Huge accumulations of Upper Cretaceous giant ammonite shells in benthic islands of southern North Sea Basin of Central Europe

Abstract

In the greenhouse world of the Early Upper Cretaceous of Europe giant cephalopod shells of the hemibenthic ammonite Puzosia formed huge accumulations. Their shells indicate adaptations in the body chamber morphology depending on the environment. On the sea floor, deposited ammonite shells scoured up to 50 cm depth which caught more and more large shells over extended periods of time. They built up to five square meter extended scour troughs in which the shells are enriched in chain-, fan- and fan layer orders with a maximum accumulation of 24 cephalopods. Between these hundreds of other macrofaunal remains accumulated. The ammonite shells were benthic islands and minibiotopes in carbonate soft- to firm ground environments along a submarine swell in the southern North Sea Basin of Central Europe. The empty shells encrusted by different epizoans sheltered and protected also crustaceans, which undermined the empty shells by bioturbation. Small and extremely rare squamate reptiles of the marine Dolichosaurus longicollis possibly took shelter or fed within these unique benthic submarine depression "islands".