DOI: 10.1016/j.gloplacha.2012.07.011
论文题名: Microbial ooids and cortoids from the Lower Triassic (Spathian) Virgin Limestone, Nevada, USA: Evidence for an Early Triassic microbial bloom in shallow depositional environments
作者: Woods A.D.
刊名: Global and Planetary Change
ISSN: 0921-8294
出版年: 2013
卷: 105 起始页码: 91
结束页码: 101
语种: 英语
英文关键词: Biotic recovery
; Cortoids
; Early Triassic
; Microbialite
; Ooids
Scopus关键词: Cortoids
; Depositional environment
; Microbialite
; Ooids
; Permian-Triassic Mass extinctions
; Petrographic analysis
; Shallow water environment
; Triassic
; Calcite
; Carbon dioxide
; Geology
; Laminating
; Limestone
; biofacies
; calcium carbonate
; carbon dioxide
; degassing
; depositional environment
; growth rate
; homogeneity
; mass extinction
; micrite
; microbial activity
; nutrient enrichment
; ooid
; petrography
; runoff
; sedimentary rock
; Triassic
; Nevada
; United States
; algae
; Animalia
; Bivalvia
英文摘要: Lower Triassic sedimentary rocks contain a variety of unusual facies and fabrics, with microbialites being a distinctive component of many carbonates deposited following the Permian-Triassic mass extinction. Coated grains are common in shallow water facies from the upper Lower Triassic (Spathian) Virgin Limestone (Moenkopi Formation) in southern Nevada, and were investigated in order to determine their origin. Petrographic analysis reveals that the majority of the coated grains found within the Virgin Limestone are micritic ooids with a concentric fabric, or with a homogenous fabric composed of dense, often cloudy micrite. In addition, asymmetric ooids, aggregate grains, and distorted ooids are also locally common in some oolitic units; low-Mg calcite ooids and bimineralic ooids composed of low-Mg calcite and dense, cloudy micrite are less commonly found, but are also documented from the Virgin Limestone. Cortoids (i.e., grains that are coated with constructive micrite envelopes) are a minor component of oolitic grainstones and packstones (typically 10-15% of the grains), although they may also comprise entire beds. The cortoids are coated with micrite similar to that which comprises the ooid cortices, and may be finely laminated or dense and cloudy in nature. The micrite ooids and constructive micrite envelopes are interpreted as microbial in origin based on the finely laminated or cloudy, dense nature of the micrite, as well as coatings that are uneven, or often of greater thickness on one side of elongate nuclei, such as bivalve shells or phylliod algae blades. The origin of the low-Mg calcite ooids and layers is less certain, but may also be microbial. The results of this study suggest that a microbial bloom occurred in shallow water environments, which was the result of 3 factors: (1) the unusual chemistry of Early Triassic oceans; (2) runoff of nutrient-rich waters, which enhanced microbialite growth; and, (3) wave agitation and warm waters that led to CO2 degassing and further supersaturation of shallow waters with respect to calcium carbonate. © 2012 Elsevier B.V. URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876981415&doi=10.1016%2fj.gloplacha.2012.07.011&partnerID=40&md5=5f470f66f24ca9e34901476d54ab9f33
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/11200
Appears in Collections: 全球变化的国际研究计划
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作者单位: Department of Geological Sciences, California State University Fullerton, 800 N. State College Blvd., Fullerton, CA 92834-6850, United States
Recommended Citation:
Woods A.D.. Microbial ooids and cortoids from the Lower Triassic (Spathian) Virgin Limestone, Nevada, USA: Evidence for an Early Triassic microbial bloom in shallow depositional environments[J]. Global and Planetary Change,2013-01-01,105.