Last glacial maximum ecology and climate from terrestrial gastropod assemblages in Peoria loess, western Kentucky. (4th May 2020)

• Record Type: Journal Article
• Authors: Grimley, David A.; Counts, Ronald C.; Conroy, Jessica L.; Wang, Hong; Dendy, Sarah N.; Nield, Catherine B.
• Is Part Of: Journal of quaternary science. Volume 35:Number 5(2020)
• Page Start: 650
• Page End: 663
• Publication Date: 2020-05-04
• Subjects: Kentucky -- last glacial -- loess -- stable oxygen and carbon isotopes -- terrestrial gastropods; Geology, Stratigraphic -- Quaternary -- Periodicals; Paleontology -- Quaternary -- Periodicals; 551.79
• DOI: 10.1002/jqs.3206
• Languages: English
• ISSNs: 0267-8179

Abstract

ABSTRACT: The Rocks loess section, in unglaciated western Kentucky, provides a high‐resolution environmental record during the last glacial maximum onset. The Peoria Silt (9 m thick) contains 26 terrestrial gastropod species, with up to 15 species within a single 5 cm interval. Thirteen radiocarbon ages, using shells or charcoal, range between 30 and 24.5 cal ka; younger loess has been leached or eroded. Stratigraphic shifts in gastropod assemblages imply significant cooling, particularly ~27 cal ka, as solar insolation was decreasing and the southern Laurentide Ice Sheet rapidly advancing. Midwestern to southern species (e.g. Anguispira kochi, Gastrocopta pentodon, Hawaii miniscula, Helicodiscus parallelus, Vallonia perspectiva ) occur only in the lowermost Peoria Silt (~30–27 cal ka). In contrast, cold‐tolerant species ( Columella alticola, Vertigo modesta, Vallonia gracilicosta) occur only in full glacial Peoria Silt (27–24.5 cal ka). Inferred mean July temperatures, from mutual climatic range methods, range from ~23 °C at 30 cal ka, cooling to ~18 °C by 26 cal ka; about 3–8 °C cooler than today (~26 °C). Superimposed on this cooling trend are multi‐centennial variations in detrital carbonate, fossil shell concentrations, palaeotemperature estimates, and oxygen isotope values ( Vertigo, Discus, Helicodiscus ). The finer‐scale variations imply relatively synchronous fluctuations in glacial sediment supply, loess sedimentation, and climate.