Thaw lakes, thaw sinks and soils in northern Alaska
DOI:
https://doi.org/10.26485/BP/1969/20/19Keywords:
aeolian deposits, thermokarst, organic sediments, Tundra soil, Umiat, AlaskaAbstract
Thaw lakes and thaw sinks are present in the aeolian silts just south of Umiat, Alaska. Through headward erosion, thawing of perennially frozen ground and filling, most lakes have undergone partial drainage exposing the lake floors. The lake floors are in step-like fashion, usually with 1 to 5 feet in elevation between the steps. The steps are a result of a complex of downcutting of drainage channels and collapse of underlying ground together with erosion and filling along the·lake margins. Two 14C dates from buried organic matter in the aeolian silts yielded ages of 9325 and 9130 yr. BP. whereas one date from the 5-foot depth of the exposed lake floor yielded an age of 4590 yr. BP.
Whereas the original aeolian silts were once virtually organic-free, the sediments of the lake floors have a considerable quantity of organic matter mixed throughout the substrate. This increased organic matter content in the lower positions is reflected in the soil morphology.
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