ENVIRONMENTAL MAGNETISM OF SEDIMENTS FROM WHITE LAKE, NORTHWESTERN NEW JERSEY: INVESTIGATING THE POSSIBLE MAGNETIC MINERAL - CLIMATE LINK IN ORGANIC-RICH LAKE SEDIMENTS

Recent interest in reconstructing climate change has focused on employing multiple proxies. Interpretation of magnetic properties of lake sediments as a proxy for climate change often involves climatically-controlled detrital inputs into lakes, but little is known about the magnetic mineral - climate link in organic-rich lake sediments. Here we conducted a magnetic study of sediments from White Lake, a hardwater lake in northwestern New Jersey, to determine whether magnetic properties of organic-rich sediments could also serve as a climate proxy. Loss-on-ignition (LOI) results indicate that the 6.15 m long core from the deepest part of the lake shows lithological succession from clay, through marl, to gyttja. Pollen analysis was conducted to reconstruct vegetation and to provide an estimate of relative ages. AMS ¹⁴C dating is in progress and will provide a numerical chronology. The pollen data indicate a major shift in vegetation from tundra, through spruce woodland and pine forest, to oak forest.

Preliminary results of magnetic data at 4 cm sampling interval suggest that magnetic variations of sediments from White Lake probably indicate Late Quaternary climatic change. Downcore anhysteretic remanent magnetizations (ARMs) show a pronounced decrease during the glacial period and cyclonic variations during the late glacial period. The ARMs show an 80% drop by the onset of the Holocene and remain low throughout the Holocene. The ARMs of the Holocene organic-rich sediments are not inversely correlated with the amount of organic matter, indicating that magnetic signatures were not controlled by organic matter dilution. Also, the variation in ARM intensity for the past ~3 ky can apparently be correlated with magnetic mineral concentration of sediments from Lake Waynewood in eastern Pennsylvania, suggesting that White Lake sediments might have recorded a regional climate signature. Furthermore, the ARM variations during the middle and late Holocene appear to display centennial to millennial scale cycles that were not seen in either pollen or LOI data, implying that magnetic mineral techniques hold the promise of providing high-resolution records. Additional magnetic parameters will be obtained to evaluate possible mechanisms responsible for magnetic variations.