EL ASHGILLIANO TARDIO (IDRNANTIANO) DEL CERRO LA CHILCA, PRECORDILLERADE SAN JUAN, ARGENTINA

Ricardo A. Astini, Juan L. Benedetto

Abstract


Ashgillian (Himantian) shelly fauna from the Cerro La Chilca section is reported for the first time. It is composed by the brachiopods Paromalomena polonica, Drabovia undulata n. sp. and Plectothyrclla crassicosta, among other well known genera. The strata, which contain this fauna belong to the Don Braulio Formation that is intercalated between the GuaIcamayo (Caradoc) and the La Chilca (Llandovery) formations. The fossiliferous beds are correlated with other Himantian sequences from the Precordillera basin. The environmental and paleoclimatic importance of this shallow marine fauna is constrained. The basal unconformity of the Ashgillian beds is interpreted as a first order sequence boundary related to glacio-eustatic lowering

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