T102 Lacustrine Systems across Space and Time I

Monday, 23 October 2017
8:00 AM - 12:00 PM
Room 307/308

A 5600-YEAR RECORD OF PALEOHYDROCLIMATE FROM LOWER PAHRANAGAT LAKE, SOUTHERN GREAT BASIN

Paper number: T102-8
Program: Technical Sessions
Time: 9:40 AM – 9:55 AM

Authors

Abstract

Continuous, high-resolution archives of paleoclimate are rare for the arid Great Basin province of the United States. Such records provide valuable paleoclimate context for a region of the United States that is especially fast-growing and drought-prone in the midst of rapid climate change. Here, we present a 5600-year sediment core-based record of hydroclimate spanning the later mid-Holocene to recent from Lower Pahranagat Lake (LPAH) in southern Nevada. LPAH is a shallow, spring-fed, alkaline lake and our 13.2 m – long sequence of overlapping cores is dominated by Mg carbonate-rich muds (carbonate typically 50-80%) with evidence of microbial-influenced carbonate precipitation. We extend and build on our earlier core-based work on LPAH (Hickson et al., 2016), applying stable isotopic values (δ18O and δ13C) from downcore fine-fraction (<63 µm) carbonates which are sensitive to hydroclimate in this highly evaporative region. Additional geochemical proxies (TOC/TN/C:N, %CaCO3, and XRD data) provide supporting information on regional hydroclimate and paleoecological change in and around the lake. Numerous records from across the Great Basin have established the Middle Holocene (~7000 – 4000 years B.P.) as a warmer and drier period than the Late Holocene for this region. Especially low δ18O values and a sharp facies change from a peat layer to carbonate mud near the base of the LPAH core record 14C age-dated to ~4800 yrs BP signals a shift to wetter conditions at the latter part of the Middle Holocene and the filling of the lake. Following this, our geochemical data suggest a series of century-scale fluctuations in the hydroclimate of the region. We compare and contrast our record with others from the Great Basin with special emphasis on the high-resolution Leviathan Cave stalagmite record (Lachniet et al., 2014) collected near LPAH. We evaluate the significance of Pacific Ocean SSTs and other relevant forcings to the LPAH record of paleohydroclimate.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-305857

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