Paleoenvironmental changes in the western Tethys carbonate platforms during OAE-2: Implications from phosphorus, δ18O, δ13C and facies analysis

Oceanic anoxic event 2 (OAE-2) is one of the largest paleoclimatic events of the whole Phanerozoic which occurred at the Cenomanian/Turonian Boundary (CTB). It caused major perturbation of the C-cycle at global scale together with changes in other geochemical cycles. OAE-2 severely impacted marine and terrestrial settings causing faunal turnovers both in pelagic and neritic environments. The exact mechanisms triggering OAE-2 are debated but it is believed that the main driver was a massive injections of volcanic CO₂ in the atmosphere. The effect of OAE-2 on deep-water communities has been extensively documented in literature. In contrast, less data are available for their shallow-waters counterparts. Geochemical and semiquantitative facies analysis on samples from two carbonate platforms located in Italy (former western Tethys) are presented in this paper, where new data from the Friuli-Adriatic Carbonate Platform are compared with a well-known section from the Apennine Carbonate Platform. Our data show a good correlation between these platforms, located 1000 km apart. Phosphorus concentrations are low except for two intervals: (1) at the onset of the OAE-2 and (2) in the late phase of the event. The δ¹⁸O record shows an increase of the Sea Surface Temperature (SST) during the event interrupted by a cooler interval. Our data indicate a correlation between geochemical changes and faunal turnover of benthic foraminifera and rudists, suggesting the co-occurrences of several causes for the demise of these groups during OAE-2.