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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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The Jameson reef is an elongate, strike-trending mud buildup that occurs within the Middle Pennsylvanian (Desmoinesian) Strawn reef trend of west-central Texas. It consists primarily of carbonate wackestones, mudstones, and packstones with smaller units of Chaetetes framestones and grainstones.
Microfacies analyses indicate that the buildup was deposited on a warm, shallow-water carbonate platform characterized by downslope mud accumulations and upslope calcarenite beaches and islands. The shape of the buildup was controlled by ocean currents, which spread the sediments laterally and downdip.
The sediments were exposed to early marine and meteoric diagenesis as well as late subsurface diagenetic processes. Marine diagenesis includes primarily micritization of component grains. Leaching occurred in the meteoric phreatic environment following micritization. The leaching produced intergranular, intragranular, moldic, and vuggy porosity. A later transgression placed the buildup in the meteoric phreatic environment that induced cementation, partially filling pore spaces. The grainier rocks were cemented to a greater degree than the wackestones. Dolomitization occurred in the mixing zone where dolomite rhombs generally filled pores in the micrite matrix. Diagenesis culminated with stylolitization in the deep subsurface reducing porosity.
The middle zone of wackestone makes up the best reservoir rock mainly because selective cementation of the grainier rocks occurred in the meteoric phreatic environment.
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