An integration of geological and geophysical evidence of impact at Manicouagan

Abstract

The Manicouagan impact structure has been assigned a revised collapsed cavity diameter of 65 - 85 km. This updated value reflects the results of geological mapping, analysis of the gravity anomaly, and the distribution of shock features. The minimum of 65 km is dictated by the presence of collapsed rim material at a radial distance of ~33 km from the centre of the structure. The maximum is based on the greatest possible diameter of damage zone found to replicate the observed gravity anomaly. A shock barometry survey has been carried out and finds a broad trend of decreasing shock pressures with increasing radial distance. Interestingly, relic β-quartz is identified in several of the shocked samples. Based on the observations described in the first five chapters of this work, a hydrocode model of the formation of the Manicouagan impact structure has been generated.