The stratigraphic record of Quaternary transgressions due to glacio-eustatic rise varies as a function of sediment supply from rivers to the paralic realm. Extremes from low to high sediment supply are represented by the Atlantic and Gulf coasts of the United States, respectively.
The vertical sequence produced by these transgressions at the low sediment supply end of the spectrum consists of paralic and fluvial lithosomes erosionally truncated by shoreface retreat and overlain by shelf marine lithosomes. The lithosomes produced in the landward portion of the paralic realm are commonly preserved, whereas the lithosomes from the more shoreward part are less likely to be preserved. Thus, beach facies are rarely incorporated into the transgressive stratigraphic record, except as a peak sea-level deposit preserved by abandonment. Erosional truncation of the paralic section produces a unique stratigraphic surface, the ravinement surface, which exhibits many of the physical characteristics of a major break in deposition. The surface is then overlain by nearshore to offshore shelf facies in a deepening-upward succession.
When encountered in the stratigraphic record, the ravinement surface is likely to be interpreted as a depositional sequence boundary. When this occurs, a continuous cycle of deposition during transgression is not recognized. When a ravinement and its associated facies are properly interpreted, a complete cycle of transgression and regression in response to changing sea level can be recognized.
Figures & Tables
Sea-Level Fluctuation and Coastal Evolution - This Special Publication is the result of a symposium in honor of W. Armstrong Price held at the first SEPM Midyear Meeting at San Jose, California, on August 12, 1984. The factors controlling relative sea-level change along our shores are varied and, at best, imperfectly understood. Yet, the relative rate of change is what controls shoreline erosion, the arrangement of sedimentary facies of the coastal zone, and the character of deformities within the coastal stratigraphic record. Therefore, these papers address sea-level changes, shoreline responses, and the controls on the three-dimensional geometry of the consequent lithosomes; in short, the architecture of the coastal depositional systems.