DOI: 10.1016/j.palaeo.2014.07.025
论文题名: Foraminiferal and nannofossil paleoecology and paleoceanography of the Cenomanian-Turonian Eagle Ford Shale of southern Texas
作者: Lowery C.M. ; Corbett M.J. ; Leckie R.M. ; Watkins D. ; Miceli Romero A. ; Pramudito A.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2014
卷: 413 起始页码: 49
结束页码: 65
语种: 英语
英文关键词: Calcareous nannofossil paleoecology
; Eagle Ford Shale
; Foraminiferal paleoecology
; OAE2
; Western Interior Seaway
英文摘要: The Upper Cretaceous of central Texas is dominated by a broad, shallow carbonate platform called the Comanche Platform that occupies an important gateway between the epeiric Western Interior Seaway (WIS) of North America to the open-marine Gulf of Mexico/Tethys. We investigated the Cenomanian-Turonian Eagle Ford Shale on and adjacent to the Comanche Platform to determine whether the Eagle Ford Shale has an affinity with the Western Interior, and if so, determine where the transition from Western Interior to open ocean is located. We were also interested in the relationship, if any, between the organic-rich facies of the Eagle Ford and Oceanic Anoxic Event 2 (OAE2). Our work is based on quantitative foraminiferal population counts and associated sedimentary particles (including inoceramid prisms, sand, glauconite, and pyrite grains), calcareous nannofossil assemblages, carbon isotopes, and total organic carbon (TOC) from three sites across a range of paleowater depths: an outcrop in Lozier Canyon in Terrell County, west of Langtry, TX, an outcrop at Bouldin Creek outside of Austin, TX, and Swift Energy's Fasken A #1H core in Webb County, TX.The highest TOC in the Eagle Ford occurs before the onset of OAE2 (6% at Lozier Canyon, 7% at both Bouldin Creek and the Fasken Core) and then declines steadily through the rest of the section (except for a small increase at the end of OAE2 at Lozier and a fairly large post-OAE2 increase at Bouldin Creek). Nannofossil paleoproductivity indicators (%. Zeugrhabdotus and %. Biscutum) track TOC at Bouldin Creek and in the Fasken Core and display similar trends to those observed in the Western Interior Seaway to the north. Benthic foraminiferal abundances increase as TOC decreases and the lithology shifts from laminated black shale to bioturbated light gray shale; low-oxygen-tolerant infaunal Neobulimina spp. appear first and gradually increase in abundance; epifaunal benthics appear soon after. This oxygenation trend continues through the OAE2 interval and the upper Eagle Ford contains a diverse epi- and infaunal benthic foraminiferal assemblage and macrofossil assemblage. This trend of decreasing TOC and nannofossil paleoproductivity indicators coupled with increasing benthic foraminiferal abundance and diversity (and seafloor oxygenation) corresponds to rising sea level.Based on foraminiferal and nannofossil events, TOC trends, and changes in lithology, both platform sites have a strong affinity with the Western Interior, with Lozier Canyon being the most similar; the Fasken Core bears all the characteristics of an open ocean site, except for the fact that peak TOC occurs before OAE2. This suggests that the oceanographic boundary between WIS and Tethys can be placed on the edge of the Comanche Platform.Productivity was likely driven by bathymetry-induced upwelling caused by restriction between the WIS and Tethys during times of low sea level; as sea level rose, upwelling diminished and productivity decreased. This explains why the Fasken Core, adjacent to the platform margin and in the center of this upwelling zone, displays the same TOC trends as the platform sites. Organic carbon content in the seaway was controlled by stratification and enhanced preservation, but this was also reduced by rising sea level, which is why the two areas show parallel trends. © 2014 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/69504
Appears in Collections: 过去全球变化的重建
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作者单位: Univeristy of Massachusetts, Dept. of Geosciences, 233 Morrill Science Center, 611 N. Pleasant St., Amherst, MA, United States; University of Nebraska, Dept. of Earth and Atmospheric Sciences, 214 Bessey Hall, PO Box 80330, Lincoln, NE, United States; University of Oklahoma, School of Geology and Geophysics, 100 East Boyd St., Norman, OK, United States; BP, 501 Westlake Park Blvd., Houston, TX, United States
Recommended Citation:
Lowery C.M.,Corbett M.J.,Leckie R.M.,et al. Foraminiferal and nannofossil paleoecology and paleoceanography of the Cenomanian-Turonian Eagle Ford Shale of southern Texas[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2014-01-01,413