Sedimentary Environments of Inner Continental Shelf, West Florida

Joseph F. Donoghue

Near-surface sediments of the Apalachicola region of the west Florida shelf reflect a fluvial origin with strong evidence of reworking in a moderate-energy shallow marine environment. The inner shelf sediments are moderately sorted, fine quartz sands with only minor amounts of gravel and fines. High-resolution seismic records reveal a continual interplay of fluvial, deltaic, and nearshore environments during sea level fluctuations of the late Quaternary. Subsurface geomorphology includes large fluvial channels, prograding clinoforms, and ridge-and-swale topography. These relict features have been buried during the Holocene beneath a transgressive sand sheet with sediment supplied from massive nearshore shoals.

The same source has contributed to the formation of a chain of barrier islands that forms a rim around the modern Apalachicola River delta. Barrier formation began approximately 3,000 years ago. Modern migration rates of the islands are high, in both landward and longshore directions, providing evidence for the rapid rate of transition from one type of sedimentary environment to another. The ample sedimentary supply appears at present to be keeping pace with moderate subsidence and sea level rise.

AAPG Search and Discovery Article #91029©1989 AAPG GCAGS and GC Section of SEPM Meeting, October 25-27, 1989, Corpus Christi, Texas.