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Glacial Lake Devlin and the chronology of Pinedale Glaciation on the east slope of the Front Range, Colorado

1980; United States Department of the Interior; Linguagem: Inglês

10.3133/ofr80725

2332-4899

Richard F. Madole,

Fire effects on ecosystems

Glacial Lake Devlin was damned in a tributary valley 2.3 km upvalley from the limit of Pinedale Glaciation in North Boulder Creek valley, Boulder County, Colorado.Lake Devlin was about 2 km long, 200-460 m wide, and as much as 60 m deep.The distribution of till along Korth Boulder Creek indicates that lakes should have fomed during both the Pinedale and Bull Lake Claciations, but evidence that an older lake existed is not unequivocal.The shoreline of the Pinedale-age lake is relatively distinct and occurs at an altitude of about 2,975 n (9,760 ft).Coring and auger ing at three localities revealed 36 ni of lake sediment including, from the top down, 13 rri of silt and clay rhythmites, 10 01 of sand and gravel, and at least 8 n (bottom not reached) of clay with interbedded sand and gravel.The 10 in of sand and gravel is believed to be proglacial outwash of Pinedale age from three snail glaciers in the upper part of the Caribou Creek drainage basin deposited before Caribou Creek was dammed.The underlying clayey sediment probably was deposited in a lake of pre-?ine;lale age.Organic matter concentrated from core samples of the rhythnites provided nine C ages that indicate that the latest phase of Lake Devlin persisted from about 22,400+1230 (DIC-870) to 12,180+240 (OaK-4834) 14 C years ago.Because Lake Devlin formed as ice of the Pinedale Glaciation was nearing its maximum expansion, this maximum expansion is inferred to have occurred within or relatively shortly after the interval between 23,000 and 21,000 years B.P.