Magnetostratigraphic and sedimentological insights into the Late Campanian Uberaba Formation of the Bauru Group, southeast Brazil

Abstract

The Uberaba Formation, a significant paleontological site within the Bauru Group, was deposited over the Early Cretaceous volcanic rocks of the Paraná Basin in southern Brazil. It occupies a restricted northeastern area of the basin surrounding the homonymous city. Recent works on stratigraphy and paleontology indicate a Campanian age, a novel finding that challenges the previously held belief of a Cenomanian age based on dinosaur bones. Paleomagnetic work on seven sections of the Uberaba formation has resulted in the calculation of a paleomagnetic pole at 82.2°S 350.8°E (N = 89; k = 23; A₉₅ = 3.2°) after correcting for the shallowing of the magnetic inclination caused by overload. The formation is dated to ∼73 Ma (Campanian) age based on magnetostratigraphic data and comparisons with other Late Cretaceous poles. This age implies an interval of about 40 Myr separates the deposition of the Uberaba and Caiuá formations– the latter being the first post-magmatic sedimentation in the Paraná Basin. The area stayed as a highland until the tectonic events related to the northward emplacement of the alkaline provinces. High deposition rates were determined, at least for the upper part of the formation, based on the magnetostratigraphic characteristics.