Kentland crater

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Deformation involving bending and overturning is evident in the layered limestones exposed by quarrying at the Kentland crater.

The Kentland crater, also known as the Kentland structure or the Kentland disturbed area, is a meteor crater located near the town of Kentland in Newton County, Indiana, USA.

It was discovered about 1880 when two farmers began to quarry crushed rock there. The presence of shatter cones and deformed bedrock led geologists to conclude by the late 1960s that the Kentland structure is an impact crater, rather than volcanic in origin. Deformation at the site is so great that vertical contacts between normally horizontal rock formations of different ages are common.

The crater itself is a circular dome, about 7.24 km (4.5 miles) in diameter, deeply eroded and buried in glacial debris. Its age is estimated to be less than 97 million years (Cretaceous or younger). The Shakopee dolomite at the center of the structure is about 450 million years old (Ordovician period) and is uplifted about 2,000 feet higher than the level of the same rock in the surrounding area. The entire disturbed area is about 13 km (8 miles) in diameter.

The crater's structure was studied in 1978. John Weber and his associates presented fission track dating of apatite from the crater at the Society for Sedimentary Geology (SEPM) Research Conference, "The Sedimentary Record of Meteor Impacts" (21-23 May 2003, Springfield, Missouri). Coesite and shatter cones are found in the uplift near its center. The crater is exposed to the surface, resulting in erosion. It is currently being worked as a quarry.

[edit] See also

List of impact craters on Earth

[edit] References

Laney, R.T., and W.R. Vanschmus, 1978. "A structural study of the Kentland, Indiana impact site" in Lunar and Planetary Science 9, pp 627-629.
Mark J. Camp and Graham T. Richardson, Roadside Geology of Indiana, (Mountain Press Publishing Co.: Missoula, MT, 1999), pp. 215-216. ISBN 0-87842-396-6