Archosauriform footprints in the Lower Triassic of Western Alps and their role in understanding the effects of the Permian-Triassic hyperthermal

Abstract

The most accepted killing model for the Permian-Triassic mass extinction (PTME) postulates that massive volcanic eruption (i.e., the Siberian Traps Large Igneous Province) led to geologically rapid global warming, acid rain and ocean anoxia. On land, habitable zones were drastically reduced, due to the combined effects of heating, drought and acid rains. This hyperthermal had severe effects also on the paleobiogeography of several groups of organisms. Among those, the tetrapods, whose geographical distribution across the end-Permian mass extinction (EPME) was the subject of controversy in a number of recent papers. We here describe and interpret a new Early Triassic (?Olenekian) archosauriform track assemblage from the Gardetta Plateau (Briançonnais, Western Alps, Italy) which, at the Permian-Triassic boundary, was placed at about 11° North. The tracks, both arranged in trackways and documented by single, well-preserved imprints, are assigned to Isochirotherium gardettensis ichnosp. nov., and are here interpreted as produced by a non-archosaurian archosauriform (erytrosuchid?) trackmaker. This new discovery provides further evidence for the presence of archosauriformes at low latitudes during the Early Triassic epoch, supporting a model in which the PTME did not completely vacate low-latitude lands from tetrapods that therefore would have been able to cope with the extreme hot temperatures of Pangaea mainland.

The Alps-Apennines Interference Zone: A Perspective from the Maritime and Western Ligurian Alps

“…Similarly, in the Preit valley, the Permian (? )-Early Triassic quartzite have a marked gneissic structure (sample SRV in Figures 5 and 6b,d), while the quartzarenite and dolostone cropping out SW of the IBF, in the Rocca la Meja tectonic slice do not show evidence of major metamorphic transformations, as also suggested by the presence of preserved microfacies in the Triassic dolostone (sample PRE6, Figure 6e) and very wellpreserved Archosauriform footprints recently discovered [82] a few hundred meters from the IBF. The IBF cuts across the Middle-Upper Triassic evaporites and the Lower Triassic quartzite/quartzarenite layers, which, conversely, in the external (SW) part of the GVZ and in the fold and thrust belt comprised between the IBF and the Argentera northern boundary faults, are not displaced by high angle faults and seem to have played a role of regional detachment horizons.…”

Pre-Orogenic Tectonostratigraphic Evolution of the European Distal Margin-Alpine Tethys Transition Zone in High-Pressure Units of the Southwestern Alps

“…This succession corresponds to the "Werfenian quartzites" [47] and can be compared to the Ponte di Nava Quartzite, which represents the upper part of the Late Permian-Early Triassic Briançonnais Verrucano [86] in the Ligurian Alps (i.e., the southeastern prosecution of the Briançonnais Domain; Figure 1). Comparable siliciclastic metasediments also occur in the IBD successions [66], where their top has been referred to the Olenekian Stage based on local vertebrate footprints [87].…”