Geologic setting and stratigraphy of the Ziegler Reservoir fossil site, Snowmass Village, Colorado

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.Published by Elsevier Inc. on behalf of University of Washington.

Preserved Proteins from Extinct Bison latifrons Identified by Tandem Mass Spectrometry; Hydroxylysine Glycosides are a Common Feature of Ancient Collagen

“…Recently, a series of large extinct mammal bones were unearthed at a reservoir near Snowmass Village, Colorado, USA (49,50). The finding was made during a construction project at the Ziegler Reservoir, a fossil site that was originally a lake formed at an elevation of ϳ2,705 m during the Bull Lake glaciations ϳ140 ky ago (49,51).…”

“…The finding was made during a construction project at the Ziegler Reservoir, a fossil site that was originally a lake formed at an elevation of ϳ2,705 m during the Bull Lake glaciations ϳ140 ky ago (49,51). The original lake area was ϳ5 hectares in size with a total catchment of ϳ14 hectares and lacked a direct water flow inlet or outlet.…”

“…The original lake area was ϳ5 hectares in size with a total catchment of ϳ14 hectares and lacked a direct water flow inlet or outlet. This closed drainage basin established a relatively unique environment that resulted in the exceptional preservation of plant material, insects (52), and vertebrate bones (49). In particular, a cranial specimen from extinct Bison latifrons was unearthed from the Biostratigraphic Zone/Marine Oxygen Isotope Stage (MIS) 5d, which dates back to ϳ120 ky (53,54).…”

Chronology of terraces in the Rio Grande rift, Socorro basin, New Mexico: Implications for terrace formation

“…11). The Valle de la Parida surface (135 ± 10 ka) was abandoned close to the transition from marine isotope stage (MIS) 6 (191-130 ka; Lisiecki and Raymo, 2005, corresponding to the Bull Lake glaciation in the Rocky Mountains, dated there 155-130 ka; Mahan et al, 2014;Pigati et al, 2014) to interglacial MIS 5.5 at 130 ± 2.5 ka (Lisiecki and Raymo, 2005). Thereafter, the Rio Grande incised by >40 m before 79 ka when the Jornada del Muerto flow was emplaced ~12 m above the historical river level, likely during the mildly glacial stages 5.4 and 5.2.…”

A geochronologic framework for the Ziegler Reservoir fossil site, Snowmass Village, Colorado

“…We did not have a modern analog sample for the lake sediment since the surrounding lake basin and overlying material had been either very heavily modified or removed prior to the arrival of scientists at the site. However, since fluvial input to the lake was likely minimal (see Pigati et al, 2014), accumulation of eolian sediments would have been interrupted occasionally by the near-shore slumps that consisted of reddish-brown coarse sediments as compared to the mostly gray, finegrained lacustrine material. We did not sample for OSL anywhere near the debris flows.…”