CONICET | Buscador de Institutos y Recursos Humanos

The Triassic/Jurassic boundary (TJB) in Argentina is represented mainly by continentalsediments deposited in fluvial, lacustrine, deltaic and alluvial environments, with locallyimportant deposits of volcanic and volcaniclastic rocks. They have been previously studied bySpalletti (1997) and Stipanicic (2002), among others. The Arroyo Malo Formation is the onlyknown marine deposit of Triassic age in Argentina. It represents a transgressive event withinthe Atuel-Valenciana Rift, in the northwestern sector of the Neuquén Basin (MendozaProvince, central-western Argentina), which formed during the initial subsidence stage of thatbasin. These fine-grained marine rocks were first described by Riccardi et al. (1997), andsubsequent study of their ammonoid, bivalve, and brachiopod faunas has demonstrated amid-Rhaetian to Hettangian age (Riccardi & Iglesias Llanos, 1999; Damborenea & Maceñido,2005). Detailed facies analysis showed that the Arroyo Malo Formation was deposited in anoffshore setting into which fine-grained siliciclastics were delivered by low-density turbiditeflows (Lanés, 2002; Lanés et al., 2005; Spalletti et al., 2005). Renewed interest in thesedeposits arises from their potential to provide a window into oceanic chemical andenvironmental conditions in the southern Panthalassic Ocean during the Triassic-Jurassictransition. Recently, studies of the Hg cycle revealed perturbations at the TJB that have beenlinked to CAMP volcanism (Percival et al., 2017; Thibodeau et al., 2017). However, theglobality of this signal has not been established yet owing to a lack of data from Panthalassicsites, especially in the paleo-Southern Hemisphere. Work in progress on the Hg cycle of theArroyo Malo Formation may provide a key test of the globality ofpaleoclimatic/paleoenvironmental changes associated with the CAMP eruptions.