Tetrapod tracks taphonomy in eolian facies from the Permian of Argentina

MARSICANO, CLAUDIA; OTTONE, EDUARDO; MANCUSO, ADRIANA; BENAVENTE, CECILIA; KRAPOVICKAS, VERONICA; DE LA FUENTE, M.

PALAIOS

SEPM-SOC SEDIMENTARY GEOLOGY

Lugar: Lawrence; 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 detailedsedimentological study of the trackway-bearing levels, in order to find evidence of processes that may have enhancedtheir preservation. We defined four taphonomic modes based on preservation quality, and the morphological andextra-morphological features of the footprints.Mode 1 includes footprints with detailed impressions of the palm, digitsand claws. Mode 2 includes tracks with palm and digit impressions associated with small bulbous-shape marginalrims. Mode 3 includes tracks characterized by large, bulbous, marginal rims and randomly preserved palmimpressions. 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 slippingdown-slope structures and (2) subsurface damp sand, evidenced by digit impressions and claw drag traces. Also, wefound vertical water content variations along the dune foresets, evidenced by a varying amount of sediment slippingdown-slope in the same trackway. Moreover, differences in the time of entombment are suggested by the morphologyof rims (bulbous-shape or sand-crescent). The stratigraphic genetic framework resulting from the Los Reyunostaphonomic analysis supports changes in the interstitial subsurface water and rapid entombment of the trackingsurface due to a high rate of sediment supply as the main factor for footprint preservation.