TETRAPOD TRACKS TAPHONOMY IN EOLIAN FACIES FROM THE PERMIAN OF ARGENTINA

MANCUSO, ADRIANA CECILIA; KRAPOVICKAS, VERONICA; MARSICANO, CLAUDIA; BENAVENTE, CECILIA; BENEDITO, DARIO; DE LA FUENTE, MARCELO; OTTONE, EDUARDO G.

PALAIOS

SEPM-SOC SEDIMENTARY GEOLOGY

Año: 2016 vol. 31 p. 374 - 388

0883-1351

Ancient desert deposits preserve a copious ichnofossil record, particularly Permian-age deposits wherethe record of tetrapod footprints is present and abundant in almost all desert settings. We propose to analyze, from ataphonomic perspective, Permian footprints preserved in eolian deposits from Argentina with a detailed sedimentological study of the trackway-bearing levels, in order to find evidence of processes that may have enhanced their preservation. We defined four taphonomic modes based on preservation quality, and the morphological and extra-morphological features of the footprints.Mode 1 includes footprints with detailed impressions of the palm, digits and claws. Mode 2 includes tracks with palm and digit impressions associated with small bulbous-shape marginal rims. Mode 3 includes tracks characterized by large, bulbous, marginal rims and randomly preserved palm impressions. Mode 4 includes footprints with shallow digit and palm impressions associated with sand-crescentmarginal rims. The Los Reyunos footprints suggest preservation in: (1) dry sand, evidenced by sediment slipping down-slope structures and (2) subsurface damp sand, evidenced by digit impressions and claw drag traces. Also, we found vertical water content variations along the dune foresets, evidenced by a varying amount of sediment slipping down-slope in the same trackway. Moreover, differences in the time of entombment are suggested by the morphology of rims (bulbous-shape or sand-crescent). The stratigraphic genetic framework resulting from the Los Reyunos taphonomic analysis supports changes in the interstitial subsurface water and rapid entombment of the tracking surface due to a high rate of sediment supply as the main factor for footprint preservation.