Paleogeography and sedimentary evolution of the Southern Adriatic province in the Permian-Triassic

Through the study of different exploration wells, the Permian-Triassic sedimentary and paleogeographic evolution of the Southern Adriatic province is here constrained. During Permian continental settings laterally grading to coastal lagoons developed. Successively, in the Ladinian, after a generalized subaerial exposure and a marked erosional phase, the extensional tectonic inputs linked to the Tethys rifting brought to a relative sea-level rise and to the formation of carbonate shelves in NWSE oriented tectonic depressions. During Carnian-early Norian a further extensional tectonic pulse coupled with a relative sea-level drop, led to the isolation of the basin from the open sea with a consequent enhancing of salinity and settlement of evaporative conditions. This triggered a massive evaporite deposition that culminated during Norian, with the evaporite filling of the basin. Lastly, In the late Norian-Rhaetian a marked relative sealevel rise, restored all the connections with the open-sea and shifted the evaporite deposition to the margins of the basins that previously remained under subaerial conditions. The late Norian-Rhaetian shift of the evaporative sedimentary environments is recorded in Puglia 1 wellborehole from which two cores were recovered and studied. The first core (5.048-5.056 m) is characterized by the presence of laminated dolomudstones with remnants of thinly microbial laminae alternated to lenticular/ tabular shaped anhydrite crystal levels, suggesting a sabkha-type environment of formation. The second core (6.067-6.075 m), is dominated by massive coarse-grained crystalline dolomite with remnants of oolites and undetermined shell fragments, indicating a shallow-water environment of deposition (e.g., shore-face/offshore transition setting). Syn-sedimentary and late-stage diagenetic processes affected both facies. Primary anhydrite crystals deposited in the sabkha, were at least affected by one hydration/dehydration cycle. Dolomitization, which is widespread in both cores, occurred mainly during the burial stage as the circulation of high saline and Srdepleted dolomitizing fluids under general reducing conditions.