Geology of Paraguay
Encyclopedia
The country of Paraguay lies geologically at the borderzone between several craton
s being most of the country covered by Tertiary
sediments and thick regolith
. Due to thick Tertiary sediment and regolith development few outcrop
s are available in Paraguay. East of Paraguay River that Precambrian
and Early Paleozoic
crystalline basement crop out mainly in the heights of Caapucú and Apa. The geologial processes that have shaped Paraguay's bedrock and sedimentary basin
s are diverse including rifting
, marine sedimentation, metamorphism
, eruption of flood basalt
s and alkaline potassic volcanism
.
. The rocks found in the Caapucú High include porphyritic
granitic rocks, orthogneisses, paragneisses, amphibolite
s, migmatite
s, talc
schist
s and rhyolite
dyke
s. During the Brasiliano Cycle (576-480 Ma ago) the area of the Caapucú height suffered a major magma
tic event.
limestone
of Vendian Age
and granites, metasediments, mafic
gneiss
es and granitoid
-pegmatititic
intrusvies of Late Proterozoic
age. The Apa high is oftern considered the southernmost outcrop of the Central Brazilian Shield (also called Guaporé Shield) which is sometimes considered to form one sole shield
(or at least craton) with the Guyana Shield called the Amazonian Shield
.
is a large 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 do Sul
states. The remainder area is distributed in eastern Paraguay, northeastern Argentina
and northern Uruguay
. The shape of the depression is elliptical and covers an area of about 1500000 square kilometre, of which 110,000 km2 are in Paraguay. The basin developed during the Paleozoic
and the Mesozoic
with a sedimentary record comprising rock
s from the Ordovician
right up to the Cretaceous
, thus spanning the time interval between 460 and 65 million years. The maximum thickness of the infill reaches 7,000 m in its central area and is composed of sedimentary and igneous rocks.
The Paraná Basin is a typical intra-cratonic
flexural basin, although during the Paleozoic it was a gulf
that opened to the southwest. The basin genesis is related to the convergence
between the former Gondwana
supercontinent
and the oceanic crust
of the former Panthalassa
ocean. The basin formed, at least during the Paleozoic orogenesis of the Gondwanides, a foreland basin
.
The Paraná River
, that forms Paraguay's eastern boundary, flows along the central axis of the Paraná Basin and drains it.
region that makes up the northwestern half (~60%) of Paraguay is a modern foreland basin
that extends into Argentina
and Bolivia
where it borders the Andean
thrust front. Superficially the Chaco Basin is an alluvial basin composed of land-derived (in contrast to marine sediments) material, mostly fine sand and clays of Tertiary
and Quaternary
age. On deeper levels the Paraguayan Chaco is made up by four sub-basin
s, the Pirizal, Pilar, Carandaity and Curupaity basins.
Carandaity and Curupaity in the northwest are chieftly composed of Paleozoic
sediment
s.
Pirizal (also called Pirity) Basin is made up mostly of Late Cretaceous
and younger sediments. The Pilar Basin is located mainly on Presidente Hayes Department
and borders the Paraná Basin
across Paraguay River
to the east, geologically the basins are separated by the Asunción Anticline that roughly follows the path of Paraguay River.
240 Ma old alkaline volcanic rocks underlies younger sediments. In the 1970s these rocks were studied for their potential to host valuable phosphate
and uranium
minerals.
tholeiitic basalts belonging to the Paraná Traps makes up most of the bedrock and overlies earlier sediments of the Paraná Basin
. These tholeiites were erupted in the Early Cretaceous in association with the initial opening of the South Atlantic. The Creataceous volcanism did also created minor outcrops of potassic alkaline volcanics in a graben
structure developed between Asunción
and Villarrica
and in Amambay Department
. Cretaceous volcanism did also left small units of sodic alkaline rocks in Misiones Department
in southern Paraguay.
Craton
A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
s being most of the country covered by Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...
sediments and thick regolith
Regolith
Regolith is a layer of loose, heterogeneous material covering solid rock. It includes dust, soil, broken rock, and other related materials and is present on Earth, the Moon, some asteroids, and other terrestrial planets and moons.-Etymology:...
. Due to thick Tertiary sediment and regolith development few outcrop
Outcrop
An outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. -Features:Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be...
s are available in Paraguay. East of Paraguay River that Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
and Early Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
crystalline basement crop out mainly in the heights of Caapucú and Apa. The geologial processes that have shaped Paraguay's bedrock and sedimentary basin
Sedimentary basin
The term sedimentary basin is used to refer to any geographical feature exhibiting subsidence and consequent infilling by sedimentation. As the sediments are buried, they are subjected to increasing pressure and begin the process of lithification...
s are diverse including rifting
Aulacogen
In geology, an aulacogen is a failed arm of a triple junction of a plate tectonics rift system. A triple junction beneath a continental plate initiates a three way breakup of the continental plate. As the continental break-up develops one of the three spreading ridges typically fails or stops...
, marine sedimentation, metamorphism
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
, eruption of flood basalt
Flood basalt
A flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalts have occurred on continental scales in prehistory, creating great plateaus and mountain ranges...
s and alkaline potassic volcanism
Volcanism
Volcanism is the phenomenon connected with volcanoes and volcanic activity. It includes all phenomena resulting from and causing magma within the crust or mantle of a planet to rise through the crust and form volcanic rocks on the surface....
.
Pre-Silurian basement
Caapucú High
Caapucú High (formely called Precámbrico Sur and Saliente del Pilar) is the Northwesternmost outcrop of Rio de la Plata CratonRio de la Plata Craton
The Río de la Plata craton is one of the five cratons of the South American continent. The other four cratons are: Amazonian, São Francisco, Río Apa and Arequipa–Antofalla.It crops out in southern Uruguay and parts of Argentina...
. The rocks found in the Caapucú High include porphyritic
Porphyritic
Porphyritic is an adjective used in geology, specifically for igneous rocks, for a rock that has a distinct difference in the size of the crystals, with at least one group of crystals obviously larger than another group...
granitic rocks, orthogneisses, paragneisses, amphibolite
Amphibolite
Amphibolite is the name given to a rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks. The modern terminology for a holocrystalline plutonic igneous rocks composed primarily of hornblende amphibole is a hornblendite, which are...
s, migmatite
Migmatite
Migmatite is a rock at the frontier between igneous and metamorphic rocks. They can also be known as diatexite.Migmatites form under extreme temperature conditions during prograde metamorphism, where partial melting occurs in pre-existing rocks. Migmatites are not crystallized from a totally...
s, talc
Talc
Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg34 or Mg3Si4O102. In loose form, it is the widely-used substance known as talcum powder. It occurs as foliated to fibrous masses, its crystals being so rare as to be almost unknown...
schist
Schist
The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is...
s and rhyolite
Rhyolite
This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...
dyke
Dike (geology)
A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across* planar wall rock structures, such as bedding or foliation...
s. During the Brasiliano Cycle (576-480 Ma ago) the area of the Caapucú height suffered a major magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
tic event.
Apa High
The formations at the Apa High include metamorphosedMetamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
of Vendian Age
Ediacaran
The Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon...
and granites, metasediments, mafic
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
gneiss
Gneiss
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...
es and granitoid
Granitoid
A granitoid or granitic rock is a variety of coarse grained plutonic rock similar to granite which mineralogically are composed predominately of feldspar and quartz. Examples of granitoid rocks include granite, quartz monzonite, quartz diorite, syenite, granodiorite and trondhjemite. Many are...
-pegmatititic
Pegmatite
A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic....
intrusvies of Late Proterozoic
Proterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...
age. The Apa high is oftern considered the southernmost outcrop of the Central Brazilian Shield (also called Guaporé Shield) which is sometimes considered to form one sole shield
Shield (geology)
A shield is generally a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. In all cases, the age of these rocks is greater than 570 million years and sometimes dates back 2 to 3.5 billion years...
(or at least craton) with the Guyana Shield called the Amazonian Shield
Amazonian shield
The Amazonian shield is a geologic province located in South America and occupies much of the eastern part of the continent. Smaller areas of Precambrian rocks to the North and South of the Amazonian shield are the Guiana Shield, Rio Apa and Platian cratons, to the West there is the Sao Francisco...
.
Paraná Basin
The Paraná BasinParana Basin
The Paraná Basin is a large 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 do Sul states. The remainder area is distributed in eastern Paraguay, northeastern Argentina and northern...
is a large sedimentary basin
Sedimentary basin
The term sedimentary basin is used to refer to any geographical feature exhibiting subsidence and consequent infilling by sedimentation. As the sediments are buried, they are subjected to increasing pressure and begin the process of lithification...
situated in the central-eastern part of South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. About 75% of its areal distribution occurs in Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, from Mato Grosso
Mato Grosso
Mato Grosso is one of the states of Brazil, the third largest in area, located in the western part of the country.Neighboring states are Rondônia, Amazonas, Pará, Tocantins, Goiás and Mato Grosso do Sul. It also borders Bolivia to the southwest...
to Rio Grande do Sul
Rio Grande do Sul
Rio Grande do Sul is the southernmost state in Brazil, and the state with the fifth highest Human Development Index in the country. In this state is located the southernmost city in the country, Chuí, on the border with Uruguay. In the region of Bento Gonçalves and Caxias do Sul, the largest wine...
states. The remainder area is distributed in eastern Paraguay, northeastern Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
and northern Uruguay
Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
. The shape of the depression is elliptical and covers an area of about 1500000 square kilometre, of which 110,000 km2 are in Paraguay. The basin developed during the Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
and the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
with a sedimentary record comprising rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
s from the Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
right up to the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
, thus spanning the time interval between 460 and 65 million years. The maximum thickness of the infill reaches 7,000 m in its central area and is composed of sedimentary and igneous rocks.
The Paraná Basin is a typical intra-cratonic
Craton
A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
flexural basin, although during the Paleozoic it was a gulf
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
that opened to the southwest. The basin genesis is related to the convergence
Convergent boundary
In plate tectonics, a convergent boundary, also known as a destructive plate boundary , is an actively deforming region where two tectonic plates or fragments of lithosphere move toward one another and collide...
between the former Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
and the oceanic crust
Oceanic crust
Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...
of the former Panthalassa
Panthalassa
Panthalassa , also known as the Panthalassic Ocean, was the vast global ocean that surrounded the supercontinent Pangaea, during the late Paleozoic and the early Mesozoic years. It included the Pacific Ocean to the west and north and the Tethys Ocean to the southeast...
ocean. The basin formed, at least during the Paleozoic orogenesis of the Gondwanides, a foreland basin
Foreland basin
A foreland basin is a depression that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithosphere to bend, by a process known as lithospheric flexure...
.
The Paraná River
Paraná River
The Paraná River is a river in south Central South America, running through Brazil, Paraguay and Argentina for some . It is second in length only to the Amazon River among South American rivers. The name Paraná is an abbreviation of the phrase "para rehe onáva", which comes from the Tupi language...
, that forms Paraguay's eastern boundary, flows along the central axis of the Paraná Basin and drains it.
Chaco Basin
The ChacoChaco
Chaco may refer to:in South America:* Chaco Department, a historical department in Paraguay and proposed in Bolivia* Chaco Province, a province in the northeastern part of Argentina* Chaco , a native American tribe in Paraguay...
region that makes up the northwestern half (~60%) of Paraguay is a modern foreland basin
Foreland basin
A foreland basin is a depression that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithosphere to bend, by a process known as lithospheric flexure...
that extends into Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
and Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
where it borders the Andean
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
thrust front. Superficially the Chaco Basin is an alluvial basin composed of land-derived (in contrast to marine sediments) material, mostly fine sand and clays of Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...
and Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
age. On deeper levels the Paraguayan Chaco is made up by four sub-basin
Basin
Basin may refer to:* Basin , a poem about Charlemagne's childhood* basin , the area of a drydock which can be flooded and drained* basin of attraction , an area of a nonlinear system with an attractor...
s, the Pirizal, Pilar, Carandaity and Curupaity basins.
Carandaity and Curupaity in the northwest are chieftly composed of Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s.
Pirizal (also called Pirity) Basin is made up mostly of Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
and younger sediments. The Pilar Basin is located mainly on Presidente Hayes Department
Presidente Hayes Department
Presidente Hayes is a department in Paraguay. The capital is the city of Villa Hayes. The department was named after U.S. President Rutherford B. Hayes, who was the arbitrator in a boundary dispute between Paraguay and Argentina after the War of the Triple Alliance.-Districts:The department is...
and borders the Paraná Basin
Parana Basin
The Paraná Basin is a large 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 do Sul states. The remainder area is distributed in eastern Paraguay, northeastern Argentina and northern...
across Paraguay River
Paraguay River
The Paraguay River is a major river in south central South America, running through Brazil, Bolivia, Paraguay, and Argentina...
to the east, geologically the basins are separated by the Asunción Anticline that roughly follows the path of Paraguay River.
Alto Paraguay volcanics
In Alto Paraguay DepartmentAlto Paraguay Department
Alto Paraguay is a sparsely populated department of Paraguay. The capital is the town of Fuerte Olimpo.In 1992 the Chaco Department was merged with Alto Paraguay, effectively recreating the original department Olimpo as it existed until 1945....
240 Ma old alkaline volcanic rocks underlies younger sediments. In the 1970s these rocks were studied for their potential to host valuable phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
and uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
minerals.
Paraná Igneous Province
In a strip along Paraná RiverParaná River
The Paraná River is a river in south Central South America, running through Brazil, Paraguay and Argentina for some . It is second in length only to the Amazon River among South American rivers. The name Paraná is an abbreviation of the phrase "para rehe onáva", which comes from the Tupi language...
tholeiitic basalts belonging to the Paraná Traps makes up most of the bedrock and overlies earlier sediments of the Paraná Basin
Parana Basin
The Paraná Basin is a large 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 do Sul states. The remainder area is distributed in eastern Paraguay, northeastern Argentina and northern...
. These tholeiites were erupted in the Early Cretaceous in association with the initial opening of the South Atlantic. The Creataceous volcanism did also created minor outcrops of potassic alkaline volcanics in a graben
Graben
In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....
structure developed between Asunción
Asunción
Asunción is the capital and largest city of Paraguay.The "Ciudad de Asunción" is an autonomous capital district not part of any department. The metropolitan area, called Gran Asunción, includes the cities of San Lorenzo, Fernando de la Mora, Lambaré, Luque, Mariano Roque Alonso, Ñemby, San...
and Villarrica
Villarrica, Paraguay
Villarrica is a city located in the middle of the Oriental Region of the Paraguayan territory, is capital of the Guairá Department. It was founded by the Spanish Captain Ruy Diaz de Melgarejo on May 14, 1570 in the old Guaira, today in Brazilian territory....
and in Amambay Department
Amambay Department
Amambay is a department in Paraguay. The capital is Pedro Juan Caballero.The name comes from the way is called a part of the Caaguazú Cordillera, “Amambay Cordillera”...
. Cretaceous volcanism did also left small units of sodic alkaline rocks in Misiones Department
Misiones Department
Misiones is a department located in the southern region of Paraguay. Its capital is San Juan Bautista. The eighth of Paraguay's 17 departments, it was created in 1906, then known as the San Ignacio Department, and was not given its present name until 1945...
in southern Paraguay.
