Integrated Chitinozoan and Miospore Zonation of the Serra Grande Group (Silurian-Lower Devonian), Parnaíba Basin, Northeast Brazil

Silurian and Early Devonian chitinozoans and miospores have been identified from samples of the Serra Grande Group, Parnaíba Basin, northeast Brazil. The chitinozoans indicate a Llandovery (late Aeronian-early Telychian) age for the uppermost Ipu, Tianguá, and lowermost Jaicós formations. The upper part of the Jaicós Formation yielded chitinozoan species similar to those from the latest Pragian age strata in Bohemia. The miospore age determinations agree with those based on chitinozoans. The Laevaconsiella diellomedia Subzone is recognized from the Early Silurian interval, and the Su (Dictyotriletes subgranifer) Interval Zone (latest Pragian-earliest Emsian) in the uppermost Jaicós Formation. The overlying Itaim Formation is separated from the Serra Grande Group by a hiatus comprising a yet undetermined amount of Emsian time. Therefore the total age range of palyniferous parts of the Serra Grande Group is Early Silurian (Llandovery) through possibly earliest Emsian. Three chitinozoan species, Angochitina gurupiense, Pogonochitina tianguaense, and Sphaerochitina palestinense, are newly described. Two chitinozoan biozones are defined: the Interval Zone of Pogonochitina tianguaense n. sp. (late middle-early late Llandovery, equivalent to the upper part of the L. diellomedia Subzone) and the Assemblage Zone of Ramochitina sp. A and Ramochitina sp. B (latest Pragian or possibly earliest Emsian, equivalent to the older part of the Su Interval Zone).