The Araripe Basin () is a
rift basin
In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics.
Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben wi ...
covering about ,
[Neto et al., 2013, p.1] in
Ceará
Ceará (, pronounced locally as or ) is one of the 26 states of Brazil, located in the northeastern part of the country, on the Atlantic coast. It is the eighth-largest Brazilian State by population and the 17th by area. It is also one of the ...
,
Piauí
Piaui (, ) is one of the states of Brazil, located in the country's Northeast Region. The state has 1.6% of the Brazilian population and produces 0.7% of the Brazilian GDP.
Piaui has the shortest coastline of any coastal Brazilian state at 66&n ...
and
Pernambuco
Pernambuco () is a state of Brazil, located in the Northeast region of the country. With an estimated population of 9.6 million people as of 2020, making it seventh-most populous state of Brazil and with around 98,148 km², being the 19 ...
states of northeastern
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
. It is bounded by the Patos and Pernambuco
lineament ''See also Line (geometry)''
A lineament is a linear feature in a landscape which is an expression of an underlying geological structure such as a fault. Typically a lineament will appear as a fault-aligned valley, a series of fault or fold-aligne ...
s, and is situated east of the
Parnaíba Basin
The Parnaíba Basin (Portuguese: ''Bacia do Parnaíba'') is a large cratonic sedimentary basin located in the North and Northeast portion of Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the ...
, southwest of the
Rio do Peixe Basin and northwest of the
Tucano and
Jatobá Basin Jatobá may refer to:
* '' Hymenaea courbaril'', tree common to the Caribbean, Central, and South America
* Jatobá, Maranhão, municipality in Brazil
* Jatobá, Pernambuco, city in Brazil
* Jatobá Hydroelectric Power Plant, planned hydroelectr ...
s.
The basin has provided a variety of unique fossils in the
Crato and
Santana Formation
The Santana Group is a geologic group, formerly included as the middle part of the Araripe Group, in the Araripe Basin of northeastern Brazil. The group comprises the Crato, Ipubi and Romualdo Formations and is dated to the Aptian to Albian sta ...
s and includes the
Araripe Geopark
Araripe is a municipality in the state of Ceará in the Northeast region of Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At an ...
, a member of the
UNESCO Global Geopark
UNESCO Global Geoparks (UGGp) are geoparks certified by the UNESCO Global Geoparks Council as meeting all the requirements for belonging to the Global Geoparks Network (GGN). The GGN is both a network of geoparks and the agency of the United Nati ...
s since 2006.
[Chapada do Araripe vira parque geológico]
/ref> The pterosaur
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...
s ''Araripesaurus
''Araripesaurus'' is a genus a pterosaur belonging to the suborder Pterodactyloidea, it was discovered in the Romualdo Formation of the Santana Group in northeastern Brazil, which dates back to the Aptian and Albian of the Early Cretaceous. The ...
'' and ''Araripedactylus
''Araripedactylus'' was a large genus of pterodactyloid pterosaur, known from a single wing bone found in the Early Cretaceous Santana Formation of Brazil.
The genus was in 1977 named by Peter Wellnhofer who, unaware that the name '' Araripesaur ...
'' (now considered a ''nomen dubium
In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application.
Zoology
In case of a ''nomen dubium'' it may be impossible to determine whether a s ...
''), crocodylian ''Araripesuchus
''Araripesuchus'' is a genus of extinct crocodyliform that existed during the Cretaceous period of the late Mesozoic era some 125 to 66 million years ago. Six species of ''Araripesuchus'' are currently known. They are generally considered to be n ...
'', the turtle ''Araripemys
''Araripemys'' is an extinct marine turtle genus from 112 to 109 million years ago, in the Early Cretaceous Crato and Romualdo Formations of the Araripe Basin in northeastern Brazil. It is one of the oldest known pleurodire
The Pleurodira ar ...
'', amphibian '' Arariphrynus'', the fish ''Araripelepidotes
''Araripelepidotes'' is a genus of ginglymodian fish.
Habitat
''Araripelepidotes'' was probably endemic to the Araripe Basin, and was commonly found in Santana formation, and rare in the Crato Formation, mostly in carbonate concretions, but ...
'' and the insect '' Araripenymphes'' were named after the basin. The bituminous shales of the Ipubi Formation in the Araripe Basin have potential for shale gas
Shale gas is an unconventional natural gas that is found trapped within shale formations. Since the 1990s a combination of horizontal drilling and hydraulic fracturing has made large volumes of shale gas more economical to produce, and some a ...
development.[Neto et al., 2013, p.3]
Basin history
The tectono-sedimentary evolution of the Araripe Basin, located in the Borborema Geologic Province, encompasses four stages, with five tectonostratigraphic phases:[Fabin et al., 2018, pp.2051-2052]
1) Syneclise phase - Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...
to Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
- characterized by tectonic quiescence in the Borborema Province. It is represented by the deposits of the Cariri Formation, that include medium to coarse-grained quartz sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) ...
s, locally conglomeratic, deposited in large braided
Braided is a musical group consisting of Casey LeBlanc, Ashley Leitão, and Amber Fleury, who all competed on the third season of '' Canadian Idol'' in 2005. They are the third music group to come from an Idol show in the world, after Young Div ...
fluvial
In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviog ...
systems
2) Pre-rift phase - Tithonian
In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by the K ...
- characterized by the mechanical subsidence due to lithosphere thinning that preceded the rift. It is represented by the Brejo Santo Formation, that comprises red shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...
s and claystone
Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...
s, and the Missão Velha Formation, constituted by medium to coarse-grained quartz-feldspathic sandstones, locally conglomeratic, that contains entire trunks and fragments of silicified wood ('' Dadoxilon benderi'') conifer
3) Rift phase - Berriasian
In the geological timescale, the Berriasian is an age/stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago) ...
to Hauterivian
The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.9 ± 2 Ma and 129.4 ± 1.5 Ma (million years ago). The Hauterivian is preceded by the Va ...
- characterized by increasing mechanical subsidence that created a system of grabens and half grabens. It is represented by the Abaiara Formation, that includes shales, siltstone
Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...
s, sandstones and conglomerates
4) Post-Rift I phase - Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...
to Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0.9 M ...
- characterized by thermal subsidence. The lowermost unit Barbalha Formation, represents a fluviolacustrine phase and is composed of red and gray shales, siltstones and claystones.
The Santana Group was formed during this stage and comprises three stratigraphic units:
* Crato Formation that is composed of six intervals of laminated limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
s (C1 to C6), interbedded with calciferous siltstones and marl
Marl is an earthy material rich in carbonate minerals, clays, and silt. When hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae.
Marl makes up the lower part o ...
s, and is very rich in fossils of vertebrate and invertebrate organisms
* Ipubi Formation, that is mainly composed of organic-rich, black greenish bituminous
Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...
shales, claystones and algal
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
limestones that are interbedded with gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...
-anhydrite
Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...
beds
* Romualdo Formation, that represents a calciferous siliciclastic succession composed of fine to medium-grained sandstones, argillaceous siltstones, calciferous shales, and limestones, very rich in fossils. This formation recorded the marine proto-Atlantic incursion that involved the Araripe Basin, and other interior basins and created a large seaway throughout the Borborema Province during the Albian
5) Post-rift II phase - Albian to Cenomanian
The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...
- characterized by a major sag phase, and is formed by two stratigraphic units:
* Araripina Formation, that occurs in the western region of the basin and is composed by rhythmite
A rhythmite consists of layers of sediment or sedimentary rock which are laid down with an obvious periodicity and regularity. They may be created by annual processes such as seasonally varying deposits reflecting variations in the runoff cycle, b ...
s and heterolithic layers of reddish, purplish and yellowish fine-grained sandstone and mudstone
* Exu Formation, that comprises medium-to coarse grained sandstones, fine grained clayey sandstones and local conglomeratic beds
Stratigraphy
See also
* Chapada do Araripe
The Chapada do Araripe, also known as the Serra do Araripe, is a ''chapada'' ( plateau) in northeastern Brazil. The chapada forms the boundary of Ceará and Pernambuco states, and forms the watershed between the Jaguaribe River of Ceará, which fl ...
* Paraná Basin
The Paraná Basin ( pt, Bacia do Paraná, es, Cuenca del Paraná) is a large cratonic sedimentary basin situated in the central-eastern part of South America. About 75% of its areal distribution occurs in Brazil, from Mato Grosso to Rio Grande d ...
* Santos Basin
The Santos Basin ( pt, Bacia de Santos) is an approximately large mostly offshore sedimentary basin. It is located in the south Atlantic Ocean, some southeast of Santos, Brazil. The basin is one of the Brazilian basins to have resulted from th ...
References
Bibliography
*
*
*
*
*
*
Further reading
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
{{Sedimentary basins of Brazil
Drainage basins of Brazil
Sedimentary basins of Brazil
Rift basins
Mesozoic rifts and grabens
Paleontology in Brazil
Geography of Ceará
Geography of Pernambuco
Geography of Piauí