The Cenomanian of northern Germany: facies analysis of a transgressive biosedimentary system

Abstract

A facies analysis of the epicontinental marine Cenomanian sediments of northern Germany shows the presence of 17 facies types (FTs, including several subtypes) which can be assigned to three facies associations: 1) an inner shelf facies association (FT 1-8) with high amounts of terrigenous material and/or high-energy depositional features, 2) a middle shelf facies association (FT 9-15) of predominantly calcareous sediments with moderate amounts of generally fine siliciclastics, and 3) an outer shelf facies association (FT 16-17) of low-energy, fine-grained, pure limestones. These three facies associations roughly correspond to the well-known lithological units of the Cenomanian of northern Germany, i.e., the Essen Greensand/Cenomanian Marls complex, the Pläner Limestones, and the Poor rhotomagense Limestones. The sediments were deposited on a northward-dipping homoclinal ramp with more-or-less shoreline-parallel facies belts. The sediment composition on this ramp-like shelf was a function of the varying importance of three different sediment sources: 1) terrigenous input from the south (Rhenobohemia), generally fining/decreasing in a proximal-distal (i.e., S-N) direction; 2) production of skeletal grains, mainly by macrobenthic organisms; and 3) settling of planktic carbonate (mainly calcispheres and calcareous nannofossils). In response to decreasing water energy with increasing water depth, the seaward decreasing terrigenous influence, and increasing planktic carbonate production, increasingly finer and more calcareous sediments were deposited in a proximal-distal transect. This rather straightforward picture was slightly modified by highest carbonate accumu-M. Wilmsen ( ) · B. Niebuhr

Imbalanced nutrients as triggers for black shale formation in a shallow shelf setting during the OAE 2 (Wunstorf, Germany)

“…Looking at the Hesseltal Formation as deposited in Westphalia and Lower Saxony (Germany) in special or other OAE 2 in general, BS are often interpreted to represent eutrophic conditions in conventional views (Hadras and Mutterlose, 2007;Linnert et al, 2010), while the white intercalated calcareous nannofossil limestones are -as in the case of the underlying Brochterbeck Formation (Fig. 2) -seen to result from biomineralisation in oligotrophic surface waters (Linnert et al, 2010;Wilmsen et al, 2005). These terms, however, are misleading as they are simply nonquantitatively/non-proportionally used to indicate low and high availabilities of nutrients irrespective of its composition and its origin (internal cycling vs. continental run-off).…”

“…It developed due to the worldwide Cenomanian transgression, which caused stepwise drowning of wide continental areas ( Fig. 1) and the progressive establishment of nutrient-depleted shelf seas (Gale et al, 2000;Wilmsen et al, 2005). In basinal/subsident areas of the former north German shelf seas (Fig.…”

“…Here, we present biomarker data from the Wunstorf core (Lower Saxony, Germany), deposited at water depths around 100-150 m water depth (Wilmsen et al, 2005) on the central European shelf, possibly the shallowest OAE 2 BS recorded so far.…”

Taxonomy and taphonomy of Cenomanian (Upper Cretaceous) nautilids from Annopol, Poland

“…The classic regressive Rouen Fossil Bed replete with phosphatised ammonite moulds (Juignet and Kennedy 1976) may be a close analogue. Also, a glauconite-stained "Hg grün" in the Hannover area, for which Ernst et al (1983) coined the term "Mid-Cenomanian Event", seems to represent a comparable horizon (see also Wilmsen 2003 andWilmsen et al 2005).…”

High-resolution Campanian–Maastrichtian carbon and oxygen stable isotopes of bulk-rock and skeletal components: palaeoceanographic and palaeoenvironmental implications for the Boreal shelf sea

“…An episodic stratification with the development of a weak seasonal thermocline during summertime has been suggested by Wilmsen et al (2005) for the Cenomanian shelf sea of northern Germany. Since palaeogeography, climate, and sea-level stand are not fundamentally different, a similar scenario is plausible for the investigated time interval (Text-fig.…”