Impact Craters: Their Importance in Geologic Record and Implications for Natural Resource Development
Donn Levie, Jr.
A cursory investigation of the surfaces of the terrestrial planets and the natural satellites of the Jovian and Saturnian systems indicates a violent early history of the Solar System. It is apparent that the most widespread geomorphic process to have been active in the Solar System is impact cratering, and certainly the primary factor responsible in the formation of planetary regolith. Geologically active planetary bodies will have much of their early geologic history severely altered or destroyed through tectonics and/or volcanism. The presence of an atmosphere further eradicates ancient impact events through the effects of weathering and erosion.
Impacting bodies of sufficient size traveling at hypervelocities carry tremendous potential energy. This relatively infrequent process results in the instantaneous formation of unique structures that are characterized by extensive fracturing and brecciation of the target material. Impacts onto continental shield areas can create rich ore deposits, such as the Sudbury mining district in Canada. Impacts into the sedimentary column can instantaneously create hydrocarbon reservoirs out of initially nonporous rocks, such as at Red Wing Creek and Viewfield in the Williston basin. Associated reservoirs are usually limited to a highly deformed central uplift in larger craters, or to the fractured rim facies in smaller craters. The presence of reservoirs and trapping mechanisms is largely depe dent, however, upon the preservation state of the crater in the subsurface.
A catastrophic extraterrestrial event (a large asteroid impact) has also been suggested as the cause for the extinction of the dinosaurs, but the latest theory proposes a companion star with a 26 m.y. periodicity as the cause for numerous lifeform extinctions over a similar time interval.
Regardless of their magnitude and distribution over the earth, it is clear that catastrophic extraterrestrial events have been responsible for altering the geologic column locally, regionally, and quite possibly on a global scale.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.