The Latemar: A flat-topped, steep fronted platform dominated by microbialites and synsedimentary cements

Facies analyses on the Latemar isolated carbonate platform suggest a higher proportion of microbial carbonates compared to literature. This is evident especially in the margin-upper slope zone, where microbial boundstone associated with Tubiphytes, calcareous sponges, botryoidal aragonite and radiaxial fibrous cements extended down to 250 m water depth. The Latemar flat-topped high-relief platform has been subdivided into five different fades belts: inner and outermost platform, margin, upper and lower slope. Each fades belt represents subtidal environments except for the inner platform, which is characterized by a peritidal facies association. Point counting analysis was carried out on ca. 90 thin sections to quantify the different platform components. Microbialite and cements are most abundant: they represent, respectively, ca. 40% and ca. 34% of the whole platform volume. These results suggest that carbonate production at Latemar occurred in a M-Factory. Microbial carbonates, as well as early marine cements are most abundant on the upper slope, margin and outermost platform, although microbialites are found in all facies belts. The presence of supratidal sedimentary fades restricted only to the inner platform and of a completely subtidal outermost platform suggests a new depositional profile for the Latemar. The central portion is occupied by the flat platform interior, cyclically subaerially exposed. Facies of the subtidal outermost platform surround the inner platform and display a progressive increase in depth toward the margin. The margin is submerged and essentially constituted by microbial and cement boundstone. The slope is characterized by steep clinoforms (similar to 35 degrees) dominated by in situ microbialites in the upper-middle portion (0-250 m depth), evidently precipitated by non light-dependent microbially influenced processes. The lower slope is mostly detrital, poor in platform top-derived sediments and dominated by margin and upper-slope derived rudstone and grainstone. All these observations are in agreement with the slope-shedding model observed in the Pennsylvanian microbial margin in Asturias (N Spain) and allow the interpretation of the Latemar as a flat-topped, steep fronted platform dominated by microbialites and cement boundstones. (C) 2011 Elsevier B.V. All rights reserved.