Original paper
The Upper Cretaceous - Lower Tertiary marine to continental transition in the Bagua basin, northern Peru Paleontology, biostratigraphy, radiometry, correlations
Mourier, Thomas; Bengtson, Peter; Bonhomme, Michel; Buge, Emile; Cappetta, Henri; Crochet, Jean-Yves; Feist, Monique; Hirsch, Karl F.; Jaillard, Etienne; Laubacher, Gerard; Lefranc, Jean Philippe; Moullade, Michel; Noblet, Christophe; Pons, Denise; Rey, J
published: 10/20/1988
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ArtNo.: ESP026001903002
Abstract
Various fossils (invertebrates, vertebrates, plants) and radiometric data have been obtained from the uppermost part of the marine Celendin Fm. and the lowermost part of the overlying Bagua Fm. (redbeds). After description of the stratigraphy and sampled localities, the fossils are discussed in terms of systematics, biostratigraphy, paleoecology and biogeography. On the basis of ammonites, the uppermost Celendin Fm. is dated as mid-Campanian. On the basis of a charophyte assemblage and other evidence, the lowermost Bagua Fm. (Fundo El Triunfo Member) is dated as mid-Campanian to early Maastrichtian. Higher in the section, a layer of the Sambimera Member has yielded another charophyte assemblage characteristic of the Early Tertiary. These data are consistent with a K-Ar age of 66.0 ± 1.6 Ma obtained from an overlying volcanic tuff. In this Andean area, the emergence is dated as late Campanian to early Maastrichtian. The Peruvian tectonic phase, characterized by a weak unconformity between the F.E. Triunfo and the Rentema Members, seems to be somewhat younger, late Campanian to Maastrichtian. The Cretaceous - Tertiary boundary is restricted to the 170 m thick section between the two charophyte bearing layers. From the north of Peru to the south of Bolivia, the charophytes provide the main support for a rather constant and consistent double correlation between, first: units referred to the Campanian - Maastrichtian (F.E. Triunfo, Arenisca de Azucar, Sol 1, K'ayra, Soncco, Vilquechico, El Molino) and, second: units referred to the Paleocene - Lower Eocene (Sambimera, Upper Sol 3, Contamana, Puna Cancha, Muñani, Santa Lucia).