Jaibaras trough: an important element in the early tectonic evolution of the Parnaı́ba interior sag basin, Northern Brazil

Abstract

The Jaibaras Trough (JT) is a late Precambrian to Early Paleozoic basin that is related to the subsequent formation of the Paleozoic–Mesozoic Parnaı́ba intracratonic basin in northern Brazil. Based on available geological and geophysical data, we propose that the JT is a prototypical rift basin formed by brittle reactivation processes along ancient shear zones associated with the NE–SW Transbrasiliano Lineament of the Brazilian–Panafrican Orogeny. The JT evolution is partially constrained by the stratigraphic sequences outcropping at the border of the basin or drilled by exploratory boreholes. The preserved sedimentary column records, in a broad sense, the sedimentary and tectonic controls on the early subsidence in the Parnaiba Basin. These sequences are constituted by basal fault-scarp-related paraconglomerates followed laterally and vertically by fluvial–lacustrine sandstones interbedded with reddish shale. The JT geological evolution is also constrained by petrology of four magmatic events (Coreaú Dike Swarm, Mucambo and Meruoca plutons and mafic Parapuı́ Suite) related to continental rifting. The Late Precambrian–Early Paleozoic age of JT is perfectly compatible with continental fragmentation during the processes of lithospheric stretching that affected western Gondwana at that time. The contemporaneous development of a magmatic-sedimentary system, dated as Cambrian to Ordovician and confined to the rift trend, raised the thermal gradient and produced a mantle softening discontinuity, giving rise to a broad uplifted region. This might explain the close temporal and spatial association between the Transbrasiliano Lineament and the Early Paleozoic depositional axis of the Parnaı́ba Basin. An integrated interpretation of the JT and the early tectonostratigraphic behaviour of the Parnaı́ba Basin indicates that the JT might constitute a precursory stage that was slightly inverted before the initiation of sag deposition in the intracratonic basin.