Trace fossil analysis in the Miocene Pindamonhangaba Formation, Taubaté Basin

Abstract

The Taubaté Basin comprises continental deposits formed within the central segment of the Continental Rift of Southeastern Brazil. The paleontological record of this basin is limited to the lacustrine deposits of the Tremembé Formation, with rare fossil evidence from other units. The Pindamonhangaba Formation, likely of Miocene age, was deposited in a meandering fluvial system during a post-rift phase. While its sedimentological and stratigraphic aspects are well-documented, trace fossils have not been described in this basin. Trace fossil analysis offers valuable insights into paleoenvironmental reconstructions, as they are generally preserved in situ and reflect the behavior of tracemakers, which is controlled by paleoecological parameters. Consequently, trace fossil studies are essential for interpreting paleoenvironmental conditions concurrent with or subsequent to sediment deposition. This study aims to characterize the ichnoassociations of the Pindamonhangaba Formation using a paleoecological approach. A 33-meter-thick section in Taubaté city, composed predominantly of mud-rich deposits with pedogenic features interbedded with sandy channel deposits, reveals diverse trace fossils. These include Skolithos, Taenidium, and Palaeophycus in sandstones; Skolithos, Palaeophycus, Beaconites, and Vondrichnus in pedogenized mudstones; and rhizoliths. The ichnological record reflects the dominance of Scoyenia ichnofacies (composed of Skolithos, Palaeophycus, Taenidium, and Beaconites), indicating a transition from subaqueous to subaerial conditions, and a single level with of the Termitichnus ichnofacies (Vondrichnus, Beaconites), indicating a greater paleoecological stability in paleosols, likely influenced by lateral changes in depositional settings.

Keywords: Scoyenia ichnofacies, Termitichnus ichnofacies, meandering river, Taenidium, Vondrichnus.