- Source: Geste Formation
The Geste Formation (Spanish: Formación Geste) is a fossiliferous geologic formation of the Puna Plateau in the western Salta Province and northern Catamarca Province of the Argentine Northwest, northwestern Argentina.
The formation, reaching a thickness of 1,500 metres (4,900 ft), is the oldest unit of the Pastos Grandes Group, underlying the Pozuelos Formation and unconformably overlying various Paleozoic formations. The Geste Formation comprises red sandstones and conglomerates deposited in a fluvial to alluvial environment. The formation was initially dated to the Mustersan (Middle Eocene), but subsequent research proved the formation to date to the Late Eocene (Divisaderan in the SALMA classification, ranging approximately from 42 to 36 Ma.
The Geste Formation has provided a faunal assemblage of vertebrates unique for the Argentine Northwest, with several groups of mammals, most notably the only Paleogene interatheres of northwestern Argentina, reptiles and frogs. Only partly they correspond to other fossiliferous formations in the area; the upper part of the Lumbrera Formation and the Quebrada de los Colorados Formation.
Description
The Geste Formation crops out in isolated patches on the Puna Plateau, stretching from the Salar de Arizaro in the north to the Colorado Ridge, southeast of the Salar de Antofalla in the south. covering the western part of Salta Province and the northern part of Catamarca Province. The most extensive outcrops of the formation occur between three volcanoes in the area; the Tebenquicho in the west, Cerro Ratones in the east and Hombre Muerto to the southeast. The formation was defined based on a type section of the Pastos Grandes Basin by Turner in 1960, 1961 and 1964. The formation comprises mainly coarsening upward sandstones, conglomerates and subordinate shales, deposited in a fluvial and alluvial environment. The Geste Formation is the lowermost unit of the Pastos Grandes Group and unconformably overlies different Paleozoic basements; the Late Ordovician Copalayo or Coquena Formation in the Pastos Grandes Basin, Ordovician Falda Ciénaga Formation in Antofagasta de la Sierra and Cordón del Gallego, Coquena Formation in the Sierra de Calalaste, or the Permian Patquía de la Cuesta Formation in the area surrounding the Antofalla volcano.
The formation, reaching a thickness of 1,500 metres (4,900 ft), is overlain by the evaporites and claystones of the Pozuelos Formation of the Pastos Grandes Group. The small Pastos Grandes Basin was formed during the Incan orogeny in the Eocene. The Geste Formation is the only fossiliferous Paleogene formation cropping out in the Argentine Northwest. In the Pastos Grandes Basin, in outcrops located on the eastern flank of the Sierra de Copalayo in Salta Province, the Geste Formation was divided by Alonso (1992) into three members: lower, middle, and upper. The middle member contains fossils of vertebrates and represents deposition by medium-to-fast-flowing rivers, laying down the fine-to-medium-grained micaceous sandstones, grading into coarser sandstones towards the top of the middle member.
The sediments of the Geste Formation were sourced by the provenance area of the Oira Eruptive Complex, which formed a paleohigh between the Puna Plateau and the Calchaquí Valley where the contemporaneous Quebrada de los Colorados Formation was deposited.
The middle member of the formation has been dated at maximum 37.5 ± 0.1 and minimum 35.4 ± 1.5 Ma, corresponding to the Priabonian stage of the Eocene.
= Paleoecology
=The paleoclimate of the time was much more humid than today, with elevated temperatures compared to the present-day climate and the area was at lower altitudes before the final phase of the Andean orogeny which did not take place before the Miocene. In this subtropical fluvial biome, a diverse fauna established, with fossils of various groups found in the formation. Several clades found in the Geste Formation have not been found elsewhere in northwestern Argentina. The fauna of the area is only partly overlapping with the upper Lumbrera Formation and that of the Quebrada de los Colorados Formation.
Paleontological significance
The Geste Formation is an important Paleogene formation, as it is the only formation that has provided interathere fossils. Two fossil localities on the Puna Plateau are known, Antofagasta de la Sierra in Catamarca at an approximate altitude of 3,440 metres (11,290 ft) and Pozuelos in Salta Province at 3,900 metres (12,800 ft). The faunal assemblage comprises mammals of various groups, with notoungulates and armadillos dominating, reptiles (crocodiles, turtles and snakes not assigned to specific genera) and frog fossils.
= Fossil content
=The formation has provided the following fossils:
See also
South American land mammal ages
Guabirotuba Formation, contemporaneous fossiliferous formation of the Curitiba Basin, Brazil
Seca Formation, contemporaneous fossiliferous formation of Ecuador
La Meseta Formation, contemporaneous fossiliferous formation of Antarctica
References
= Bibliography
=Geology
Alonso, R.N.; Viramonte, J.G. (1987), "Geología y metalogenía de la Puna", Estudios Geológicos, 43: 393–407
Aramayo, Alejandro J.; Hongn, Fernando D.; Del Papa, Cecilia E. (2017), "Acortamiento Paleógeno en el tramo medio de los Valles Calchaquíes: depositación sintectónica de la Formación Quebrada de los Colorados" (PDF), Revista de la Asociación Geológica Argentina, 74: 524–536, retrieved 2019-04-05
Grosse, Pablo; Guzmán, Silvina; Petrinovic, Ivan A. (2017), Volcanes compuestos cenozóicos del noroeste argentino, XX Congreso Geológico Argentino, pp. 484–517, retrieved 2019-04-05
Koukharsky, Magdalena María Luisa (1988), Geología de la Puna en la región que media entre el cerro Socompa y el cerro Tul Tul, Pcia. de Salta (PhD thesis) (PDF), Universidad de Buenos Aires, pp. 1–103, retrieved 2019-04-05
Paleontology
Babot, María Judith; Rougier, Guillermo W.; García Lopez, Daniel; Davis, Brian M. (2020), "New small bunodont metatherian from the Late Eocene of the Argentinean Puna", Journal of Mammalian Evolution, 27 (3): 373–384, doi:10.1007/s10914-019-09468-7
Babot, Judith; García López, Daniel; Deraco, Virginia; Herrera, Claudia M.; Del Papa, Cecilia (2017), Mamíferos paleógenos del subtrópico de Argentina: síntesis de estudios estratigráficos, cronológicos y taxonómicos, XX Congreso Geológico Argentino, pp. 730–753, retrieved 2019-04-05
Ciancio, Martín R; Herrera, Claudia; Aramayo, Alejandro; Payrola, Patricio; Babot, Judith (2016), "Diversity of cingulate xenarthrans in the middle–late Eocene of Northwestern Argentina" (PDF), Acta Palaeontologica Polonica, 61: 575–590, doi:10.4202/app.00208.2015, retrieved 2019-04-05
García López, Daniel Alfredo (2015), "New information on the interatheriid Antofagastia turneri García-Lopez and Babot (Mammalia, Notoungulata) from Northwestern Argentina", Ameghiniana, 52 (2): 286–293, doi:10.5710/AMGH.18.10.2014.2816, retrieved 2019-04-05
García López, D.A.; Babot, M.J. (2014), "Notoungulate faunas of north-western Argentina: new findings of early-diverging forms from the Eocene Geste Formation", Journal of Systematic Palaeontology, 13 (7): 557–579, doi:10.1080/14772019.2014.930527, retrieved 2019-04-05
López, Guillermo; Bond, Mariano (1995), "Un nuevo Notopithecinae (Notoungulata, Typotheria) del Terciario Inferior de la Puna argentina - A new Notopithecinae (Notoungulata, Typotheria) of Lower Tertiary from the argentinian Puna", Studia Geologica Salmanticensia, 31: 87–99, retrieved 2018-04-05
López, Guillermo M (1997), "Paleogene faunal assemblage from Antofagasta de la Sierra (Catamarca Province, Argentina)", Palaeovertebrata, 26: 61–81
López, Guillermo M (1995), Suniodon catamarcensis gen et sp. nov. y otros Oldfieldthomasiidae (Notoungulata, Typotheria) del Eoceno de Antofagasta de la Sierra, Catamarca, Argentina, VI Congreso de Paleontología y Bioestratigrafía, pp. 167–172, retrieved 2019-04-05
Powell, J.E.; Babot, M.J.; García López, D.A.; Deraco, M.V.; Herrera, C. (2011), Eocene vertebrates of northwest Argentina: annotated list in J. Salfity, R. A. Marquillas (eds.), Cenozoic Geology of the Central Andes of Argentina, SCS Publisher, pp. 349–370, retrieved 2019-04-05
Reguero, M.A.; Croft, D.A.; López, G.M.; Alonso, R.N. (2008), "Eocene archaeohyracids (Mammalia: Notoungulata: Hegetotheria) from the Puna, northwest Argentina", Journal of South American Earth Sciences, 26 (2): 225–233, Bibcode:2008JSAES..26..225R, doi:10.1016/j.jsames.2008.05.004, retrieved 2019-04-05
Kata Kunci Pencarian:
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