INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
New insights for the paleobiogeographic analysis of the Early Ordovician graptolite fauna of the Northwestern Argentina
VENTO, B.A.; TORO, B.A; MALETZ, J.
COMPTES RENDUS PALEVOL
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
A multivariate analysis was used to determine the faunistic relationships of the Northwestern Argentinian graptolite faunas of Floian age to faunas from Baltica, Avalonia and Laurentia. The statistical analysis at species level between the four geographic regions for the Lower Floian was made with the classic Jaccards index. The resulting affinity dendrogram shows stronger relationships between early Floian graptolite faunas of northwestern Argentina and those from Baltica with less obvious similarities with Great Britain (Avalonia) faunas and only weak affinities to North American graptolite faunas. The statistical analysis confirms the paleobiogeographic relationships previously observed in other areas of the Cordillera Oriental, and supports the hypothesis that during the Early Ordovician, northwestern Argentina was located in middle to high latitudes, corresponding to the Atlantic Faunal Realm of cold water graptolite biofacies. The studied graptolite material from the Quinilicán and Agua Chica sections is preserved in shales and silstones interbeded with fine to medium grained sandstones corresponding to the lower part of the Acoite Formation. The biostratigraphical implications of the associated graptolites are briefly discussed, and Trichograptus dilaceratus (Herrmann), Acrograptus gracilis (Törnquist), Expansograptus latus (T. S. Hall) and Corymbograptus v-fractus tullbergi (Monsen) are described from the Argentine Cordillera Oriental for the first time.