Abstract: Unconformities--Neglected Exploration Tool

James A. Baird

Unconformities in the Gulf Coast province have been given too little emphasis as an exploration tool. They can be used to identify and find relict local and regional structure with potential stratigraphic traps. Their identification and reconstruction can be used to determine both the past and present location of hydrocarbons and their economic potential. Late structural deformation can cause secondary migration and/or change dip rate and direction, concealing the location of the trapped hydrocarbons. Structural-stratigraphic relations are modified by collapse-fault systems, piercement domes, and younger unconformities which may intersect older unconformities. The present location of trapped hydrocarbons can be found on an original buried relict structure, on a later structure, or on both depending on the nature of the trap and subsequent movement. Structure and stratigraphy related to time of movement dated by unconformities and paleontology can be used on a regional and local basis to find embayments, prodelta fronts, wedges, turbidites, and relict structures. The lower Hackberry trend and Planulina trend of South Louisiana are examples to which these techniques can be applied. Local areas where this approach has been successful are Gillis-English Bayou field, North Chacahoula field, and the Grand Bayou field of Louisiana.

AAPG Search and Discovery Article #90967©1977 GCAGS and GC Section SEPM 27th Annual Meeting, Austin, Texas