Journal Title

Quaternary Research

Carleton Author

Camill, Phil

Department

Biology

Year

2004

Publisher

Elsevier

File Name

002_Camill-Phil_Sediment-magneticSignatureOfLandUse.pdf

Keywords

Sediment magnetism; Holocene; Limnology; Drought; Reductive dissolution; Magnetotactic bacteria

Abstract

Sediment magnetic properties of a short core from Sharkey Lake, MN, record the effects of Euroamerican settlement and climate change over the last 150 yr. The onset of European-style farming led to increased erosion, reflected in high values of concentration-dependent parameters such as magnetic susceptibility (j), Isothermal Remanent Magnetization (IRM), and Anhysteretic Remanent Magnetization (ARM). These high values are only partially due to increased supply of terrigenous material to the lake, and recent sediment contains an additional component of authigenic fine (single-domain) magnetite, most likely magnetosomes from magnetotactic bacteria. High organic productivity in the lake during the 1920s to 1940s drought increased this authigenic component resulting in highly magnetic fine-grained sediment. A comparison with older Holocene sediment from the same lake shows that, over time, most of the fine magnetic signal is lost after deposition, leading to decreases in magnetization and a bimodal grain size distribution of ultrafine, superparamagnetic grains and coarser multidomain particles, evident from measurements of ARM/IRM ratios, hysteresis measurements, and low-temperature analyses. The effects of dissolution and the superposition of climate and land-use signals complicate the use of recent sediments as modern analogs for sediment magnetic analyses.

Rights Management

Yes

RoMEO Color

RoMEO_Color_Green

Preprint Archiving

Yes (with link to journal home page)

Postprint Archiving

Yes

Publisher PDF Archiving

No

Contributing Organization

Carleton College

Type

Article

Format

application/pdf

Included in

Biology Commons

Share

COinS