ABSTRACT: Late Pennsylvanian Depositional Cycles and Fusulinid Zonations for the Salt Creek Reef of the Horseshoe Atoll of West Texas -- Implications for a Sea Level Curve and Regional Correlations

JENSEN, JOSEPH M., Mobil Exploration and Producing U.S. Inc., Midland, TX

The Salt Creek reef is one of a number of carbonate reef-mound complexes that makes up the Horseshoe Atoll. At least eleven depositional cycles have been delineated from the Strawn Formation (Late Desmoinesian) through the Canyon Limestone (Missourian) to the Cisco Formation (Early Virgilian). A typical cycle consists of a basal unit of intraclastic and skeletal grainstone to dark-gray lime-mudstone with black shale laminations, chert nodules, and scattered crinoid fragments; an intermediary unit of crinoid wackestone and packstone grading up to interbedded skeletal packstone and algal baffle-boundstone; and a capping unit of skeletal and oolitic grainstone. The cycle is bounded by unconformities. These cycles were deposited in a starved basin as a fringing reef-mound complex on an is lated, drowned platform.

Nine fusulinid biostratigraphy zones established for the Permian basin are recognized at Salt Creek: one Strawn zone; seven zones in the Canyon, and one in the Cisco. These zones coincide with the eleven major depositional cycles at Salt Creek. I have correlated these eleven lithostratigraphic-biostratigraphic units to a series of 14 major transgressive sequences in north Texas and 16 sequences in the mid-continent of North America. These correlations suggest that glacial eustasy is the basic control of these cycles. Differences in the correlation between the cycles may be due to the unique setting of the Salt Creek reef, variations in sea level fluctuations and basin subsidence, or variations in sedimentation rates between carbonate platforms and cratonic shelves with mixed lithologi s.

AAPG Search and Discovery Article #91018©1992 AAPG Southwest Section Meeting, Midland, Texas, April 21-24, 1992 (2009)