Fossil Record 24(2): 395-441, doi: 10.5194/fr-24-395-2021
Albian to Turonian agglutinated foraminiferal assemblages of the Lower Saxony Cretaceous sub-basins – implications for sequence stratigraphy and paleoenvironmental interpretation
expand article infoRichard M. Besen, Ulrich Struck, Ekbert Seibertz§
‡ Department of Earth Sciences, Institute of Geological Sciences, Freie Universität Berlin, Malteserstraße 74–100, 12249 Berlin, Germany§ Institute of Geoecology, University of Braunschweig, Langer Kamp 19c, 38106 Braunschweig, Germany
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Albian to Turonian carbonate deposits at three different locations of theLower Saxony Cretaceous and thereby of the European mid-Cretaceous epeiricshelf sea were investigated for their fossil agglutinated foraminiferalfauna. In this study, 71 samples from two quarries and three drill coreswere treated with formic acid, which enabled the study of agglutinatedforaminiferal assemblages even in highly lithified limestones. In total, 114species were determined and classified as belonging to nine morphogroups. Ingeneral, four agglutinated foraminiferal assemblages are distinguished: (1) an uppermost Albian–lowermost Cenomanian assemblage from the Wunstorf drillcores, with the dominant taxaBathysiphon spp., Nothia spp., Psammosphaera fusca, Reophax subfusiformis, Bulbobaculites problematicus, Tritaxia tricarinata, Flourensina intermedia, Vialovella frankei, Arenobulimina truncata, and Voloshinoides advenus; (2) a Cenomanianassemblage from the Baddeckenstedt quarry and Wunstorf drill cores, withAmmolagena clavata, Tritaxia tricarinata, Vialovella frankei, Arenobulimina truncata, and Voloshinoides advenus; (3) an assemblage related to the Cenomanian–Turonian Boundary Event inWunstorf and Söhlde dominated by Bulbobaculites problematicus; and (4) a Turonian assemblage in theWunstorf and Söhlde sections with high numbers of Ammolagena contorta, Repmanina charoides, Bulbobaculites problematicus, Gerochammina stanislawi, andSpiroplectammina navarroana. The latest Albian–earliest Cenomanian assemblage consists of tubular,globular, and elongate foraminiferal morphogroups which are typical for thelow- to mid-latitude slope biofacies. All other assemblages are composed ofelongate foraminiferal morphogroups with additionally globular forms in theproximal settings of Baddeckenstedt and Söhlde or flattened planispiraland streptospiral forms in more distal settings of Wunstorf. For theseassemblages, a new agglutinated foraminiferal biofacies named “mid-latitudeshelf biofacies” is proposed herein. Changes in the relative abundance ofdifferent morphogroups can often be referred to single features ofdepositional sequences. Furthermore, classical macro-bioevents, which areoften depositional-related, of the Lower Saxony Cretaceous seem to have amicro-bioevent or acme equivalent of the agglutinated foraminiferal fauna.