A geochronologic framework for the Ziegler Reservoir fossil site, Snowmass Village, Colorado. Issue 3 (November 2014)

• Record Type: Journal Article
• Authors: Mahan, Shannon A.; Gray, Harrison J.; Pigati, Jeffrey S.; Wilson, Jim; Lifton, Nathaniel A.; Paces, James B.; Blaauw, Maarten
• Is Part Of: Quaternary research. Volume 82:Issue 3(2014)
• Page Start: 490
• Page End: 503
• Publication Date: 2014-11
• Subjects: Luminescence dating, -- Radiocarbon dating, -- Surface exposure dating, -- U-series dating, -- Ziegler Reservoir; Geology, Stratigraphic -- Quaternary -- Periodicals; Glacial epoch -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; Époque glaciaire -- Périodiques; Geology, Stratigraphic; Glacial epoch; Quaternary Geologic Period; Electronic journals; Periodicals; 551.79
• DOI: 10.1016/j.yqres.2014.03.004
• Languages: English
• ISSNs: 0033-5894

Abstract

Abstract: The Ziegler Reservoir fossil site near Snowmass Village, Colorado (USA), provides a unique opportunity to reconstruct high-altitude paleoenvironmental conditions in the Rocky Mountains during the Last Interglacial Period. We used four different techniques to establish a chronological framework for the site. Radiocarbon dating of lake organics, bone collagen, and shell carbonate, and in situ cosmogenic 10 Be and 26 Al ages on a boulder on the crest of a moraine that impounded the lake suggest that the ages of the sediments that hosted the fossils are between ~140 ka and >45 ka. Uranium-series ages of vertebrate remains generally fall within these bounds, but extremely low uranium concentrations and evidence of open-system behavior limit their utility. Optically stimulated luminescence (OSL) ages (n = 18) obtained from fine-grained quartz maintain stratigraphic order, were replicable, and provide reliable ages for the lake sediments. Analysis of the equivalent dose (DE ) dispersion of the OSL samples showed that the sediments were fully bleached prior to deposition and low scatter suggests that eolian processes were likely the dominant transport mechanism for fine-grained sediments into the lake. The resulting ages show that the fossil-bearing sediments span the latest part of Marine Oxygen Isotope Stage (MIS) 6, all of MIS 5 and MIS 4, and the earliest part of MIS 3.