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The Capitan Reef complex may be subdivided into western, northern, and eastern segments by major differences in structure and sedimentation. The western segment is characterized by a barrier "stratigraphic" reef and simple shelf folds paralleling the basin-shelf margin. In contrast, the northern segment has current-oriented mounds formed by shelf beds draped over biohermal cores that extend at approximately right angles to the basin-shelf margin, and shelf domes of irregular orientation superimposed on larger structures and distributed at random in the shelf. Test drilling suggests that primarily detrital and recrystallized dolomite and dolomitic limestone lie between the current-oriented mounds in what are interpreted as ancient Capitan channels. The current-oriented mou ds of the Capitan shelf and tidal-current ridges of the Great Bahama Bank have some similarities: (1) both are on an innermost shelf margin facing a deep basin or oceanic tongue, and (2) the long structural axes of both appear to have been determined by prevailing marine-currents. Shelfward from the tidal-current ridges of the Bahama Banks are moundlike accumulations of sand, which are similar in shape to the Capitan shelf domes. The Bahama mounds and tidal-current ridges were formed by marine-current deposition of oolites and carbonate detritus, whereas the Capitan current-oriented mounds and shelf domes were probably formed by marine-current deposition of carbonate detritus and by organic biohermal growth. The channels between current-oriented mounds probably provided a ready passagewa for Permian marine currents and allowed a large influx of quartzose clastics into the Delaware basin.
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