Facies architecture of an isolated carbonate platform: tracing the cycles of the Latemar (Middle Triassic, northern Italy)

The 720-m-thick succession of the Middle Triassic Latemar Massif (Dolomites , Italy) was used to reconstruct the lagoonal facies architecture of a smal l atoll-like carbonate platform. Facies analysis of the lagoonal sediments yields a bathymetric interpretation of the lateral facies variations, which reflect a syndepositional palaeorelief. Based on tracing of lagoonal flood ing surfaces, the metre-scale shallowing-upward cycles are interpreted to b e of allocyclic origin. Short-term sea-level changes led to subaerial expos ure of wide parts of the marginal zone, resulting in the development of a t epee belt of varying width. Occasional emergence of the entire lagoon produ ced lagoon-wide decimetre-thick red exposure horizons. The supratidal tepee belt in the backreef area represented the zone of maximum elevation, which circumscribed the sub- to peritidal lagoonal interior during most of the p latform's development. This tepee rim, the subtidal reef and a sub- to peri tidal transition zone in between stabilized the platform margin. The asymme tric width of facies belts within individual metre-scale cycles was caused by redistribution processes that reflect palaeowinds and storm paths from t he present-day south and west. The overall succession shows stratigraphic c hanges on a scale of tens of metres from a basal subtidal unit, overlain by three tepee-rich intervals, separated by tepee-poor units composed of subt idal to peritidal facies. This stacking pattern reflects two third-order se quences during the late Anisian to early middle Ladinian.