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衣阿华州北中部的曼森撞击构造(MIS),直径35km,是美国已知最大的撞击点,尽管撞击构造把元古代、古生代和中生代的岩石置换成象上白垩统那样年轻的岩石,但陨石坑是被更新世冰碛物完全覆盖的,而且没有地表特征显示。MIS地区异常的地质特征是自1912年钻水井开始发现的,当时,这种特征一般被解释为隐火山构造,直到Short(1966)从这个构造内重新发现的火山岩的矿物中观察到多组面状特征,并确定为冲击特征后,才证
The Manson Impact Structure (MIS) in the north central Iowa, 35 km in diameter, is the largest point of impact known in the United States. Although the strike structure replaces Proterozoic, Paleozoic, and Mesozoic rocks with young rocks like the Cretaceous, However, the craters were completely covered by Pleistocene moraines and no surface features were shown. The unusual geological features of the MIS area were discovered in the drilling wells in 1912 when this feature was generally interpreted as a crag formation until Short (1966) observed multiple sets of minerals from the volcanic rocks that rediscovered within this structure Shaped feature, and identified as the impact characteristics, evidence