Benthic assemblages in the Northwestern of Gondwana: a test of the Ordovician evolutionary radiation model

SÁNCHEZ, T.M.; WAISFELD, B.G.

Las Vegas

Congreso; 7th International Symposium on the Ordovician System; 1995

Detailed paleoecologic studies in both basins were the ground for analyzing thecorrespondencebetween the expansion of global evolutionary faunas during the lower Ordovician and local marine communities developed in distinct paleogeographic areas.As a result suspension feeder-rich associations in San Juan limestone could be included in the Paleozoic fauna. By contrast, fossil associations that devoloped long the rest of the western part of Argentina in coeval siliciclastic units fit in the Cambrian fauna with the complete absence of suspension feeders communities. Our purpose is to discuss this discrepancy concerning the Ordovician radiation model. We suggest that the discrepancy might arise from different ecological properties underline by the paleogeographic positions of both areas durin the Arening times. For this reason, we analyze main features of fossil associations in other gondwanic localities in order to test if similar patterns of distribution among fossil associations could be stated.