Title

Coastal barriers, Gulf of Mexico: Holocene Evolution and Chronology

Document Type

Article

Publication Date

3-1-2005

Department

Coastal Sciences, Gulf Coast Research Laboratory

Abstract

A database of newly acquired and published absolute dates and archaeological data provides a generalized regional background for the chronological comparison of regressive mainland and island barriers and strandplains on the northern and eastern Gulf coast. Sea-level reconstruction from barrier lithosomes may be complicated by temporarily and locally elevated wave runup levels, subsidence, and other factors. These landforms were initiated at different times at a variety of coastal sites since the late mid Holocene. Alternating erosional/aggradational phases characterize all sites. Contrary to the general consensus, strandplain progradation was not always restricted to relatively stable or falling Gulf levels but has accompanied slowly rising sea-levels as well. In avoiding submergence, aggradation of high foredune ridges occasionally kept pace with and compensated for sea-level rise, sediment compaction, and adjacent to the Mississippi delta complex, minor subsidence of tectonic origin. The earliest barrier platforms and the overlying mainland and island ridgeplains emerged on the northern and eastern Gulf shores between ca. 5.2-4.0 C-14 ka BP. Members of the Mississippi barrier chain underwent the greatest changes in areal extent and geographic position. Dates of St. Bernard and South Hancock-Pearl River delta development that stranded and buried the western islands chronologically constrain a late mid Holocene phase of island chain evolution. The oldest barrier island sectors in northwest and west Florida date from ca. 4.5-3.0 ka BP. Two Louisiana ridgeplains began ca. 2.9 ka BP. Most of the Alabama-Florida mainland strandplain evolved after 4.5-to-2.5 ka BP. Several smaller Florida strandplains and extensions formed at near present sea-level as late as 1100-300 yr BP. Two of these evolved in the expanding energy shadow of the prograding St. Joseph barrier. For reasons not yet understood, numerous replicated dates from repeated samplings consistently yielded highly anomalous OSL and TL values in the Morgan-Perdido and St. Vincent Island-Indian Peninsula strandplains.

Publication Title

Journal of Coastal Research

First Page

141

Last Page

163