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Palaeoceanography of Lower Cretaceous (Barremian–Lower Aptian) black shales from northwest Germany evidenced by calcareous nannofossils and geochemistry

Palaeoceanography of Lower Cretaceous (Barremian–Lower Aptian) black shales from northwest Germany evidenced by calcareous nannofossils and geochemistry

Pauly, Sebastian, Mutterlose, Jörg and Wray, David S. (2013) Palaeoceanography of Lower Cretaceous (Barremian–Lower Aptian) black shales from northwest Germany evidenced by calcareous nannofossils and geochemistry. Cretaceous Research, 42. pp. 28-43. ISSN 0195-6671 (doi:10.1016/j.cretres.2013.01.001)

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Abstract

During the Barremian-Early Aptian, the Lower Saxony Basin (LSB) of northwest Germany was covered by a shallow epicontinental sea where restricted conditions resulted in the formation of black shales. This study focuses on a 103-m-thick succession of Lower Barremian-Lower Aptian dark claystones and black shales exposed in a temporary road cut in northwest Germany (A39). Calcareous nannofossils and the delta C-13(org) record have been used to determine the timing of black shale deposition (Hauptblatterton, Blatterton, Fischschiefer events). Redox-sensitive trace elements indicate anoxic conditions with free H2S causing the formation of black shales and dysoxic conditions during deposition of the dark claystones. The palaeoecological reconstructions based on calcareous nannofossils suggest that during the Lower Barremian Hauptblatterton event a stratification of water masses existed, caused by high surface water temperatures and reduced terrigenous run-off. During the deposition of the Upper Barremian clay-Blatterton alternation warm surface water prevailed, accompanied by meso-eutrophic surface water conditions. The formation of the Barremian black shales was mainly caused by restricted conditions related to the palaeogeography and palaeoceanography of the LSB. Global processes associated with the Oceanic Anoxic Event la most likely induced the deposition of the Lower Aptian Fischschiefer. High weathering rates, high primary production, and restricted conditions in the LSB led to increased burial of organic matter and thereby to the formation of the Fischschiefer.

Item Type: Article
Uncontrolled Keywords: Barremian, Lower Aptian, Northwest Germany, Calcareous nannofossils, Major and minor elements, Palaeoceanography, Depositional environment, Black shaless
Subjects: Q Science > QD Chemistry
Q Science > QE Geology
Pre-2014 Departments: School of Science
Last Modified: 14 Oct 2016 09:25
Selected for GREAT 2016: None
Selected for GREAT 2017: None
Selected for GREAT 2018: None
URI: http://gala.gre.ac.uk/id/eprint/10589

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