Stratigraphy, fauna, palaeoenvironment and palaeocology of the Stollenbank Member (Suntel Formation, mutabilis/eudoxus zonal boundary, KIM 4, Upper Kimmeridgian) of NW Germany

Abstract

The bivalve dominated macrofauna of the Stollenbank Member (Suntel Formation, middle Upper Kimmeridgian), from NW Germany is described from three dinosaur track localities. First ammonite remains of Orthaspidoceras schilleri from the Nanogyra Bed date this member around the mutabilis/eudoxus ammonite zonal boundary (KIM 4). This is important for the dating of dinosaur megatracksites, especially that of Barkhausen, into the Sand-Tonkomplex Member in-between the KIM 3 and 4. New marker beds with bivalve-dominated taphocoenoses from shallow subtidal environments are distinguished. The biocoenosis types depend on the sediments such as oolites, marls, and limestones. Gryphaea tempestitic marls in the Oolithic Beds are built of these medium-sized oysters in-between the oolith bars along the coast. The calcareous Eocallista/Thracia Beds are allochthonous tempestites of the outer bar system dominated by aragonitic bivalves that were postmortally rapidly buried. The marly Nanogyra Bed is a softground of the outer bar facies and was strongly colonized by the small pioneer gryphaeate ecotype of the oyster Nanogyra accumulated by storm events. The Sellithyris Bed, another tempestitic limestone, was deposited in the subtidal environment, later representing a firmground, and was colonized especially by the terebratulid Sellithyris subsella, but also by some epifaunal bivalves. Eocallista seems to be a Subboreal bivalve. All taxa found in the Subboreal Upper Kimmeridgian of NW Germany also Occur in the twice more diverse Tethys- (Switzerland, France, Tunisia) bivalve-dominated benthic palaeocommunities of the same age. Finally, a few nectonic vertebrates such as pycnodontid teleosts (Macromesodon, Proscinetes, Lepidotes), and a few crocodile remains (Steneosaurus) are recorded.