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

KRAPOVICKAS, VERONICA; MANGANO, MARIA GABRIELA; MANCUSO, ADRIANA; MARSICANO, CLAUDIA; VOLKHEIMER, WOLFRANG

AMEGHINIANA

APA

Lugar: Buenos Aires; Año: 2008 vol. 45 p. 463 - 472

0002-7014

Alluvial fan deposits of the Cerro Puntudo Formation (Triassic, Cuyo Basin, San Juan province) contain a low-diversity ichnofauna. The analyzed section records 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 sandstone, filling small channelized bodies, hosts 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.