A summary of the geographic location, amount, and results of petroleum exploration, including an atlas showing explored and delineated prospective areas through 1990. This report updates and expands Circular 981.

The area evaluated in this study consists of that part of the southwestern continental margin of Mexico situated within the Gulf of Tehuantepec. Through the use of surface geology, paleomagnetic data, gravity surveys, and continuous seismic reflection profiles, the evolution of the Gulf of Tehuantepec has been detailed as a progression from an open ocean basin to a more restrictef basinal setting.