Abstract: Gulf Coast Transgressions and Regressions

By

Gene B. Martin

Utilizing a paleontological logging technique, the continuous paleoecologic log, in the identification of the types of stratigraphic boundaries and the frequencies of the various types--the solution to problems of subsurface correlations, the interpretation of the depositional history and the delineation of depositional trends are greatly improved.

Two types of stratigraphic boundaries: (1) the transgressive discontinuity boundary and (2) the regressive discontinuity boundary are probably the most common and important events in the geological history of the Gulf Coast and in many other basins of the world. The two types of boundaries occur mainly within depositional cycles and may be local events or widespread major eustatic sea level events.

Examples of Transgression and Regression are presented, ranging in age from Lower Cretaceous to the Recent.

The term "marinity" is a new term which may be used in a relative sense to distinguish and designate sediments deposited in a marine environment from sediments deposited in fresh water or brackish environments, and it may be used in describing paleogeographic and paleodepositional settings.

The majority of hydrocarbon accumulations in the Gulf Coast occur within the regressive facies. It is the regressive facies where the main reservoir sediment deposition takes place and also the major growth structures occur here.

Many of the producing zones are overlain by a transgressive discontinuity boundary; therefore some reservoirs are within the transgressive facies.

To understand the geological history of any basin is to recognize the regressive and transgressive facies.

End_of_Record - Last_Page 2---------------

Copyright © 2005 by Houston Geological Society. All rights reserved.