Sources of Sediment in Lake Pepin on the Upper Mississippi River in Response to Holocene Climatic Changes |
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| Authors: | David W Kelley Stefanie A Brachfeld Edward A Nater Herbert E Wright Jr |
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| Institution: | (1) Department of Geography, University of St. Thomas, 2115 Summit Ave., St. Paul, JRC 432, 55105, MN, USA;(2) Department of Earth and Environmental Studies, Montclair State University, 07043, NJ, Montclair, USA;(3) Department of Soil, Water, and Climate, University of Minnesota, St. Paul, 55108, MN , USA;(4) Department of Geology, & Geophysics, University of Minnesota, 55455 Minneapolis, MN, USA |
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| Abstract: | Sediments from Lake Pepin on the Mississippi River, southeastern Minnesota, are used as provenance tracers to assess variations
in hydrology and sediment-transport during the middle Holocene. Three rivers contribute sediment to Lake Pepin, and each catchment
is characterized by a distinctly different geologic terrain. The geochemical fingerprint for each drainage basin was determined
from the elemental composition of heavy minerals in the silt-sized fraction of modern sediment samples. Down-core elemental
abundances were compared with these fingerprints by use of a chemical-mass-balance model that apportions sediment to the source
areas. We observed a decreased contribution from the Minnesota River during the interval ~6700–5500 14C yr BP, which we attribute to decreased discharge of the Minnesota River, likely controlled by a combination of precipitation,
snow melt, and groundwater input to the river. This hydrologic condition coincides with the mid-Holocene prairie period recorded
by fossil pollen data. The occurrence of this feature in a proxy record for hydrologic variations supports the hypothesis
that the mid-Holocene prairie period reflects drier conditions than before or after in midwestern North America. |
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| Keywords: | Geochemical fingerprinting Holocene Lake Pepin Lake sediments Mass balance Paleoclimatic reconstruction |
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