FRACTURED ROCK

FRACTURED ROCK

by: Charles O’Dale

  1. introduction;
  2. specific crater fractured rock.

1. INTRODUCTION

A fracture is any separation in a geologic formation, such as a joint or a fault that divides the rockinto two or more pieces. One of the impact shock effects I noticed in my crater explorations was the fractured rocks around the perimeter of the structure where there should have been solid rock outcrops. Though this phenomenon IS NOT firm evidence of an impact but is a feature of impacting and would indicate that further investigation of the structure is warranted.

2. SPECIFIC CRATER FRACTURED ROCK

  • Barringer;
  • Brent;
  • Manicouagan;
  • Pingualuit;
  • Presqu’ile;
  • Sudbury.

One of the impact shock effects I noticed in my crater explorations was the fractured rocks around the perimeter of the structure where there should have been solid rock outcrops. Though this phenomenon IS NOT firm evidence of an impact but is a feature of impacting and would indicate that further investigation of the structure is warranted.

Barringer

Examples of fractured bedrock are scattered randomly around rim of the Barringer Crater

An overturned rim sequence is also present at the rim of the Barringer Crater and is now recognized as one of the hallmarks of an impact crater.

Brent

This block of exposed fractured bedrock is on the rim of the Brent Impact Crater.
Fossilized crater wall talus slope deposit on the floor of the Brent crater.

Manicouagan

Outside the annular moat of the Manicouagan Impact Crater some of the rock cuts along the highway change from solid granite faces to fractured walls. The rocks in this image were fractured by the energy release from a large meteorite impact, approximately 40 kilometres from this spot.
The “smaller” rocks fragmented from the impact surrounded the “melt rock” central peak at the Manicouagan Crater. They were easily evacuated by glaciation and erosion creating the circular annular moat.

Pingualuit

This is one of the few in situ samples of bedrock that I had found in the vicinity of the Pingualuit Crater. This bedrock example was completely shattered by the impact. The rim of the crater is visible as the small hill over 6km away on the horizon.

Presqu’ile

These shatter cones and fractured rock surfaces occur within meta-basalt and rhyodacite rocks 5 km east of the crater, Lac de la Presqu’ile. The cones have angles of ~90° and their apparent position is vertical (Grieve). The discovery of these shatter cones at this site confirmed that an impact formed the Presqu’ile structure.

Sudbury

This Sudbury Crater fractured bedrock is outside of the Sudbury Igneous Complex (SIC), north-west of Windy Lake on highway 144 approximately 30 Km from the centre of the crater. At the time of impact this fractured rock was several kilometres underground. It has since been exposed by 1.8 billion years of erosion.

RETURN TO: CRATER REFERENCE