Sudbury meteorite-impact structure modeling with LITHOPROBE high-resolution seismic refraction results

Abstract

The Sudbury Structure is well known but is still being investigated extensively because the origin and formation history have many questions. Geologically it is believed to be a meteorite-impact structure and is composed of the Sudbury Igneous Complex along the border, young sedimentary rocks in the Basin, and Levack Gneiss Complex outside the north range of the basin structure. The 1992 high-resolution refraction seismic survey, carried out as a part of the LITHOPROBE Abitibi—Grenville Transect experiments, included two in-line profiles in cross pattern and two fan-shot profiles perpendicular to them. Scientific objectives of these profiles includ 2-D and 3-D imaging of the crustal structures beneath the Sudbury Structure and the surrounding areas. Results of forward and inverse modelings, tomographic inversion, and preliminary interpretation of the refraction seismic data indicate that there is a distinctive high-velocity layer with a lenticular shape below the Sudbury Basin structure at a depth range of approximately 4.5–9.0 km. Even after 2 billion years of deformation, including the truncation by erosion and several stages of subsequent geological evolution, the concave-upward shape of the velocity anomaly conforms to the proposed original meteorite-impact model and has close correlation.