Revision of the upper Cretaceous rudists from Northwestern Peru.

Revision of the Upper Cretaceous of northwestern Peru led to new discoveries of rudists and allowed to specify their taxonomy and stratigraphic repartition. Different species have been identified: Biradiolites cf. jamaicensis Trechmann 1924, Radiolites cf. macroplicatus Whitfield 1897, Praebarrettia sparcilirata (Whitfield, 1897) of Late Campanian age, Macgillavryia nicholasi (Whitfield, 1897), of “Middle” to Late Maastrichtian age. During Campanian and Maastrichtian times, rudists of Peru show palaeobiogeographic affinities with those of the Mexican and Caribbean domains. A palaeogeographic route for rudist migrations probably existed at that time along the Caribbean arc and the Curaçao-Ecuador coastline

Nature, signification et répartition du détritisme dans la zone briançonnaise de Vanoise

Mémoire HS n° 13 - Géologie Alpine : Le détritisme dans le Sud-Est de la France - Colloque Association des Géologues du Sud-est - Grenoble 11-12 décembre 1986De nouvelles études permettent de reconnaître trois types principaux de détritisme dans la zone briançonnaise de Vanoise. 1 - Des niveaux argilo-gréseux, minces mais de vastes extension sont associés aux transgressions (Anisien inférieur, Dogger supérieur), mais certains niveaux gréseux du Callovien sont accompagnés de légers mouvements tectoniques. 2 - Des brèches carbonatées, parmi lesquelles il faut distinguer : a/ des formations résultant de glissements et fragmentations synsédimentaires (Carnien et certaines brèches du Lias-Dogger (?) ; b/ des brèches polygéniques provenant d'escarpements de failles (Lias à Dogger inférieur et Callovo-Oxfordien). Ces brèches carbonatées sont liées à l'évolution en extension de la marge passive téthysienne . 3 - Un détritisme mixte (siliceux fin et carbonaté grossier) caractérisant certaines zones internes de Vanoise au Crétacé supérieur (et au Tertiaire ?). L'absence des brèches massives dans ces niveaux suggère que les failles n'y ont joué qu'un rôle mineur. Ce détritisme semble en relation avec l'apparition d'un régime compressif dans la zone briançonnaise

Rocas detríticas cretácicas - paleógenas de la Cordillera Occidental del Ecuador (0° - 4°30' S). Estratigrafía, sedimentología, significado tectónico y geodinámico.

62 pagesThis report synthetizes new field data obtained on the latest Cretaceous-Paleogene clastic deposits of the Western Cordillera of Ecuador in the Latacunga, Riobamba, Cuenca and Celica areas

Late Cretaceous marine transgressions in Ecuador and northern Peru: a refined stratigraphic framework.

Study of ammonites and bivalves along selected sections on the Andean margin of northern Peru and Ecuador has made it possible to recognize correlatable marine transgressions and to propose a refined stratigraphic framework for the Upper Cretaceous of the region. Six maximum flooding events are recognized: latest Turonian–early Coniacian (major event), late Coniacian–early Santonian, late Santonian–early Campanian, mid Campanian–early late Campanian (major event), early Maastrichtian (major event), and terminal early Maastrichtian. Most of these events can be correlated with global eustatic sea-level rises, but their relative manifestations indicate that the Andean margin was already being deformed by the late Cretaceous “Peruvian” tectonic events. The onset of fine-grained clastic sedimentation in the Oriente and East-Peruvian basins in the mid Turonian–earliest Coniacian is taken as the first event of the “Peruvian” phase. The Campanian regional transgression in the Peruvian-Ecuadorian forearc zones concealed the “Peruvian” deformational event. The latter caused a palaeogeographic upheaval, indicated by the subsequent development of a NNE-trending forearc basin, which extended from Paita in northwestern Peru to northern Ecuador. In the forearc zones only short-lived transgressions are recorded in the late Campanian and early Maastrichtian as a result of nearly continuous tectonic activity. This culminated with a significant tectonic event in the late Maastrichtian, causing a widespread hiatus