Middle Jurassic crustacean microcoprolites and their association with terebellid polychaetes in prodelta deposits from the Neuquén Basin, Argentina

Abstract

We present the oldest record of crustacean microcoprolites in the Neuquén Basin, and the first record of these coprolites for the Bajocian–Callovian of South America. They correspond to three crustacean microcoprolite ichnospecies in prodelta and turbiditic fan facies from Los Molles Formation: 1) Octotriangulella bonenburgensis Blau, Lukas and Stein from the upper Bathonian - lower Callovian (Rotundum and Vergarensis Standard Zones), 2) Palaxius salataensis Brönnimann, Cros, and Zaninetti, from the upper Bathonian (Steinmanni Standard Zone), and 3) Parafavreina ziczac Rindsberg and Kopaska-Merkel from the upper Bathonian (Steinmanni Standard Zone). Octotriangulella bonenburgensis also occurs in association with terebellid agglutinated polychaetes that make use of these coprolites to build the wall of their tubes. Sedimentological evidence indicates that microcoprolites were transported from shallower waters, whereas the presence of terebellids indicates dysoxic, low-energy microenvironments within prodelta facies with high sedimentation rates.