A paleomagnetic estimate of the age and thermal history of the Kentland, Indiana cryptoexplosion structure ( USA).

The Kentland, Indiana, cryptoexplosion structure consists of a centrally uplifted zone of steeply-dipping fault blocks surrounded by a ring depression and a low-amplitude structural high with a radius of 12 km. The age of the deformation is constrained stratigraphically to the interval between Mississippian and Quaternary. Paleomagnetic samples were collected from 7 carbonate formations and one siltstone unit. Magnetic blocking theory suggests that the magnetization was acquired at temperatures of 150oC or less, over a timescale of approximately 1000 years. A thousand- year cooling time scale requires either continuous heating or a blanketing overburden of about 300 m, thus providing an estimate of the depth of subsequent erosion of the Kentland structure.-from Authors