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Depósitos messinianos do sul de Portugal, mamíferos (incluindo Rodentia e Logomorpha) e idades K-Ar
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In the southern part of Tagus basin, North of paleozoic rocks of Valverde-Senhor das Chagas (near Alcácer do Sal) horst, a marine transgression has been recognized, Upper Serravallian, and maybe Lower Tortonian in age. There are no earlier marine deposits, and no younger ones are known either. Paleozoic behaved as a barrier separating two basins, distinct at least since Middle Miocene until Upper Pleistocene. Until now, both were regarded as a single entity, the so-called «Sado basin»
Southwards (Alvalade basin) there has been a single transgression. It was assummed that it was the same one as the former. Indeed it is not definitely so. Later transgression accounts for Esbarrondadoiro Formation, whose deposits have been ascribed to Tortonian or even to Middle Miocene. However they are Upper Messinian to Lower Zanclean.
Esbarrondadoiro Formation is younger than Lower Member of Cacela Formation in Algarve and, with even stronger reason, than the upper-most well dated marine levels in Tagus basin.
Age of Miocene units dealt with here has been based on small mammals found in marine sands.
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Messinian Mammals Glauconite K-Ar ages South of Portugal