Skip to Main Content
GEOREF RECORD

Calcareous nannofossils from Eastbourne (southeastern England) and the paleoceanography of the Cenomanian-Turonian boundary interval

Christian Linnert, Joerg Mutterlose and Rory Mortimore
Calcareous nannofossils from Eastbourne (southeastern England) and the paleoceanography of the Cenomanian-Turonian boundary interval
Palaios (May 2011) 26 (5): 298-313

Abstract

The Cenomanian-Turonian (C-T) boundary interval is marked by one of the most prominent perturbations of the Mesozoic carbon cycle, Oceanic Anoxic Event 2 (OAE2). Increased fertilization of surface waters caused by greater fluvial input of nutrients may have caused the widespread deposition of organic-rich black shales during the OAE2 (productivity model). Alternatively, sluggish oceanic circulation may have enhanced stratification of the water column favoring the preservation of organic matter due to anoxic bottom-water conditions (preservation model). In order to gather evidence for the driving mechanism behind the deposition of the OAE2 black shales, calcareous nannofossils from the midlatitudinal Holywell section (Eastbourne, southeastern England) were studied. Ten bioevents, including last occurrences of six species and first occurrences of four, were recognized throughout the 11-m-thick interval. Preservation of calcareous nannofossils was moderate to good in all studied samples. The C-T interval here contains an abundant (mean 2.4X10 (super 9) specimens/g sediment) and highly diverse (mean 58 spp./sample) calcareous nannoflora, with Watznaueria, Zeugrhabdotus, Biscutum, and Prediscosphaera the most common taxa. The most remarkable change in assemblage composition through the OAE2 is the decrease of Biscutum spp. Low abundances of Biscutum, combined with elevated numbers of Watznaueria spp. and/or Polycyclolithaceae, indicate reduced surface-water fertility during the OAE2 in midlatitudinal European shelf areas. A reduction of primary productivity seems to be quite common in midlatitudinal sections, whereas calcareous nannofossils and geochemistry indicate an increase in primary productivity in low-latitudinal sections. It is therefore likely that the origin of the OAE2 in mid latitudes was caused by sluggish ocean circulation, which intensified stratification. Reduced rates of mixing prevented the oxygenation of bottom waters in these regions, causing black shale deposition.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 26
Serial Issue: 5
Title: Calcareous nannofossils from Eastbourne (southeastern England) and the paleoceanography of the Cenomanian-Turonian boundary interval
Affiliation: Ruhr-University Bochum, Bochum, Germany
Pages: 298-313
Published: 201105
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 91
Accession Number: 2011-052070
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus. incl. strat. col., 1 table, geol. sketch map
N50°46'00" - N50°46'00", E00°16'60" - E00°16'60"
Secondary Affiliation: University of Brighton, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 201129
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal