LATE GLACIAL TO EARLY HOLOCENE PALEOLIMNOLOGY INFERRED FROM BARLEY LAKE SEDIMENTS (NORTHERN COASTAL RANGES, CALIFORNIA)

The hydroclimate of the western US changed abruptly during the Pleistocene to Holocene boundary. Here, we present a multi-proxy study on a sediment core from Barley Lake (BL) that provides insight into past variations in lake-level and productivity during the late-Glacial to Holocene transition between 12,850 – 8,130 cal yrs BP. BL is a small (presently shallow), landslide formed lake that is characterized by a small, steep-sided drainage basin with an ephemeral outlet lake located in Mendocino County, California. BL (39.6° N) is located south of the average latitudinal position of the California precipitation dipole (~40° N) (Dettinger et al., 1998; Wise, 2010; Wise, 2016), BL represents an essential location for recording changes in the dipole's position and strength over time. A combination of physical and chemical analyses was collected, including magnetic susceptibility, total organic matter, total carbonate, total organic carbon, bulk d13C(bulk organic C), and grain size. Age control is constrained by twelve radiocarbon dates on discrete organic materials between the depths 474 and 746 cm. An age model was constructed using Bacon version 2.2 (Blaauw and Christen, 2011). The results are used to reconstruct a 4700-year history of lake-level and productivity and used to infer past hydrologic conditions at decadal to multi-decadal resolution. The data reveal two distinct lake states: 1) an oligotrophic, deep lake during the late-Glacial (12,850 – 11,500 cal yrs BP), and 2) a eutrophic, shallow lake during the early Holocene (11,500-8,130 cal yrs BP). The former encapsulates the Younger Dryas chronozone, suggesting wet conditions in Northern Coast Range during the Younger Dryas. At the same time, lakes in the southwest US, such as Lake Elsinore (Kirby et al., 2013) and Silver Lake (Kirby et al., 2015) indicate dry and/or variably dry/wet conditions. Comparison to regional records in the western US demonstrates an apparent north-south wet-dry dipole with shifts between wetter or drier conditions during the Younger Dryas and into the Holocene. A closer look at the early Holocene record shows a long-term transgression between 11,500 – 8,130 cal yrs BP, with a notable change in lake status ca. 10,200 cal yrs BP. Climatic forcings are explored (SSTs, Insolation, AMOC) to explain the reasons for the inferred changes.