Late Pleistocene–Holocene stress in the South American intraplate evidenced by tectonic instability in central Amazonia

Abstract

Documenting neotectonic instabilities and determining the style and time of deformation in the vast and difficult to access central Amazonia region is challenging. We focus on these issues by investigating a large area of the Negro River drainage basin, applying morphostructural analysis based on synthetic aperture radar data. The digital elevation models of the C-band Shuttle Radar Topography Mission and the L-band Protection System of Amazonia were used as the database. We also used subsurface magnetic information from the Earth Magnetic Anomaly Grid global model to validate the morphostructures. The results revealed NW-oriented morphostructural lineaments bounding multiple depositional valley fills. These were extensively fragmented to form regularly distributed en échelon rectangular blocks commonly offset horizontally by several kilometers. Strike-slip faults and oblique, either normal or reverse, faults are present. These structures were reactivated along the main NE- and SW-oriented regional structural trends due to N-S-oriented horizontal compression and E-W-oriented horizontal extension in the late Pleistocene and Holocene. The extensive neotectonic faulting results from the interplay of plate motion and Andean uplifting since the late Pleistocene, combined with local stresses.

The Acre Basin basement (NW Brazil) and the transition from the intracratonic to retroarc foreland basin system

“…On the other hand, the deeper structures tend to approach the sub‐Andean trends (Figure 12c,d), indicating that the Andean deformation may have affected only the deep basement of the Acre Basin, without major implications for shallower depths. Despite the record of dozens of earthquakes in the Acre Basin (Chamani, 2020; Miotto, 1993; Santos et al, 2019), it was not possible to correlate the magnetic lineament trends with the tectonic structures reactivated during the Quaternary in Amazon (Costa et al, 1996; Rossetti, 2014; Rossetti et al, 2021). The occurrence of a granitic block about 70 km long in the modelled profile of the basin southern portion (Figures 4 and 14), differs from the other granitic intrusions and suggests the occurrence of smaller allochthonous crustal blocks related to Rodinia accretion in a pre‐Sunsás tectonic context analogous to the Paragua Block (Boger et al, 2005) in northern Bolivia (Figure 1).…”

Morphostructural influence and neotectonic activity in the geomorphological configuration of southeast Paraíba and northeast Pernambuco, Brazil

“…The evolution of terrain in northeastern Brazil has predominantly been attributed to climatic influences, given the region's location on the eastern passive margin of South America. Nonetheless, an expanding body of research indicates that Neogene and Quaternary tectonic reactivations have significantly contributed to the formation of terraces in this area [ 14 , 15 ]. The Paraíba Basin is of particularly noteworthy for its neotectonic records in eastern South America, attributed to its late disconnection from the African plate [ 16 ].…”