A paleo- and environmental magnetic record from Prince William Sound, Alaska

The dynamic changes in the Earth's magnetic field, caused by fluid motions in its outer core, can be captured in global marine sediments. The fidelity of the paleomagnetic record depends on sediment characteristics, governed by environmental factors. Here we extend recent efforts to reconstruct Holocene paleomagnetic secular variation and environmental conditions in the mid-high latitude North Pacific with analyses of a marine sediment core taken from Prince William Sound, southern Alaska. Natural and laboratory remanent magnetizations were studied by progressive alternating field (AF) demagnetization of u-channel samples from jumbo piston core EW0408-95JC (60.66278N, 147.70847W, water depth 745m). The lithology is monitored by physical properties measurements, including CT Scans and core descriptions. The lithology of the upper 8.5 m of the 17.6 meter core consists of magnetically homogenous bioturbated muds characterized by high intensities and low coercivities consistent with dominantly (titano)magnetite mineralogy. Component directions calculated by PCA analysis are characterized by low MAD values (<4°) with inclinations consistent with GAD predictions and declinations varying in a manner consistent with PSV. Normalized remanences are comparable using a variety of normalizers and show minimal scatter through demagnetization suggesting that reliable paleointenisty estimates may be preserved. In contrast, the lower half of core 95JC is marked by significant variations in the sediment matrix, making it less suitable for geomagnetic studies - as indicated by higher MAD values of 4-15°, inclinations that deviate greatly from GAD, and a marked decrease of and greater variability in magnetic susceptibility and other rock magnetic paratmeters. Presently limited, though ongoing radiocarbon dating suggest that the upper, paleomagnetically reliable record extends back approximately 3,000 years. The magnetic variability in the lower part of the record will provide insight into glacial development moving into neoglaciation, while the upper part of the record will provide important paleo-geomagnetic constraints at high temporal resolution with sedimentation rates >250 cm/kyr.