DOI: 10.1016/j.epsl.2021.116746
论文题名: Novel watermass reconstruction in the Early Mississippian Appalachian Seaway based on integrated proxy records of redox and salinity
作者: Gilleaudeau G.J. ; Algeo T.J. ; Lyons T.W. ; Bates S. ; Anbar A.D.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 558 语种: 英语
中文关键词: epeiric sea
; iron speciation
; lateral gradient
; paleosalinity
; Sr/Ba
; trace metals
英文关键词: Core drilling
; Deposition
; Iron
; Organic carbon
; Regional planning
; Shale
; Water
; Direct measurement
; Eastern north america
; Fundamental properties
; Regional development
; Sedimentary records
; Spatial variability
; Total Organic Carbon
; Trace metal contents
; Trace elements
英文摘要: Redox state and salinity are fundamental properties of watermasses, and in modern environments, detailed analysis of spatial variability in redox and salinity is possible through direct measurement. Watermass reconstruction is difficult in deep-time systems, however, because the sedimentary record of ancient watermasses is often incomplete or difficult to access on spatial scales large enough to permit basin-scale reconstruction. During the Middle Devonian to Early Mississippian periods, the Appalachian Basin of eastern North America was characterized by a variably restricted watermass, leading to extensive deposition of organic-rich black shale associated with the regional development of bottom-water anoxia. Watermass reconstruction during deposition of these units has previously been attempted, but only on small spatial scales, with most studies focused on trace element proxies applied to individual study sections. Here, we focus instead on a broader geographic reconstruction of watermasses in the Lower Mississippian (Tournaisian) Sunbury Shale and present a new geochemical dataset that spans five drill cores across a basin transect from northeastern Ohio to southern Kentucky (USA). Iron speciation and trace metal abundances reveal a strong paleoredox gradient that can be related to water depth and basin hydrography. In the northeastern-most core of Ohio, iron speciation reveals largely ambiguous redox conditions; however, oxic conditions are potentially indicated by very low total organic carbon and trace metal contents. These oxygenated conditions were likely related to proximity to the Catskill deltaic wedge complex that fed freshwater into the basin and lowered the position of the regional pycnocline. In contrast, in central and southern Ohio, paleoredox indicators reveal the development of ferruginous conditions associated with rapid deepening to the south into the central axis of the Appalachian Basin. Further to the south in Kentucky, our data reveal dominantly euxinic conditions, which developed as environments shoaled towards the basin-bounding Cumberland Sill. We also investigated paleosalinity across the Appalachian Basin using strontium/barium (Sr/Ba) ratios. Our data reveal a subtle paleosalinity gradient from low-brackish (i.e., close to freshwater) conditions close to the Catskill Delta complex to increasingly brackish conditions to the southwest. This trend was disrupted by large paleosalinity variation across a shallow mixing zone in the southwestern-most core. Lastly, strong enrichments of redox-sensitive trace metals in both ferruginous and euxinic environments are parsimoniously attributed to the operation of an iron-manganese particulate shuttle that continuously supplied oxide-sensitive metals to the Appalachian Basin. Ultimately, this study is among the first to present detailed watermass reconstruction in an ancient epeiric sea using both redox and salinity proxies applied over a large lateral transect. We suggest that a similar approach may be useful in other deep-time systems of geobiological, paleoclimatic, and paleoceanographic significance. © 2021 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165479
Appears in Collections: 气候变化与战略
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作者单位: Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, VA, United States; Department of Geology, University of Cincinnati, Cincinnati, OH, United States; State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, China; Department of Earth and Planetary Sciences, University of California, Riverside, CA, United States; School of Earth and Space Exploration, Arizona State University, Tempe, AZ, United States; School of Molecular Sciences, Arizona State University, Tempe, AZ, United States
Recommended Citation:
Gilleaudeau G.J.,Algeo T.J.,Lyons T.W.,et al. Novel watermass reconstruction in the Early Mississippian Appalachian Seaway based on integrated proxy records of redox and salinity[J]. Earth and Planetary Science Letters,2021-01-01,558