Large mammal burrows in late Miocene calcareous paleosols from central Argentina

MARÍA CRISTINA CARDONATTO; RICARDO NESTOR MELCHOR; FATIMA DEL ROSARIO MENDOZA BELMONTES; CLAUDIA MONTALVO

Indanha-a-Nova

Congreso; Ichnia 2016, Fourth International Congress on Ichnology; 2016

International Association of Ichnologists

Laminated burrow fills occurring in calcareous paleosols of the late Miocene Cerro Azul Formation of Argentina (Fig. 1) are described and interpreted. A total of 111 fossil burrows were studied from two localities: Salinas Grandes de Hidalgo and near Carhué (La Pampa and Buenos Aires provinces, respectively). The burrow fills are mostly composed of laminated claystone and siltstone that contrast with the structureless hosting siltstone or sandstone (Fig. 2). They exhibit a horizontal diameter ranging from 0.15 m to 1.50 m and a maximum preserved length of 8 m. Most burrow cross-sections are elliptical and the remaining are subcircular or plano-convex (Fig. 3). In plan view, burrow fills are slightly curved to sinusoidal and rarely U-shaped. Average angle of inclination is 8° (range= ≈0°-27°) and burrow openings were mainly facing west, similar to burrow orientation in extant armadillos. Frequency distribution of burrow horizontal diameter suggests a normal distribution with three subpopulations: 0.15-0.34 m (8%, body mass