A high-elevation MIS 5 hydrologic record using mollusks and ostracodes from Snowmass Village, Colorado, USA

Abstract

Sediments containing terrestrial and aquatic mollusks and ostracodes from the Ziegler Reservoir fossil site (2705 m elevation) near Snowmass Village, Colorado, span ~130–87 ka (MIS 5e through 5b). The southeastern area of the site where taxa were recovered was a relatively fresh, shallow, well-vegetated wetland during MIS 5e through 5c time, approximately 2 m deep, with a total dissolved solids value of ~200–1000 mg L− 1. The wetland was seasonally or annually variable and groundwater discharged along the margins of the bounding moraine. Groundwater likely contributed solutes to the system and may have contributed 18O-enriched water. Based on stable isotopes from ostracode calcite (δ18OOST and δ13COST), seasonal evaporation occurred and the dissolved inorganic carbon pool was unexpectedly enriched in 13C. The mollusk and ostracode faunas changed little across the MIS 5e/5d/5c boundaries, whereas a distinct change in the ostracode fauna occurred between the deposition of Unit 11 and Unit 13, which corresponds in time to the MIS 5c/5b boundary, indicating some combination of increased surface and/or groundwater flow, a decrease in water temperature, and a freshening and a possible deepening of the wetland.

North American Hydroclimate During Past Warms States: A Proxy Compilation‐Model Comparison for the Last Interglacial and the Mid‐Holocene

“…Lake records from the western US track vegetation changes and shifts in water levels, with lakes from the northern US Rocky Mountains (Jiménez‐Moreno et al., 2007), the Pacific Northwest (Whitlock & Bartlein, 1997), and northern California (Adam & West, 1983) indicating relative aridity during the LIG, while Great Basin lakes document wetter conditions or conditions similar to the present (Forester et al., 2005; Reheis et al., 2012; Woolfendon, 2003). Other lake records from the Rocky Mountains (Anderson et al., 2014; Baker, 1986; Balch et al., 2005; Miller et al., 2014; Sharpe & Bright, 2014) and southern California (Glover et al., 2017) do not display clear signals of LIG hydroclimate.…”

Freshwater plumes and brackish lakes: Integrated microfossil and O-C-Sr isotopic evidence from the late Miocene and early Pliocene Bouse Formation (California-Arizona) supports a lake overflow model for the integration of the lower Colorado River corridor

“…For example, Echo Lake, situated at nearly 3000 m asl in Colorado, has a low electrical conductivity that equates to a salinity of ~50 mg L -1 , yet its water has a d 18 O value of about -4‰ VSMOW (Henderson and Shuman, 2009). This decoupling between salinity and d 18 O in some lakes readily explains how Candona valves with high, marine-like d 18 O OST values could be produced in a low-salinity, closed-basin environment at Villarroya Lake, Spain (Anadón et al, 2008), and in a freshwater alpine pond at Snowmass Village, Colorado (Sharpe and Bright, 2014). A similar decoupling of salinity and d 18 O values in both the Chemehuevi and Blythe basins effectively accounts for the marine-like Candona d 18 O OST values in both basins.…”

“…The relationships between salinity and carbonate d 18 O-d 13 C values can be fairly complex in lakes, and at times, they may even be counterintuitive (Li and Ku, 1997). It is not uncommon to find examples where terminal but freshwater or mildly brackish lakes generate carbonate d 18 O-d 13 C values that overlap with or even exceed those found in marine carbonates (e.g., Anadón et al, 2008;Sharpe and Bright, 2014). Thus, lakes can produce carbonates that display a wide range of d 18 O-d 13 C relationships (e.g., Talbot, 1990).…”