气候变化领域集成服务门户(CCPortal): Cryogenian cap carbonate models: a review and critical assessment

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DOI	10.1016/j.palaeo.2020.109727
	Cryogenian cap carbonate models: a review and critical assessment
	Yu W.; Algeo T.J.; Zhou Q.; Du Y.; Wang P.
发表日期	2020
ISSN	0031-0182
卷号	552
英文摘要	The Cryogenian Period spans two major glaciations, the Sturtian Ice Age (~720–660 Ma) and the Marinoan Ice Age (~650–635 Ma), the termination of each of which was associated with a unique type of cap carbonate deposit. Cap carbonates are significant in providing a record of as-yet not fully understood ocean-chemical changes during the deglaciations following Snowball Earth events and in serving as readily recognizable event beds useful in global stratigraphic correlation of Neoproterozoic successions. Debate regarding the formation of cap carbonates has focused on three key issues: (1) alkalinity sources, (2) abiotic (chemical) versus biotic (microbial) precipitation, and (3) formation rates. Multiple hypotheses regarding cap carbonate formation have been advanced, including the weathering alkalinity model, the oceanic overturn model, the gas hydrate destabilization model, the plumeworld model, the starvation sediment model, the enhanced microbial activity model, and the calcareous loess model. We evaluated these models by considering their proposed solutions to the key issues above in the context of a global compilation of location, thickness, carbonate C-isotope, and paleomagnetic data for Cryogenian cap carbonates. Cap carbonates were probably produced through a combination of chemical and microbial processes in a strongly stratified deglacial ocean with a low-salinity lid. Correlation of δ13Ccarb profiles shows that cap carbonate precipitation began synchronously but terminated diachronously at a global scale. Cap carbonates are markedly thicker in low-paleolatitude regions, suggesting greater alkalinity production and/or more rapid carbonate precipitation in those regions, which favors alkalinity production through continental weathering rather than through oceanic upwelling or methane oxidation. Calculation of alkalinity production rates based on a range of cap carbonate masses and formation intervals shows that minimum masses (~2.2 × 1021 g, i.e., comprising only known continental deposits) could have been produced through intense continental weathering at short timescales (103–104 yr), validating rapid deposition models. Longer timescales of cap carbonate formation (105–106 yr) are not precluded by these calculations but are hard to reconcile with physical evidence of rapid accumulation and near-complete lack of terrigenous clastic impurities. Alkalinity production rate calculations also show that maximum cap carbonate masses (to ~14.4 × 1021 g; i.e., assuming unproven deep-ocean cap carbonate deposits) are probably unrealistic, requiring more alkalinity than could be generated even through a combination of mechanisms including continental weathering, deep-ocean microbial sulfate reduction, and methane release. © 2020 Elsevier B.V.
英文关键词	alkalinity; deglaciation; Marinoan; Neoproterozoic; Snowball Earth; Sturtian
语种	英语
scopus关键词	alkalinity; assessment method; carbonate system; chemical weathering; deglaciation; glaciation; Little Ice Age; microbial activity; Pleistocene; precipitation (chemistry); Proterozoic; stratigraphy
来源期刊	Palaeogeography, Palaeoclimatology, Palaeoecology
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/150460
作者单位	State Key Laboratory of Biogeology and Environmental Geology, School of Earth Sciences, China University of Geosciences-Wuhan, Wuhan, 430074, China; Innovation Center of Ore Resources Exploration Technology in the Region of Bedrock, Ministry of Natural Resources of People's Republic of China, Guiyang, 550004, China; State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences-Wuhan, Wuhan, 430074, China; Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, United States; Guizhou Bureau of Geology and Mineral Exploration and Development, Guiyang, 550004, China
推荐引用方式 GB/T 7714	Yu W.,Algeo T.J.,Zhou Q.,et al. Cryogenian cap carbonate models: a review and critical assessment[J],2020,552.
APA	Yu W.,Algeo T.J.,Zhou Q.,Du Y.,&Wang P..(2020).Cryogenian cap carbonate models: a review and critical assessment.Palaeogeography, Palaeoclimatology, Palaeoecology,552.
MLA	Yu W.,et al."Cryogenian cap carbonate models: a review and critical assessment".Palaeogeography, Palaeoclimatology, Palaeoecology 552(2020).