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| Solimões Basin | |
|---|---|
| Name | Solimões Basin |
| Location | Amazonas, Brazil |
| Type | intracratonic sedimentary basin |
| Area | ~1,000,000 km² |
| Named for | Solimões River |
Solimões Basin is a major intracratonic sedimentary basin in northwestern Brazil underlying parts of the Amazon Basin and adjacent to the Andes foreland. The basin records Neoproterozoic to Cenozoic sedimentation and hosts significant petroleum systems that have drawn exploration by companies such as Petrobras, Repsol, and Shell plc. It interacts with regional elements including the Amazon River, the Bolivian Orocline, and the South American craton.
The basin lies on the western Amazonian craton adjacent to the Precambrian shield exposures and is bounded to the west by the active deformation of the Andes Mountains and to the north by the Guiana Shield. Regional mapping links the basin to Pan-African orogenic remnants correlated with the Sao Francisco Craton and the Cauca-Patía Basin provinces. Basement control involves shear zones related to the Trans-Amazonian Orogeny and the Brasiliano orogeny, influencing basin architecture and structural highs comparable to features in the Borborema Province.
Stratigraphic frameworks compile units from the Neoproterozoic through the Cenozoic, with major divisions comparable to successions in the Solimões Group nomenclature used in Brazilian stratigraphy. Notable units include siliciclastic successions analogous to the Içá Formation, carbonate intervals correlated with the Marília Formation in adjacent basins, and extensive Cenozoic alluvial and floodplain deposits. Biostratigraphic and chemostratigraphic correlations employ markers used across South America such as palynological assemblages tied to the Aptian–Albian and Paleogene stages referenced in global schemes by the International Commission on Stratigraphy.
Tectonic history involves intracratonic subsidence, flexural loading from the Andean orogeny, and far-field stresses from the opening of the South Atlantic Ocean. Early rift-related subsidence is comparable to events seen in the Paraná Basin and influenced by the breakup of Gondwana and motions recorded in the South American Plate. Cenozoic reactivation produced growth-fault systems and listric faults similar to structures in the Chaco Basin, with inversion related to Andean shortening and foreland flexure documented in regional seismic surveys by industry and academic groups such as CPRM and Brazilian universities.
Sedimentary facies range from deep lacustrine shales to fluvial channel sandstones and widespread floodplain overbank fines, comparable to facies models developed for the Amazon Fan and Solimões River archives. Paleosol horizons and coal seams indicate intervals of peat accumulation analogous to occurrences in the Roraima Basin, while evaporitic and palustrine deposits record climatic oscillations mirrored in records from the Paleogene of Peru and the Neogene of Colombia. Provenance studies link detritus to uplifted sources in the Eastern Cordillera and Precambrian shields, supported by detrital zircon age spectra comparable to datasets from the Congo Craton correlations.
Hydrocarbon systems include Triassic–Jurassic to Cretaceous source rocks, reservoir-quality fluvial sandstones, and regional seals formed by marine shales and altered floodplain clays. Exploration by Petrobras and international operators has targeted structural traps and stratigraphic pinch-outs analogous to discoveries in the Reconcavo Basin and Campos Basin. Play types mirror those in other South American foreland and intracratonic settings such as the Maranhão Basin, with risks from lateral seal continuity and thermal maturity influenced by burial history and heat flow variations related to Andean uplift studies by researchers affiliated with UFRJ and USP.
The basin preserves terrestrial and freshwater fossil assemblages including palynomorphs, freshwater bivalves, and vertebrate remains comparable to those recovered from the Ituzaingó Formation and Neogene localities in Acre. Palynological records provide biostratigraphic control tied to regional chronostratigraphic schemes used by institutions such as the Brazilian Geological Survey. Occurrences of fossil mammals and reptiles contribute to correlations with South American Land Mammal Ages recognized in the SALMA framework, aligning with faunas described from Argentina and Bolivia.
Surface and subsurface hydrography are integrated with the Amazon River drainage system and seasonal dynamics of the Solimões River flood pulse, affecting sediment delivery and organic matter preservation similar to dynamics documented for the Amazon floodplain and the Marañón River. Climate influences spanning the Neogene and Quaternary include monsoonal variability linked to the uplift history of the Andes and paleoclimatic signals comparable to records in the Lake Titicaca basin and marine sediments off the Brazilian coast. Modern hydrological studies involve agencies such as ANA (Brazil) and research groups at INPA examining links between basin sedimentation, fluvial processes, and regional biodiversity patterns described by the Instituto Nacional de Pesquisas da Amazônia.
Category:Geology of Brazil Category:Sedimentary basins of South America