The microcrinoid taxonomy, biostratigraphy and correlation of the upper Fredericksburg and lower Washita groups (Cretaceous, middle Albian to lower Cenomanian) of northern Texas and southern Oklahoma, USA

Abstract

The stratigraphy of the upper Fredericksburg and lower Washita groups of northern Texas and southern Oklahoma is described, and biostratigraphical correlation within the region, and further afield, using microcrinoids, ammonites, planktonic foraminiferans and inoceramid bivalves is summarised. The taxonomy of the roveacrind microcrinoids is revised by the senior author, and a new genus, Peckicrinus, is described, with the type species Poecilocrinus porcatus (Peck, 1943). New species include Roveacrinus proteus sp. nov., R. morganae sp. nov., Plotocrinus reidi sp. nov., Pl. molineuxae sp. nov., Pl. rashallae sp. nov. and Styracocrinus thomasae sp. nov. New formae of the genus Poecilocrinus Peck, 1943 are Po. dispandus forma floriformis nov. and Po. dispandus forma discus nov. New formae of the genus Euglyphocrinus Gale, 2019 are E. pyramidalis (Peck, 1943) forma pyramidalis nov., E. pyramidalis forma radix nov. and E. pyramidalis forma pentaspinus nov. The genera Plotocrinus Peck, 1943, Poecilocrinus and Roveacrinus Douglas, 1908 form a branching phylogenetic lineage extending from the middle Albian into the lower Cenomanian, showing rapid speciation, upon which a new roveacrinid zonation for the middle and upper Albian (zones AlR1–12) is largely based. Outside Texas and Oklahoma, zone AlR1 is recorded from the lower middle Albian of Aube (southeastern France) and zones AlR11–CeR2 from the Agadir Basin in Morocco and central Tunisia. It is likely that the zonation will be widely applicable to the middle and upper Albian and lower Cenomanian successions of many other regions.