Microbial biomineralization in biotic crusts from a Pleistocene marine cave (NW Sicily, Italy)

Biotic crusts occurring in the Early Pleistocene Rumena Cave, in NW Sicily, have been analyzed from ageomicrobiological point of view. The crusts consist largely of scleractinians and of subordinate bryozoansand serpuloideans, all typical of submarine cave biota. Encrustations document a blind cave in a shadowedsetting, or possibly below the fair weather swell zone. Autochthonous and, subordinately, detrital fractionswere observed within the skeletal framework of biotic crusts. The syndepositional lithified fraction occursmainly as very fine-grained laminations. Clotted peloidal and aphanitic (structureless) textures occur in themicrites as well. Autochthonous micrite is always associated with a significant amount of organic matterremains. In caves from the Plemmirio area in SE Sicily, the autochthonous microbial micrite, occurring in thebioconstructions, contains bacterial lipid biomarkers, including abundant compounds derived from sulfatereducingbacteria. It is likely that a similar microbial mediation was involved in the formation of theautochthonous micrite present in the biotic crusts of the Rumena Cave.