Middle Wisconsinan Mammals, Stratigraphy, and Sedimentology at the Ketza River Site, Yukon Territory

Abstract

Remains of Middle Wisconsinan mammoth, bison, horse, moose, hare, ground squirrel and lemming were recovered from sediments that stratigraphically underlie till of the Late Wisconsinan McConnell Glaciation along the Ketza River valley. The bone-bearing sediments are a complex of colluvium, fan, and outwash sediments. Similar fossil sites are likely to occur where glaciofluvial watercourses abut hillside deposits laid down prior to the onset of McConnell Glaciation.Les restes de mammouth, de bison, de cheval, d'orignal, de lièvre, d'écureuil et de lemming ont été recueillis dans des sédiments sous-jacents au till de la Glaciation de McConnell du Wisconsinien supérieur, le long de la vallée de Ketza. Les sédiments renfermant ces ossements représentent un complexe de colluvions, d'alluvions et de sédiments fluvio-glaciaires. D'autres sites fossilifères risquent de se trouver là où les cours d'eau fluvio-glaciaires traversent des colluvions déposées avant le début de la Glaciation de McConnell.Reste von Mammut, Bison, Pferd, amerikanischem Elch, Hase, Eichhörnchen und Lemming aus dem mittleren Wisconsinium sind in Sedimenten, die stratigraphisch unter dem Till der McConnell-Vereisung des späten Wisconsiniums liegen, entlang des Ketza River-Tals gefunden worden. Dièse knochenhaltigen Sedimente bestehen aus einem Komplex von Kolluvium, Alluvialfachern und glazifluviatilen Sedimenten. Ähnliche Fossil-Fundstellen befinden sich wahrscheinlich da, wo glazifluviatile Wasserläufe auf Berghang-Ablagerungen treffen, die vor dem Beginn der McConnell-Vereisung abgelagert worden sind

Investigating the glacial history of the northern sector of the Cordilleran Ice Sheet with cosmogenic 10Be concentrations in quartz

“…The McConnell glaciation is firmly dated to OIS 2 (Late Wisconsin). Radiocarbon ages from wood and fossils underlying McConnell till indicate that the McConnell glaciation began after 29,600±300 14 C yr BP (Matthews et al, 1990), but glaciers did not advance into major valleys before 26,350±280 14 C yr BP (Jackson and Harington, 1991), and a fully developed CIS did not exist until after 23,900±1140 14 C yr BP (Lowdon and Blake, 1981). Published radiocarbon ages indicate that the St. Elias lobe of the CIS was in retreat by 13,660±180 14 C yr BP (Rampton, 1971) and the Selwyn lobe by 12,590±120 14 C yr BP (Ward, 1989) (Fig.…”

The Last Cordilleran Ice Sheet in Southern Yukon Territory

“…Bone-bearing gravels and colluvium beneath McConnell till immediately adjacent to the PeIIy Mountains along Ketza River have been radiocarbon dated at 26,350 ± 280 BP (TO-393; Jackson and Harington, 1991). This age indicates that glacial ice had not expanded out of the PeIIy Mountains, a centre of ice accumulation, by that time.…”

“…Pacific Ocean Harington, 1991 ). This last Cordilleran Ice Sheet was the least extensive of known Yukon regional glaciations (Fig.…”

Soil genesis in relation to glacial history, Central Yukon.

“…(Matthews et al 1990). Mammal fossils (~ 26.4 ka BP) below McConnell till along the Ketza River similarly date the glaciation to Late Wisconsinan (Jackson and Harington 1991). Expansion of alpine glaciers in source areas may have begun as early as 29 ka BP but a continuous ice sheet did not develop until after approximately 24 ka BP .…”

“…Since multiple glaciations were first identified by Bostock, efforts have been made to establish their ages using a variety of methods including radiocarbon dating (Matthews et al 1990;Jackson and Harington 1991), fission track dating and tephrochronology (Westgate et al 2001;Westgate et al 2008), paleomagnetic and 40 Ar-39 Ar dating (Jackson et al 2003;Huscroft et al 2004), and terrestrial cosmogenic nuclide (TCN) dating (Ward et al 2007).…”