The Gulf Coast geosyncline was first described by Barton and Ritz in 1933 as a long, narrow trough-shaped depression located parallel with and just inland from the shore of the Gulf of Mexico in Jefferson County, Texas. Since that time well data have made it impossible for such a trough to be present at drillable depths under the land. Geophysical data completed within the last few years seems to eliminate the possibility of such a trough under the continental shelf. In light of the new data, the former idea of the Gulf Coast geosyncline in the form of a long, narrow trough must be changed to a new concept of a bowl-shaped depression corresponding more or less with the form of the present Gulf of Mexico. Many additional data on sedimentation and structure, particularly fa lting, supports this change in views.

This change in ideas may necessitate radical revision in the Tertiary history of the Gulf Coast, and doing so may cause radical revision of ideas of the thickness and character of the Tertiary and post-Tertiary sediments near shore and under the continental shelf.

In general it now seems that the Tertiary history of the Gulf Coast involves the following fundamental principles.

1. A large semiround bowl-shaped depression at the close of the Cretaceous and remaining relatively stable through the Tertiary.

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2. Sedimentary filling of this depression during the Tertiary from the sides toward the middle.

3. Subsequent minor elevation of the north and west shores perhaps due to isostatic adjustment.

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