The Permian-Triassic boundary in Northern Patagonia (Argentina): Geochronological and palaeobiolontological issues of the Los Menucos Basin

Abstract

In the last five years, a profound revision of the stratigraphy and geochronology of northern Patagonia has been carried out. The volcanic and sedimentary succession of the LosMenucos Basin has become the focus of paleontological and geochronological studies to determine and correlate the Permian-Triassic boundary in Argentina. Luppo et al. (2018) have initially proposed a correlative of the P-T boundary (Fig. 1) within a 6 km thick concordant volcanic and sedimentary succession, which was dated between 257 ± 2 and 248 ± 2 Ma (SHRIMP U-Pb inzircon). More recently, Falco et al. (2020, 2022a, 2022b) revised the volcanic and sedimentary stratigraphy of the same succession, proposing the existence of a low angle unconformity betweenthe volcanic and sedimentary beds. With this unconformity in mind, a novel stratigraphic scheme for the Los Menucos Group was proposed, in which the P-T boundary is expected to be foundwithin the succession because it was constrained between 253 ± 3 (LAICMPS U-Pb in zircon) and 250 ± 2 Ma (see further details in Falco et al., 2020, 2022b).