engleski

Campanian Pseudosabinia from Pučišća Formation on the island of Hvar (Adriatic Sea, Croatia)

The Upper Cretaceous carbonates on the Island of Hvar are typical of the central Tethyan (‘ peri-Adriatic’ ) intra-oceanic carbonate platforms. During the Late Cretaceous, the carbonates were deposited within the southern part of the Adriatic-Dinaridic carbonate platform. The Upper Cretaceous stratigraphy of the Adriatic carbonate platform (s.str.) has been described in detail from the island of Brač, and has been subdivided into a few lithostratigraphical units. The Pučišća Formation (Santonian to Campanian) was deposited mainly within migrating rudist-bearing marginal facies of intra-platform basin(s). Within the uppermost part of the Pučišća Formation, in the Križna luka locality (town of Hvar, island of Hvar), we collected rudist valves characterized by a complex canaliferous inner shell structure. Shell symmetry, myocardinal arrangements, and cellulo-prismatic structure of the right valve outer shell layer lead us to refer the specimens to the family Radiolitidae. The valves are embedded in white peloidal-bioclastic limestones, along with abundant foraminifera (orbitoids and siderolitids) and small radiolitids, as well as rare hippuritids and Mitrocaprina sp. The limestones were probably deposited on the fore-slope of a migrating marginal bank. The right valves are massive, conical in shape, and ellipsoidal (oval) in transverse section. The slightly depressed posterodorsal parts of the shells mark the radial bands. Outer shell layers are mostly eroded, while the inner shell layers are recrystallized, but nicely preserved. The inner shell has relatively big quadrangular canals in its thicker inner part and radially elongated canals in its thinner outer part. The ligamental ridge is well developed, with a thin neck and relatively thick oval T-form tip. Sockets of cardinal teeth and myophore scars are well developed within the inner shell layer. The left valves are also massive and conical in shape, while centrally placed body cavity covers less than a quarter of the.transverse section. The shells are referred to Pseudosabinia klinghardti (Boehm), probably the most widely distributed species of the genus.

Adriatic region; carbonate platform; Campanian; intraplatform basin margin; Radiolitidae

nije evidentirano