Glacial diamictites of Serra Azul Formation (Ediacaran, Paraguay belt): Evidence of the Gaskiers glacial event in Brazil

Abstract

Discontinuous outcrops of diamictites and siltstones are found above post-Marinoan carbonates from the Araras Formation and represent the record of a second glaciation in the northern Paraguay belt, Brazil. This new stratigraphic unit, named the Serra Azul Formation, varies in thickness between 250 and 300 m; it lies on top of dolomites of the Araras Group and is overlain by sandstones of the Raizama Formation. Massive diamictite, approximately 70 m thick, composes the basal unit (Unit A), followed by 200 m thick laminated siltstones (Unit B), which contain sparse intercalations of very fine-grained sandstone lenses. This new diamictite level is probably related to the Gaskiers Glaciation, with an age of approximately 580 Ma, and represents the youngest Neoproterozoic glacial event recorded in South America.