The Erieau Excursion revisited

Paleomagnetic results from two cores collected from the central and eastern basins of Lake Erie contain the same remanence direction shift from positive to negative inclination at a depth of approximately 9 m. Confirmation of the existence of this boundary over a wider extent of Lake Erie may initially appear to support the interpretation of this feature as the record of a geomagnetic excursion: the Erieau Excursion. Many details in the paleomagnetic record of these cores indicate that this feature is not of geomagnetic origin: the lack of synchroneity of this event across the lake; the association of the reversed directions with deformed sediments; the lack of any record of the transitional magnetic field; and the absence of any correlation between the reversed directions from the two cores. In core EK, the apparent magnetic transition is coincident with the stratigraphic boundary between the lacustrine and glaciogenic sediments. The model most compatible with this new paleomagnetic data involves regional deformation of the substrate of Lake Erie by some mechanism prior to 9500 years ago. The most likely mechanism to have produced this regional deformation was subglacial deformation of the underlying sediments.