The Maastrichtian–Danian Maimará tracksite (Yacoraite Formation, Salta Group), Quebrada de Humahuaca, Argentina: environments and ichnofacies implications

Abstract

The shoreline carbonate lagoon deposits of the Yacoraite Formation in the Maimará locality, Quebrada de Humahuaca (Jujuy, northwestern Argentina) reveal invertebrate and vertebrate trace fossils that are distributed in two distinct subenvironments: (A) the subtidal-lower intertidal zone (S-LI), a moderate/high energy shoreline under wave and tide action, and (B) the playa-lake zone (PL), a protected supratidal/eulittoral zone that characterizes low energy ephemeral bodies of water. In the S-LI zone there are three suites: I, composed of Skolithos linearis and dinosaur tracks (Hadrosauropodus isp., titanosaurian, ornithischian and theropod tracks); II, composed of monoichnospecific tiers with cf. Taenidium isp.; and III, constituted by abundant didactyl tracks maybe belonging to swimming tracemakers. The trace fossils of the PL zone are included in two suites: I, composed of Lockeia siliquaria and ?Ptychoplasma isp., and II, composed of Palaeophycus tubularis and Planolites cf. montanus with avian tracks (cf. Alaripeda isp.; Avipeda isp., cf. Gruipeda isp., cf. Yacoraitichnus avis) and indeterminate biped dinosaur tracks. The invertebrate trace fossils in both zones (S-LI and PL) display low ichnodiversity and are restricted to the shallow tier with substrate penetration of a few centimeters, which is characteristic of an unfavorable environment for the establishment of a permanent benthic community. Dinosaur tracks were preserved in an “optimal preservation area”, located in between both zones. The trace fossils of the S-LI zone are ascribed in general sense to the Scoyenia and Skolithos Ichnofacies. Following the current knowledge, the trace fossils of the PL zone are assigned to the shorebird ichnosubfacies, within the Scoyenia Ichnofacies.