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DOI	10.1130/B31925.1
	The decorah structure, northeastern Iowa: Geology and evidence for formation by meteorite impact
	French B.M.; McKay R.M.; Liu H.P.; Briggs D.E.; Witzke B.J.
发表日期	2018
ISSN	167606
起始页码	2062
结束页码	2086
卷号	130 期号:2021-11-12
英文摘要	The Decorah structure, recently discovered in northeastern Iowa, now appears as an almost entirely subsurface, deeply eroded circular basin 5.6 km in diameter and ~200 m deep, that truncates a near-horizontal series of Upper Cambrian to Lower Ordovician platform sediments. Initial analysis of geological and well-drilling data indicated characteristics suggestive of meteorite impact: a circular outline, a shallow basin shape, discordance with the surrounding geology, and a filling of anomalous sediments: (1) the organic-rich Winneshiek Shale, which hosts a distinctive fossil Lagerstätte, (2) an underlying breccia composed of fragments from the surrounding lithologies, and (3) a poorly known series of sediments that includes shale and possible breccia. Quartz grains in drill samples of the breccia unit contain abundant distinctive shock-deformation features in ~1% of the individual quartz grains, chiefly planar fractures (cleavage) and planar deformation features (PDFs). These features provide convincing evidence that the Decorah structure originated by meteorite impact, and current models of meteorite crater formation indicate that it formed as a complex impact crater originally ~6 km in diameter. The subsurface characteristics of the lower portion of the structure are not well known; in particular, there is no evidence for the existence of a central uplift, a feature generally observed in impact structures of comparable size. The current estimated age of the Decorah structure (460-483 Ma) suggests that it may be associated with a group of Middle Ordovician impact craters (a terrestrial "impact spike") triggered by collisions in the asteroid belt at ca. 470 Ma. © 2018 Geological Society of America.
语种	英语
来源期刊	Bulletin of the Geological Society of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/184983
作者单位	Department of Paleobiology, Smithsonian Institution, Washington, DC 20013-7012, United States; Iowa Geological Survey, IIHR-Hydroscience and Engineering, University of Iowa, 340 Trowbridge Hall, Iowa City, IA 52242, United States; Department of Geology and Geophysics and Yale Peabody Museum of Natural History, Yale University, New Haven, CT 06520, United States; Department of Earth and Environmental Sciences, University of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242, United States
推荐引用方式 GB/T 7714	French B.M.,McKay R.M.,Liu H.P.,et al. The decorah structure, northeastern Iowa: Geology and evidence for formation by meteorite impact[J],2018,130(2021-11-12).
APA	French B.M.,McKay R.M.,Liu H.P.,Briggs D.E.,&Witzke B.J..(2018).The decorah structure, northeastern Iowa: Geology and evidence for formation by meteorite impact.Bulletin of the Geological Society of America,130(2021-11-12).
MLA	French B.M.,et al."The decorah structure, northeastern Iowa: Geology and evidence for formation by meteorite impact".Bulletin of the Geological Society of America 130.2021-11-12(2018).