EES Geoscience Seminar Series: Dr. B. Brandon Curry - Principal Research Scientist, Quaternary Geologist - Illinois State Geological Survey - University of Illinois Urbana-Champaign

Feb 16, 2024

03:30 PM - 05:00 PM

Trowbridge Hall, 125 TH

123 South Capitol Street, Iowa City, IA 52240

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Title: "LGM loess chronology and composition as seen through the lens of fossiliferous lake sediments in central Illinois"

Silty lacustrine and paludal records spanning from the penultimate deglaciation (late Illinois Episode) to the present are preserved in kettles with marine isotope stage (MIS) 6 ages that lie adjacent to MIS 2 outwash terraces along the valleys of the Sangamon and Illinois Rivers. Geochemical, mineralogical, particle-size, and chronological records from two basins, Smith Lake and Lake Ben, provide a unique opportunity to assess loess age and provenance. Other than subtle laminations and fossils of emergent and aquatic plants and animals, the silty texture, chemical composition, and mineralogy of the lake sediment closely resemble Peoria Silt (loess). Sediment-core confirm rapid deposition of proximal loess derived from the nearby Manito plain from ca. 31.1–18.0 cal k.y. B.P. From 18.0–15.9 cal k.y. B.P., deposition of proximal loess was gradually replaced by far-traveled (distal) loess chiefly derived from Superior lobe provenance and global dust. The succession is capped by a cumulic gleysol that formed until ca. 14.0 cal k.y. B.P. Of interest to the Iowans in the audience is trace element evidence of Des Moines lobe-derived distal loess from at least 45 cal k.y. B.P. to 31 cal k.y. B.P., and much less contribution, if any, from 18 to 14 cal k.y. B.P.

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