The Francisco Formation and an Oxfordian ammonite faunule from the Artemisa Formation, Sierra del Rosario, western Cuba

Abstract

The Francisco Formation of Oxfordian age is proposed for the strata separating the San Cayetano and the Artemisa Fm. in the Sierra del Rosario, western Cuba. Moreover, an Oxfordian ammonite faunule with Mirosphinctes Schindewolf and Cubaspidoceras Myczyński is described from the basal part of the Artemisa Formation. The stratigraphy of the Jurassic sediments from the Sierra del Rosario is briefly discussed on the basis of the new data. There appears to be a sedimentary continuity from the (?) Lower/Middle Jurassic-Oxfordian San Cayetano Fm. Through the Oxfordian Francisco Fm. to the Oxfordian–Lower Cretaceous Artemisa Fm. which indicates that this area has not been affected by the Nevadan orogeny. From the new stratigraphic correlations of the Jurassic formations of the Sierra del Rosario and the Sierra de los Organos it follows that the lithology of isochroneous sediments of these regions is markedly less contrasted than it was hitherto assumed.