Shatter Cones at Charlevoix Impact Structure

October 05, 2006


Provided by: Charles O'Dale
Summary authors & editors: Charles O'Dale

This image illustrates a shatter cone formation imprinted on a rock outcrop within the Charlevoix Impact Structure in Quebec, Canada. Approximately 342 million years ago, a bolide punched through our atmosphere impacting here and creating a crater whose initial dimensions were 28 kilometres across and 10 kilometres deep. Subsequent post impact crater collapse created the central peak and peripheral modifications resulting in a final structure 54 kilometres in diameter.

The hypothesis that the Charlevoix structure might be the result of a bolide impact originated here in 1965 when this Precambrian age outcrop was first studied. Since then it has been determined that shatter cones represent a distinctive and unique shock-deformation feature that develops on a megascopic scale (e.g., hand sample to outcrop scale). Shatter cones are shock-deformation features formed from impact pressures of typically 2-10 giga pascals (GPa) and up to ~30 GPa. This “shatter-coned” bedrock outcrop is situated on the annular plateau to the west of the central peak of the Charlevoix Impact Structure.

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