Carbon isotope signatures of latest Permian marine successions of the Southern Alps suggest a continental runoff pulse enriched in land plant material

摘要

The latest Permian mass extinction, the most severe Phanerozoic biotic crisis, is marked by dramatic changes in palaeoenvironments. These changes significantly disrupted the global carbon cycle, reflected by a prominent and well known negative carbon isotope excursion recorded in marine and continental sediments. Carbon isotope trends of bulk carbonate and bulk organic matter in marine deposits of the European Southern Alps near the low-latitude marine event horizon deviate from each other. A positive excursion of several permil in δ~(13)C_(org) starts earlier and is much more pronounced than the short-term positive δ~(13)C_(carb) excursion; both excursions interrupt the general negative trend. Throughout the entire period investigated, δ~(13)C_(org) values become lighter with increasing distance from the palaeocoastline. Changing δ~(13)C_(org) values may be due to the influx of comparatively isotopically heavy land plant material. The stronger influence of land plant material on the δ~(13)C_(org) during the positive isotope excursion indicates a temporarily enhanced continental runoff that may either reflect increased precipitation, possibly triggered by aerosols originating from Siberian Trap volcanism, or indicate higher erosion rate in the face of reduced land vegetation cover.