ABSTRACT: Lacustrine sedimentary response to external geomorphic changes in the early Holocene, Western Canada.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Sedimentary records from closed basin lakes are most often used to infer past climatic changes on the assumption that changes in sedimentation are largely autochthonous. On the basis of cores from closed basin lakes throughout Alberta and Yukon, it is suggested that apparent changes in allochthonous sediment flux and water levels during the early Holocene may in part be explained by large scale changes in post-glacial drainage patterns. Incision of glacial sedimentary fills in river valleys appears to have begun in many places immediately after 10,000 BP, resulting in lowering of local base levels to modern elevations during the Early Holocene. It is suggested that this rapid incision radically altered the drainage of water across the landscape, resulting in the 'locking in' of major hydrological features on the landscape. These geomorphic changes would have resulted in the diversion of flow from many formerly open lake basins, reduced surface runoff and greatly reducedsediment transport as these lakes became closed basins. An additional consequence of this rapid incision would have been lowering of local water tables in response to lowered base level. This would have resulted in lower water levels in lakes adjacent to incised river systems, particularly small lakes formed in hydraulically conductive glacial sediments. Such lake level fluctuations, taken separately from geomorphic forcing, would appear to indicate a strong negative water balance. While a negative water balance may have existed in the early Holocene, this geomorphic forcing mechanism wouldaugment direct climatic effects and could also explain disparate water level records from lakes in different locations.

Bibliography of Canadian Geomorphology