Subtidal carbonate cycles - GeoScienceWorld

Subtidal carbonate cycles: Implications for allocyclic vs. autocyclic controls David Osleger* Department of Geological Sciences, University of Southern California Los Angeles, California 90089

ABSTRACT Thick successions of repetitive metre-scale subtidal carbonate cycles require that short-term sedimentation rates approximate longterm accumulation rates in order to maintain submergence below peritidal depths. Intrinsic processes such as storm and wave reworking and redistribution may act to inhibit aggradation into the zone of optimal carbonate production. The presence of subtidal vs. peritidal carbonate cycles may be a function of energy regime that in turn may relate to platform morphology. The ultimate control on stacked subtidal cycles appears to be eustasy acting in concert with intrinsic processes such as storm and wave reworking. INTRODUCTION Metre-scale cycles composed of purely subtidal carbonate lithofacies Have been increasingly recognized throughout the geologic record (Lohmann, 1976; Markello and Read, 1982; Aigner, 1985; Calvet and Tucker, 1988). Subtidal cycles are distinct from classic peritidal cycles, the basic genetic unit of many carbonate platforms (Wilson, 1975; James, 1984), in that they do not shoal to intertidal levels but remain submergent throughout their depositional history. Given the relatively rapid sedimentation rates of many modern shallow carbonate environments, subtidal cycles should, upon aggradation into the zone of maximum carbonate productivity (