First record of the Coprinisphaera Ichnofacies Genise et al., 2000, in Chile: diversity and paleoenvironmental interpretation

BOSTELMAN, J. E.; BELLOSI E. S.; BOBE, R.; ALLOWAY, B.

Valdivia

Simposio; IV Symposium Paleontology in Chile; 2014

Symposium Paleontology in Chile

The middle Miocene pyroclastic deposits of the Río Frías Formation (RFF) in the AltoRío Cisnes are well-known for its vertebrate fossils of the Friasian SALMA (Ameghino, 1906).Our current investigations in the RFF also show the existence of an outstanding fossilichnocoenoces constituted by insect nesting structures, galleries and root traces preservedmostly in distinctly developed paleosols (Bellosi et al., 2014). The biogenic structures displaylow diversity, good preservation, and low to moderate abundances in their hosting beds. Abrief account on the taxonomic diversity includes the classic dung-beetle brood ball chambersof the genus Coprinisphaera, represented by three ichospecies: C. murguiai, C. lazai andprobably C. akatanka. Directly associated are small to medium size specimens of Celliformasp. representing nesting cells of solitary bees. In one outcrop (locality 17) basal paleosolsdisplays horizons with Teisseirei barattinia, an elongated and horizontally-placed, walled trace,referred to pupation chambers of sphinx moths (Genise et al., 2013). Less numerous arespecimens of Feoichnus challa, pan-shaped burrowing traces of cicadas. Irregular mediumsizedgalleries present almost exclusively in pyroclastics mudflows are interpreted asexcavated by small-size mammals or crayfish (parastacid) crustaceans. Rhizoliths are quitecommon, mostly in the lower and middle sections (i.e., base of locality 10). The depositionalsettings, taxonomic identity and type of paleosols support the occurrence of theCoprinisphaera ichnofacies in the RFF as previously indicated by Bostelmann et al., (2012),allowing the identification for the first time this archetypical association in Chile. Following theedaphic and ichnological features recorded, a mixed environment covered by open(mediterranean/ sclerophyllous type?) forests and grasslands, under a warm-temperate, humidto sub-humid and seasonal climate, is suggested.