The Paso Flores Formation exposed in the Pancho creek is mainly composed of fine-grained sediments. The pelitic rocks have been deposited from aqueous suspensions in deep lacustrine settings. Some upward fining sequences from shale to sandstone represent shallower lacustrine (wave formed) bars. To the top of the PFF. clast-supported conglomerates and cross-bedded sandstones show the progradation of a braided fluvial system upon the lacustrine succession. The paleo- floristic association, composed of Corystosperms, Cycadals, Ginkgoals and Conifers, is characteristic for lacustrine deposits formed during the late Triassic.Facultad de Ciencias Naturales y Museo