The reconstruction of coastal carbonate sequence stratigraphy: A modern-systems approach

Sequence stratigraphy is the primary tool used by sedimentologists to predict bed-scale flow properties of both marine carbonate reservoirs (associated with carbon sequestration and hydrocarbon recovery) and groundwater aquifer systems. Coastal carbonate sequence stratigraphic models have been predicated upon the existence of parasequences, shallowing-upward successions bounded by marine flooding surfaces. Transgressive deposits in such models have been assumed to be mostly absent, whereas regressive deposits are presumed to form through the successive basinward stepping of shoals and their associated lagoons over open platforms. A review of modern coastal systems calls these assumptions into question. Transgressive deposits are substantive. In particular, in situ lagoonal and tidal-flat deposits left behind by overriding landward-migrating barriers are common across Holocene carbonate platforms. Furthermore, regressive deposits are not represented by prograding shoals and lagoons, but by lagoonal abandonment, and grainy shoreface progradation capped by strandplains, with overlying accommodation restricted to swales where only thin, discontinuous, intertidal mud flats form. We present a novel sequence-stratigraphic model based on these modern-systems observations with significant implications for subsurface geobody connectivity and fluid-flow prediction.