ABSTRACT: Severe drought in the early Holocene (10,000-6800 BP) interpreted from lake sediment cores, southwestern Alberta, Canada.

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Abstract

Beginning at about 10,000 BP, immediately following the Younger Dryas cold period, climate warmed dramatically and precipitation decreased. Previous research has identified this warm interval, however new results have improved resolution of regional scale effects, timing and severity. Vibracores from 3 glacially-fed subalpine lakes indicate that sedimentation regimes in lakes of the southern Canadian Rocky Mountains changed from allochthonous to autochthonous between 10,000 and 9400 BP. The shift from clastic to biogenic facies suggests decreased suspended sediment load caused by the complete ablation of alpine glaciers. Macrofossil assemblages and stable oxygen isotope data on organic matter from lower Burstall Lake further support total glacial melting. Decreased water levels in closed basin lakes suggest increased warmth and aridity in foothills areas during the early Holocene. Sequence stratigraphic correlation of multiple cores from Frederick Lake and an unconformity in a core from Cartwright Lake suggest that lake water levels decreased by up to 6.5 m. Stable oxygen isotope values measured on organic matter from Sibbald Lake become progressively heavier from ca. 10,000 BP to ca. 6800 BP indicating that evaporation from the lake exceeded atmospheric inputs, evaporatively enriching lake waters in heavy oxygen, and lowering lake levels. Given the disastrous consequences of drought in the 1930's and predictions of global warming, a drought of similar magnitude to that in the early Holocene may re-occur in the next century and cause widespread agricultural catastrophe in the interior of North America.

Bibliography of Canadian Geomorphology