New radiocarbon dates for early deglaciation from the southeastern Coast Mountains of British Columbia

Souch, Catherine

doi:10.1139/e89-182

Cited by 11 publications

(7 citation statements)

References 10 publications

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“…A number of workers (e.g. Souch, 1989) have commented on the apparent rapid disintegration of the Cordilleran ice about 11,000 BP, and Clague and Evans (1993) used the rapid modern retreat of large glaciers in the Yukon as an analogue for latePleistocene retreat of the Cordilleran ice sheet.…”

Section: Discussionmentioning

confidence: 99%

The geomorphic and paleoenvironmental record in the sediments of Atlin Lake, northern British Columbia

et al. 2006

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Section: Discussionmentioning

confidence: 99%

The geomorphic and paleoenvironmental record in the sediments of Atlin Lake, northern British Columbia

et al. 2006

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“…The upstream parts of many drainage basins became ice free before the valleys downstream, resulting in the formation of many proglacial lakes. Some montane valleys on the drier east side of the southern Coast Mountains were ice free and forested prior to 11 500 years BP (Souch, 1989), suggesting that déglaciation may have been well underway in the southern interior by that time. A few minor readvances occurred at various times during the period of general recession.…”

Section: La Séquence De Sédiments Quaternaires De Grande Puissance Dementioning

confidence: 99%

The Cordilleran Ice Sheet and the Glacial Geomorphology of Southern and Central British Colombia

Ryder¹,

Fulton²,

Clague³

2007

gpq

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This paper reviews the current state of knowledge about the Cordilleran Ice Sheet in southern and central British Columbia. Reconstructions of the ice sheet and the styles of ice expansion and déglaciation are based on extensive and varied glacigenic sediments and landforms that date from Late Wisconsinan (Fraser) Glaciation. Late-glacial lakes and sea level changes are also described and related to isostatic and eustatic effects. The timing of ice expansion and recession during Fraser Glaciation was markedly asymmetric: ice build-up commenced about 29 000 years BP, culminated between 14 500 and 14 000 years BP1 and déglaciation was largely completed by 11 500 years BP. Most of this interval appears to have been dominated by montane glaciation, which produced striking erosional landforms. A Cordilleran Ice Sheet existed from only about 19 000 to 13 500 years BP. An older glaciation, probably of Early Wisconsinan age, has been recognized from widespread exposures of drift that underlies Middle Wisconsinan non-glacial sediments. Pre-Wisconsinan drift is present near Vancouver. Drifts of late Tertiary to Middle Pleistocene age have been dated by association with volcanic sequences in the southern Coast Mountains and the central Interior, and by paleomagnetic studies in the southern Interior.On résume ici l'état des connaissances sur l'Inlandsis de la Cordillère du sud et du centre de la Colombie-Britannique. Les reconstitutions de l'inlandsis et les modes d'englaciation et de déglaciation sont fondés sur les formes et les sédiments glaciaires qui datent de la glaciation du Wisconsinien supérieur (Fraser). On décrit également les lacs tardiglaciaires et les changements du niveau marin en relation avec les conséquences sur les niveaux isostatique et eustatique. Les rythmes de la progression et du retrait glaciaire ont été tout à fait différents; la giaciation a commencé vers 29 000 BP, a connu son optimum entre 14 500 et 14 000 BP et la déglaciation était à toutes fins utiles terminée dès 11 500 BP. La plus grande partie de cette époque a été dominée par une glaciation de type alpin, qui a engendré des formes d'érosion remarquables. L'Inlandsis de la Cordillère n'a existé que de 19 000 à 13 500 BP. On a identifié une glaciation plus ancienne, probablement du Wisconsinien inférieur, à partir des affleurements répandus de dépôts glaciaires sous-jacents aux sédiments non glaciaires du Wisconsinien moyen. On a observé des dépôts glaciaires pré-wisconsiniens près de Vancouver. Les dépôts glaciaires datant du Tertiaire supérieur au Pleistocene moyen ont été datés par association aux séquences volcaniques du sud des montagnes Côtières et du centre de l'Intérieur et grâce à des études de paléomagnétisme menées dans le sud du système de l'Intérieur.Dieser Artikel gibt einen uberblick ûber den gegenwartigen Forschungsstand zur Kordilleren-Eisdecke im Sùden und im Zentrum von British Columbia. Die Rekonstruktionen der Eisdecke und der Art und Weise der Eisausdehnung und Enteisung stùtzen sich auf extensive und mannigfache glazig...

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“…Thicknesses in both cases would have reached the order of 2 km at the maximum phase, and less at other times. Durations are uncertain, but the glacial maximum is thought to have been short-lived, with deglaciation by about 11000 radiocarbon years ago (Souch, 1989). According to Booth (1987), the Puget Lobe entered Washington State for only 4500 years.…”

Section: Ice-stream Gradients and Velocitiesmentioning

confidence: 99%

Abraded rock landforms (whalebacks) developed under ice streams in mountain areas

Evans

1996

Ann. Glaciol.

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Like many mountain ranges, the Coast Mountains of British Columbia, Canada, have undergone both local and ice-sheet glaciation. Effects of ice sheets are concentrated along major valleys and on adjacent spurs and passes which carried strong flows of diffluent ice. The major valleys are broad glacial troughs with frequent rock basins. Their slopes are broken into rounded, steep-sided bosses whalebacks abraded on all sides: they are of the order of 100 m to 1 km long, and 10 m high. In the southern Coast Mountains, the distribution of these whalebacks is consistent with a proposed pattern of former ice streams 1.0–2.1 km thick, within the Cordilleran ice sheet. They are best developed where geological structures parallel the valley and thus the former ice-flow direction, but they are found on a range of lithologies and some are transverse to structure. The whalebacks provide an impression of glacial streamlining, and occasionally grade into rock drumlins. Roches moutonnées are rare in the major troughs.It is hypothesised that these whalebacks and rock drumlins develop under ice streams of Greenland or East Antarctic type, sliding rapidly over bedrock and exploiting rock weaknesses to produce streamlined features. Lee slopes are abraded when thick ice suppresses bed separation, even with rapid flow; basal ice of low viscosity would aid this suppression. Water pressures under the ice streams may have remained high, so that lee-side plucking was rare; such plucking is most likely where pressure fluctuates dramatically, and especially when lee cavities under active ice reach atmospheric pressure.

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New radiocarbon dates for early deglaciation from the southeastern Coast Mountains of British Columbia

Cited by 11 publications

References 10 publications

The geomorphic and paleoenvironmental record in the sediments of Atlin Lake, northern British Columbia

The geomorphic and paleoenvironmental record in the sediments of Atlin Lake, northern British Columbia

The Cordilleran Ice Sheet and the Glacial Geomorphology of Southern and Central British Colombia

Abraded rock landforms (whalebacks) developed under ice streams in mountain areas

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