Icnofaunas triásicas en abanicos aluviales distales: evidencias de la Formación Cerro Puntudo, Cuenca Cuyana, Argentina

Verónica Krapovickas, María Gabriela Mángano, Adriana Mancuso, Claudia A. Marsicano, Wolfgang Volkheimer


Alluvial fan deposits of the Cerro Puntudo Formation (Triassic, Cuyo Basin, San Juan province)
contain a low-diversity ichnofauna. The analyzed section indicates sedimentation in the most distal portion of an
alluvial fan system. Palaeophycus tubularis Hall, Palaeophycus striatus Hall, and small sub-horizontal and inclined trace
fossils occur in laterally extensive tuffaceous limestone, interpreted as playa-lake deposits originated by flash
floods. They are attributed to the Scoyenia ichnofacies. Massive and trough cross-stratified medium- and fine-grained
sandstones, filling small channelized bodies, contains a monospecific association of sparse Skolithos isp. illustrating
the Skolithos ichnofacies. Low diversity, moderate abundance, and the presence of simple dwelling structures
suggest an opportunistic association. Based on cross-cutting relationships among biogenic structures and preservation
of morphological details, an evolution from a soft to a relatively firm substrate is proposed. Two suites
have been distinguished in connection to progressive dewatering of floodplain sediments: 1) Palaeophycus tubularis
Hall and small sub-horizontal and inclined trace fossils, developed in a soft substrate, and 2) Palaeophycus striatus
Hall associated with small sub-horizontal and inclined trace fossils, developed in a relatively firm substrate.

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