Sequence Stratigraphy of the Smackover Formation in the Northern Half of the Manila Embayment, Southwestern Alabama
KING, DAVID T., JR., and E. GLENN HARGROVE, Auburn University, Auburn, AL
The Smackover Formation in the northern half of the Manila Embayment, southwestern Alabama, ranges from 100 to 400 ft thick and encompasses two genetic packages of facies. These genetic packages developed within a single cycle of relative sea level change during the Oxfordian (Late Jurassic) and thus comprise a single stratigraphic sequence. The sequence boundaries, genetic packages, and constituent facies are recognized in core and on gamma-ray logs. The base of the lower genetic package is the sharp contact between (1) either deep-water argillaceous packstones and wackestones or laterally equivalent shelf-margin algal boundstones of the lower Smackover and (2) terrestrial clastics of the underlying Norphlet Formation. The upper part of the lower Smackover genetic package includes bo h shelf packstones and wackestones and algal patch-reef boundstones arranged in a backstepping pattern. The lower genetic package as a whole represents the transgressive systems tract; the contact between the upper and lower genetic packages is a maximum flooding surface delineated by a sharp lithic change to ramp-generated grainstone, packstone, and wackstone facies. The upper genetic package generally coarsens upward; high-energy carbonate and clastic facies dominate the section near the top of the upper genetic package. The high-energy facies include oolitic and nonoolitic grainstones and quartz-rich hummocky cross-stratified sand beds (storm-generated deposits) which are intercalated with lagoonal carbonate wackestone and mudstone facies. The top of the upper genetic package is the s arp transition to anhydritic and dolomitic sabkha facies in the overlying Buckner Anhydrite Member of the Haynesville Formation. As a whole, the upper genetic package of the Smackover represents a prograding highstand systems tract set of carbonate ramp facies.
AAPG Search and Discovery Article #91006 © 1991 GCAGS and GC-SEPM Meeting, Houston, Texas, October 16-18, 1991 (2009)