book chapters, theses, dissertations, government and private industry reports, conference proceedings) as well as unpublished data contributed by researchers. Compared to the previous version of the Midden Database (i.e., ver. 4), this version of the database (ver. 5.0) has been expanded to include more precise midden-sample site location data, calibrated midden-sample age data, and plant functional type (PFT) assignments for the taxa in each midden sample. In addition,...
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Comprehensive sampling of peat, underlying lakebed sediments, and coexisting waters of a naturally uraniferous montane wetland are combined with hydrologic measurements to define the important controls on uranium (U) supply and uptake. The major source of U to the wetland is groundwater flowing through locally fractured and faulted granite gneiss of Proterozoic age. Dissolved U concentrations in four springs and one seep ranged from 20 to 83 ppb (µg/l). Maximum U concentrations are ~300 ppm (mg/kg) in lakebed sediments and >3000 ppm in peat. This study documents the conditions and processes controlling the efficient uptake of U in a relatively remote, natural wetland that is absent of reported U occurrences, mining...
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Studies of marine terraces and their fossils can yield important information about sea level history, tectonic uplift rates, and paleozoogeography. The marine terrace record on Santa Rosa Island, California is complex. Two prominent low-elevation terraces appear to record the ~80 ka (MIS 5a) and ~120 ka (MIS 5e) high-sea stands, based on U-series dating of fossil corals, but interpretations are tentative because of clear indications of open-system behavior with respect to U-series nuclides. Nevertheless, low uplift rates are implied by a preferred interpretation of the ages. It is inferred that low late Pleistocene uplift rates, combined with glacial isostatic adjustment (GIA) processes likely resulted in reoccupation...
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