Impact-pressure controlled orientation of shatter cone magnetizations in Sierra Madera, Texas, USA
- 62 Downloads
A suite of Sierra Madera Impact deformed rocks was studied and magnetic analyses were performed. We characterized the magnetic signatures of two locations, sites A and B that have different physical characteristics of shock fractured structures as well as the magnetic signatures. Shatter cone at site A has a fine-scale (few to ∼10 mm) distributed array of complete shatter cones with sharp apex. Natural remanent magnetization (NRM) of site A shatter cone is distributed within the plane that is perpendicular to the apexes of the cones. Shatter cone at site B shows no apparent cone shape or apex, instead, a relatively larger scale and multiple striated joint set (MSJS) and sinusoidal continuous peak. NRM of site B shatter cone is clustered along the apexes. The difference in magnetization direction is a likely indicator of the shock pressure where parallel to apex indicates pressures larger than 10 GPa and perpendicular to apex indicate pressures less than 10 GPa. Intensities of NRM and saturation isothermal remanent magnetization (SIRM) contrast and fluctuate within a shatter cone as well as in between two sites. We observed a random orientation of magnetic vector directions and amplitudes changing over small scales leading to the absence of coherent macro-scale signature.
Key wordsshatter cones demagnetization remagnetization impact crater shock fractures magnetism magnetic efficiency magnetic signatures magnetic anomaly Mars
Unable to display preview. Download preview PDF.
- Boon J.D. and Albritton C.C. Jr., 1936. Meteorite craters and their possible relationship to “cryptovolcanic structures”. Field and Laboratory, 5, 1–9.Google Scholar
- Eggleton R.E. and Shoemaker E.M., 1961. Breccia at Sierra Madera, Texas. U.S. Geological Survey Professional Paper, 424-D, D151–D153.Google Scholar
- French B.M., 1998. Traces of Catastrophe, a Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures. Lunar and Planetary Institute, Contribution No. 954.Google Scholar
- Gibson H.M. and Spray J.G., 1998. Shock-induced melting and vaporization of shatter cone surfaces: evidence from the Sudbury impact structure. Meteorit. Planet. Sci., 33, 329–336.Google Scholar
- Grieve R.A.F., Langenhorst F. and Stoffler D., 1996. Shock metamorphism of quartz in nature and experiment. 2. Significance in geosciences. Meteorit. Planet. Sci., 31, 6–35.Google Scholar
- Huson S.A., Foit F.F., Watkinson A.J. and Pope M.C., 2006. X-ray diffraction powder patterns and thin section observations from the Sierra Madera Impact Structure. Lunar and Planetary Science, XXXVII, 2377.pdf (http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2377.pdf).
- Kletetschka G., Kohout T. and Wasilewski P.J., 2003a. Magnetic remanence in the Murchison meteorite. Meteorit. Planet. Sci., 38, 399–405.Google Scholar
- Kletetschka G., Connerney J.E.P., Ness N.F. and Acuna M.H., 2004b. Pressure effects on martian crustal magnetization near large impact basins. Meteorit. Planet. Sci., 39, 1839–1848.Google Scholar
- Pohl J., 1981. Planetary and lunar magnetism: In: ESA The Solar System and Its Exploration, 115–120 (SEE N82-26087 16-88).Google Scholar
- Stoffler D. and Langenhorst F., 1994. Shock metamorphism of quartz in nature and experiment. 1. Basic observation and theory. Meteoritics, 29, 155–181.Google Scholar
- Wilshire H.G., Offield T.W., Howard K.A. and Cummings D., 1972. Geology of the Sierra Madera cryptoexplosion structure, Pecos County, Texas. USGS Professional Paper, No. 599-H, 1–49.Google Scholar