Upper Ordovician cryptostomatid bryozoans and microfossils from the Don Braulio Formation, Eastern Precordillera, Argentina.

JIMÉNEZ-SÁNCHEZ, ANDREA; BERESI MATILDE S.; MESTRE A.; HEREDIA, S.E.

Serie de Correlacion Geologica

Instituto de Correlación Geológica, Tucumán

Lugar: Tucumán; Año: 2014 vol. 30 p. 25 - 32

In the classical section of the Don Braulio Creek at the Villicum Range, Eastern Precordillera of San Juan Province, crops out the siliciclastic Don Braulio Formation of Hirnantian age. Fragments of bryozoan colonies, few poorly preserved sponge spicules and a crinoidal ossicle, were recovered from these shelf sediments. The bryozoan colonies remains are characterized by its erect growth habit, its small diameter, and for showing clear longitudinal striations. These fragments have a poor preservation, but they have been compared with the genus Nematopora belonging to the Arthrostylidae family (Rhobdomesina suborder, Cryptostomata order), that had numerous representatives during the Ordovician. Very scarce and highly fragmented sponge spicules are classified as hexactins. These microfossils have been recovered in the post-glacial deposits from the Don Braulio section at the Villicum range.