Palaeobiology, morphology and diversity of macrofaunas: A case study on Early Cretaceous ammonites

点击翻译按钮获取中文摘要

The background for control mechanism regarding fluctuations in the abundance, diversity and morphological changes of fossil invertebrates is a complex but seminal field. Particularly the nutrient and sediment supply may be a major affluent on macrofossil fluctuations and essential for reconstructing their environmental background, but is not yet in the focus of current research. We plan to use associations of benthic and planktic foraminifers and calcareous nanoplankton to reconstruct oxygen and nutrient levels for Early Cretaceous oceans and to apply these data to the interpretation of ammonite ecology as a case for other macrofossil groups. This is considered an urgent matter of research, since ammonites are among the dominant and most important invertebrates of their times and their position in the food web may be a key for understanding marine ecosystems on the Mesozoic shelf. Only a few pioneer studies support this hypothesis yet, underlining the urgency of the matter. We propose to cover the bio- and lithofacies interpretation by sedimentological data and the independent time-control and correlation of sections by stable isotope supported by gamma ray data. Since nutrient supply is steered by climate conditions, we chose prime profiles across climatic belts in the Tethys, the central Atlantic as well as in northern Europe. We choose the Lower Aptian as a key substage, since this time interval contains the most prominent Early Cretaceous Oceanic Anoxic Event with a very wide distribution of low oxygen conditions, excellent carbon isotope records and the chance to study long and short term changes prior to, during and subsequent to the event.