Late Cretaceous (Maastrichtian) echinoid-mollusc-coral assemblages and palaeoenvironments from a Tethyan carbonate platform succession, northern Oman mountains

Faunal associations observed in a Maastrichtian carbonate platform succession in the western borders of the North Oman mountains are established, based on field collections of more than 7000 macrofossils belonging to some 200 species. Lithofacies are also distinguished from petrographic analysis. The succession was deposited during a single sea-level cycle and the basal transgression preserves beach hardground faunas, with characteristic echinoid and coral taxa, and subtidal shore-face sands with an abundance of the cassiduloid echinoid Faujasia. Shallow-water offshore sediments deposited below active wave base make up the majority of the lower beds. This facies includes several distinct faunal associations, broadly divisible into those living in or on unconsolidated sands (with infaunal cassiduloids and bivalves), and those associated with stable, possibly algal-bound sedimentary bottoms (with pycnodont oysters, small solitary corals and the larger benthic foraminiferan Loftusia). The semi-reclining rudist Dictyoptychus is most abundant in the transition facies between these two assemblages. The upper beds are composed of well-sorted calcarenites deposited within active wave base. These unconsolidated, but generally stable shoals had a fauna of large, infaunal, deposit-feeding holasteroid and cassiduloid echinoids with only occasional large algivorous gastropods (Campanile, Pyrazus) and large epifaunal regular echinoids (Noetlingaster).