DOI: 10.1016/j.gloplacha.2015.01.007
论文题名: Oceanic response to Pliensbachian and Toarcian magmatic events: Implications from an organic-rich basinal succession in the NW Tethys
作者: Neumeister S. ; Gratzer R. ; Algeo T.J. ; Bechtel A. ; Gawlick H.-J. ; Newton R.J. ; Sachsenhofer R.F.
刊名: Global and Planetary Change
ISSN: 0921-8181
出版年: 2015
卷: 126 起始页码: 62
结束页码: 83
语种: 英语
英文关键词: Allgäu Formation
; Alpine Tethys
; Anoxia
; Bächental marl
; Carbon isotopes
; Karoo-Ferrar
; Northern Calcareous Alps
; Oceanic anoxic event
; Sachrang Member
; Sea level
Scopus关键词: Biogeochemistry
; Biological materials
; Carbon
; Deposition
; Fertilizers
; Isotopes
; Organic compounds
; Petroleum geology
; Sea level
; Stratigraphy
; Surface waters
; Alpine Tethys
; Anoxia
; Carbon isotopes
; Karoo-Ferrar
; Northern Calcareous Alps
; Oceanic Anoxic Event
; Sachrang Member
; Organic carbon
; basin evolution
; bathymetry
; bioturbation
; caatinga
; chemostratigraphy
; environmental conditions
; euxinic environment
; isotopic analysis
; magmatism
; marl
; mass transport
; organic geochemistry
; Pliensbachian
; redox conditions
; salinity
; sea level change
; stratification
; succession
; Tethys
; Toarcian
; water mass
; Allgau
; Bavaria
; Germany
; Ammonoidea
; Posidonia
英文摘要: The Bächental bituminous marls (Bächentaler Bitumenmergel) belonging to the Sachrang Member of the Lower Jurassic Middle Allgäu Formation were investigated using a multidisciplinary approach to determine environmental controls on the formation of organic-rich deposits in a semi-restricted basin of the NW Tethys during the Early Jurassic. The marls are subdivided into three units on the basis of mineralogical composition, source-rock parameters, redox conditions, salinity variations, and diagenetic processes. Redox proxies (e.g., pristane/phytane ratio; aryl isoprenoids; bioturbation; ternary plot of iron, total organic carbon, and sulphur) indicate varying suboxic to euxinic conditions during deposition of the Bächental section. Redox variations were mainly controlled by sea-level fluctuations with the tectonically complex bathymetry of the Bächental basin determining watermass exchange with the Tethys Ocean. Accordingly, strongest anoxia and highest total organic carbon content (up to 13%) occur in the middle part of the profile (upper tenuicostatum and lower falciferum zones), coincident with an increase in surface-water productivity during a period of relative sea-level lowstand that induced salinity stratification in a stagnant basin setting. This level corresponds to the time interval of the lower Toarcian oceanic anoxic event (T-OAE). However, the absence of the widely observed lower Toarcian negative carbon isotope excursion in the study section questions its unrestricted use as a global chemostratigraphic marker. Stratigraphic correlation of the thermally immature Bächental bituminous marls with the Posidonia Shale of SW Germany on the basis of C27/C29 sterane ratio profiles and ammonite data suggests that deposition of organic matter-rich sediments in isolated basins in the Alpine realm commenced earlier (late Pliensbachian margaritatus Zone) than in regionally proximal epicontinental seas (early Toarcian tenuicostatum Zone). The late Pliensbachian onset of reducing conditions in the Bächental basin coincided with an influx of volcaniclastic detritus that was possibly connected to complex rifting processes of the Alpine Tethys and with a globally observed eruption-induced extinction event. The level of maximum organic matter accumulation in the Bächental basin corresponds to the main eruptive phase of the Karoo-Ferrar large igneous province (LIP), confirming its massive impact on global climate and oceanic conditions during the Early Jurassic. The Bächental marl succession is thus a record of the complex interaction of global (i.e., LIP) and local (e.g., redox and salinity variations, basin morphology) factors that caused reducing conditions and organic matter enrichment in the Bächental basin. These developments resulted in highly inhomogeneous environmental conditions in semi-restricted basins of the NW Tethyan domain during late Pliensbachian and early Toarcian time. © 2015 Elsevier B.V. URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921809963&doi=10.1016%2fj.gloplacha.2015.01.007&partnerID=40&md5=305436b8de3d084df6f4ad6b32ea6fc9
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/11554
Appears in Collections: 全球变化的国际研究计划 气候变化与战略
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作者单位: Department of Applied Geosciences and Geophysics, Montanuniversitaet Leoben, Peter-Tunner-Str. 5, Leoben, Austria
Recommended Citation:
Neumeister S.,Gratzer R.,Algeo T.J.,et al. Oceanic response to Pliensbachian and Toarcian magmatic events: Implications from an organic-rich basinal succession in the NW Tethys[J]. Global and Planetary Change,2015-01-01,126.