Biofacies and palaeoenvironments of conodonts in Cambro-Ordovician sequences of the Quebrada de Humahuaca, Cordillera Oriental of Jujuy, Argentina

Abstract

The taxa frequencies and cluster analysis of 10837 conodonts recovered from the Santa Rosita Formation on the eastern flank of the Quebrada de Humahuaca, Cordillera Oriental of Argentina, were carried out for palaeoenvironmental interpretations. The first type of analysis allowed us to identify three conodont biofacies: Variabiloconus-Teridontus, Utahconus-Acanthodus and Tilcarodus-Drepanoistodus, and the cluster analysis helps define respective sub-biofacies. The first biofacies is not constrained to a particular environment, the second biofacies, which is characterized by typical Laurentian genera, is related to sandstones from shallow-water environments, while the third one is better represented in deeper water siliciclastic lithofacies. A nektobenthic mode of life is suggested for Utahconus and Acanthodus, but a pelagic behaviour is apparent for the rest of the taxa, well adapted to off-shore biotopes in particular cases (proto- and paraconodonts). The faunal composition reveals a mixture of Baltic and Laurentian taxa, as well as endemic forms that define the Southwestern Gondwana Province from the Cold Domain in the Shallow-Sea Realm. The presence of typical species from low latitudes (e.g. Australia) confirms the installation of an oceanic perigondwanian corridor, which was open to faunal migration during the late Cambrian-early Ordovician. © 2012 John Wiley & Sons, Ltd.