The Quaternary stratigraphy of the Sao Paulo Basin, southeastern Brazil

Detailed sedimentological studies of the university main campus of Sao Paulo city, Brazil, revealed a significant unconformity at the top of the Cenozoic sedimentary deposits of the Sao Paulo Formation. This unconformity is overlapped by Quaternary sediments which can be traced in 1:20,000 scale and are here named as the Bosque Formation. This unit is characterized by poorly sorted mud deposits and very fine-grained red sand with granule- and pebble-sized clasts of the underlying Sao Paulo Formation. Furthermore, it overlies topographic highs of the Precambrian basement, and is laterally interfingered with fluvial terraces; it is eroded by the modern river at the lower reaches of the outcrops. The Bosque Formation records sedimentation characterized by a widespread mudflow that overlays old alluviums sediments, and was likely deposited during the beginning of the Holocene.