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Abstract

The Pitkin Limestone overlies black shale of the Fayetteville Formation and is the youngest Mississippian unit in the Paleozoic succession of northwest Arkansas. Five major fades have been delineated within the formation by apetrographic examination of samples collected from 17 measured sections: (1) oolith facies, (2) bioclast facies, (3) nodular limestone-shale facies, (4) mudstone facies, and (5) lime mud mound facies. The distribution of these facies in the Pitkin Formation suggests that Fayetteville terrigenous sedimentation was succeeded by the deposition of widespread oolith shoals and skeletal blanket sand bodies across the northern Arkansas structural platform. Sparse accumulations of lime mud formed in quiet protected areas within the coalescing carbonate complex. Increasing water depth and decreasing turbulence as Pitkin sedimentation proceeded allowed the establishment of bryozoan and blue-green algal communities. The entrapment and stabilization of carbonate mud by these organisms promoted mound development and growth. Scattered oolith shoals formed adjacent to the growing mounds in more turbulent water. Mound development was terminated in shallower water by extensive oolith and by the appearance of extensive skeletal sand accumulations in more turbulent water as regression was initiated.

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