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Geophysical signature of the Pretoria Saltpan impact structure and a possible satellite crater
Author(s) -
Brandt Dion,
Reimold Wolf Uwe,
Durrheim Raymond J.
Publication year - 1994
Publication title -
meteoritics
Language(s) - English
Resource type - Journals
eISSN - 1945-5100
pISSN - 0026-1114
DOI - 10.1111/j.1945-5100.1994.tb00601.x
Subject(s) - impact crater , geology , breccia , volcano , geophysics , petrography , magnetic anomaly , gravity anomaly , meteorite , impact structure , seismology , geochemistry , astrobiology , paleontology , physics , oil field
— The genesis of the 1.13‐km‐diameter Pretoria Saltpan crater has long been the focus of a controversy. Its origin has been explained by either meteorite impact or “cryptoexplosive” volcanic activity, but it was recently confirmed, through detailed petrographic and chemical analysis of a breccia layer forming part of the crater fill, that the crater was formed by impact. As the limited previous geophysical work failed to support an impact origin, a more detailed gravity and magnetic study was conducted. A possible 400‐m‐diameter circular crater located 3 km to the southwest of the main crater was also investigated with geophysical methods, including resistivity, seismics and ground‐probing radar. The gravity signature of the main crater is compatible with that of a simple impact crater and the magnetic signature (no magnetic anomaly could be detected) rules out the possibility of a central magnetic volcanic body below the crater‐fill sediments. The results for the possible twin or satellite crater are inconclusive. As it is the only such feature in the entire region, it should not be overlooked. A drilling program may reveal interesting results.