Microbial-dominated carbonate depositional systems: a biosedimentary and stratigraphic reconstruction in the Late Triassic of Western Tethys (northern Calabria, Italy)

摘要: The northern Calabria Norian-Rhaetian carbonate platform system is characterized by three depositional units: early-middle Norian Corvino Unit (CU), middle-late Vaccuta (VU) and late Grisolia (GU). CU presents a deep barrier reef consisting of an oligotypic framebuilder community sponges, serpulids, algae, stromatolitic microbialites. intra-supratidal facies mainly comprise flat to low-relief, frequently subaerial-exposed, stromatolites thrombolites, whereas subtidal include high-relief skeletal packstones. In the outer shelf, debrites, turbidites, mudstones, slumped layers are present. VU, bioclastic sand-barriers, inhabited monospecific bivalve clusters (Isognomon exilis) low- small-scale stromatolites, protected peritidal domain thrombolites stromatolites. outer-ramp laminated mudstones tempestites interbedded with sporadic Finally, marlstones, characterizing GU overlie all previous shallow- deep-water facies, testifying terrigenous input end factory. fossil associations VU imply anoxia eutrophy, likely due limited water circulation, related basin isolation from open ocean. During whole interval syn-depositional down-faulting pulses was accompanied gradual eustatic sea-level drop, inducing episodes opening basin. Tectonic influenced sequence stratigraphic architecture creating atypical system-tracts succession retrogradation progradation followed for GU.