Precambrian Paleomagnetism: Magnetizations Reset by the Grenville Orogeny

Abstract

Paleomagnetic results from iron-rich metasediments folded during the Grenville orogeny (∼1000 million years ago) indicate that stable remanence was acquired after folding as the rock cooled from above 615°C through 550°C. As well as imparting a new remanence, the thermal event destroyed any preexisting magnetizations. In a proposed model, virtually all Grenville paleomagnetic poles have been reset and can provide no evidence of plate tectonic processes before 1000 million years ago, The polar sequence suggested by potassium-argon age trends within the Grenville province does, however, indicate rapid drift of North America between 1000 and 900 million years ago.