The Coniacian–Campanian Latium–Abruzzi carbonate platform, an example of a facies mosaic

Abstract

This paper presents the results of a high-resolution analysis of Upper Cretaceous shallow-water limestones in the northeast sector of the Lepini Mountains (Central Apennines, Italy) that belong to the Latium–Abruzzi platform domain. The studied succession is entirely referred to as the “Accordiella conica & Rotorbinella scarsellai Biozone”. The analyzed Coniacian–Campanian succession is primarily characterized by three lithofacies associations (LF-A, LF-B, LF-C) deposited on an open shelf. The intertidal and shallow-subtidal environments are characterized by mudstone to wackestone and laminated bindstone (LF-C), whereas in the low to moderate energy environments of the inner shelf there developed rudist biostrome (rudist pillarstone) and rudist rudstone to floatstone (LF-A). A lithofacies association dominated by cross-bedded grainstone (LF-B) represents the reworking of bioclastic grains (rudist fragments) derived from the areas of the shelf colonized by rudist biostrome; lime-sand shoals related to storm channels passed into submarine dunes in an open-shelf setting. Correlation of the five investigated stratigraphic sections shows how the recognized LF are laterally associated to form a facies mosaic over a few hundred meters. The stratigraphic architecture shows five intervals (I–V) each of which is dominated by one or two LF. Interval I is intensely dolomitized. The following intervals (II and III) record a gradual increase in hydrodynamic energy as evidenced by the presence of rudist biostromes passing upward into cross-bedded grainstone. An increase in mud-supported textures in the interval IV suggests more restricted conditions, which were terminated by a period of emergence. More open-marine conditions in the final interval (V) are shown by the dominance of LF-A and LF-B.