Late Pennsylvanian cycles with thin, carbonate-dominated transgressive sequences and thick clastic-dominated regressive sequences have been considered the norm for cyclic sequences in north Texas, but they represent only a special case associated with higher rates of clastic sedimentation prevailing during falling sea levels. There are many cycles with carbonates in regressive as well as transgressive portions of cycles. Completely exposed cycles usually begin on an exposure surface and, between the exposure surface and the transgressive carbonate, have a thin clastic sequence showing upward change to normal marine conditions. Transgressive carbonates generally contain large amounts of clay muds and quartzose silts. The transgressive sequence culminates in a deeper water, dark-colored phosphatic shale. The regressive sequence is thicker, begins with a richly fossiliferous offshore marine shale, and continues upward into either limestone or sand-dominated sediments. Regressive limestones tend to be thicker and composed of more pure carbonate than transgressive ones, and to be capped with shoal calcarenites. These usually are overlain by nonmarine clastics, which may contain redbed layers, and a paleosol horizon at the top. In clastic-dominated regressive sequences, the offshore marine shales are overlain by an interval with upward-increasing sand content, and are capped by nonmarine deposits. Carbonate deposition in these cycles occurred only within a limited range of water depths. These cycles are similar to mid-continent cyclothems, and support the case or allogenic control and major fluctuations in sea level during cycle deposition.

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