Verteilung,Eigenschaften und Entstehung der Auswurfsmassen des Impaktkraters Nördlinger Ries |
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| Authors: | Dr Horst Gall Dr Dieter Müller Prof Dr Dieter Stöffler |
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| Institution: | 1. Institut für Pal?ontologie und historische Geologie der Universit?t München, Richard-Wagner-Stra\e 10, 8 München 2
2. Institut für Mineralogie der Universit?t Münster, Gievenbecker Weg 61, 44 Münster
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| Abstract: | Regarding the importance of the Ries impact structure in the field of planetary geology an attempt is made to synthesize the presently known results of geologic mapping in the Ries area and of general field and laboratory observations. The ballistic bulk ejecta of the crater (diameter about 23 km) form a continuous blanket of mixed breccia (“Bunte Trümmermassen”). Outside the crater more than 90% of its constituents are derived from unshocked fragments of the 750 m thick pre-Ries sedimentary rock strata. This blanket is overlain with a sharp discontinuity by suevite breccia which forms a continuous layer inside the crater and patch-like isolated occurrences outside the crater. Their pattern of distribution is believed to be primary. Suevite is mainly composed of fragments of all stages of shock metamorphism derived from the crystalline basement. The present asymmetrical distribution of éjecta outside the crater rim results from relatively young erosion during the Pliocene and Pleistocene periods. The erosional history indicates that the primary distribution of ejecta was symmetrical with respect to the center of the crater extending up to a distance of at least some 40 km from the impact center. A number of characteristics of the structure and composition of the Ries ejecta formations are discussed and verified quantitatively by new field data. It is shown that the structure and composition of the ejecta formations can be explained qualitatively by the physics of impact cratering and be duplicated by hypervelocity cratering experiments. |
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