The depositional model of the Cabeças Formation is re-evaluated in the context of the Devonian paleogeography of the Parnaíba Basin, and with particular reference to similarities between the formation's facies associations on the eastern border of the basin and the flood-dominated fluvio-deltaic system facies that have been discussed in recent literature. The widespread occurrence and nature of sigmoidal clinoforms (with asymptotic cross-stratification and climbing ripples) of the Cabeças Formation are here considered as strong evidence of flood-influenced depositional settings. Sandy strata of the Passagem Member, in the vicinity of Pimenteiras and Picos (Piauí State), are interpreted as the distal part of fine-grained mouth-bar deposits interbedded with delta-front sandstone lobes showing hummocky cross-stratification. Richly fossiliferous levels, with diverse megainvertebrates and plant cuticles, occur within the delta-front lobes and the distal mouth-bar deposits, reflecting continuation of shallow marine conditions.
Parnaíba Basin; Devonian; Cabeças Formation; flood-dominated fluvio-deltaic system; delta-front sandstone lobes; mouth-bar deposits; hummocky cross-stratification
