Small lakes can be good recorders of local paleoclimate variations, and rock magnetic measurements have been shown to be a valuable complement to classic paleoclimatic parameters, such as pollen assemblages or isotope data. However, the processes that
affect the sedimentological and rock magnetic properties of small lakes can change dramatically. Since different environmental processes can result in quite similar rock magnetic properties of the sediments, a simple model that is based only on a few magnetic parameters might lead to serious misinterpretation of the magnetic record.
We studied cores from Pittsburg Basin, a small kettle lake in southern Illinois, whose sedimentary record spans the Sangamon interglacial and goes back into late Illinoian glacial sediments. X-ray diffraction analysis and Curie temperature measurements
indicate that the main magnetic carrier throughout the core is partially oxidized magnetite. Grain size dependent magnetic parameters , such as anhysteretic remanent magnetization (ARM) normalized by saturation isothermal remanent magnetization
(SIRM), show an apparent correlation with the marine oxygen isotope record where fine grained magnetic fractions correspond to the warm substages of marine isotope stage 5. Susceptibility variations, on the other hand, suggest multiple hydrological
events that defy a consistent interpretation. We show that cooling through the Verwey transition in the presence or absence of a 2.5 T field, temperature and frequency dependence of susceptibility, and lithologic variations, taken together, lead to a more accurate, self consistent interpretation.
Annales Geophysicae Supplement I, V.15, p. C101, 1997
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