Constraining water balance in the Bonneville Basin during the last glacial period and deglaciation using 87Sr/86Sr and δ18O of lacustrine carbonates
Abstract
Geochemical records from closed basin lakes provide important constraints on past changes in regional precipitation - evaporation (P-E). This study refines our understanding of paleohydrology in the Bonneville Basin and explores the Basin's response to past abrupt changes, including Heinrich Event 2. We present Sr and O isotope records from lacustrine carbonates deposited in caves and other protected spaces during periods of higher lake levels (McGee et al., 2012). These records, anchored by precise U/Th and 14C dating, offer new insights into changes in lake level and water balance during the last glacial period and deglaciation. The Sr isotope composition of lake water is determined by the relative contributions of the two major fluvial inputs to the lake, the Bear River in the north and the Sevier River in the south, which have distinct 87Sr/86Sr ratios (Hart et al. 2004). Sr ratios of lake water, as recorded in lacustrine carbonates from different locations and elevations in the basin, offer insight into both lake mixing and changes in the position of the winter storm track, the primary source of precipitation to the Great Basin. High-resolution δ18O data from the carbonates trace changes in basin P-E and water column mixing. Trace element concentrations in the carbonates, especially those of Mg, Rb and Ba, are used to test interpretations of Sr and O isotope changes. Hart, W.S. et al., The 87Sr/86Sr ratios of lacustrine carbonates and lake-level history of the Bonneville paleolake system. GSA Bulletin 2004; 116: 1107-1119. McGee, D., et al. Lacustrine cave carbonates: Novel archives of paleohydrologic change in the Bonneville Basin (Utah, USA). EPSL 2012; In press.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMPP51A2099S
- Keywords:
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- 1040 GEOCHEMISTRY / Radiogenic isotope geochemistry;
- 1833 HYDROLOGY / Hydroclimatology