Andean foreland basins

The Andean foreland basins or Sub-Andean basins are a group of foreland basins located in the western half of South America immediately east of the Andes mountains. The Andean foreland basins in the Amazon River's catchment area are known as the Amazonian foreland basins.

In part sediment accumulation, uplift and subsidence of the Andean foreland basins is controlled by transverse zones of "structural accommodation", likely corresponding to ancient continent-wide faults. From the Bolivian Orocline (20° S, also known as Arica Deflection or Arica Elbow) north these zones of accommodation runs with a NEE-SWW orientation and south of the orocline they run with a NW-SE orientation. The Andean foreland basins in Bolivia have largely accumulated continental sediments, most of them of clastic nature.

Beginning in 1920 the Ecuadorian and Peruvian basins were explored for petroleum and in the 1970s their hydrocarbon production increased greatly.

A 2018 synthesis of previous research looked at the sedimentary record of eight foreland basins and 5 hinterland basins to reconstruct a composite model for their development as a single Andean foreland basin system. During the Mesozoic, rapid accumulation of sediment occurred at the onset of back arc extension between 250 and 140 Ma. A dramatic pulse of sediment accumulation occurred during the late Cretaceous linked to the inception of large scale shortening, occurring from 70 to 60 Mya in the northern basins and 100-600 Mya in the southern basins. The Paleogene saw a phase of limited accumulation due to a lull of Andean shortening, 60-20 Mya in the south, 50-30 Mya in the north. From 20 to 30 Ma, rapid accumulation occurred with the highest sedimentation rate recorded in the central Andes, between 3–8 km of sediment was accumulated. Detrital Zircon data aided in identifying sediment source reversals from cratonic sediment sources to magmatic orogenic sources. This inflection occurred in the northern Andes from 70 to 30 Ma, depending on the basin, central Andes around 50 Ma, and in the southern Andes around 100 Ma. Interplay of local climate, uplift histories, shortening and subducting slab geometries influenced the development of individual foreland basins and shaped continent scale drainage patterns, offshore sediment dispersal and ecological development on the South American continent.