Monospecific brachiopod mass occurrences have been known from the Triassic Hallstatt facies of the Calcareous Alps in Austria for nearly two centuries, but their origin has never been satisfyingly explained.
Our aim is to test the recent hypothesis that such deposits, especially when found in neptunian dikes, represent ancient methane-seep deposits. This hypothesis is based on recent findings of closely related brachiopods at ancient methane-seep deposits in Oregon, USA.
Furthermore, present-day methane seeps in the Gulf of Mexico are typically associated with salt diapirism. Neptunian dikes in the Calcareous Alps are related to diapirism of underlying Permian salts and, therefore, we will focus on mass occurrences of the brachiopods Halorella, Halorelloidea and Sulcirostra that are found in such dikes.
Our approach to test this hypothesis includes:
In a second line of research, we will investigate the adaptations of these brachiopods to their environment. Here we will focus on potential adaptations to cope with different fluid flow regimes and predation pressure, which will be assessed by comparing petrographic and geochemical proxies for seepage intensity with size and predation scar pattern among the brachiopods.
Universität Hamburg, Germany
Universität Wien, Austria
Kiel S et al. 2017. Late Triassic mollusk-dominated hydrocarbon-seep deposits from Turkey. Geology 45: 751-754.
Kiel S et al. 2014. The paleoecology, habitats, and stratigraphic range of the enigmatic Cretaceous brachiopod Peregrinella. PLoS One 9, e109260.
Peckmann J, Kiel S, Sandy MR, Taylor DG, Goedert JL 2011. Mass occurrences of the brachiopod Halorella in Late Triassic methane-seep deposits, Eastern Oregon. Journal of Geology 119: 207-220.