ALBIAN CYCLIC PERITIDAL FACIES OF ADRIATIC PLATFOM INTERIOR IN SOUTHERN CROATIA

The Adriatic Platform in southern Croatia contains approximately 400 meters of Albian carbonates. Above late Aptian exposure breccias basal Albian, subtidal laminated limestone several meters thick occur. These limestones are thin-bedded, platy, evenly laminated pellet packstone and lime mudstone with a petroliferous odor, are locally dolomitic, and most likely were deposited during oceanic anoxic event 1b, in a local depression on the platform. The overlying highly cyclic peritidal carbonates dominate the remainder of the Albian succession. These upward-shallowing meter-scale cycles, from deep to shallow consist of: (i) local thin, transgressive lags of muddy intraclast-oncoid floatsone overlain by lime mudstone that contain scattered clam fragments, gastropods, oncoids, and locally abundant peloidal burrow fills; (ii) pellet-skeletal wackestone with calcareous algae, oncoids, and benthic foraminifera; (iii) skeletal-peloid-intraclast wacke-packstone with scattered rudists, gastropods, benthic foraminifera, and an abundance of calcareous algae; (iv) intraclast-skeletal-peloid grainstone; (v) rudist-gastropod-oncoid floatstone to rudstone with lime mudstone, peloid-skeletal, or coarse dolomite matrix. Cycle tops include; (vi) barren lime mudstone or wackestone/mudstone with tubular fenestrae and root/burrow structures and rare gastropod molds, all filled by green argillaceous dolomite; (vii) fenestral laminite with minor microbal laminae; and (viii) intraclast/lithoclast floatstone-rudstone with black or tan lime fenestral mudstone clasts or pebbles in a matrix of green dolomitic clay (emergence breccias). Lack of evaporites, and presence of microkarstic cycle tops with green dolomitic mud-filled vugs and mollusk molds along with clay seams, abundant root traces and burrow fenestrae suggest that Albian carbonate sequence was deposited in a humid platform setting. Cycle stacking suggests precessional sea level forcing.