Rise of Sea Level Along Northwest Gulf of Mexico1
Samples and borings on the continental shelf and in the bays along the Texas coast have provided relict nearshore and shallow-bay macro-organisms, allowing the dating of the Holocene (postglacial) rise of sea level along this relatively stable coast. The rise of sea level has been dated from 300 feet below the present at 17,000 years before the present, to about 40 feet at 8,000 years B.P. There is evidence suggesting that the rise has continued very slowly during most of the remaining period, but there is a possibility that the data are deceptive and that either the levels have fluctuated or the sea has been fairly constant for several thousand years.
Fluctuations during the 17,000–8,000 B.P. interval are indicated by eastward sloping drowned barriers that can be best explained as due to brief periods of regression produced by renewed growth of glaciers on the lands. These periods appear to correspond with some of the known readvances of the continental ice sheets.
The history of rise along the Texas coast appears to agree with that along other stable areas. On the other hand, the records obtained from the area around the Mississippi Delta appear to indicate an independent subsidence of that area of the order of about 1 foot per century.