Sedimentary Facies and History of Upper Jurassic (Oxfordian) Smackover Formation in Conecuh Embayment of South Alabama: ABSTRACT

Abstract

The Upper Jurassic (Oxfordian) Smackover Formation is an important petroleum-bearing unit in the deep subsurface of the gulf rim. The authors studied the sedimentary facies and sedimentary history of the Smackover in Escambia County, Alabama. The wells studied form an east-west strike section across the Conecuh embayment in south Alabama. In the central part of the embayment, the Smackover is 350 ft (107 m) thick and consists of a vertical sequence of the following correlative sedimentary facies. In stratigraphic order, they are: (1) basal, shallow-water facies that rests conformably on the underlying Norphlet and forms a discontinuous interval a few feet thick, consisting of algal-laminated mudstones, sandy packstones and grainstones, and clast horizons; (2) basinal, deep-water facies, 175 ft (53 m) thick, consisting of resedimented debris beds (oolitic-pisolitic-graded beds, 8 in or 24 cm thick) intercalated with laminated, very argillaceous mudstone and wackestone; (3) parallel and wavy-laminated, sparsely fossiliferous packstone and wackestone, 80 ft (24 m) thick, interpreted as a carbonate slope deposit that accumulated below storm wave base; (4) bioturbated oolitic, pelletal, and fossiliferous packstone with faint relict laminations, 45 ft (14 m) thick, containing abundant Thalassinoides and Zoophycus traces and interpreted as below normal wave base deposits; andmore » (5) oolitic and fossiliferous grainstone, 50 ft (15 m) thick, interpreted as deposits formed above wave base (shelf-platform deposits). The above sequence suggests progradation of a carbonate shelf. This progradation probably followed the rapid eustatic sea-level rise of the Oxfordian.« less