Trace fossils from Furnas formation (Paraná Basin) reveal a marine depositional environment

Trace fossils are important biogenic signatures in sedimentary environments because they indicate the paleoecologic controls during deposition. In some cases, trace fossils are the unique preserved biologic evidence, allowing to infer paleoenvironments in controversial stratigraphic units. This is the case of Furnas Formation from Paraná Basin, Brazil. This unit was widely interpreted as fluvial-generated up to 1990's, but facies association analysis and the ichnologic data have been used as tools to suggest a marine origin for the unit. However, some recent studies have been ignored that information and continuous to interpret Furnas Formation as a fluvial-generated unit. In this study we analyzed some outcrops at northeast of the Ponta Grossa Arch aiming to infer depositional processes and paleoenvironments for basal and intermediated units of Furnas Formation (Lower Silurian). Nine ichnotaxa (Cruziana, Didymaulichnus lyelli, Didymauliponomos rowei, Heimdallia chatwini, Palaeophycus tubularis, Rusophycus, Skolithos, Taenidium dieslingi, and Thalassinoides) expressing proximal and depauperate Cruziana ichnofacies were reported for the studied outcrops, corroborating the shallow marine paleoenvironment inferred for the unit. •The Furnas Formation presents Cruziana ichnofacies.•Lower and middle units of Furnas Formation were deposited in Lower Silurian.•Trace fossils from Furnas Formation indicate a shallow marine depositional setting.