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Bowers Crater

Title: Once Again About Kainozoic Meteorite Structures in the Ross Sea, Antarctica.
Authors: L. P. Hrjanina, Institute of Physics of the Earth, Russian Academy of Sciences, b. Grusinskaja, 10, 123810, Moscow, Russia.

Two Kainozoic meteorite structures were discovered during the study of coastal seas of Antarctica. The first structure, the Ross Crater, is giant "saucer", a hollow in crystalline basement of Antarctic plate, more 600 km in diameter and some 4 km deep - Challenger basin. We had found allogenous and autigenous breccias on core photos of DSDP, site 270, and later founded signs of shock metamorphism in thin sections. The bottom of crater is covered in whole by allogenous breccia (seismic velocity 4,7 km/s, in specimen - 4,4 km/s, and velocity of underlying crystalline rocks - 5,2 km/s). The Ross Crater is surrounded by Joides arc graben, which is dead and buried, and actively developing coastal graben connected with one-sided horst of Transantarctic Mountains, which had raised more than 4 km in 5 m.y. .
The Bowers Crater (diameter 100 km, visible depth 800 m) have spider net of faults and also is surrounded by horsts and grabens. The gravity anomalies over crater and grabens are -40-50 mgl, thickness of sediments 4 and 2 km accordingly, over the rim and horsts +20-40 mgl, and thickness of sediments about 0,5 km. The formation of the Ross Crater (about 38 m.y. ago) was the cause of climatic threshold, formation of Drake Passage fault and the Circumpolar Stream with later formation of continental ice cap.

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Latitude: 7112'0.00"S, Longitude: 176 0'0.00"E

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