Sedimentologic role of microproblematica Donezella in a Lower Pennsylvania Donezella-siliceous sponge-dominated carbonate buildup, frontal Ouachita thrust belt, Oklahoma, U.S.A.

The problematic organism Donezella emerged worldwide as one of the main carbonate mound builders in the middle Carboniferous. Donezella is composed of thin (70-160 mu m in diameter), bifurcating (45 to 90 degrees) tubes. Microfacies analysis of a Donezella buildup from the Wapanucka Formation, Frontal Ouachita thrust belt, Oklahoma, U.S.A., was undertaken to examine the role of Donezella in a carbonate buildup. Donezella is the predominant biotic component of the Wapanucka buildup, and the buildup is composed of irregular pockets of boundstone dominated by Donezella, worm tubes, peloids and micritic crusts, siliceous sponge spicules, less common siliceous sponge boundstone, and peloidal wackestone with other bioclasts. In the lower part of the buildup, Donezella colonies are robust, convex upward, and up to several centimeters in diameter. These colonies are composed of delicately branching Donezella with an enclosed constructional pore system. These robust, upward-growing Donezella structures formed a substrate for other binders; therefore it appears that, on a microscale, Donezella, together with siliceous sponges and worm tubes, played the role of a constructor. Donezella occurs as a long, semicontinuous row of thalli when encrusting other framework grains, and encrusts siliceous sponges, Donezella colonies, corals, and worm tubes; thus, it also acted as a member of the binder guild. Deciphering these various roles of Donezella is a crucial first step toward documenting a possible spectrum of Donezella-dominated lithologies that constitute key elements in carbonate buildups in the Early to Middle Pennsylvanian.