Portal de Periódicos da CAPES

Cryostratigraphy of the Klondike "muck" deposits, west-central Yukon Territory

2000; NRC Research Press; Volume: 37; Issue: 6 Linguagem: Inglês

10.1139/e00-013

1480-3313

Erica Kotler, C. R. Burn,

Geological Studies and Exploration

Four late Quaternary cryostratigraphic units are recognized in the unconsolidated valley-bottom deposits of the Klondike area, Yukon Territory. Three of the units, in ice-rich, loessal sediments of pre-Wisconsinan or Wisconsinan age, collectively compose the King Solomon Formation. They are overlain by a Holocene organic unit. The units are distinguished by their cryostratigraphic characteristics and oxygen-isotope ratios of included ground ice. The basal unit is the Last Chance Creek Member, a pre-Late Wisconsinan deposit, containing preserved ice wedges δ 18 O ~ -28 to -26‰; δD ~ -225 to -209‰). The overlying Quartz Creek Member, a Late Wisconsinan unit, is dominated by organic-rich loess. Massive ice is noticeably absent, although the sediments are ice rich. The isotopic composition of ice in this unit is characteristic of full-glacial conditions (δ 18 O ~ -32 to -29‰; δD ~ -234 to -257‰). An abrupt change to warmer and wetter conditions at the end of glaciation, prior to the Holocene, is recorded by the ice-rich, colluviated Dago Hill Member (δ 18 O ~ -28 to -21‰; δD ~ -164 to -225‰), which began accumulating by 11.62 14 C ka BP. Large ice wedges originate in this unit, and, in places, penetrate the underlying full-glacial sediments. Even higher δ 18 O and δD values occur for ice in the Holocene organic unit (δ 18 O ~ -25 to -20‰; δD ~ -164 to -189‰). The majority of the massive icy bodies in the King Solomon Formation are ice wedges, but pool ice and aggradational ice are also exposed, especially in the Dago Hill Member. Massive icy beds formed by groundwater intrusion into permafrost occur at the lower contact of the Quartz Creek Member.