Geologic setting and stratigraphy of the Ziegler Reservoir fossil site, Snowmass Village, Colorado. Issue 3 (November 2014)

• Record Type: Journal Article
• Authors: Pigati, Jeffrey S.; Miller, Ian M.; Johnson, Kirk R.; Honke, Jeffrey S.; Carrara, Paul E.; Muhs, Daniel R.; Skipp, Gary; Bryant, Bruce
• Is Part Of: Quaternary research. Volume 82:Issue 3(2014)
• Page Start: 477
• Page End: 489
• Publication Date: 2014-11
• Subjects: Bull Lake glaciation, -- Pleistocene fossils, -- Snowmastodon, -- Paleoclimate, -- Stratigraphy; 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.2013.12.011
• Languages: English
• ISSNs: 0033-5894

Abstract

Abstract: The geologic setting of the Ziegler Reservoir fossil site is somewhat unusual — the sediments containing the Pleistocene fossils were deposited in a lake on top of a ridge. The lake basin was formed near Snowmass Village, Colorado (USA) when a glacier flowing down Snowmass Creek Valley became thick enough to overtop a low point in the eastern valley wall and entered the head of Brush Creek Valley. When the glacier retreated at about 155–130 ka, near the end of Marine Oxygen Isotope Stage 6, the Brush Creek Valley lobe left behind a moraine that impounded a small alpine lake. The lake was initially ~ 10 m deep and appears to have been highly productive during most of its existence, based on the abundant and exquisitely preserved organic material present in the sediments. Over time, the basin slowly filled with (mostly) eolian sediment such that by ~ 87 ka it contained a marsh or wetland rather than a true lake. Open-water conditions returned briefly between ~ 77 and 55 ka before the impoundment was finally breached to the east, establishing ties with the Brush Creek drainage system and creating an alpine meadow that persisted until historic times.