Late Albian ammonites from the carbonate cover of the Teloloapan arc volcanic rocks (Guerrero State, Mexico)
Résumé
In the Guerrero province of Mexico, the calc-alcaline lavas of the Teloloapan volcanic arc unit are overlain by carbonates with reworked neritic faunas of Aptian–Albian age (La Evolucion Geologica y la Metalogénesis del Noroccidente de Guerrero. Universidad Autonoma de Guerrero, Serie Técnico-Cientifica, 1 (1979) 84). The discovery of an ammonite fauna at the top of the Teloloapan limestone provides a latest Albian age assignment for that horizon. The fauna includes: Pervinquieria rostrata, P. gr. inflata, Turrilitoides hugardianus, Stoliczkaia cf. blancheti, S. cf. tenuis, Desmoceras latidorsatum, Oxytropidoceras cf. cantianum, Puzosia aff. mayoriana, Lechites moreti, Hamites cf. gardneri, H. cf. maximus, and Falciferella campae n. sp. A pelagic microfauna is associated with the ammonites and contains Hedbergella sp. and Colomiella recta. The fossiliferous horizon may thus be restricted to the Inflatum and lower Dispar zones. The overlying flysch contains Hamites sp. gr. intermedius near the base. Therefore, volcanism in the Teloloapan arc ceased before the end of the Early Cretaceous, while flysch deposition began in latest Albian times.