Abstract: Evolutionary Model of the Jurassic Sequences of the East Texas Basin: Implications for Hydrocarbon Exploration 

Abstract

ABSTRACT Recent large discoveries in the Jurassic Bossier and Cotton Valley Lime Formations of the East Texas Basin have sparked renewed interest in models of the distribution and alteration of these rocks. The Upper Jurassic sediments of the East Texas Basin were deposited on a salt supported shelf that has undergone extensive modification as a result of salt tectonism since Late Jurassic time. Understanding the distribution of Jurassic rocks and their eustatically driven depositional cycles cannot be achieved without solving the salt movement history. Examination of recent geophysical and geological data suggests that the East Texas Basin has an earlier sequence of sedimentary rocks of probable Early to Middle Jurassic age below the Louann Salt. An evolutionary model incorporating these concepts is proposed. This model suggests deposition of Early to Middle Jurassic sediments that are areally limited to the axial portions of the present basin. Multiple desiccation events have resulted in stacked evaporite deposits. The thickest, most mobile and most areally extensive of these, the Louann Salt, plays a dominant role in the facies distribution of the post-Louann section. The Louann Salt may also provide the trapping and maturation environment for viable sub-salt accumulations. Understanding the complex sedimentary and tectonic history of these sequences will undoubtedly provide additional exploration opportunities in this prolific hydrocarbon basin.