CICTERRA   20351
CENTRO DE INVESTIGACIONES EN CIENCIAS DE LA TIERRA
Unidad Ejecutora - UE
capítulos de libros
Título:
Early-Mid Ordovician conodont palaeobiogeography with special regard to the geographic origin of the Argentine Precordillera: A multivariate data analysis.
Autor/es:
GUILLERMO LUIS ALBANESI; BERGSTRÖM, S. M.
Libro:
Global Ordovician Earth System.
Referencias:
Año: 2008; p. 1 - 1
Resumen:
Statistical comparisons of conodont faunas from many parts of the world
were carried out in an effort to shed light on one of the most
discussed, and most controversial, problems in the lower Paleozoic
geology of South America, namely the geographic origin of the exotic
terrane in western Argentina known as the Precordillera. The similarity
between the conodont faunas from the Precordilleran La Silla, San Juan,
Gualcamayo, and Yerba Loca formations and many coeval faunas from
Laurentia, as well as from other parts of the world, was assessed using
the Jaccard Index. The analysis of faunas from six biostratigaphic
intervals in the Lower and lower Middle Ordovician shows that the
earliest Ordovician (Tremadocian) faunas cluster with those of
Laurentia whereas slightly younger faunas show less obvious
provincialism. The conodont faunas of the early Mid Ordovician (early
Darriwilian) of the Precordillera again show dominantly Laurentian
affinities. The hypothesis that the Precordillera rifted from the
Ouachita embayment and moved across part of the Iapetus to dock with
western Gondwana in Ordovician time is not clearly supported by the
conodonts (and other non-conodont phosphatic microfossils). The
similarity with faunas in southern Laurentia (mainly from the El Paso
area of Texas and southern New Mexico) is high in the Tremadocian. The
expected similarity decrease with presumed increase in distance from
Laurentia later in the Early Ordovician is not evident in the conodont
faunas. Similarity between the two regions (mainly the Precordillera
and the Marathon area of Texas) remains about the same through the
early Middle Ordovician. It is concluded that the conodonts, the best
known and most widespread fossil group in the study areas, do not
provide conclusive evidence of the geographic origin of the
Precordillera.