Indicators of Euro-American land-use change as geochronologic markers in Midwest floodplain lake sediment archives

Abstract

In association with predicted rising global average temperatures, spring and winter precipitation in the Midwest is projected to increase by up to 30% by the end of this century. Enhanced by the alteration of natural environments, this increase will likely result in more frequent extreme flood events. To best prepare for these circumstances, interest has risen in reconstructing the dynamics between changing climate, altered landscapes, and fluvial systems with age-depth modeling, often using radiocarbon (14C) and 210Pb dating and multi-proxy evidence from floodplain lake sediment archives. Age- depth modeling over the last 300 years can be difficult, however, due to a large plateau in the radiocarbon calibration curve, and 210Pb dating is not reliable for all sediment records. Here, indicators of land-use change, magnetic susceptibility, Rb/Sr, Pb/Zr, and d15N values, were used to create age-depth control for Shannon Lake, IN, a difficult-to-date 600-year-old oxbow lake of the White River near Indianapolis. Age control for Shannon Lake was completed by correlating the timing in the rise of the same proxies from a previously well-dated lake record from Half Moon Pond, an oxbow lake of the White River near Petersburg, IN. The Shannon and Half Moon records were compared to those of three floodplain lake records of the Ohio River floodplain: Avery Lake, IL, Goose Pond, IN, and Grassy Pond, KY to investigate how these proxies varied in floodplain lake sediment from the lower Ohio River. The land-use indicators provided age-control for Shannon Lake, and the indicators of land-use change for the White River records resembled those of the Ohio River records over the last 600 years, where the onset of Euro-American land-use changes were detected at or around 1750 CE. MS, Rb/Sr, and d15N values displayed the greatest resemblance, while greater variations in Rb/Sr values were observed across the five lake records, potentially due to differences in regional setting or differences in the scale of the White River and Ohio River watersheds.