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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 57 (1973)

Issue: 9. (September)

First Page: 1835

Last Page: 1835

Title: Wave-Power Gradient--Approach to Holocene Depositional History: ABSTRACT

Author(s): R. S. Murali

Article Type: Meeting abstract

Abstract:

Wave-power gradient studies along the mainland in the St. Joseph Bay area (panhandle coast of Florida) indicate that the dominant wave approach direction, responsible for littoral drift toward the south-southeast, is from the west. Using this information, attempts have been made to arrive at a relative depositional sequence in this region consisting of: bay, shoal, spit with beach ridges, and mainland beach ridges.

On a smoothed coast without the beach ridges, but with the present bathymetric conditions, the wave-power gradient was determined. There was no noticeable drift component indicating deposition. Then, the bathymetry was made smooth by the removal of the offshore shoal, the longshore component of wave power was computed and plotted to get an idea of the littoral drift. As a third stage, successive beach ridges were deleted from the spit one after the other and the drift component was determined in each case. At a certain stage, after the removal of a specific number of ridges in the spit and making the bathymetry smooth, the longshore component showed a strong south-southeast drift, accounting for deposition, and in turn leading to the growth of the mainland beach ridges (which original y had been smoothed out).

This model produced one possible depositional history of this region: initially, the simultaneous growth of the mainland beach ridges after the closing of the channel east of Cape San Blas and the northern part of the spit and associated beach ridges extending northward from the cape. This growth is followed by the development of the remaining part of the spit and the formation of the shoal attached to it; and finally the termination of growth of the mainland beach ridges. The age of the beach ridges on the mainland is thought to be between 400 and 600 years.

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