STUDIES OF THE TRIASSIC/JURASSIC BOUNDARY IN ARGENTINA: A REVIEW AND PROSPECTIVE

The Triassic/Jurassic boundary (TJB) in Argentina is represented mainly by continental sediments deposited in fluvial, lacustrine, deltaic and alluvial environments, with locally important deposits of volcanic and volcaniclastic rocks. They have been previously studied by Spalletti (1997) and Stipanicic (2002), among others. The Arroyo Malo Formation is the only known marine deposit of Triassic age in Argentina. It represents a transgressive event within the Atuel-Valenciana Rift, in the northwestern sector of the Neuquén Basin (Mendoza Province, central-western Argentina), which formed during the initial subsidence stage of that basin. These fine-grained marine rocks were first described by Riccardi et al. (1997), and subsequent study of their ammonoid, bivalve, and brachiopod faunas has demonstrated a mid-Rhaetian to Hettangian age (Riccardi & Iglesias Llanos, 1999; Damborenea & Maceñido, 2005). Detailed facies analysis showed that the Arroyo Malo Formation was deposited in an offshore setting into which fine-grained siliciclastics were delivered by low-density turbidite flows (Lanés, 2002; Lanés et al., 2005; Spalletti et al., 2005). Renewed interest in these deposits arises from their potential to provide a window into oceanic chemical and environmental conditions in the southern Panthalassic Ocean during the Triassic-Jurassic transition. Recently, studies of the Hg cycle revealed perturbations at the TJB that have been linked to CAMP volcanism (Percival et al., 2017; Thibodeau et al., 2017). However, the globality of this signal has not been established yet owing to a lack of data from Panthalassic sites, especially in the paleo-Southern Hemisphere. Work in progress on the Hg cycle of the Arroyo Malo Formation may provide a key test of the globality of paleoclimatic/paleoenvironmental changes associated with the CAMP eruptions.