Sequence stratigraphy of wave-dominated and wave-influenced shoreface deposits: Systems tracts, stratigraphic surfaces and facies contacts

Abstract

Shoreface deposits are usually associated with high-energy sedimentary structures, as well as with erosional surfaces produced by waves and currents that may have sequence stratigraphic or sedimentological significance. Typical sequence stratigraphic surfaces associated with shoreface deposits are the ravinement surface (RS), the maximum flooding surface (MFS), the basal surface of forced regression (BSFR), the regressive surface of marine erosion (RSME), the subaerial unconformity (SU) and the correlative conformity (CC). However, some of these surfaces, such as the MFS, the BSFR and the CC can be cryptic and difficult to pinpoint in outcrops and cores. Facies contacts in the shoreface are represented by the local flooding surface (LFS), the downlap surface (DLS), the surf diastem (SD) and bedset boundaries (BB), which are usually well recognizable. All downstream-controlled systems tracts may form in shoreface deposits, including the lowstand systems tract (LST), transgressive systems tract (TST), highstand systems tract (HST) and falling-stage systems tract (FSST). Among these systems tracts, TSTs and HSTs are most commonly recognized. A challenge in these settings is the distinction between HSTs, FSSTs and LSTs, due to the more subtle physical expression of the BSFR and the CC in fully shoreface successions. Sequence stratigraphic surfaces and facies contacts can be identified on the basis of several criteria, including sedimentological, ichnological, diagenetic, mineralogic, geophysical, and micropaleontological. Due to their easy recognition with all kinds of data, RSs are commonly chosen as boundaries of stratigraphic sequences composed of shoreface or mixed shoreface-shelf deposits, commonly referred to as transgressive-regressive (T-R) sequences.