New geomagnetic paleosecular-variation results from the Old Crow Basin, Yukon Territory, and their use in stratigraphic correlation

Abstract

A total of 626 fully orientated samples were collected from two laterally equivalent vertical sections (each approximately 20 m thick) in Pleistocene sediments exposed in riverbank outcrops on the Old Crow River, Yukon Territory. The paleomagnetic records recovered reveal a sequence of three features correlatable with results obtained from previously sampled sections some 5 km upstream. This correlation, which is confirmed by magnetic-susceptibility measurements, allows the stratigraphic position of the Old Crow Tephra to be inferred, even though it does not actually occur at this locality; it also provides strong support for the reality of these paleosecular-variation signals. The most prominent of these take the form of repeating linear perturbations, which are here interpreted as evidence of stationary sources of reversely directed flux in the outer core. Such reverse-flux patches exist elsewhere in the modern field, but a simple magnetostatic model suggests that the paleosources were apparently an order of magnitude stronger.