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This study explores Aptian aged platform-interior carbonate facies exposed on the Peljesac Penninsula and the islands of Korcula, Hvar, and Mljet in Southern Croatia. The Lower Aptian succession is characterized by non-cyclic, thick-bedded to massive subtidal facies of lime mudstone and skeletal-intraclastic lime mudstone and wackestone with rare benthic foraminifera, calcareous algae, microbial encrusters (Bacinella), bivalve fragments, as well as subordinate pelagic crinoids (Saccocoma) and planktic foraminifers (Hedbergella). The shallowest facies are skeletal-peloid wacke-packstones and grainstones with rudists ; these are calculated to occur in about 0-3 meters water depth. The cyclicity of the facies increases with proximity to the Early-Late Aptian boundary. The Upper Aptian is more cyclic, with parasequences consisting of basal skeletal mudstone-wackstone overlain by peloid-intraclast-skeletal packstone and grainstone, and barren mudstone, fenestral lime mudstone or microbial laminite. The emersion breccia horizons and/or residual clay horizons as parasequence caps are very common ; up to seven horizons are recorded in the lower, and six in the upper part of Upper Aptian.Maximum water depths of facies are estimated at 5 meters based on the range of stratigraphic distances of facies below base of laminate cap, breccias, or top of barren lime mudstone. 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. The thickness variations between the columns may be due to syndepositional tectonics combined with sea level oscillations.

The Jurassic-Cretaceous Adriatic Platform provides a window into tropical shallow-marine carbonate deposition in the western Tethys. The highly cyclic Barremian sediments are superbly exposed on the islands and mainland of southern Croatia . Five logged sections, ranging from 20 to 100 m thick, display superbly developed peritidal parasequences ; the extensive Barremian microbial laminite facies likely contain the best preserved tidal flat facies compared to any Lower Cretaceous interval of the Adriatic Platform. The Barremian consists of 2 supersequences. The sequence boundary zone 1 in the Lower Barremian consists of up to 3 breccias. Supersequence 1 has at least 2 high frequency sequences. Sequence boundary zone 2 contains one to 2 breccias. Supersequence 2 has four high frequency sequences (HFS). Each HFS consists of shallowing upward succession with dominantly subtidal lower part, and laminated to fenestral upper part. Individual parasequences within each sequence 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 breccias with green clayey matrix). Presence of platform-wide subaerial exposure surfaces capping some cycles suggest relative sea level falls affected the platform over large areas. Most parasequences were formed by high-frequency sea level fluctuations 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 associated with the impending (Aptian) collision between the Adriatic microplate and Eurasia. Rapid thickness variations and facies changes over several tens of kilometers indicate that the synsedimentary differential subsidence (possibly over fault blocks) was a strong influence, with a superimposed sea-level fluctuations generating the sequences and component cycles.

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.