GAO, GUOQIU, and LYNTON S. LAND, Department of Geological Sciences, University of Texas at Austin, Austin, TX

ABSTRACT: Complex Dolomitization History of the Arbuckle Group, Arbuckle Mountains, Oklahoma

The Cambro-Ordovician Arbuckle Group in the Arbuckle Mountains, Oklahoma, has a complex history of dolomitization which resulted in two types of massive dolomite: stratal dolomite and discordant (fault-related?) dolomite bodies. Stratal dolomite, commonly with medium to coarsely crystalline textures, is present in the lower Arbuckle Group. Most stratal dolomite samples have {87}Sr/{86}Sr ratios similar to associated limestones and coeval seawater, suggesting an early marine origin. However, all stratal dolomite samples are characterized by low delta{18}O values (-7.2 to -11.9 %o, PDB), indicating post-depositional meteoric modification during the development of unconformities at Ordovician time.

Discordant dolomite bodies are developed mainly in the middle and upper Arbuckle Group. This type of dolomite is commonly finely to medium crystalline and has a large range of delta{18}O values (+6.8 to -5.8 %o, PDB). Strontium isotopic compositions suggest that this type of dolomite has originated from at least two different processes. In the Tishomingo Anticline area, dolomitization was probably related to post-early Ordovician seawater circulating through karst conduits because {87}Sr/{86}Sr ratios (0.70772 to 0.70901) of most discordant dolomite samples are lower than Cambro-Ordovician seawater. In the Arbuckle Anticline area, discordant dolomite probably formed from basinal fluids at Permo-Pennsylvanian time because this dolomite is characterized by radiogenic {87}Sr/{86}Sr ratio (0.70951 to 0.70974) as well as high Fe and Mn concentrations.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.