A comparison of magnetic susceptibility measurement techniques and ferrimagnetic component analysis from recent sediments in Lake Pepin (USA)

Abstract

AbstractMagnetic susceptibility (MS) is commonly measured on lake sediments and used as a proxy for clastic input and soil erosion, for correlating among cores in the same lake basin and aligning successive overlapping drives of the same core. There are several common techniques for measuring MS, each with its own advantages. Here we compare three such techniques measured on a sediment core from Lake Pepin: (a) loop-sensor MS logging on wet sediment of the intact core; (b) point-sensor MS logging on wet sediment of a split (lengthwise) core; and (c) discrete MS measurements of dried subsamples using a susceptibility bridge. To obtain further information about the origin of downcore MS variability, additional magnetic measurements were performed on discrete samples to model ferrimagnetic sedimentary components. Overall trends and individual features in MS curves agree reasonably well between techniques; however, the amplitude of local minima and maxima varies according to the technique used. All three MS techniques captured distinct events c. 1900 and 1940, attributed to increases in allochthonous ferrimagnetic components. The ferrimagnetic particle flux has declined over the past half-century despite increasing sediment accumulation in Lake Pepin, suggesting a possible shift in sediment sources from fields to stream banks.