Abstract

Mid-Holocene eolian dune and sand-sheet deposits, rare in the northern Great Plains, are buried under a meter or more of younger sediment in the glacial Lake Hind Basin, southwestern Manitoba. Six facies observed in three cut-bank exposures allow reconstruction of sedimentary processes and resulting landscape at the study site in the basin center around 6100 cal (calibrated) BP. A mosaic of parabolic dunes with interdune and dune-marginal lightly vegetated sand sheets developed in the Souris River flood plain that was least partly covered with woodlands and wetlands. During floods, nearby interdune areas were inundated. Dune foreset orientation and stratification indicate a more easterly sand transport direction, lending support to the hypothesis that more pervasive westerly “zonal” flow contributed to mid-Holocene aridity evident elsewhere in the northern Great Plains. More arid conditions during the mid-Holocene may have helped trigger eolian activity. However, with the exception of a more active eolian component, the flood-plain environment may have been similar to that of the late Holocene. Mid-Holocene Gowen (Mummy Cave Complex) artifacts, the first found in Manitoba, indicate that people inhabited the resource-rich environment where eolian and flood-plain landforms occurred together. Protection of mid-Holocene dune and sand-sheet strata during late Holocene phases of eolian reactivation is attributed to rapid rise in the local water table soon after deposition.

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