Supercritical Flow Bedforms Related to the Late Paleozoic Ice Age in the Paraná Basin: An Archive to Be Explored

The recent increase in available data on upper-flow regime bedforms in glacigenic settings improved our understanding on the relationship between ice-marginal and proglacial deposits and associated meltwater discharges, thereby enhancing our knowledge on near-critical and supercritical flow morphodynamics. Concerning the Late Paleozoic Ice Age (LPIA), previous papers have reported large-scale, unusual bedforms from Carboniferous and Permian sandstones of the Itararé Group (Paraná Basin). However, by the time of these reports, knowledge on supercritical flow bedforms was incipient, hampering an accurate interpretation of these structures. To improve the characterization of these deposits, we present a dataset of sandy and gravelly bedforms suggesting supercritical-flow conditions. The Itararé Group comprises multiple glaciation-deglaciation episodes characterized by thinning-upward packages containing sandy/conglomeratic bodies at the base which are capped by mudstones and diamictites. In several of these sandy-gravelly deposits we observe characteristics related to high-discharge events materialized in scours filled by metric sets of cross-bedded facies. Some of the internal stratifications of these bodies may exhibit sub-parallel, sinusoidal, and lenticular laminations resulting from the deposition of near-critical and supercritical bedforms. In addition, climbing mega-ripples in coarse-grained sediments (up to pebbles) suggest high magnitude, flood-related flows. These preliminary observations demonstrate that the Paraná Basin is an open field for the investigation of upper-flow regime bedforms, whose analysis could improve the understanding of paleoenvironmental conditions during the LPIA.