Doctoral Dissertation Research: The Nature and Rate of Environmental Change in the Sierra Nevada -- AMS Radiocarbon Analysis of the Pleistocene/Holocene Transition

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9406575 BYRNE Research on global change has focused on understanding contemporary natural and human processes, but an important ancillary line of inquiry consists of reconstruction of historical records of change, thereby enhancing knowledge of the outcomes of natural processes upon which patterns of human- induced change now are superimposed. Paleoenvironmental records from around the world indicate that dramatic changes took place during the transition from the Pleistocene to Holocene periods roughly 10,000 years ago. The primary driving forces behind these changes are thought to have been fluctuations in global atmospheric and oceanic patterns. More accurate timing of paleoenvironmental records is necessary in order to understand these processes, however. This doctoral dissertation research project will focus its attention on advancing the synchronous record of change in the Sierra Nevada of eastern California over the period from 14,000 years to 9,000 years before the present. Sediment cores have been drawn from a number of lakes in the region, and pollen and macrofossil evidence in the cores have been identifies. Preliminary analyses using traditional radiocarbon dating techniques indicate strong synchroneities among the sites. More detailed analyses will be conducted by making higher-resolution AMS (accelerator mass spectrometry) 14-C measurements on conifer needle fragments and pollen grains. This project will improve the chronological precision of records that document the nature and rates of environmental change in the Sierra Nevada during the Pleistocene/Holocene transition. Of particular value will be improved understanding of how abruptly climates may change. As a doctoral dissertation improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.