Cephalopods of the Triassic-Jurassic boundary in west-central Argentina

RICCARDI, ALBERTO CARLOS

NEUES JAHRBUCH FUR GEOLOGIE UND PALAONTOLOGIE-ABHANDLUNGEN

E SCHWEIZERBARTSCHE VERLAGS

Lugar: Stuttgart; Año: 2019 p. 135 - 157

0077-7749

The section of arroyo Alumbre, in the rio Atuel area, Malargue province, west central Argentina, consists of a c. 300 m thick continuous succession of uppermost Triassic and basal Jurassic strata, ascribed to the Arroyo Malo Formation. The sequence lower half contains, a succession of levels with different taxa, from base, Rhabdoceras suessi Hauer, ?Peripleurites sp., Aulacoceras cf. carlottense Whiteaves, and Choristoceras marshi Hauer. Higher up are other levels with Psiloceras tilmanni Lange, Psiloceras cf. primocostatum, P. cf. pressum Hillebrandt spp., Psiloceras cf. polymorphum Guex, and Psiloceras cf. rectocostatum Hillebrandt. All these taxa are here described. Choristoceras marshi is indicative of the Upper Rhaetian Marshi Zone, and the taxa occurring below indicate that the lowermost part of the section is Norian-Lower Rhaetian, whereas the taxa of the overlying beds are indicative of the Tilmanni, Primocostatum and Rectocostatum Zones of the Hettangian South American zonation. The Triassic-Jurassic boundary is located between the occurrences of Choristoceras marshi and Psiloceras tilmanni. This fauna can be referred and/or correlated with those recorded at the Triassic-Jurassic boundary in Chile, Peru and North America