A Tournaisian (earliest Carboniferous) conglomerate-preserved non-marine faunal assemblage and its environmental and sedimentological context [post]

Jennifer A Clack, Carys E Bennett, Sarah J Davies, Andrew C Scott, Janet Sherwin, Timothy R Smithson
2018 unpublished
A conglomerate bed from the Tournaisian Ballagan Formation of Scotland preserves a rich array of vertebrate and other non-marine fossils providing an insight into the wider ecosystem and palaeoenvironment that existed during this pivotal stage of Earth history. It challenges hypotheses of a long-lasting post-extinction trough following the end-Devonian extinction event. The fauna recovered includes a wide size range of tetrapods, rhizodonts and dipnoans, from tiny juveniles or small-bodied taxa
more » ... r small-bodied taxa up to large adults, and more than one taxon of each group is likely. Some fauna, such as actinopterygians and chondrichthyans, are rare as macrofauna but are better represented in the microfossil assemblage. The fauna provides evidence of the largest Carboniferous lungfish ever found. The specimens are preserved in a localised, poorly-sorted conglomerate which was deposited in the deepest part of a river channel, the youngest of a group of channels. In addition to the fossils (micro- and macro-), the conglomerate includes locally-derived clasts of palaeosols and other distinctive elements of the surrounding floodplains. Charcoal fragments represent stem and possible trunk tissue from arborescent pteridosperms. Preservation of the fossils indicates some aerial exposure prior to transport, with abrasion from rolling. The findings presented here contrast with other published trends in vertebrate size that are used to interpret a reduction in maximum sizes during the Tournaisian. The richness of the fauna runs counter to the assumption of a depauperate non-marine fauna following the end-Devonian Hangenberg event, and charcoal content highlights the occurrence of fire, with the requisite levels of atmospheric oxygen during that stage.
doi:10.7287/peerj.preprints.27102v1 fatcat:cbcjaxlxuvbpbjqofcalczwrte