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Abstract: Permian (Leonardian) Crinoidal/Tubiphytes Bioherms of the Wilkie Ranch Formation, Finlay Mountains, West Texas

James Rathjen

Permian (Leonardian) sponge/tubiphytes, crinoidal/tubiphytes, and multi-taxa bioherms occur in at least three major stratigraphic zones within the Wilkie Ranch formation of the Finlay Mountains, Hudspeth County, Texas.

The lowest zone of outcropping bioherms occurs 400-430 m above the subsurface base (Stewart, 1980) and contains excellent examples of the crinoidal/tubiphytes type of biohermal development. Exposed bioherms are approximately 3 m in thickness and 13 m in width. Bioherms may be roughly divided into four horizontal zones, which are interpreted to be (from current orientation) (1) a winnowed bioclastic debris pile, (2) a crinoidal thicket (approximately 70% crinoids), (3) a core complex zone consisting of tubiphytes, laminated algae and crinoids (10%), and (4) muddier flank beds consisting of allochthonous and bioclastic debris. Vertically, three different stages of development are recognized within the bioherms. The colonization (pioneer) stage of development is dominated by a crinoidal hicket growing on a topographic high on the sea floor. Climax communities (intermediate) are represented by a group of abundant brachiopods, bryozoans, and solitary rugose corals. The stabilization (mature) stage is typified by tubiphytes, algal laminae, and large, rare, sparse crinoids forming a bindstone.

AAPG Search and Discovery Article #90980©1994 AAPG Southwest Section Meeting, Ruidoso, New Mexico, April 24-26, 1994