ALBIAN FACIES WITHIN A CYCLIC PERITIDAL PLATFORM-INTERIOR SEQUENCE, ADRIATIC PLATFORM, SOUTHERN CROATIA

The Albian carbonate succession (approximately 400 m thick) of Adriatic Platform in southern Croatia, although predominantly peritidal, locally contains basal several meters thick sequence of subtidal laminated limestones that overlie late Aptian exposure breccias. These limestones are thin-bedded, platy, evenly laminated pellet packstone and lime mudstone, locally dolomitic with petroliferous odor; they are deeper lagoon facies deposited in a local depression during oceanic anoxic event 1B. The overlying cyclic peritidal carbonates dominate the Albian succession. These meter-scale shallowing upward cycles consist of, from bottom to top: (1) local thin transgressive lags of muddy intraclast-oncoid floatstone overlain by lime mudstone, locally heavily burrowed, with peloidal fills and scattered clam and gastropod fragments and oncoids; (2) pellet-skeletal wackestone with oncoids, calcareous algae and benthic foraminifera; (3) peloid-skeletal-intraclast wacke-packstone with abundant calcareous algae (Salpingoporella), benthic foraminifera, and scattered rudists and gastropods; (4) intraclast-peloid-skeletal grainstone; (5) gastropod/rudist/oncoid floatstone to rudstone with lime mudstone, skeletal-peloid, or coarse dolomite matrix; (6) barren lime mudstone with green, argillaceous dolomite-filled tubular fenestrae (roots and burrows), and rare gastropod moulds; (7) fenestral laminite with minor microbial laminite; (8) intra/lithoclast floatstone-rudstone with black and/or tan lime fenestral mudstone clasts or pebbles in a matrix of green clay, tubular fenestral wacke-mudstone, or dolomite (emergence breccias). Cycle tops are commonly microkarstic with green dolomitic mud-filled vugs of leached mollusks and fenestrae, along with clay seams, and this, along with the abundant rootlets and burrow fenestrae and lack of evaporites suggest deposition in a humid peritidal platform setting, with cyclicity suggestive of precessional forcing.