Brachiopoda Taxonomy and Biostratigraphy of the Redwall Limestone (Lower Mississippian) of Arizona

Abstract

Forty-six species, assignable to 36 brachiopod genera, are recognized, described, and illustrated from the Lower Mississippian Redwall Limestone of northern Arizona. Seven new species are recognized, four of which are named. Named species are: Spinocarinifera (Seminucella) costatula, new species; Magnumbonella ampla, new species; Setigerites gutschicki, new species; and Spirifer redwallensis, new species. The remaining three newly recognized species remain in open nomenclature because study material was too poorly preserved to justify naming. The majority of brachiopod species studied were recovered from the Thunder Springs and Mooney Falls members near the middle of the formation. The basal Whitmore Wash Member and uppermost Horseshoe Mesa Member contain only sparse and poorly preserved brachiopod material. The spotty stratigraphic distribution of collections, which were recovered from largely geographically disparate locations, resulted in the creation of a stratigraphic range chart that exhibits no recognizable segregation into any potential brachiopod zones. Many of the Redwall Limestone's brachiopod species are known from contemporaneous formations elsewhere in the Cordillera or central United States. Biostratigraphically key species such as Marginatia fernglenensis (Weller, 1909), Marginatia burlingtonensis (Hall, 1858), Stegacanthia bowsheri Muir-Wood and Cooper, 1960, Fernglenia vernonensis (Swallow, 1860), Voiseyella novamexicana (Miller, 1881), and Punctospirifer subtexta (White, 1862), indicate that much of the Thunder Springs and Mooney Falls members is correlative with latest Kinderhookian (late Tournaisian) through latest Osagean (early Vis an) formations of the American Midcontinent. These correlations indicate that the Redwall Limestone is temporally equivalent to the Fern Glen-Burlington formations of the central United States. These correlations are consistent with other Redwall forms that are biostratigraphially useful, such as foraminifers.