Determining the Cause of a Magnetic Mineral-Paleorainfall Correlation in Recent Lake Sediments

Lehigh University, Bethlehem PA

Investigators

Abstract

This is a proposal to investigate the mechanism causing a correlation observed between magnetic mineral concentration and paleorainfall variations in recent lake sediments from northeastern Pennsylvania. We propose to study the recent sediments from two different small glacial lakes, one dominated by sediment from allochthonous sources (Lake Waynewood) and one dominated by authigenic sources (Lake Ely), so a general model of the relationship between rainfall and mineral magnetism can be developed. Freeze cores will be collected at several locations in each lake. Mineral magnetic parameters (c, SIRM, ARM, ARM/SIRM, SIRM/c, HIRM) will be measured to magnetically characterize the lake sediments. Elemental analyses will be conducted to determine the importance of erosion (Na, Mg, K) or the possibility of reduction diagenesis (S, Mn, Fe). Electron microscopic (SEM, TEM) examination of magnetic extracts will look for magnetosotnes and evidence of dissolution due to reduction diagenesis. EDS will be used to determine if authigenic, ferromagnetic iron sulfides have been created. High resolution (1 mm) magnetic scanning of the cores with an FIT scanning magnetometer will allow a more detailed look at the SIRM variations and extension of the record into the low sedimentation rate, pre-settlement horizons.