Abstract: Holocene Stability of the Gulf of Mexico Coast
William F. Tanner
Gulf of Mexico beach ridges permit one to estimate vertical stability (tectonic, isostatic, compaction) of local shoreline segments for much of the Holocene.
Stability can be deduced by comparison with a detailed Holocene sea level history from northern Denmark. The global reference frame has been moving; sea level hasn't held a fixed position for the last 12,000 yr. The local frame (where defined) moves with the global one, or it does not. If not, then the local area was not stable.
The Danish sea level history, extending back 12,000 yr, can be verified along the shores of the Gulf of Mexico, as far back as the record goes at each place, and therefore appears to be global.
Downward motion tends to destroy (wave action) or bury (deposition) features such as beach ridges. If they are still exposed to the air, well preserved, and only partly drowned, as on St. Vincent Island (Florida), they have not been moved any significant amount. This area has recorded the same small sea level changes as in Denmark during the last 3000-3500 yr, and hence has been stable for this interval.
Important compaction in the middle-to-late Holocene was confined largely to the Mississippi River delta area. Tectonic effects can be seen near the estuaries of the Alabama and Panuco rivers. Probable isostatic effects (warping) are present east of the Ochlockonee River estuary (Florida).
AAPG Search and Discovery Article #90983©1994 GCAGS and Gulf Coast SEPM 44th Annual Meeting, Austin, Texas, October 6-7, 1994