Existence of marine upper Triassic and lowermost Jurassic strata was first recorded in the Andes of Argentina in 1986 (cf. Riccardi et al., 1988, 1991, 1997) at Arroyo Alumbre, in the Atuel River area, Malargue province. The section, exposed in an anticline nucleus, consists of a c. 300 m thick continuous succession of uppermost Triassic and basal Jurassic strata, ascribed to the Arroyo Malo Formation, containing a relatively diverse, but rather scarce and poorly preserved fauna of marine invertebrates. Since then, this section has been sampled several times and its sedimentology, biostratigraphy and fossil content exposed in a number of papers (cf. Riccardi et al., 2004; Lanés, 2005; Riccardi, 2008; Damborenea & Manceñido, 2012).