Paleoenvironmental changes across the Mid Cenomanian Event in the tropical Atlantic Ocean (Demerara Rise, ODP Leg 207) inferred from benthic foraminiferal assemblages

Friedrich, Oliver, Erbacher, Jochen, Wilson, Paul A., Moriya, Kazuyoshi and Mutterlose, Jörg (2009) Paleoenvironmental changes across the Mid Cenomanian Event in the tropical Atlantic Ocean (Demerara Rise, ODP Leg 207) inferred from benthic foraminiferal assemblages Marine Micropaleontology, 71, (1-2), pp. 28-40. (doi:10.1016/j.marmicro.2009.01.002).

This is the latest version of this item.


Full text not available from this repository.


This study is based on Cenomanian sediments of Ocean Drilling Program (ODP) Sites 1258 and 1260 from Demerara Rise (Leg 207, western tropical Atlantic, off Suriname, ~1000 and ~500 m paleo-water depth, respectively). Studied sediments consist of laminated black shales with TOC values between 3 and 18 % and include the Mid Cenomanian Event (MCE), a positive carbon isotope excursion predating the well-known Oceanic Anoxic Event 2 (OAE 2). Benthic foraminiferal assemblages of the continuously eutrophic environment at Demerara Rise are characterized by low diversities (? 9 species per sample) and large fluctuations in abundances, indicating oxygen depletion and varying organic matter fluxes. Dominant species at both sites are Bolivina anambra, Gabonita levis, Gavelinella dakotensis, Neobulimina albertensis, Praebulimina prolixa, and Tappanina cf. laciniosa. Benthic foraminiferal assemblages across the MCE show a threefold pattern: (1) stable ecological conditions below the MCE interval indicated by relatively high oxygenation and fluctuating organic matter flux, (2) decreasing oxygenation and/or higher organic matter flux during the MCE with decreasing benthic foraminiferal numbers and diversities (Site 1258) and a dominance of opportunistic species (Site 1260), and (3) anoxic to slightly dysoxic bottom-water conditions above the MCE as indicated by very low diversities and abundances or even the absence of benthic foraminifera. Slightly dysoxic conditions prevailed until OAE 2 at Demerara Rise. A comparison with other Atlantic Ocean and Tethyan sections indicates that the MCE reflects a paleoceanographic turning point towards lower bottom-water oxygenation, at least in the proto-North Atlantic Ocean and in the Tethyan and Boreal Realms. This general trend towards lower oxygenation of bottom waters across the MCE is accompanied by ongoing climate warming in combination with rising sea-level and the development of vast shallow epicontinental seas during the Middle and Late Cenomanian. These changes are proposed to have favoured the formation of warm and saline waters that may have contributed to intermediate- and deep-water masses at least in the restricted proto-North Atlantic and Tethyan Ocean basins, poor oxygenation of the Late Cenomanian sediments, and the changes in benthic foraminiferal assemblages across the MCE.

Item Type: Article
Digital Object Identifier (DOI): doi:10.1016/j.marmicro.2009.01.002
ISSNs: 0377-8398 (print)
Keywords: Benthic foraminifera, Mid Cenomanian Event, Cenomanian, Ocean Drilling Program, Cretaceous
ePrint ID: 65029
Date :
Date Event
April 2009Published
Date Deposited: 27 Jan 2009
Last Modified: 16 Apr 2017 17:16
Further Information:Google Scholar

Available Versions of this Item

Actions (login required)

View Item View Item