جغرافیای زیستی دیرینه کنودونتهای کوههای البرز در گذر کامبرین به اردوویسین

Abstract

To assess biogeographic affinity of the Late Cambrian (Furongian) and the Early Ordovician (Late Tremadocian) faunas of Eastern Alborz, a multivariate cluster analysis using the pair-group Raup-Crick similarity index has been applied. The Late Cambrian fauna of Alborz shows clear Gondwanan signatures with the closest affinities to the contemporaneous faunas of temperate latitude peri-Gondwana (Central Iran, Oaxaquia terrane in southern Mexico) and in slightly lesser degree with low latitude faunas of the Karatau Naryn microplate (southern Kazakhstan) and the Australasian segment of Gondwana. Thus, outcome of the analysis suggests that by the second half of the Furongian, which was the time of proliferation of the early euconodonts, the Alborz terrane approached and probably entered temperate latitudes. In the Late Tremadocian links of Alborz conodont faunas with temperate latitudes faunas of Gondwana and Baltica became more evident. Assessment of the Cambrian (Furongian) and Early Ordovician (Late Tremadocian) conodont faunas of the Alborz are in favor of its isolated position at some distance the western Gondwanan coast.