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The Adriatic Platform provides a window into carbonate deposition spanning the Jurassic-Cretaceous transition in the western Tethys. The sediments exposed on the islands of southern Croatia are highly cyclic. The Barremian section is characterized by extensive microbial laminite facies that is by far the best preserved tidal flat facies compared to any Lower Cretaceous interval of the Adriatic platform. Three logged sections, each between 150 and 200 m thick, display superbly developed peritidal parasequences. The parasequences are composed of shallow subtidal (lime mudstone and peloid-intraclast-skeletal packstone-grainstone) to intertidal (microbial laminites and fenestral lime mudstone) and subaerial exposure facies (greenish clay sheets or breccia with greenish clay or mud matrix). The majority of the cycles may have been formed by high-frequency changes in sea level perhaps related to orbital forcing ; possible durations of the interval and its component parasequences are being evaluated to see if these are compatible with a precessional vs longer term obliquity or eccentricity signals. Some parasequences probably also formed by autocyclic processes and local tectonics. Presence of platform-wide subaerial exposure surfaces capping some cycles suggest a relative sea level falls affected the platform over wide areas.

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.