Observaciones sobre la posición estratigráfica de las formaciones de rudistas de Sant Corneli (cuenca cretácica surpirenaica central)

Abstract

Rudist formations crop out around the Sant Corneli anticline (South-Central Pyrenees), both on its southern flank (les Collades de Basturs) and on its northern flank (Vilanoveta). Earlier biostratigraphical studies assigned different ages to these two exposures, the first being considered Middle-Upper Santonian and the second, Coniacian-Lower Santonian, and these assignments have been uncritically accepted in a number of recent sequence stratigraphical studies of the Cretaceous basin. However, no direct evidence for any difference in age of the two formations is provided by the (benthic) fossils contained in them, which comprise similar, broadly ranging taxa. Rather, ages had been asssigned by interpreted correlations with other units, which we dispute. Our studies of the Vilanoveta rudist formation suggest that it is not equivalent to the Coniacian-Lower Santonian Montagut Member, but is instead correlable with the Lower-Middle Santonian sediments of the Prats de Carreu Member. This conclusion in turn implies a similar (if not identical) age of deposition to that of the lithologically comparable rudist formation of les Collades de Basturs, to the South. Our preliminary studies of stratigraphically sensitive taxa from the two formations (e.g. inoceramids) support the latter interpretation, so casting doubt on the sequence stratigraphical models that have been based on the old biostratigraphical data