Tremadocian graptolite-conodont biostratigraphy of the Cordillera Oriental, NW Argentina

ORTEGA, G; ALBANESI G.L

Geologica Acta

Universitat de Barcelona

Lugar: Barcelona; Año: 2005 vol. 3 p. 355 - 371

1695-6133

The Tremadocian graptolite and conodont faunas of the Gondwana Margin recorded at the Eastern Cordillera(EC) of Salta and Jujuy provinces (northwestern Argentina) are studied. The previous data and the new providedinformation indicate that a ?no nominated interval? and several graptolite zones (Anisograptus matanensis,Rhabdinopora flabelliformis anglica, Bryograptus, Kiaerograptus, Kiaerograptus supremus, Araneograptusmurrayi, and Hunnegraptus copiosus zones), as well as several conodont zones (Iapetognathus, Cordylodusangulatus, Paltodus deltifer, and Acodus deltatus - Paroistodus proteus zones) occur in the Ordovician successionsstudied. New or reappraised data from sections such as Angosto del Moreno, Angosto de Lampazar, Parcha-Incamayo-Incahuasi area, and Cajas range (EC western margin), and Alfarcito area and Mojotoro range(EC eastern margin), provide new information on the composition of the fossil faunas. A composite graptoliteconodontbiostratigraphic framework, including records of key trilobites as external control group, is proposedfor the Tremadocian of the South American margin of Gondwana. Both fossil groups are generally recordedfrom outer platform to ocean basin environments, showing significant similarities with the Baltoscandian faunas.Nevertheless, particular shallow-water facies include either specific forms or species associations that arecommon to the epeiric shallow-water seas of Laurentia. This fact demonstrates an important interplay betweenfaunas of different regions of the Iapetus Ocean during the Tremadocian.