气候变化领域集成服务门户(CCPortal): Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth

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DOI	10.1073/pnas.1913131117
	Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth
	Flowers R.M.; MacDonald F.A.; Siddoway C.S.; Havranek R.
发表日期	2020
ISSN	0027-8424
起始页码	10172
结束页码	10180
卷号	117 期号:19
英文摘要	The Great Unconformity marks a major gap in the continental geological record, separating Precambrian basement from Phanerozoic sedimentary rocks. However, the timing, magnitude, spatial heterogeneity, and causes of the erosional event(s) and/or depositional hiatus that lead to its development are unknown. We present field relationships from the 1.07-Ga Pikes Peak batholith in Colorado that constrain the position of Cryogenian and Cambrian paleosurfaces below the Great Unconformity. Tavakaiv sandstone injectites with an age of ≥676 ± 26 Ma cut Pikes Peak granite. Injection of quartzose sediment in bulbous bodies indicates near-surface conditions during emplacement. Fractured, weathered wall rock around Tavakaiv bodies and intensely altered basement fragments within unweathered injectites imply still earlier regolith development. These observations provide evidence that the granite was exhumed and resided at the surface prior to sand injection, likely before the 717-Ma Sturtian glaciation for the climate appropriate for regolith formation over an extensive region of the paleolandscape. The 510-Ma Sawatch sandstone directly overlies Tavakaiv-injected Pikes granite and drapes over core stones in Pikes regolith, consistent with limited erosion between 717 and 510 Ma. Zircon (U-Th)/He dates for basement below the Great Unconformity are 975 to 46 Ma and are consistent with exhumation by 717 Ma. Our results provide evidence that most erosion below the Great Unconformity in Colorado occurred before the first Neoproterozoic Snowball Earth and therefore cannot be a product of glacial erosion. We propose that multiple Great Unconformities developed diachronously and represent regional tectonic features rather than a synchronous global phenomenon. © 2020 National Academy of Sciences. All rights reserved.
英文关键词	Great Unconformity; Injectites; Snowball Earth; Thermochronology; Zircon (U-Th)/He
语种	英语
scopus关键词	zirconium; Article; astronomy; chronology; climate change; Colorado; environmental erosion; exhumation; geographic and geological phenomena; glaciation; granite; great unconformity; landscape; Neoproterozoic; Neoproterozoic snowball earth; priority journal; rock; sand; sediment; Sturtian; thermochronology
来源期刊	Proceedings of the National Academy of Sciences of the United States of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/160290
作者单位	Flowers, R.M., Department of Geological Sciences, University of Colorado, Boulder, CO 80309, United States; MacDonald, F.A., Earth Science Department, University of California, Santa Barbara, CA 93106, United States; Siddoway, C.S., Department of Geology, Colorado College, Colorado Springs, CO 80903, United States; Havranek, R., Department of Geological Sciences, University of Colorado, Boulder, CO 80309, United States
推荐引用方式 GB/T 7714	Flowers R.M.,MacDonald F.A.,Siddoway C.S.,et al. Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth[J],2020,117(19).
APA	Flowers R.M.,MacDonald F.A.,Siddoway C.S.,&Havranek R..(2020).Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth.Proceedings of the National Academy of Sciences of the United States of America,117(19).
MLA	Flowers R.M.,et al."Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth".Proceedings of the National Academy of Sciences of the United States of America 117.19(2020).