NEW EXTENDED RECORD OF HOLOCENE PALEOECOLOGY AND PALEOHYDROLOGY FROM LOWER PAHRANAGAT LAKE, GREAT BASIN

The Lower Pahranagat Lake (LPAH) is a shallow alkaline lake located in the Pahranagat National Wildlife Refuge in southeastern Nevada. As a natural, long-lived lake, LPAH is significant to paleohydrology and paleoclimatology research in the Great Basin region where lake records are not common. A 4-m sediment core collected from LPAH in 2012 by our research group spans ~2400 years based on ¹⁴C age dating (Theissen et al., 2013). However, a longer ¹⁴C age dated core collected by Wigand (1997) suggests that the sediment record in the lake potentially extends to at least 5500 years. During 2016 we used a new coring system, and were able to collect a >13 m long core likely capturing the full ~5500 year record. Here we report preliminary results of the geochemical record for LPAH from this longer core record. In our effort to investigate the Holocene paleoecology and paleohydrology of the region, we did an elemental analysis of core sediments to determine C, N, and CaCO₃ contents of the core. LPAH sediments are highly enriched in CaCO₃ (typically 50-80%). TOC and TN in the core are both generally low (1 – 3.5% and 0.03 – 0.29% respectively), while organic C/N values are generally high (12 – 86) reflecting dominant input of aquatic vascular plants and terrestrial sources of OM. All of these indicators show some evidence of decade to century-scale variability, that is consistent with our earlier findings. We also present new results of δ¹⁸O and δ¹³C measurements from authigenic carbonates, both previously established as robust indicators of water balance, extending our record of the paleohydrology of the region as well.