The Altiplano Cundiboyacense, in the Eastern Ranges of the Colombian Andes, was formed late in the regional uplift of the Andean orogeny. It is estimated that the main stage of uplift happened during the Plio-Pleistocene. The Western and Central Ranges were submerged much earlier, leaving a corridor to the Caribbean in the Neogene.
The compression in the Andean orogenic belt caused the formation of fold and thrust belts in the Eastern Ranges, where Cretaceous and Jurassic normal faults were inverted as thrust faults lifting up the Paleozoic (Floresta and Cuche Formations), Mesozoic and Paleogene strata. A hiatus existed on the Altiplano between the Late Eocene and Late Miocene, in several parts of the Altiplano continuing until the Pleistocene.
During the glacials and interglacials of the Pleistocene ("ice ages"), several paleolakes formed on the Altiplano Cundiboyacense, of which Lake Humboldt on the Bogotá savanna was the most extensive (approximately 4,500 square kilometres (1,700 sq mi)). Rivers were restricted during the drier glacial periods and the vegetation changed from páramo to Andean forest between the glacials and stadials and interglacials and interstadials.[2]
The middle, younger unit is composed of basal greyish claystones with non-uniform matrix-supportedconglomerates at the upper section. The uppermost layer contains siltstones, probably of volcaniclastic origin.[3]
The youngest sediments are found deepest in the basin and consist of claystones and greenish matrix-supported conglomerates. Rootlets and mammal fossils are more abundant in this layer.[3]
Stratigraphy
The Soatá Formation unconformably overlies the CretaceousCapacho Formation, and is overlain by the Holocene infill sediments of the Chicamocha River, the course of which severely eroded and fragmented the Soatá formation.[4] The formation is subdivided into three units of different lithological character and sedimentary dip in a terrace setting. The Soatá Formation is time-equivalent with the upper part of the Sabana Formation on the Bogotá savanna and the Chinauta deposits near Fusagasugá in the southwest of the Altiplano.[5][6] Two samples were analysed for radiometric dating and provided ages of 45,900 ± 1,600 and 39,600 ± 800 years BP.[7] This corresponds to the Chicagota interstadial and the Tagua stadial, when the glaciations were at their maximum extent.[8][9]
Depositional environment
The depositional environment has been interpreted as lacustrine (Lake Soatá) and fluvio-deltaic. Contrasting with the wide and shallow Lake Humboldt on the Bogotá savanna, Lake Soatá was probably close to 400 metres (1,300 ft) deep.[10] The paleolake was approximately 30 kilometres (19 mi) long and widest between Soatá and Boavita at 7 kilometres (4.3 mi).[11]
Type locality of the Soatá Formation to the northeast of the Altiplano Cundiboyacense. The Chicamocha River valley is clearly visible.
The Soatá Formation is apart from its type locality Portugalete found around Soatá (Jútua), and stretches to the north near the border of Boyacá and Santander, northeast of Tipacoque. To the south, the formation may have reached until Socotá.[10]
Regional correlations
Stratigraphy of the Llanos Basin and surrounding provinces
Van der Hammen, Thomas (1986), "Cambios medioambientales y la extinción del mastodonte en el norte de los Andes", Revista de Antropología, Universidad de los Andes, II: 27–34
Hoyos, Natalia; Monsalve, O.; Berger, G.W.; Antinao, J.L.; Giraldo, H.; Silva, C.; Ojeda, G.; Bayona, G.; Escobar and C. Montes, J. (2015), "A climatic trigger for catastrophic Pleistocene–Holocene debris flows in the Eastern Andean Cordillera of Colombia", Journal of Quaternary Science, 30 (3), John Wiley & Sons, Ltd.: 258–270, Bibcode:2015JQS....30..258H, doi:10.1002/jqs.2779
Rutter, N.; Coronato, A.; Helmens, K.; Rabassa, J.; Zárate, M. (2012), Glaciations in North and South America from the Miocene to the Last Glacial Maximum, Springer, pp. 1–67
Urrego, Dunia H.; Hooghiemstra, Henry; Rama Corredor, Oscar; Martrat, Belén; Grimalt, Joan O.; Thompson, Lonnie; Bush, Mark B.; González Carranza, Zaire; Hanselman, Bryan Valencia and César Velásquez Ruiz, Jennifer (2016), "Millennial-scale vegetation changes in the tropical Andes using ecological grouping and ordination methods", Climate of the Past, 12 (3): 697–711, Bibcode:2016CliPa..12..697U, doi:10.5194/cp-12-697-2016, hdl:10871/20575