Post-rift regional volcanism in southern Santos Basin and the uplift of the adjacent South American coastal range

摘要

The Serra do Mar coastal mountain range plays a crucial role in the sedimentary budget of both the South American continent and its adjacent Atlantic margin. This 1500-km range began to rise during the Late Cretaceous. The uplift prevented the direct input of sediments from the continent to Santos Basin, thus diverting the Parana River drainage inland and southwards. However, the cause for the uplift is still debated: distinct phases of the Andean orogeny, thermal activity of the Trindade hotspot, and a general thermal weakening caused by earlier mantle plume activity. The current study attempts to explain the uplift initiation by introducing a previously unknown 150-km wide magmatic cluster discovered in multichannel seismic reflection data across the southern Santos Basin. The newly discovered "Santos cluster" includes plutons, sills, and volcanic edifices within the Turonian-Campanian stratigraphic interval, indicating an Early Campanian magmatic phase. We suggest that the widespread magmatism uplifted the southern Santos Basin, and included lateral NNE salt migration. The marine magmatism occurred along with previously reported Campanian volcanic activity in three localities along the Serra do Mar, which uplifted the coastal range and diverted the drainage inland (westward). We suggest that both marine and continental magmatism relate to the SW sub-crustal flow of the Trindade hotspot head.