M. Bjornerud, Juliana E. Olsen-Valdez, Emily E. Zawacki, Drae Rogers, Kirstin Edwards, Colin Nevins
{"title":"布鲁塞尔山,门县,威斯康辛州:一个神秘的不安的基岩区域","authors":"M. Bjornerud, Juliana E. Olsen-Valdez, Emily E. Zawacki, Drae Rogers, Kirstin Edwards, Colin Nevins","doi":"10.1086/709276","DOIUrl":null,"url":null,"abstract":"Brussels Hill in southern Door County, Wisconsin, is a localized area of faulted and brecciated bedrock in a region of otherwise undeformed lower Silurian dolostone that has been tentatively interpreted as an impact crater. The area of disturbed rock coincides with a nearly circular, 2-km-wide, flat-topped hill that stands about 40 m above the surrounding landscape. Glacial till and polished, striated surfaces on the brecciated bedrock indicate that the disturbance predated the last ice advance and suggest that the hill may have been even higher before glaciation. Anomalous, apparently intrusive bodies of glauconite-bearing sandstone within the brecciated dolostone were likely derived from Cambrian strata, which are normally 400 m in the subsurface in the area. A 103-m drill core into the center of the disturbance recovered 70 m of brecciated dolostone and shale, much of it vesicular, but with no features diagnostic of shock metamorphism. The lowest 33 m of the core sampled the upper Ordovician Maquoketa Formation, which appeared to be subhorizontal and only locally disrupted. This is puzzling, given that material from greater depth must have been brought up through this level. The fact that an area of such fragmented rock stands as a topographic high is also hard to explain. Brussels Hill may have been the site of supersonic impact, but an endogenous process such as violent fragmentation in the upper part of a diatreme cannot be ruled out.","PeriodicalId":54826,"journal":{"name":"Journal of Geology","volume":"128 1","pages":"325 - 336"},"PeriodicalIF":1.5000,"publicationDate":"2020-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/709276","citationCount":"0","resultStr":"{\"title\":\"Brussels Hill, Door County, Wisconsin: An Enigmatic Area of Disturbed Bedrock\",\"authors\":\"M. Bjornerud, Juliana E. Olsen-Valdez, Emily E. Zawacki, Drae Rogers, Kirstin Edwards, Colin Nevins\",\"doi\":\"10.1086/709276\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Brussels Hill in southern Door County, Wisconsin, is a localized area of faulted and brecciated bedrock in a region of otherwise undeformed lower Silurian dolostone that has been tentatively interpreted as an impact crater. The area of disturbed rock coincides with a nearly circular, 2-km-wide, flat-topped hill that stands about 40 m above the surrounding landscape. Glacial till and polished, striated surfaces on the brecciated bedrock indicate that the disturbance predated the last ice advance and suggest that the hill may have been even higher before glaciation. Anomalous, apparently intrusive bodies of glauconite-bearing sandstone within the brecciated dolostone were likely derived from Cambrian strata, which are normally 400 m in the subsurface in the area. A 103-m drill core into the center of the disturbance recovered 70 m of brecciated dolostone and shale, much of it vesicular, but with no features diagnostic of shock metamorphism. The lowest 33 m of the core sampled the upper Ordovician Maquoketa Formation, which appeared to be subhorizontal and only locally disrupted. This is puzzling, given that material from greater depth must have been brought up through this level. The fact that an area of such fragmented rock stands as a topographic high is also hard to explain. Brussels Hill may have been the site of supersonic impact, but an endogenous process such as violent fragmentation in the upper part of a diatreme cannot be ruled out.\",\"PeriodicalId\":54826,\"journal\":{\"name\":\"Journal of Geology\",\"volume\":\"128 1\",\"pages\":\"325 - 336\"},\"PeriodicalIF\":1.5000,\"publicationDate\":\"2020-06-11\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://sci-hub-pdf.com/10.1086/709276\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Geology\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.1086/709276\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"GEOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Geology","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1086/709276","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOLOGY","Score":null,"Total":0}
Brussels Hill, Door County, Wisconsin: An Enigmatic Area of Disturbed Bedrock
Brussels Hill in southern Door County, Wisconsin, is a localized area of faulted and brecciated bedrock in a region of otherwise undeformed lower Silurian dolostone that has been tentatively interpreted as an impact crater. The area of disturbed rock coincides with a nearly circular, 2-km-wide, flat-topped hill that stands about 40 m above the surrounding landscape. Glacial till and polished, striated surfaces on the brecciated bedrock indicate that the disturbance predated the last ice advance and suggest that the hill may have been even higher before glaciation. Anomalous, apparently intrusive bodies of glauconite-bearing sandstone within the brecciated dolostone were likely derived from Cambrian strata, which are normally 400 m in the subsurface in the area. A 103-m drill core into the center of the disturbance recovered 70 m of brecciated dolostone and shale, much of it vesicular, but with no features diagnostic of shock metamorphism. The lowest 33 m of the core sampled the upper Ordovician Maquoketa Formation, which appeared to be subhorizontal and only locally disrupted. This is puzzling, given that material from greater depth must have been brought up through this level. The fact that an area of such fragmented rock stands as a topographic high is also hard to explain. Brussels Hill may have been the site of supersonic impact, but an endogenous process such as violent fragmentation in the upper part of a diatreme cannot be ruled out.
期刊介绍:
One of the oldest journals in geology, The Journal of Geology has since 1893 promoted the systematic philosophical and fundamental study of geology.
The Journal publishes original research across a broad range of subfields in geology, including geophysics, geochemistry, sedimentology, geomorphology, petrology, plate tectonics, volcanology, structural geology, mineralogy, and planetary sciences. Many of its articles have wide appeal for geologists, present research of topical relevance, and offer new geological insights through the application of innovative approaches and methods.