The sediment routing systems of Northern South America since 250 Ma

2022

Article référencé dans le Web of Science WOS:000843391900001

Bajolet F., Chardon Dominique, Rouby D., Dall'Asta M., Loparev A., Coueffe R., Roig J. Y.

Earth-Science Reviews, 2022, 232, 104139 [24 p.] ISSN 0012-8252

The present study is a contribution to the understanding of continental-scale source-to-sink sedimentary systems over geological time scales. The northern half of South America is taken as a case study to explore the relations between (i) continental tectonic boundary conditions (active / passive margin, orogenic activity) and intra-continental deformation, (ii) the spatial distribution of clastic sediment sources and sinks over the continent and its margins and (iii) the configuration of the main sediment routes. To do that, the evolving surface configuration of northern South America is investigated through a series of 10 paleo-geological maps compiled for key periods of the Meso-Cenozoic. The maps display (i) sedimentation areas and their depositional environments, (ii) sedi-ment transport routes based on paleocurrent measurements and provenance studies, (iii) magmatic occurrences, (iv) active faults, (v) denudation/burial histories deduced from low-temperature thermochronology studies and (vi) areas of extensive Cenozoic lateritic cover. Three main successive continental-scale regimes of the source-to-sink systems are documented. An early erosional regime until ca. 125 Ma is attested to by a major sedimentary hiatus over a long-lasting asthenosphere-supported eroding superswell at the scale of northern South America and northwestern Africa. Sediments were routed from the superswell to the proto-Andean marginal basins, the Central Atlantic rifts/rifted margin basins and the Saharan cratonic basin. After ca. 125 Ma, a cratonic regime of mixed erosion/deposition established and maintained until the onset of the Andean orogeny at ca. 85 Ma. During this period, sediment routes from eroding cratonic domains to the proto-Andean margin basins were episodically closed by inherited Paleozoic structures (i.e., ???arches???), whilst sediment fluxes to cratonic or rifted margin basins were partitioned by Atlantic rift shoulders / marginal upwarps of evolving amplitude that formed transient continental divides. After ca. 85 Ma, an Andes-dominated regime installed, in which Andean retro-foreland basins became the main sinks for orogenic sediment fluxes, while exchanges with cratonic basins were controlled by the topographic expression of foreland basins forebulges. Under that regime, cratonic domains mainly acted as by-pass zones for clastic sediments, and their extensive Paleogene and Lower Neogene lateritic covers argue for limited clastic exports from areas exposed to erosion. Very-long wavelength (x 1000 km) asthenospheric support, long-wavelength (x 100 km) lithospheric-scale deformation / vertical movements and climate-controlled erosion processes interacted to regulate cratonic sediment source-to-sink regimes of northern South America since 250 Ma.

Géologie et formations superficielles [064]

AMERIQUE DU SUD ; AMAZONIE ; ANDES

Fonds IRD [F B010085997]

fdi:010085997