Variations in loess accumulation rates in the mid-continent, United States, as reflected by magnetic susceptibility

Abstract

Detailed magnetic susceptibility records of late Wisconsin loess sequences in the southwest Indiana region show several distinct changes in magnitude that reflect variations in loess accumulation rate. The comparison of the magnetic susceptibility signal and sedimentary features within the loess reveal the following relations: (1) low magnetic susceptibility values correspond to incipient paleosols that record periods of low loess accumulation rates; (2) highly variable values within intermediate to high magnetic susceptibility zones correspond to stratified loess that represents periods of high loess accumulation rates; and (3) moderate to high magnetic susceptibility values correspond to massive loess that may reflect periods of moderate to high loess accumulation rates. We suspect that soil moisture controls the loess accumulation rate, and, if so, our work shows that soil moisture alternated about 24 times between 25 and 14 ka in the middle of North America.