Abstract: Coral Reefs and Banks of Texas Outer Continental Shelf

Richard Rezak, T. J. Bright

The topographic prominences on the Texas continental shelf may be grouped geologically into three categories: (1) Tertiary bedrock exposed by salt tectonics, as in Stetson and Claypile Banks; (2) coral reefs and banks growing on salt domes, as exemplified by the Flower Gardens and 28 Fathom banks; and (3) drowned coral reefs and banks not associated with salt domes such as, Baker, Southern, Dream, and all other banks of the South Texas shelf. North of 27°46^primeN lat. all of the banks and reefs are associated with shallow salt domes. South of this line, the drowned reefs appear to have grown on a buried carbonate shelf. High-resolution subbottom profiles in this area show no shallow salt domes. There is a considerable amount of faulting on the South Texas shelf, but the only bank associated with a fault is Baker.

Biotic assemblages on reefs and hardbanks can be grouped distinctly into four general categories: (1) the sparse Claypile Bank biota (35 to 55 m) of predominantly low-growing, filamentous, and leafy algae and sponges with occasional "meadows" of high-standing, leafy algae occupied by many fish; (2) the more diverse Stetson and 3 Hickey Rock biota (28 to 56 m) dominated by the hydrozoan fire coral Millepora alcicornis and sponges; (3) the highly diverse and abundant Flower Gardens/28 Fathom bank biota with coral reefs (22 to 49 m), algal nodule and sand-covered platforms (45 to 76 m), and drowned reefs (76 to 100+ m, bearing an assemblage of organisms directly comparable to the deep-water biota of category 4 described next); (4) the deep-water biota of the South Texas Fishing banks (53 /P>

to 78 m), and Fishnet bank (61 to 82 m) characterized by the presence of antipatharian whips, deep-water alcyonarian fans, comatulid crinoids, certain species of deep-dwelling fishes, and sparse populations of encrusting coralline algae.

Similar reefs and banks probably have existed on the Texas continental shelf throughout Tertiary time. Exploration philosophy will be dependent on the identification of the proper bank model.

AAPG Search and Discovery Article #90972©1976 AAPG-SEPM Annual Convention and Exhibition, New Orleans, LA