Colorado Basin, Argentina
Colorado Basin | |
---|---|
Cuenca del Colorado | |
Location of the basin in Argentina | |
Coordinates | 41°30′S 61°00′W / 41.500°S 61.000°W |
Etymology | Colorado River |
Country | Argentina |
State(s) | Buenos Aires & Río Negro Provinces |
Cities | Bahía Blanca, Viedma |
Characteristics | |
On/Offshore | Both |
Boundaries | Ventania High (N) (E) / (S) San Rafael Block (W) |
Part of | South Atlantic rift basins |
Area | ~180,000 km2 (69,000 sq mi) |
Hydrology | |
Sea(s) | South Atlantic |
River(s) | Río Negro & Colorado Rivers |
Geology | |
Basin type | Passive margin on rift basin |
Plate | South American |
Orogeny | Break-up of Pangea |
Age | Early Cretaceous-Quaternary |
Stratigraphy | Stratigraphy |
Field(s) | none |
The Colorado Basin (Spanish: Cuenca del Colorado) is a sedimentary basin located in northeastern Argentina. The basin stretches across an area of approximately 180,000 square kilometres (69,000 sq mi), of which 37,000 square kilometres (14,000 sq mi) onshore in the southern Buenos Aires Province and the easternmost Río Negro Province extending offshore in the South Atlantic Ocean.
The basin comprises a sedimentary succession dating from the Permian (pre-rift stage) and Early Cretaceous (rift stage) to the Quaternary, representing the passive margin tectonic phase of the basin history. The Mesozoic rifting in the basin resulted from the break-up of Pangea and the formation of the South Atlantic. Long hiatuses exist in the succession.
The basin is of paleontological significance for hosting dating to the Late Miocene. The defines the Chasicoan South American land mammal age and contains a rich mammal and other vertebrate fauna. The contemporaneous Cerro Azul Formation has provided fossil rodents, armadillos and opossums. The Middle to Late Miocene contains vertebrate fossils of the cetacean . The has provided fossils of the glyptodont . The Permian succession in the basin has provided flora microfossils.
Contrasting with the South Atlantic passive margin basins to the north (Santos Basin in southern Brazil) and south; Golfo San Jorge and Austral Basins, the Colorado Basin does not produce hydrocarbons. Exploration for petroleum started in the 1940 with the drilling of two onshore wells and several onshore and offshore wells have been drilled in the 1960s, 1970s and 1990s. The main source rocks are found in the Permian succession, with reservoir rocks the Colorado Formation. Seals are provided by the Early Paleocene .
Description[]
The Colorado Basin stretches across an approximate area of 180,000 square kilometres (69,000 sq mi) with about 37,000 square kilometres (14,000 sq mi) onshore, underlying the southernmost Buenos Aires Province and the southeasternmost Río Negro Province. Cities inside the basin are Bahía Blanca and Carmen de Patagones in Buenos Aires Province and Viedma in Río Negro Province, the earliest founded city in Patagonia. The onshore part of the basin is crossed by the eponymous Colorado and Río Negro rivers. Surrounding the Río Negro, many salt lakes are present in the basin.[1]
Some authors group the basin together with the to the north.[2] The offshore part of the Colorado Basin laterally correlates with and gradually ranges into the sub-parallel and the deeper offshore .[3][4] The offshore extension of the basin into neighboring basins led to different definitions of its area, some authors use a surface area of 125,000 square kilometres (48,000 sq mi).[5]
The Colorado Basin is bound to the north by the Ventania High,[6] Sierra de la Ventana,[7] or ,[2] separating the basin from the Claromecó Basin, and to the south by the ,[8] or .[9] In the northwest, the basin grades into the and the western boundary is formed by the San Rafael Block.[9]
Basin evolution[]
The basin started forming in the Middle to Late Jurassic with the break-up of Pangea and the formation of the Southern Atlantic.[10] The main rifting took place in the Early Cretaceous.[5] The pre-rift sequence of the basin comprises the Pennsylvanian of the ,[11] and the , , and of the ,[2] dating to the Permian.[12] During the late Paleozoic, the Colorado Basin was located in the south polar region, causing a sequence of glacial deposits in the basin. These deposits were mostly sourced from the African basin, the Karoo and Kalahari Basins. The Early Permian sediments are characterized by the presence of diamictites. A transgression in the Permian led to the deposition of the Piedra Azul Formation.[13] The succession contains several hiatuses, dating to the Triassic and Early Jurassic, Albian and Paleogene.[14]
The early Mesozoic succession is missing, and the main rifting phase happened in the Barremian and Aptian, around 120 million years ago, represented in the .[15] The post-rift sag stage dates to the early Late Cretaceous leading to the deposition of the alluvial and fluvial sediments of the Colorado Formation.[14] The drift stage is represented by the .[14] The later Cenozoic succession is characteristic of a terrestrial passive margin setting and comprises the Paleocene ,[14] Middle Miocene ,[16] and the Middle to Late Miocene .[17] This formation in most of the basin is overlain by the .[18] The Late Miocene succession in the westernmost area of the basin is represented by the and eolian Cerro Azul Formations,[19] cropping out in the northern onshore part of the basin.[20] This sequence is covered by the Late Miocene to Early Pliocene eolian and fluvial Río Negro Formation,[21][22] outcropping in a thin band along the eponymous river.[1]
Stratigraphy[]
Age | Group | Formation | Environment | Tectonic regime | Maximum thickness | Petroleum geology | Notes |
---|---|---|---|---|---|---|---|
Quaternary | alluvium | Passive margin | |||||
Early Pliocene | Eolian & fluvial | 480 m (1,570 ft) | [21][22] | ||||
Late Miocene | |||||||
Chasicoan-Huayquerian | Cerro Azul | Eolian | 180 m (590 ft) | [19][23] | |||
Chasicoan | Floodplain | [24] | |||||
Mayoan | Shallow marine | 57 m (187 ft) | [17] | ||||
Laventan | |||||||
Colloncuran | |||||||
Friasian | |||||||
Santacrucian | |||||||
Mid Miocene | Marine | 300 m (980 ft) | [16] | ||||
Oligocene | Hiatus | ||||||
Late Eocene | |||||||
Middle Eocene | [14] | ||||||
Early Eocene | Hiatus | ||||||
Late Paleocene | |||||||
Early Paleocene | Drift | Seal | [14] | ||||
Maastrichtian | Hiatus | ||||||
Campanian | Colorado | Alluvial & fluvial | Sag | Reservoir | [14] | ||
Santonian | |||||||
Coniacian | |||||||
Turonian | |||||||
Cenomanian | |||||||
Albian | Hiatus | ||||||
Aptian | Syn-rift | Reservoir Source |
[15] | ||||
Barremian | |||||||
Middle Jurassic | Hiatus | ||||||
Early Jurassic | |||||||
Triassic | |||||||
Late Permian | Pre-rift | 1,500 m (4,900 ft) | Source | [2] | |||
Early Permian | Source | [2] | |||||
[2] | |||||||
[2] | |||||||
Pennsylvanian | Basement | [11] |
Paleontological significance[]
The Miocene formations cropping out onshore have provided a rich mammal fauna. The is the defining formation for the Late Miocene Chasicoan South American land mammal age, ranging from 10 to 9 million years ago.[25] The formation contains many mammal species, birds and reptiles.[26] The Cerro Azul Formation contains fossils of the rodents ,[27] ,[28] and R. simplex,[29] the armadillos ,[23] and ,[27] and the opossum ,[30] among other mammals. The has provided fossils of the glyptodont .[31]
The marine Gran Bajo de Gualicho Formation contains many bivalve, gastropod and echinoid fossils,[32] and the cetacean .[33] The Eocene succession in boreholes of the basin has provided many species of dinoflagellates,[34] and in the Permian sequence 131 species of spores, algae, funghi and pollen were registered.[35]
Petroleum exploration[]
Contrary to other Southern Atlantic marginal basins, as the Golfo San Jorge and Austral Basins to the south, and Santos Basin of Brazil to the north, the Colorado Basin is not producing hydrocarbons. The first wells in the northern onshore part of the basin were drilled in 1946 (Pedro Luro-1) and 1948 (Ombucta-1) by YPF. Another phase of onshore exploration happened in the 1960s, with seven wells drilled by Shell.[36] Offshore drilling started in 1970 by Hunt Oil and after seismic acquisition in the 1970s by YPF,[37] some wells were drilled in 1977 by the same company. Renewed exploration started in the mid-1990s with several wells drilled by Union Texas and Shell.[38] The offshore Cruz del Sur x-1 well provided of 39° API.[39]
See also[]
References[]
- ^ a b Geologic Map Hojas 4163-II/IV & I/III, 2006
- ^ a b c d e f g Balarino, 2012, p.344
- ^ Pucci, 2006, p.17
- ^ ENARSA, s.a., p.3
- ^ a b ENARSA, s.a., p.2
- ^ Daners et al., 2016, p.285
- ^ Balarino, 2009, p.20
- ^ ENARSA, s.a., p.1
- ^ a b Barredo & Stinco, 2010, p.60
- ^ Geologic Map Hojas 3963-III & IV, 2009, p.42
- ^ a b Balarino, 2009, p.24
- ^ Balarino, 2009, p.22
- ^ Balarino, 2009, p.23
- ^ a b c d e f g ENARSA, s.a., p.4
- ^ a b Barredo & Stinco, 2010, p.52
- ^ a b Geologic Map Hojas 3963-III & IV, 2009, p.39
- ^ a b Reichler, 2010, p.192
- ^ Reichler, 2010, p.183
- ^ a b Visconti et al., 2010, p.259
- ^ Geologic Map Hojas 3963-III & IV, 2009, p.5
- ^ a b Pérez, 2010, p.7
- ^ a b Geologic Map Hojas 3963-III & IV, 2009, p.8
- ^ a b Scillato Yané et al., 2010, p.51
- ^ Zárate et al., 2007
- ^ Chasicoan at Fossilworks.org
- ^ Arroyo Chasicó at Fossilworks.org
- ^ a b Verzi et al., 2008
- ^ Madozzo Jaén et al., 2018, p.250
- ^ Sostillo et al., 2014
- ^ Goin et al., 2000, p.108
- ^ Punta Bermeja at Fossilworks.org
- ^ Reichler, 2010, pp.191-192
- ^ Buono, 2013, p.36
- ^ Daners et al., 2016, p.293
- ^ Balarino, 2012, p.343
- ^ Rossello, 2016, p.175
- ^ ENARSA, s.a., p.8
- ^ ENARSA, s.a., p.5
- ^ Pucci, 2006, p.18
Bibliography[]
- General
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- Gran Bajo del Gualicho Formation
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- Río Negro Formation
- Rift basins
- Passive margins
- Mesozoic rifts and grabens
- Sedimentary basins of Argentina
- Geology of Buenos Aires Province
- Geology of Río Negro Province
- Geology of Patagonia
- Geology of the Atlantic Ocean