Abstract

The origin of the Vredefort Structure has been in question since its discovery.  This seems partially due to distortion by post-impact tectonics and partially to the fact that out of fear human nature prefers to believe that structures of such size are of purely terrestrial origins.  Evidence to the contrary is not always apparent to the naked eye given this structureís  age of about 2000 Ma years, leaving plenty of opportunity for erosion.  This structureís origin is becoming more apparent as more impact characteristics are discovered such as shock metamorphic microdeformations in quarts and zircon.  It has also recently been shown that the Vredefort melt rocks, shatter cones, and silica polymorphs (coesite and stishovite) show evidence of impact.

Koeberl, Christian and Virgil L. Sharpton.  2001.  Terrestrial Impact Craters.  Lunar and Planetary Institute.  http://www.lpi.usra.edu/pub/publications/slidesets/impacts.html  5/9/01.

Cited References (& Database in which source material was identified)

Albat, H.M. and Mayer, J.J.  1990.  Shatter cones in Vredefort rocksóimagination or reality?  In South African Journal of Geology.  Vol. 93, no. 3.  p. 547-548. [GeoRef]

Ashley, A.J. et al.  1999. A new type of melt rock and first evidence of shock deformation in plagioclase from the Vredefort impact structure, South Africa.  In  Meteoritics and Planetary Science.  Vol. 34, A9-A126. [GeoRef]

Bisschoff, A.A.  The Geology Of the Vredefort Dome.  South Africa:  Council for Geoscience, 1999. Pg. 44-45. [OhioLink Central Catalog]

Gay, N.C. et al.  1978.  The Composition of Spherules and Other Features on Shatter Cone Surfaces From the Vredefort Structure, South Africa.  In Earth and Planetary Science Letters.  Vol. 41.  pg. 372-380. [GeoRef]

Henkel, Herbert and Wolf Uwe Reimold.  1998. Integrating geophysical modelling of a giant, complex impact structure: anotomy of the Vredefort Structure, South Africa.  In Technophysics.  Vol. 287, pgs. 1-20. [OhioLINK Electronic Journal Center]

Koeberl, Christian and Virgil L. Sharpton.  2001.  Terrestrial Impact Craters.  Lunar and Planetary Institute.  http://www.lpi.usra.edu/pub/publications/slidesets/impacts.html  5/9/01. [Google]

Martini, J.E.J. 1991. The nature, distribution and genesis of the coesite and stishovite associated with the pseudotachylite of the Vredefort Dome, South Africa.  In  Earth and Planetary Science Letters.  Vol. 103, p. 285-300. [GeoRef]

Meteorite Phenomenon ? The Cratering Process Quanitified.  2000.  University of Michigan.  http://www.umich/~gs265/meteor.htm.  5/9/01. [Google]

Nicolaysen, L.O. and W.U. Reimold.  1999. Vredefort Shatter Cones Revisited.  In Journal of Geophysical Research.   Vol. 104, no. B3.  pg. 4911-30.  [Inspec]

Reimold, W.U. et al.  1992.  Comment on "The nature, distribution and genesis of the coesite and stishovite associated with the pseudotachylite of the Vredefort Dome, South Africa" by J.E.J.  Martini.  In Earth and Planetary Science Letters.  Vol. 112, p. 213-217. [GeoRef]

Turtle, E.P. and E. Pierazzo.  1998.  Constraints on the size of the Vredefort impact crater from numerical modeling.  In Meteoritics and Planetary Science.  Vol. 33.  pg. 483-490. [Inspec]

This paper was completed as part of the course requirements for Geo117. All source materials have been acknowledged to the best of our ability. The course was taught by Mr. Bruce Simonson, Professor and Chair, Oberlin College Geology Department, with assistance related to the research process for geological and related information from Ms. Alison Ricker, Science Librarian.