November 30 , 2016:

Highlights

Maimará is one of the most important ichnosites of the Late Cretaceous in the Central Andes.
The trace fossil assemblage is presented into their palaeoenvironmental context.
It represents a lagoon shoreline associated with a playa-lake system.
A comprehensive discussion on continental ichnofacies model is presented.

Abtsract

The shoreline carbonate lagoon deposits of the Yacoraite Formation in the Maimará locality, in the Quebrada de Humahuaca (Jujuy, northwestern Argentina) reveal vertebrate and invertebrate trace fossils that are distributed in two distinct sub-environments: (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 (playa-lake system). In the S-LI zone there are three softground suites: suite I, composed of Skolithos linearis and dinosaur tracks (Hadrosauropodus isp., titanosaurian, ornithischian, and theropodan tracks); suite II, composed of monoichnospecific tiers with cf. Taenidium isp.; and suite III, constituted by abundant didactyl tracks maybe belonging to swimming tracemakers. The trace fossils of the PL zone include: suite I, composed of Lockeia siliquaria and ?Ptychoplasma isp., and suite II, composed of Palaeophycus tubularis and Planolites cf. montanus with 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) have 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 Maimará are ascribed in general sense to the Scoyenia Ichnofacies; that in the current state of knowledge characterizes lake-margin areas, being present in both open and closed lacustrine basins, and in both ephemeral and perennial lakes. However, and following the current knowledge, the trace fossils of the playa-lake zone are assigned to the Shorebird ichnosubfacies.