COROSSOL STRUCTURE

COROSSOL STRUCTURE

by: Charles O’Dale

  • Type: Central peak
  • Location: N 50°03′ W 66°23′ – underwater in the Gulf of St. Lawrence
  • Diameter: 4.0 Km;
  • Age: >12,900 yearsa
  • Possible central peak crater

a Calibrated 14C ages of shells in the sediments can be extrapolated to give an estimate of the age of the base of the sedimentary sequence of ~12,900 cal BP

The Corossol Crater is a complex crater ~4 km in diameter with a central uplift, a prominent moat, and multiple, low-relief ridges. Quebec, Canada.

Introduction

The Corossol crater (50°3’N, 66°23’W) was first discovered by the Canadian Hydrographic Service about 10 years ago while mapping the entrance to the Sept Iles harbour, Gulf of St Lawrence, Canada. It is a complex circular structure about 4 km in diameter with a central uplift that rises to about -70 m and an annular valley ~160 m deep. There are no other circular structures nearby.” (Higgins et al, 2011).

Age of impact

At present it is only possible to give age limits. The maximum age is very difficult to establish. Clearly, it is younger than Ordovician, but it is not clear if it is younger or older than the cuestas. The paucity of sediments in the crater might be taken to indicate that it is young. The minimum age was established using data from a ~7 metre core taken in the central trough, which almost reached the basement, as defined by seismic data. Calibrated 14C ages of shells in the sediments can be extrapolated to give an estimate of the age of the base of the sedimentary sequence of ~12,900 cal BP, if no hiatus or older sediments were preserved between the base of the core and the bedrock. This is taken to be the youngest possible age of the impact.” (Higgins et al, 2011).

Suevite breccia clast dredged from the central uplift and the innermost annular rim. A) Scanned image of a thin section in non-polarised light. Limestone clasts are medium-grey. B) Planar deformation features in a crystal of quartz. Cross-polarised light. C) Broken fragment of a glassy droplet. Darker areas have a composition close to apatite, pale areas are pyritic. In the matrix calcite is pale and dolomite is darker. Back-scattered electron image. D) Carbonatitic material infilling between limestone fragments. Euhedral crystals are Dolomite. Plane-polarised light.

Possible link to the Younger Dryas Extinction

References

Brent Dalrymple, Radiometric Dating Does Work! Reports of the National Center for Science Education

M. D. Higgins, P. Lajeunesse, G. St-Onge, J. Locat, M. Duchesne, J. Ortiz, R. Sanfaçon, BATHYMETRIC AND PETROLOGICAL EVIDENCE FOR A YOUNG (PLEISTOCENE?) 4-KM DIAMETER IMPACT CRATER IN THE GULF OF SAINT LAWRENCE, CANADA. 42nd Lunar and Planetary Science Conference (2011)