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The "Gulf of Mexico" Late Holocene Sea Level Curve and River Delta History

TANNER, WILLIAM F., Florida State University, Tallahassee, FL

There are four sources of information for constructing a sea level history from Gulf of Mexico coasts: beach ridges, cheniers, subdeltas, and barrier island nuclei.

Beach ridge plains around the Gulf of Mexico provide a detailed history of sea level rises and falls since 3000-3500 years ago. Dates for the initiation of Mississippi River subdeltas, as well as southwestern Louisiana cheniers, confirm the rises and high sea levels, and dates for initiation of barrier islands (island nuclei) confirm some of the lowstands. The beach ridge history is more complete and more detailed than any one of the other three; the latter three provide general support at important points, but the sequence of events and the details are best obtained from beach ridges.

Subdelta history goes farther back in time than any of the others in this area. It can be checked against data from the very wide beach ridge plain at Jerup, northernmost Denmark, where an essentially complete sequence of ridges covers almost all of Holocene time. The Jerup history, obtained from topography, carbon-14 dates, and granulometry, matches the Gulf of Mexico beach ridge history very well, as well as dates of initiation of Mississippi subdeltas. The isostatic rebound that has been measured in the Jerup area has raised the ridges so that they are now available for study; but it has been slow, compared with the local deposition rate, and has not affected the granulometry in any detectable way.

The most detailed history now available is compiled from beach ridge data, but the intent of the present paper is to show that there are other important coastal sources of information. They can provide support, corrections, or complementary information for the beach ridge history, but their precision is not very great. For time intervals and localities where beach ridges are not available or are not decipherable, these other sources may be useful.

 

AAPG Search and Discovery Article #91006 © 1991 GCAGS and GC-SEPM Meeting, Houston, Texas, October 16-18, 1991 (2009)