Abstract A regional network of five interlocking stratigraphic cross-sections compiling the published work of many geologists throughout central and southwest Texas demonstrates the true stratigraphic relationships among formations of the Lower Cretaceous Fredericksburg and lower Washita subcycles. Strongly supported by a long-established ammonite zonation, these detailed stratigraphic cross-sections show lateral relations between Edwards Group formations (Kainer, Person, Fort Terrett, Segovia, Fort Lancaster, and Devils River) of the Central Texas Platform with equivalent formations of the East Texas Basin (Walnut, Comanche Peak, Goodland, Georgetown) and the Maverick Basin of South Texas (West Nueces, McKnight, Salmon Peak). These cross-sections document the following regional stratigraphic relationships: The Burt Ranch Member (basal Segovia Formation), the Regional Dense Member (basal Person Formation), and the Kiamichi Member (basal Georgetown Formation) are stratigraphic equivalents, all three being in the Adkinsites bravoensis Ammonite Zone (lowermost Washita) The peritidal Person Formation is the shelf-interior equivalent of the pelagic-shelf Georgetown Formation, except for its uppermost member, the Main Street, which forms the thin remnant Georgetown Formation on the distal Central Texas Platform. Thus the Person Formation is properly assigned to the lower Washita subcycle, not the Fredericksburg.

Abstract Uppermost Aptian-Albian-lower Cenomanian strata of the Texas Comanchean Series represent three long-term transgressive-regressive cycles: the Trinity, Fredericksburg, and Washita groups that are composed mainly of marine limestone and shale. Each group is composed of shorter term deepening-shallowing cycles. On the Central Texas San Marcos Platform and its downdip equivalents, subsurface strata above the Trinity Group are grouped into the Edwards and Washita groups. Correlations in the 1960s were based on wireline well logs and inferred biostratigraphy that correlated the upper Edwards Group Person Formation with the lower parts of the Washita Group. This correlation crosses a widespread subaerial unconformity that separates the Washita from the underlying Fredericksburg in the northern East Texas Basin and in the Fort Stockton Basin. New biostratigraphic and sedimento-logical data show that the Person actually correlates with the upper part of the Fredericksburg in the Gulf Coast.