Jurassic Sequence Stratigraphy in Mississippi Interior Salt Basin: An Aid to Petroleum Exploration in Eastern Gulf of Mexico Area

Ernest A. Mancini, Robert M. Mink, Berry H. Tew

An understanding of sequence stratigraphy of Jurassic units in onshore basins can serve as an aid to identify potential petroleum reservoir and source rocks in the eastern Gulf of Mexico area. Three depositional sequences associated with cycles of eustatic sea level change and coastal onlap have been identified in the Mississippi Interior Salt basin. Three depositional sequences probably correspond to the J2.4, J3.1, and J3.2 sequences of Vail et al for Callovian through Kimmeridgian strata. In the Mississippi Interior salt basin, the lower depositional sequence is bounded by a basal type 2 unconformity and an upper type 2 unconformity in the Callovian. This sequence includes Louann evaporites (transgressive), Pine Hill anhydrites and shales (condensed section), and Norph et eolian sandstones (highstand regressive). The middle depositional sequence reflects relative sea level rise in the late Callovian. This sequence includes Norphlet marine sandstones and lower Smackover packstones and mudstones (transgressive), middle Smackover mudstones (condensed section), and upper Smackover grainstones and anhydrites (highstand regressive). The sequence has an upper type 2 unconformity indicating relative sea level fall in the Oxfordian. The upper depositional sequence reflects relative sea level rise in the late Oxfordian. This sequence includes lower Haynesville evaporites and clastics (transgressive), middle Haynesville carbonate mudstones and shales (condensed section), and upper Haynesville updip continental sandstones and downdip shales, limestones, and anhydr tes (highstand regressive). The sequence has an upper type 1 unconformity indicating abrupt sea level fall in the late Kimmeridgian. In these depositional sequences, highstand regressive deposits are the principal petroleum reservoirs. Condensed section deposits have the potential to be source rocks offshore; however, only the lower and middle Smackover mudstones were deposited and buried under conditions favorable for hydrocarbon generation and preservation onshore.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.