The regional and temporal significance of primary aeolian magnetic fabrics preserved in Alaskan loess

Abstract

The anisotropy of magnetic susceptibility (AMS) data presented herein underscore the resolving power magnetic anisotropy has in non-lithified poorly consolidated sediments. We turn our attention to primary aeolian sedimentary magnetic fabrics preserved along two coeval loess profiles in Central Alaska at the Halfway House (HH3) and Gold Hill Steps (GHS2) sites. We first demonstrate that published preliminary results along HH1 and HH2 are reproducible. Moreover, the new sample suite, the first ever at GHS, collected at a higher temporal resolution and statistical confidence permits a better evaluation of the significance of the inferred paleowind directions and their temporal variability. The data demonstrate that the resolvability of the magnetic lineation is independent of both the eccentricity of the AMS ellipsoid and the strength of the magnetic foliation. Furthermore, the orientations and temporal variability of the most significant magnetic lineations are not artifacts of the data filtering process developed to isolate them. We conclude that the temporal variations of inferred paleowind directions along HH3 track paleoclimatic glacial–interglacial cycles as well as provide additional constraints to the geochronology of the loess deposit. Along GHS2, the limited coeval primary magnetic fabrics suggest an influence from a local microclimate not present at the HH site, complicating the interpretation of small-scale variability in paleowind directions. However, the overall average paleowind directions are similar to those inferred along HH3 confirming a regional (spatial) consistency of past surface air circulation.