Evidence for Late Quaternary episodic uplift of the São Pedro and São Paulo Archipelago, Equatorial Atlantic

The São Paulo and São Pedro Archipelago (SPA) forms an emergent part of the São Paulo transform fault zone in the Equatorial Atlantic. In the present study, the uplift rate of this part of the transform in the Late Quaternary was investigated, in order to determine its origin. Uplift rates were determined by dating sedimentary and biological paleo-sea level indicators. The findings are: (a) paleo-sea level indicators yielded ages corresponding to the Late Pleistocene and Mid- to Late Holocene; (b) ages between 43.6 and 18.9 ka correspond to paleo-sea levels between >8.2 and >12.1 m above present sea-level, suggesting a maximum uplift rate of 3.3–2.9 and a minimum uplift rate of 0.8–1.2 mm/y; (c) the observation of a Pleistocene Megabalanus in the SPA provides a new piece of information for understanding the evolution and biogeography of the genus; (d) the ages of the Holocene sea-level indicators range between 6.2 ka and near-present (<100 years) and their altitudes range from 1.0 ± 1.0 m to >13.3 m, which are higher values than for Mid- to Late Holocene eustatic sea-level, suggesting strong uplift for that period and (e) different rates of lowering of sea-level for the last 6.2 ka; (f) ages and paleo-sea level also suggest that almost instantaneous uplifts of 3 and 2 m could have occurred at approximately 2.5 and 0.2 ka; (g) the rates of change in sea-level indicate a clear pattern of episodic uplift, which is typical of related coseismic movements in a stick-slip mode; (h) this scenario implies that the area could be affected by medium to large earthquakes (mb > 5.4), where a vertical displacement of 2–3 m could occur.