Barremian–Albian Rudist Zones, U.S. Gulf Coast

Albian rudist biostratigraphy (Bivalvia), Comanche shelf to shelf margin, Texas

“…Up dip in outcrop the RDM is a moderate yellow gray, argillic lime mudstone with small Planolites burrows and the rare infaunal bivalve, Pleuromya knowltoni (HILL), which is preserved in life position. In the uppermost Person cyclic interval caprinids are moderately preserved and identifiable as members of the Caprinuloidea Zone (SCOTT and FILKORN, 2007). Fort Terrett Formation.…”

“…Rudist bivalves have undergone multiple Early Cretaceous episodes of extinction and the group rapidly diversified throughout the Early Cretaceous making them an important tool for biostratigraphic correlation (SCOTT and FILKORN, 2007;SKELTON, 2013;STEUBER et al, 2016). Although rudists do not occur in the same beds as ammonites, they are in facies superposed with ammonites.…”

“…Five rudist zones in the Comanchean Series are defined by the ranges of sixteen rudist taxa (SCOTT and FILKORN, 2007). These zones are integrated with Barremian to Albian ammonite zones and foraminiferal ranges in the Trinity, Fredericksburg and Washita groups (COOGAN, 1973(COOGAN, , 1977SCOTT, 1990SCOTT, , 2002.…”

“…Comanchean rudists formed biostromes and bioherms on the shelf interior and at the shelf margin and were abundant members of reefal paleocommunities (SCOTT, 1990). Carbonate stratigraphic units of the Comanche Shelf record rudist evolution during the Hauterivian through the Albian ages (COOGAN, 1977) and a zonal scheme has been developed (SCOTT and FILKORN, 2007).…”

“…Rudist species are relatively well known from Lower Cretaceous outcrops in Central Texas (COOGAN, 1977;DAVIS-STRICKLAND, 1988;SCOTT and FILKORN, 2007;MITCHELL, 2013a), from shelf-margin cores (SCOTT, 1990;MANCINI and SCOTT, 2006), and on the outer Devils River platform along the southern reaches of the Pecos River in West Texas ( Fig. 1.B) (KERANS et al, 1999;SCOTT and KERANS, 2004).…”