NUEVOS HALLAZGOS DE GRAPTOLITOS EN LA FORMACION YERBA LOCA Y SU IMPLICANCIA ESTRATIGRAFICA, PRECORDILLERA DE SAN JUAN, ARGENTINA

Gladys Ortega, Edsel Brussa, Ricardo Astini

Abstract


Two new graptolite assemblages from the Yerba Loca Formation in the Precordillera of San Juan, Argentina, are described. They allow to increase the age range of this unit from early Llanvirnian to late Caradocian. The early Llanvirnian assemblage from quebrada Divisadero and from Los TĂșneles area indicates Paraglossograptus
tentaculatus Zone. The other assemblage from Sierra del Tigre, suggests a Caradocian age, post Nemagraptus gracilis Zone. The following forms are described: Sinograptid gen. et sp. indet., Cryptograptus cf, C. antennarius (Hall), Isograptus caduceus cf. I.c. caduceus (Salter), Isograptus sp., Dicellograptus sp., Orthoretiolites sp., Oelandograptus austrodentatus americanus (Bulman). Complementary geological and petrographic data are given and a correlation with other clastic formations of the western Precordillera is discussed.

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