Nautiloid cephalopod concentration beds of the San Juan Formation (Middle Darriwilian) of the Argentine Precordillera

Abstract

Concentrations of orthoconic nautiloid cephalopods on bedding planes of the San Juan Formation limestones are for first time associated to the Yangtzeplacognathus crassus Zone (Middle Ordovician). Nautiloid cephalopod accumulations occur at several localities in the Central and Eastern Precordillera of San Juan, western Argentina. The objective of this report consists in registering Precordilleran nautiloid concentrations in the Y. crassus Zone from the shallow warm waters of the carbonate platform.