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

ZEBALLO F.J., ALBANESI G.L.

GEOLOGICAL JOURNAL (CHICHESTER)

JOHN WILEY & SONS LTD

Año: 2012 vol. 48 p. 194 - 211

0072-1050

The taxa frequencies and cluster analysis of 10837 conodonts recovered from theSanta Rosita Formation on the eastern flank of the Quebrada de Humahuaca, CordilleraOriental of Argentina, were carried out for palaeoenvironmental interpretations. Theseanalyses allowed us to identify three conodont biofacies: Utahconus-Acanthodus,Tilcarodus-Drepanoistodus and Variabiloconus-Teridontus, with respective sub-biofacies.The first biofacies, which is characterized by typical Laurentian genera, is related tosandstones from shallow-water environments. The second biofacies, is better represented indeeper water environments, while the third one is not constrained to a particularenvironment. A nektobenthic mode of life is suggested for Utahconus and Acanthodus, buta pelagic behaviour is apparent for the rest of taxa, well adapted to off-shore biotopes inparticular cases (proto- and paraconodonts). The faunal composition reveals a mixture ofBaltic and Laurentian taxa, as well as endemic forms that define the SouthwesternGondwana Province from the Cold Domain in the Shallow-Sea Realm. The presence oftypical species from low latitudes (e.g. Australia) verifies the installation of an oceanicperigondwanian corridor, which was open to faunal migration during the late Cambrian ?early Ordovician.