Aptian Platform-Interior Facies of Adriatic Platform, Southern Croatia

This study explores Aptian aged platform-interior carbonate facies exposed on the islands of Korcula, Hvar, and Mljet, Croatia. The Lower Aptian succession is characterized by thick-bedded to massive predominantly non-cyclic lime mudstone and skeletal-intraclastic lime mudstone and wackestone with benthic foraminifera, calcareous algae and microbial encrusters (Bacinella), as well as subordinate pelagic crinoids (Saccocoma) and planktic foraminifers (Hedbergella). The Upper Aptian is distinguished by a cyclic alternation of facies with typically basal skeletal mudstone-wackstone overlain by peloid-intraclast-skeletal packstone and grainstone, and barren mudstone, fenestral lime mudstone or microbial laminite. Many cycles are capped by greenish residual clay sheets and partially dolomitized breccias/conglomerates. The facies stacking patterns suggest an important environmental change during Aptian, with Early Aptian transgression, coeval with drowning of numerous Tethyan carbonate platforms, and pronounced Late Aptian regression marking a significant biological crisis in the peri-Adriatic region. The published data show that accumulation rates for the southern part of the Adriatic platform were 4 cm/k.y. on average, reaching a minimum value of less than 1 cm/k.y. in the Aptian. These low accommodation and accumulation rates likely caused amalgamated subtidal facies in the Early Aptian, and periodic emergence and well-developed paleosols in the Late Aptian.