GRAPTOLITES AND CONODONTS OF EARLY KATIAN AGE (LATE ORDOVICIAN) FROM THE SIERRA DE LA INVERNADA FORMATION, SAN JUAN PRECORDILLERA, ARGENTINA.

GLADYS ORTEGA; GUILLERMO ALBANESI; ALDO LUIS BANCHIG; GUILLERMO PERALTA

Acta Palentologica Sinica

Lugar: China; Año: 2007 vol. 46 p. 357 - 363

0001-6616

Abstract       The Sierra de La Invernada Formation is a heterolithic succession that crops out in the western flank of the Sierra de La Invernada, Central Precordillera of San Juan, Argentina. Graptolites and conodonts are abundant fossils in this unit, and indicate an early Darriwilian to early Katian age for the whole succession. Upper sandstones and shales of this formation, which bear early Katian graptolites and conodonts, are exposed in the northern part of the range. Representative graptolites of the Diplacanthograptus caudatus and Climacograptus tubuliferus zones are recognized in the studied section, in association with conodonts of the Amorphognathus superbus Zone. A significant graptolite assemblage that comprises Diplacanthograptus caudatus, D. spiniferus, and Neurograptus margaritatus refers to the D. caudatus Zone. It is followed by an impoverished assemblage at the entrance of C. tubuliferus, which is the index species for the homonymous biozone, recorded in the uppermost levels of the formation.