Paleolatitude of glaciogenic upper Precambrian Rapitan Group and the use of tillites as chronostratigraphic marker horizons

Abstract

Currently available paleomagnetic evidence for the depositional paleolatitude of upper Precambrian glacial horizons is inconclusive. Unless it can be shown that glaciation occurred as a synchronous world-wide event, the use of tillities as chronostratigraphic marker horizons is not warranted. Paleomagnetic analysis of the upper Precambrian glaciogenic Lower Rapitan Subgroup in northwestern Canada has revealed three remanence directions. Remanence X is indicative of low paleolatitude, whereas remanence Y was acquired in high paleolatitudes. The preferred sequence, X is older than Y , is based on the evidence of stratigraphic considerations and prolonged chemical leaching. A third remanence, Z , is related to late deformation and (or) exhumation of the Rapitan Group.