Abstract: Carbonate Source Rocks in the Jurassic Smackover Trend of Mississippi, Alabama, and Florida

By

John H. Oehler

The Smackover trend is a belt of carbonate, evaporite, and clastic rocks of Late Jurassic age which rims the U. S. Gulf Coast from Texas to the Florida Panhandle. It has been a major petroleum fairway for decades and continues to yield new discoveries each year. One area of recent intensive activity within this trend encompasses southern Mississippi, southern Alabama, and extreme western Florida.

Pertinent Jurassic stratigraphy in the area includes, in descending order, the Haynesville formation (shallow-water carbonate rocks with minor interbedded clastic units); the Buckner Anhydrite; the Upper Smackover (carbonate grainstones); the Lower Smackover (carbonate mudstones); the Worphlet Formation (mainly sandstones), and the Louann Salt.

Most of the oil and gas in this area is reservoired in the Upper Smackover and Norphlet. Geochemical data suggest that these oils and gases belong to one family and that all were sourced from algal-rich "lime" mudstones of the Lower Smackover. The geochemical data include light hydrocarbon compositions, n-paraffin distributions, saturate and aromatic group-type distributions, tetracycloalkane distributions, and carbon-isotopic composition of saturate and aromatic fractions.

Some of the richest potential source beds are sabkha-type, algal-laminated micrites of the basal Smackover.

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