THE 33RD NORDIC GEOLOGICAL WINTER MEETING

10-12. JANUARY 2018 KGS. LYNGBY, DENMARK

HOSTED BY GEOLOGICAL SOCIETY OF DENMARK & TECHNICAL UNIVERSITY OF DENMARK

Dansk Geologisk Forening Geological Society of Denmark

POSTER POSTER

Carinodens – a new addition to the Biostratigraphy and palaeoecology of Late Cretaceous mosasaur fauna of calcareous nannofossils in the Lower Denmark Cretaceous Munk Marl Bed, Danish North Sea Jesper Milàn1, John W.M. Jagt2, Johan Lindgren3 and Anne S. Schulp2 Sarah D. Møller1, Emma Sheldon2 and Jan Audun 1Geomuseum Faxe, Denmark, 2Natuurhistorisch Rasmussen3 Museum Maastricht, The Netherlands, 3Department of 1Department of Geosciences and Natural Resource Geology, Lund University, Sweden Management, Københavns Universitet, 2GEUS, Geological Survey of Denmark and Greenland, 3Fossil- og Molermuseet, Museum Mors The small durophagous mosasaurine mosasaur (Reptilia, Mosasauridae) genus Carinodens is exceedingly rare in north European chalk The Lower Cretaceous Munk Marl Bed of the deposits, with published finds limited to a small Tuxen Formation (Danish Central Graben) marks number of shed tooth crowns and two partial a change in the depositional environment within dentaries from The Netherlands and Belgium, all a chalk unit. Here we investigate the calcareous assigned to Carinodens belgicus. A newly nannofossils from this interval of the Danish discovered isolated, shed tooth crown from the Boje-2C well with emphasis on biostratigraphy UNESCO world heritage site of Stevns Klint and palaeoecology to better understand the expands the known geographical distribution of pelagic environment at the time of deposition. A another species, C. minalmamar, first described total of seventy-two samples were analysed from from Morocco, to Denmark. The specimen was the well. The samples correlate to the upper found within the uppermost metres of the Lower Barremian nannofossil zones BC14 and Maastrichtian chalk deposits, thereby placing it LK20B. An acme of nannoconid ‘tops’ is proposed within the last 50.000 years of the Cretaceous. as a new biostratigraphical event characterising The new tooth crown represents the the middle part of the Munk Marl Bed. High northernmost occurrence of the genus abundances of thermophile taxa suggest warm Carinodens. Previous finds of mosasaur dental surface water conditions at the time of and skeletal materials from Denmark have all deposition. Indicators of increased fertility show been assigned to the hypercarnivorous particularly low abundances indicating a mosasaurids Mosasaurus hoffmannii and decrease in surface water fertility, presumably Plioplatecarpus sp. Thus, the new specimen related to an increased detrital input. provides important new information on Correspondence analysis ordinates samples in ecological niche partitioning amongst large relation to identified palaeoecological proxies marine reptiles during the latest Maastrichtian. and reflects palaeotrophic levels in the surface water within the section. The analysis shows that the calcareous nannofossils indicate a period of more oligotrophic surface water in the middle of the section.

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