The Cañadón Asfalto Basin (
Spanish : Cuenca de Cañadón Asfalto ) is an irregularly shaped
sedimentary basin located in north-central
Patagonia ,
Argentina . The basin stretches from and partly covers the
North Patagonian Massif in the north, a high forming the boundary of the basin with the
Neuquén Basin in the northwest, to the
Cotricó High in the south, separating the basin from the
Golfo San Jorge Basin . It is located in the southern part of
Río Negro Province and northern part of
Chubut Province . The eastern boundary of the basin is the North Patagonian Massif separating it from the offshore
Valdés Basin and it is bound in the west by the Patagonian Andes, separating it from the small
Ñirihuau Basin .
The basin started forming in the Early Jurassic, with the break-up of
Pangea and the creation of the
South Atlantic , when
extensional tectonics , including
rifting , formed several basins in eastern South America and southwestern Africa. The
accommodation space in the Cañadón Asfalto Basin was filled by volcanic,
fluvial and
lacustrine deposits in various geologic formations, separated by
unconformities related to
transtensional and
transpressional tectonic forces. The Cenozoic evolution of the basin is mainly influenced by the
Andean orogeny , producing
folding and
faulting in the basin.
The basin is of paleontological significance as it hosts several
fossiliferous stratigraphic units providing many fossils of
dinosaurs ,
turtles ,
mammals ,
plesiosaurs ,
pterosaurs ,
crocodylomorphs ,
fish ,
amphibians and
flora in the
Mesozoic and mammals, amphibians, fish and flora in the
Cenozoic . The
Collón Curá Formation , that is also present in the southern
Neuquén Basin , is the defining formation for the
Colloncuran , used within the
SALMA classification , the geochronology for the
Cenozoic used in South America.
Description
View of
Gastre , in the center of the basin
Altar Valley in the southern part of the basin, bounding the
Chubut River
The Cañadón Asfalto Basin was not defined as a separate sedimentary basin until the 1990s. Until then, the sediments deposited in the basin were considered part of the North Patagonian Massif. Homovc et al. (1991) and Figari & Courtade (1993) started defining the stratigraphic units in megasequences indicative of the evolution of a
rift basin , resulting from the break-up of
Pangea and
Gondwana in particular.
[1]
The basin has an irregular shape, comprising several
depocenters defining sub-basins. The basin stretches from and partly covers the North Patagonian Massif in the north and east towards the
Cotricó High to the south of the Paso del Sapo Sub-basin, separating the Cañadón Asfalto Basin from the
Golfo San Jorge Basin in the south. In the west, the basin is bound by uplifted areas with the small
Ñirihuau Basin .
[2]
The area of the basin is sparsely populated, with
Gastre and
Paso del Sapo representing some of the few villages in the basin. The
Chubut River crosses the basin in the south in the
Altar Valley .
Basin evolution
Sketch of the paleogeographic situation of South America during the Late Cretaceous and Early Paleogene, roughly 85 to 63 Ma. The Cañadón Asfalto Basin, located south of the North Patagonian Massif in the South Gondwanan Province (grey), is experiencing a marine transgression.
The Cañadón Asfalto Basin started forming in the earliest
Jurassic on top of
Permian
basement constituted by the
igneous -
metamorphic
Mamil Choique and
Cushamen Formations .
[3] Two main phases of basin evolution are recognized; the Jurassic and Cretaceous megasequences. Figari et al. in 2015 describe two Jurassic megasequences, J1 in the Early Jurassic and J2 in the Late Jurassic. During these phases, the basin went through an extensional tectonic regime, with transtensional movements. Several distinct tectonic reactivation cycles occurred, with block rotation due to transpressional forces. The geodynamic movements are noted in the stratigraphy by regional
unconformities . The predominantly extensional movement was overprinted by a compressional setting, active since the early Cenozoic. This compressional phase is noted in
folds and compressional
faults present in the basin.
[4]
The sedimentary infill of the Early and Middle Jurassic in the basin is characterized by
fluvial and
lacustrine sediments of the
Las Leoneras ,
Cañadón Asfalto and
Cañadón Calcáreo Formations covering the volcanic
Lonco Trapial Formation , which comprises intermediate volcanic rocks sourced by
magmas coming from the
mantle . This succession is unconformably covered by lacustrine, fluvial and volcaniclastic rocks of the approximately 10 to 15 million year ranging
Chubut Group comprising the older
Los Adobes Formation and the younger
Cerro Barcino Formation . The western side of the basin during the Late Cretaceous experienced a marine
transgression of the
Atlantic Ocean , depositing the fluvial and
estuarine
Paso del Sapo and
Lefipán Formations .
[5]
The marine sediments of the Lefipán Formations have been correlated to the
Salamanca Formation of the Golfo San Jorge Basin to the south and the Lefipán sediments were sourced from the North Patagonian Massif. To the west of the Cañadón Asfalto Basin, another basin started forming in these times, the
Ñirihuau Basin , characterized by the deposition of the felsic to intermediate volcanic
Don Juan Formation , the basaltic
Tres Picos Prieto Formation and the
Huitrera Formation . In the Ñirihuau Basin, this sequence is covered by the
Oligocene to
Miocene
Ventana Formation .
[6]
During the Paleogene, in the Cañadón Asfalto Basin the volcaniclastic
Laguna del Hunco Formation ,
[7] and volcanic
Sarmiento Group were deposited.
[8] The
Neogene succession in the basin comprises the Early Miocene
alluvial volcaniclastics of the
La Pava Formation ,
[8]
[9] and the Middle to Late Miocene volcaniclastic, fluvial, lacustrine and
deltaic
tuffs ,
sandstones and carbonates of the
Collón Curá Formation .
The Late Miocene to Quaternary succession comprises mostly the
basaltic lava flows
[10] of the
El Mirador Formation ,
[11] the basalts of the
Cráter Formation , and
Quaternary
alluvium .
[12]
[13] In the northern part of the basin, the Late Miocene and Early Pliocene is represented by the fluvial, marine and
eolian
Río Negro Formation , a formation extending into the
Colorado Basin .
[14]
[15]
Stratigraphy
Outcrops of the Collón Curá Formation in the basin (9 & 10)
Outcrops of the Las Leoneras and other formations
Outcrop areas of the Cañadón Asfalto and Calcáreo Formations
The stratigraphy of the Cañadón Asfalto Basin covers the following units:
Paleontological significance
The Cañadón Asfalto Basin has provided several fossils of various groups of flora and fauna. One of the largest
dinosaurs known, the
titanosaur
Patagotitan mayorum , and one of the largest
theropods ,
Tyrannotitan chubutensis , were found in the
Cerro Barcino Formation .
[30]
[31] Fossils of
Leonerasaurus taquetrensis , an early Sauropodomorph, were found in and named after the
Las Leoneras Formation .
[32] The
La Colonia Formation has provided fossils of a mammal;
Argentodites coloniensis ,
[33] and a nearly complete skeleton of the theropod
Carnotaurus sastrei . Remains of the
plesiosaur
Aristonectes parvidens were found in the Maastrichtian section of the
Lefipán Formation .
[34]
Fossil flora (
pollen ,
spores ,
algae and macroflora) have been recovered from the
Lonco Trapial Formation (
Cupressaceae ),
[35] and the
Cañadón Asfalto Formation and comprise several families of plants, indicative of climatic conditions in the Late Jurassic;
Osmundaceae ,
Caytoniaceae ,
Araucariaceae ,
Cheirolepidiaceae ,
Podocarpaceae ,
Botryococcaceae ,
Zygnemataceae ,
Prasinophyceae ,
Filicales and
Taxodiaceae .
[36] The same formation also provided fossils of two species of the
frog
Notobatrachus ,
[37] the turtle
Condorchelys antiqua ,
[38] the
pterosaur
Allkaruen koi ,
[39] and several mammals.
[40]
Fossil fish of
Condorlepis groeberi were retrieved from the
Cañadón Calcáreo Formation ,
[41] and the
crocodylomorphs
Almadasuchus figarii (Cañadón Calcáreo Formation),
[42] and
Barcinosuchus gradilis (Cerro Barcino Formation),
[43] come from the Mesozoic strata in the basin.
Fossil leaves of
Lefipania padillae and
Araucaria lefipanensis come from and were named after the latest Maastrichtian within the Lefipán Formation.
[44]
[45] The Paleocene (
Tiupampan ) strata of the Lefipán Formation have provided fossils of the mammal
Cocatherium lefipanum and fish
Hypolophodon patagoniensis .
[46]
[47]
The Early Eocene (
Casamayoran to
Mustersan )
Laguna del Hunco Formation has provided fossils of the fish
Bachmannia chubutensis ,
[48] the frog
Shelania pascuali ,
[49] and fossil flora.
[50]
The
Collón Curá Formation , that defines the
Colloncuran
South American land mammal age , stretches across the
Neuquén Basin to the northwest of the North Patagonian Massif and the western part of the Cañadón Asfalto Basin. The formation has provided many mammal, reptile and bird fossils, among which the largest
terror bird
Kelenken .
[51] Along the
Chico River in the basin (localities 9 and 10 on the map), fossils of the
sparassodont
Patagosmilus goini , two new species of
Protypotherium ,
[52] and the
rodents
Guiomys unica and
Microcardiodon williensis were found.
[53]
[54]
[55]
See also
References
^ Figari et al., 2015, p.137
^ Figari et al., 2015, p.138
^ Di Pietro, 2016, p.28
^ Di Pietro, 2016, p.23
^ Echaurren, 2017, p.94
^ Echaurren, 2017, p.95
^
a
b Figari et al., 2015, p.154
^
a
b
c
d
e Figari et al., 2015, p.155
^
a
b Di Pietro, 2016, p.46
^ Echaurren et al., 2016, p.103
^
a
b Echaurren et al., 2016, p.102
^ Echaurren et al., 2016, p.105
^ Echaurren, 2017, p.102
^
a
b Pérez, 2012, p.7
^ Pérez, 2012, p.10
^ Di Pietro, 2016, p.49
^
a
b
c Figari et al., 2015, p.153
^ Gasparini et al., 2015
^ Figari et al., 2015, p.152
^ Figari et al., 2015, p.151
^ Figari et al., 2015, p.147
^ Figari et al., 2015, p.146
^ Di Pietro, 2016, p.42
^ Figari et al., 2015, p.144
^ Di Pietro, 2016, p.39
^ Figari et al., 2015, p.142
^ Di Pietro, 2016, p.31
^ Figari et al., 2015, p.143
^ Olivera et al., 2015, p.3
^ Carballido et al., 2017
^ Novas et al., 2005
^ Pol et al., 2011
^ Kielan-Jaworowska et al., 2007, p.257
^ Gasparini et al., 2003
^ Escapa et al., 2008a
^ Olivera et al., 2015, p.6
^ Escapa et al., 2008b
^ Sterli, 2008
^ Codorniú et al., 2016
^ Gaetano & Rougier, 2011
^ López Arbarello et al., 2013
^ Pol et al., 2013
^ Leardi & Pol, 2009
^ Martínez et al., 2018
^ Andruchow‐Colombo et al., 2018
^ Cione et al., 2013
^ Goin et al., 2006
^ Azpelicueta & Cino, 2011
^ Báez & Trueb, 1997
^ Wilf et al., 2005
^ Bertelli et al., 2007
^ Vera et al., 2017, p.855
^ Forasiepi & Carlini, 2010
^ Pérez, 2010
^ Pérez & Vucetich, 2011
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Further reading
Sedimentary basins of Argentina
Onshore & offshore
Offshore Sources