科研之友
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摘要
The Ritland structure is a newly discovered impact structure, which is located in southwestern Norway. The structure is the remnant of a simple crater 2.5 km in diameter and 350 m deep, which was excavated in Precambrian gneissic rocks. The crater was filled by sediments in Cambrian times and covered by thrust nappes of the Caledonian orogen in the Silurian-Devonian. Several succeeding events of uplift, erosion, and finally the Pleistocene glaciations, disclosed this well-preserved structure. The erosion has exposed brecciated rocks of the original crater floor overlain by a thin layer of melt-bearing rocks and postimpact crater-filling breccias, sandstones, and shales. Quartz grains with planar deformation features occur frequently within the melt-bearing unit, confirming the impact origin of the structure. The good exposures of infilling sediments have allowed a detailed reconstruction of the original crater morphology and its infilling history based on geological field mapping.
- 出版日期2011-5
