Geology of Bolivia
Encyclopedia
The geology of Bolivia compromises a variety of different lithologies
as well as tectonic
and sedimentary environments. On a synoptic scale, geological units coincide with topographical units, to begin the country is divided into a mountainous western area affected by the subduction
processes in the Pacific and an eastern lowlands of stable platforms
and shields
. The Bolivian Andes
is divided into three main ranges; these are from west to east: the Cordillera Occidental that makes up the border to Chile
and host several active volcano
es and geothermal
areas, Cordillera Central (in some contexts also called Cordillera Oriental) once extensively mined for silver
and tin
and the relatively low Cordillera Oriental that rather than being a range by its own is the eastern continuation of the Central Cordillera as a fold and thrust belt. Between the Occidental and Central Cordillera the ~3,750 meter high Altiplano
high plateau extends. This basin hosts several freshwater lakes, including Lake Titicaca
as well as salt-covered dry lake
s that bring testimony of past climate changes and lake cycles. The eastern lowlands and sub-Andean zone in Santa Cruz
, Chuquisaca
, and Tarija Department
s was once an old Paleozoic
sedimentary basin
that hosts valuable hydrocarbon reserves. Further east close to the border with Brazil lies the Guaporé Shield, made up of stable Precambrian
crystalline rock.
The Andes of Bolivia begun to rise about 200 million years ago (mya) during the Jurassic
. The western margin of what is now South America had been the place of several other orogenies
before the Andes rose. It has been hypotecized that the central Andes gained its great height 26 to 14 mya as result of a compressive failure of the lithosphere
beneath Bolivia and neighboring areas. The great heights of the Altiplano, Codillera Occidental and Cordillera Oriental are isostatically compensated by a up to 70 km deep crust
. It's not known to which extent climate change
s induced by the rise of the Andes caused the extreme aridity of Atacama Desert
and adjacent parts of Bolivia or if a preexisting desert climate
and associated low erosion rates allowed the mountains to build up to their current heights. A hypothesis holds that scarce sediment supply to the Atacama Trench caused by arid climate induced high shear stress
es in the subduction
process that enchanced the Andean mountain building.
and the Pacific from the endorheic Altiplano basin. The western volcanoes of Bolivia are part of the Central Volcanic Zone of the Andes, a major upper Cenozoic
volcanic province. Volcanic eruptions in Bolivia are scarce, the latest one occurred in Irruputuncu
in 1995. Volcanic hazards do not represent any threat to the mayor populated centres which are all in the eastern Altiplano or further east, far away from the volcanic centers. Although the Western Cordillera concentrates most active volcanoes (volcanoes active in the last 10000 years) many old large stratovolcano
es rises up to 100 km away from the main line of the Western Cordillera.
The Altiplano plateau or Meseta del Collasuyu to differentiate it from other Andean high plateaux is a wide and long-lived intermontane sedimentary basin with no outlet, its endorheic
. The Altiplano is an infill of sedimentary material
from both Cordillera Occidental and Cordillera Oriental. The origin of the Altiplano and its great height has long been major question among geologists. Today the Altiplano is believed to have been an early foreland basin
of the "proto-Andes" that got uplifted by crustal shortening
in the Late Miocene
.
The Bolivian Altiplano host the world's largest reserves of lithium
. These reserves are in the salt-saturated waters of Salar de Uyuni
and Salar de Coipasa non of which are currently being commercially exploated for lithium. Salt is extracted from the saltars in minor amounts to be sold as table salt after being added iodine
from Chile
.
and corresponds to eastward proyection of the Arica
elbow, the bend of south Amicas coastline at the Peru-Chile border. North of the bend Cordillera Centrals batholith
s are northwest-southeast oriented while south of it they are north-south oriented. These bodies of granitic
to granodioritic
composition belong were formed in two episodes; the Early Mesozoic
(199–180 Ma) and the Neogene
(19–8 Ma). The emplacement of this igneous bodies have been interpreted as an effect of two temporary decreases in subduction angle
s of the ancient Farallon Plate
. This arc of magmatic material host Bolivias worldwide renown tin
belt as well the famous silver
mine of Potosí
. These mineralizations are of the porphyry
mineralization
type that are typical for convergent plate margins
. The Cordillera Real
form the northern, highly uplifted and eroded, part of the Central Cordillera.
The Sub-Andean Zone and the Northern and Eastersn Lowlands share a common ancient history but has since the Andean orogeny developed to two distinct zones. While both zones share essentially the same old sedimentary
platform
strata
the strata at the Sub-Andean Zone have been folded and thrusted into a fold and thrust belt with structural traps where hydrocarbon
fluids have accumulated. The limit between the fold and thrust belt and the Eastern Lowlands is drawn by the Serranía del Aguaragüe
a north-south range representing the Andean thrust front.
and Ordovician
age strata some of which are fossil
-bearing. The fold and thrust makes up the framework of the hydrographic network of Pilcomayo
and other rivers. Currently one of Bolivia's most seismic zone is the Cochabamba Fault Zone
located just below the city of Cochabamba
and its fertile valley. This fault zone is related to the Arica
elbow and the bend in the Andes at this latitude.
sedimentary Chaco
-Tarija
Basin that has considerable hydrocarbon reserves. During the Carboniferous
, the Chaco-Tarija Basin was covered by thick sequence
s that included sandstone
filled channels. In the 1970s these sandstone were interpreted as tillite from the late Paleozoic glaciations
, but new interpretations consider them to be of marine origin but still glacially influenced. The depositional environment
for these channel systems has been likened to that on the floor of the present day Labrador Sea
, which was influenced by repeated Pleistocene
glaciations . The late Cenozoic
deformation associated with the Andean orogeny forced hydrocarbons sourced
in Devonian
shales to migrate to shallower stratigraphical
levels.
milleau are mostly covered by Tertiary and Quaternary deposits. The bulk of these deposties correspond to laterite
s. River erosion
and sediment transport
have created a large number of oxbow lake
s and added copious meander
s to the rivers.
the crystalline and Precambrian
Guaporé Shield (also called Central Brazil Shield) makes up most of the bedrock
but is mostly covered by Tertiary
laterite
s and Quaternary
alluvial
basins. The shield expresses itself topographically as a large elevated hinterland
located north of Serranías Chiquitanas
towards the Brazilian border. High grade metamophic rocks occur in the Bolivian part of the Guaporé Shiled partly due to the 2000 millions years old "Transamazonian Tectono-Thermal Event" that affected parts of South America. Low grade metamorphic rocks occur as well. The Guaporé Shield is believed to extend beneath a the Phanerozoic
Tarija-Chaco and Beni Basin
sediments into the Andes. Weakenses in the Guaporé Shield have been suggested to be responsible for the formation of the Arica Elbow. The East-West Río Mercedes Line in the Guaporé Shield host several Proterozoic
diabase
intrusion
s. As of 1985 the rocks of Guaporé Shiled were considered to be poorly known. Near the Brazilian border the iron deposit of El Mutún
stands out as the world's largest iron ore deposit. Its located in the Serranía de El Mutún, also called Cerro Mutún or Serranía de Jacadigo in Brazil
. The shield also underlies Serrania Caparuch or Huanchaca which is the inspiration for the Lost World of Conan Doyle
Proyecto Precambrico, an Anglo-Bolivian Technical cooperation project, explored the area between 1976 and 1986. There are a series of published 1;250 000 scale maps of the area with accompanying bilingual reports, along with more detailed 1;100 000 maps of regions of economic interest. There is a published geochemical atlas. Most of this data is summarised in the overseas memoir
Lithology
The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples or with low magnification microscopy, such as colour, texture, grain size, or composition. It may be either a detailed description of these characteristics or be a summary of...
as well as tectonic
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
and sedimentary environments. On a synoptic scale, geological units coincide with topographical units, to begin the country is divided into a mountainous western area affected by the subduction
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
processes in the Pacific and an eastern lowlands of stable platforms
Platform (geology)
In geology, a platform is a continental area covered by relatively flat or gently tilted, mainly sedimentary strata, which overlie a basement of consolidated igneous or metamorphic rocks of an earlier deformation...
and shields
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...
. The Bolivian Andes
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...
is divided into three main ranges; these are from west to east: the Cordillera Occidental that makes up the border to Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
and host several active volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
es and geothermal
Geothermal
Geothermal is related to energy and may refer to:* The geothermal gradient and associated heat flows from within the Earth- Renewable technology :...
areas, Cordillera Central (in some contexts also called Cordillera Oriental) once extensively mined for silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
and tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
and the relatively low Cordillera Oriental that rather than being a range by its own is the eastern continuation of the Central Cordillera as a fold and thrust belt. Between the Occidental and Central Cordillera the ~3,750 meter high Altiplano
Altiplano
The Altiplano , in west-central South America, where the Andes are at their widest, is the most extensive area of high plateau on Earth outside of Tibet...
high plateau extends. This basin hosts several freshwater lakes, including Lake Titicaca
Lake Titicaca
Lake Titicaca is a lake located on the border of Peru and Bolivia. It sits 3,811 m above sea level, making it the highest commercially navigable lake in the world...
as well as salt-covered dry lake
Dry lake
Dry lakes are ephemeral lakebeds, or a remnant of an endorheic lake. Such flats consist of fine-grained sediments infused with alkali salts. Dry lakes are also referred to as alkali flats, sabkhas, playas or mud flats...
s that bring testimony of past climate changes and lake cycles. The eastern lowlands and sub-Andean zone in Santa Cruz
Santa Cruz Department
Santa Cruz, with an area of 370,621 km², is the largest of the nine constituent departments of Bolivia. In the 2001 census, it reported a population of 2,029,471. The capital is the city of Santa Cruz de la Sierra. The state is one of the wealthiest states in Bolivia with huge reserves of...
, Chuquisaca
Chuquisaca Department
Chuquisaca is a department of Bolivia located in the center south. It borders on the departments of Cochabamba, Tarija, Potosí, and Santa Cruz. The departmental capital is Sucre, which is also the constitutional capital of Bolivia.-Geography:...
, and Tarija Department
Tarija Department
Tarija is a department in Bolivia. It is located in south-eastern Bolivia bordering Argentina to the south and Paraguay to the east. According to the 2001 census, it has a population of 391,226 inhabitants. It has an area of 37.623 km²...
s was once an old Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
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...
that hosts valuable hydrocarbon reserves. Further east close to the border with Brazil lies the Guaporé Shield, made up of stable 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...
crystalline rock.
Andes
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
. The western margin of what is now South America had been the place of several other orogenies
Orogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
before the Andes rose. It has been hypotecized that the central Andes gained its great height 26 to 14 mya as result of a compressive failure of the lithosphere
Lithosphere
The lithosphere is the rigid outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater.- Earth's lithosphere :...
beneath Bolivia and neighboring areas. The great heights of the Altiplano, Codillera Occidental and Cordillera Oriental are isostatically compensated by a up to 70 km deep crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
. It's not known to which extent climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
s induced by the rise of the Andes caused the extreme aridity of Atacama Desert
Atacama Desert
The Atacama Desert is a plateau in South America, covering a strip of land on the Pacific coast, west of the Andes mountains. It is, according to NASA, National Geographic and many other publications, the driest desert in the world...
and adjacent parts of Bolivia or if a preexisting desert climate
Desert climate
A desert climate , also known as an arid climate, is a climate that does not meet the criteria to be classified as a polar climate, and in which precipitation is too low to sustain any vegetation at all, or at most a very scanty scrub.An area that features this climate usually experiences less than...
and associated low erosion rates allowed the mountains to build up to their current heights. A hypothesis holds that scarce sediment supply to the Atacama Trench caused by arid climate induced high shear stress
Shear stress
A shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...
es in the subduction
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
process that enchanced the Andean mountain building.
Western Cordillera
The Western Cordillera is made up by a series of active and extinct volcanoes rising from the western edge of the Altimplano plateau. This range divides the Chilean watershreds of Salar de AtacamaSalar de Atacama
Salar de Atacama is the largest salt flat in Chile. It is located south of San Pedro de Atacama, is surrounded by mountains and has no drainage outlets. To the east is enclosed by the main chain of the Andes, while to the west lies a secondary mountain range of the Andes called Cordillera de Domeyko...
and the Pacific from the endorheic Altiplano basin. The western volcanoes of Bolivia are part of the Central Volcanic Zone of the Andes, a major upper Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
volcanic province. Volcanic eruptions in Bolivia are scarce, the latest one occurred in Irruputuncu
Irruputuncu
Irruputuncu is a stratovolcano which lies on the border of Chile and Bolivia. It is a relatively small peak, lying within the collapse scarp of a debris avalanche from earlier in the Holocene, which was built up by eruptions to fill much of that feature. There are two craters lying at the summit,...
in 1995. Volcanic hazards do not represent any threat to the mayor populated centres which are all in the eastern Altiplano or further east, far away from the volcanic centers. Although the Western Cordillera concentrates most active volcanoes (volcanoes active in the last 10000 years) many old large stratovolcano
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...
es rises up to 100 km away from the main line of the Western Cordillera.
Altiplano plateau
Endorheic
An endorheic basin is a closed drainage basin that retains water and allows no outflow to other bodies of water such as rivers or oceans...
. The Altiplano is an infill of sedimentary material
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....
from both Cordillera Occidental and Cordillera Oriental. The origin of the Altiplano and its great height has long been major question among geologists. Today the Altiplano is believed to have been an early 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...
of the "proto-Andes" that got uplifted by crustal shortening
Orogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
in the Late Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
.
The Bolivian Altiplano host the world's largest reserves of lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
. These reserves are in the salt-saturated waters of Salar de Uyuni
Salar de Uyuni
Salar de Uyuni is the world's largest salt flat at . It is located in the Potosí and Oruro departments in southwest Bolivia, near the crest of the Andes, and is elevated above the mean sea level. The Salar was formed as a result of transformations between several prehistoric lakes...
and Salar de Coipasa non of which are currently being commercially exploated for lithium. Salt is extracted from the saltars in minor amounts to be sold as table salt after being added iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
from Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
.
Central Cordillera
Cordillera Central is made up of a bended arc of plutons. The bend occurs at the latitude of CochabambaCochabamba
Cochabamba is a city in central Bolivia, located in a valley bearing the same name in the Andes mountain range. It is the capital of the Cochabamba Department and is the fourth largest city in Bolivia with an urban population of 608,276 and a metropolitan population of more than 1,000,000 people...
and corresponds to eastward proyection of the Arica
Arica
Arica is a city in northern Chile. "Arica" may also refer to:Places* Arica and Parinacota Region, Chile* Arica Airport , Chile* Arica, Amazonas, town in Colombia* Rio Aricá-açu, tributary of the Cuiabá River south of Cuiabá, BrazilOther...
elbow, the bend of south Amicas coastline at the Peru-Chile border. North of the bend Cordillera Centrals batholith
Batholith
A batholith is a large emplacement of igneous intrusive rock that forms from cooled magma deep in the Earth's crust...
s are northwest-southeast oriented while south of it they are north-south oriented. These bodies of granitic
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
to granodioritic
Granodiorite
Granodiorite is an intrusive igneous rock similar to granite, but containing more plagioclase than orthoclase-type feldspar. Officially, it is defined as a phaneritic igneous rock with greater than 20% quartz by volume where at least 65% of the feldspar is plagioclase. It usually contains abundant...
composition belong were formed in two episodes; the Early 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...
(199–180 Ma) and the Neogene
Neogene
The Neogene is a geologic period and system in the International Commission on Stratigraphy Geologic Timescale starting 23.03 ± 0.05 million years ago and ending 2.588 million years ago...
(19–8 Ma). The emplacement of this igneous bodies have been interpreted as an effect of two temporary decreases in subduction angle
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
s of the ancient Farallon Plate
Farallon Plate
The Farallon Plate was an ancient oceanic plate, which began subducting under the west coast of the North American Plate— then located in modern Utah— as Pangaea broke apart during the Jurassic Period...
. This arc of magmatic material host Bolivias worldwide renown tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
belt as well the famous silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
mine of Potosí
Potosí
Potosí is a city and the capital of the department of Potosí in Bolivia. It is one of the highest cities in the world by elevation at a nominal . and it was the location of the Spanish colonial mint, now the National Mint of Bolivia...
. These mineralizations are of the porphyry
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...
mineralization
Mineralization (geology)
In geology, mineralization is the hydrothermal deposition of economically important metals in the formation of ore bodies or "lodes".The first scientific studies of this process took place in Cornwall, United Kingdom by J.W.Henwood FRS and later by R.W...
type that are typical for convergent plate margins
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...
. The Cordillera Real
Cordillera Real (Bolivia)
The Cordillera Real is a mountain range in the South American Altiplano of Bolivia. This range of fold mountains, largely composed of granite, is located southeast of Lake Titicaca, and east of the Bolivian capital of La Paz, measuring 125 km in length and 20 km in width...
form the northern, highly uplifted and eroded, part of the Central Cordillera.
Lowlands and Sub-Andean zone
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
platform
Platform (geology)
In geology, a platform is a continental area covered by relatively flat or gently tilted, mainly sedimentary strata, which overlie a basement of consolidated igneous or metamorphic rocks of an earlier deformation...
strata
STRATA
Strata Marketing Inc. is a Chicago, Illinois-based software company involved in connecting media buyers and sellers. It is owned by Comcast. As of 2010, it processes about $50 billion worth of media buys annually.-History:...
the strata at the Sub-Andean Zone have been folded and thrusted into a fold and thrust belt with structural traps where hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
fluids have accumulated. The limit between the fold and thrust belt and the Eastern Lowlands is drawn by the Serranía del Aguaragüe
Serranía del Aguaragüe
Serranía del Aguaragüe is the easternmost range of Bolivia's Cordillera Oriental. Serranía del Aguaragüe streches out in a north-south fashion from the latitude of crossing the Bolivian departments of Tarija, Chuquisaca and Santa Cruz. Geologically it corresponds to the thrust front where the Andes...
a north-south range representing the Andean thrust front.
Fold and thrust belt
The relatively low Cordillera Oriental, located east of Cordillera Central, are part of a fold and thrust belt and exposes SilurianSilurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
and 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...
age strata some of which are fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
-bearing. The fold and thrust makes up the framework of the hydrographic network of Pilcomayo
Pilcomayo River
The Pilcomayo River is a river in central South America. At long, it is the longest western tributary of the Paraguay River. Its drainage basin is in area, and its mean discharge is ....
and other rivers. Currently one of Bolivia's most seismic zone is the Cochabamba Fault Zone
Cochabamba Fault Zone
The Cochabamba Fault Zone or Cochabamba Shear Zone is a east-southeast trending zone of sinistral strike-slip faults near the city of Cochabamba in the Bolivian Andes. The movements along Cochabamba Fault Zone are related to the bend in the Andes from running in a north-west direction to a...
located just below the city of Cochabamba
Cochabamba
Cochabamba is a city in central Bolivia, located in a valley bearing the same name in the Andes mountain range. It is the capital of the Cochabamba Department and is the fourth largest city in Bolivia with an urban population of 608,276 and a metropolitan population of more than 1,000,000 people...
and its fertile valley. This fault zone is related to the Arica
Arica
Arica is a city in northern Chile. "Arica" may also refer to:Places* Arica and Parinacota Region, Chile* Arica Airport , Chile* Arica, Amazonas, town in Colombia* Rio Aricá-açu, tributary of the Cuiabá River south of Cuiabá, BrazilOther...
elbow and the bend in the Andes at this latitude.
Eastern Lowlands
The geology of the eastern lowlands is dominated by the ancient PaleozoicPaleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
sedimentary Chaco
Gran Chaco
The Gran Chaco is a sparsely populated, hot and semi-arid lowland region of the Río de la Plata basin, divided among eastern Bolivia, Paraguay, northern Argentina and a portion of the Brazilian states of Mato Grosso and Mato Grosso do Sul, where it is connected with the Pantanal region...
-Tarija
Tarija Department
Tarija is a department in Bolivia. It is located in south-eastern Bolivia bordering Argentina to the south and Paraguay to the east. According to the 2001 census, it has a population of 391,226 inhabitants. It has an area of 37.623 km²...
Basin that has considerable hydrocarbon reserves. During the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
, the Chaco-Tarija Basin was covered by thick sequence
Sequence (geology)
A sequence in geology refers to a sequence of geological events, processes, or rocks, arranged in chronological order.A rock stratigraphical sequence is a geographical, or lithostratigraphic, discrete unit greater than a group or supergroup rank, and traceable over large areas of a continent...
s that included sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
filled channels. In the 1970s these sandstone were interpreted as tillite from the late Paleozoic glaciations
Karoo Ice Age
The Karoo Ice Age from 360–260 Ma was the second major ice age of the Phanerozoic Eon. It is named after the glacial tills found in the Karoo region of South Africa where evidence for this ice age was first clearly identified....
, but new interpretations consider them to be of marine origin but still glacially influenced. The depositional environment
Sedimentary depositional environment
In geology, sedimentary depositional environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock...
for these channel systems has been likened to that on the floor of the present day Labrador Sea
Labrador Sea
The Labrador Sea is an arm of the North Atlantic Ocean between the Labrador Peninsula and Greenland. The sea is flanked by continental shelves to the southwest, northwest, and northeast. It connects to the north with Baffin Bay through the Davis Strait...
, which was influenced by repeated Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
glaciations . The late Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
deformation associated with the Andean orogeny forced hydrocarbons sourced
Source rock
In petroleum geology, source rock refers to rocks from which hydrocarbons have been generated or are capable of being generated. They form one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been deposited in a variety of environments including...
in Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
shales to migrate to shallower stratigraphical
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
levels.
Northern Lowlands
The Northern Lowlands are and have long been a depositionalDeposition (geology)
Deposition is the geological process by which material is added to a landform or land mass. Fluids such as wind and water, as well as sediment flowing via gravity, transport previously eroded sediment, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of...
milleau are mostly covered by Tertiary and Quaternary deposits. The bulk of these deposties correspond to laterite
Laterite
Laterites are soil types rich in iron and aluminium, formed in hot and wet tropical areas. Nearly all laterites are rusty-red because of iron oxides. They develop by intensive and long-lasting weathering of the underlying parent rock...
s. River erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
and sediment transport
Sediment transport
Sediment transport is the movement of solid particles , typically due to a combination of the force of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained...
have created a large number of oxbow lake
Oxbow lake
An oxbow lake is a U-shaped body of water formed when a wide meander from the main stem of a river is cut off to create a lake. This landform is called an oxbow lake for the distinctive curved shape, named after part of a yoke for oxen. In Australia, an oxbow lake is called a billabong, derived...
s and added copious meander
Meander
A meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a stream erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternately eroding sediments from the outside of a bend and depositing them on the...
s to the rivers.
Guaporé Shield
In the north and east of Santa Cruz DepartmentSanta Cruz Department
Santa Cruz, with an area of 370,621 km², is the largest of the nine constituent departments of Bolivia. In the 2001 census, it reported a population of 2,029,471. The capital is the city of Santa Cruz de la Sierra. The state is one of the wealthiest states in Bolivia with huge reserves of...
the crystalline and 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...
Guaporé Shield (also called Central Brazil Shield) makes up most of the bedrock
Bedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
but is mostly 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...
laterite
Laterite
Laterites are soil types rich in iron and aluminium, formed in hot and wet tropical areas. Nearly all laterites are rusty-red because of iron oxides. They develop by intensive and long-lasting weathering of the underlying parent rock...
s 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...
alluvial
Alluvium
Alluvium is loose, unconsolidated soil or sediments, eroded, deposited, and reshaped by water in some form in a non-marine setting. Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel...
basins. The shield expresses itself topographically as a large elevated hinterland
Hinterland
The hinterland is the land or district behind a coast or the shoreline of a river. Specifically, by the doctrine of the hinterland, the word is applied to the inland region lying behind a port, claimed by the state that owns the coast. The area from which products are delivered to a port for...
located north of Serranías Chiquitanas
Serranías Chiquitanas
The Serranías Chiquitanas are a group of low mountain ranges in the northeast of the Bolivian department of Santa Cruz. The ranges are located at the southern periphery of the discrete massif of the Guaporé shield. The Serranías Chiquitanas stands out of the sorrounding lowlands as a series of...
towards the Brazilian border. High grade metamophic rocks occur in the Bolivian part of the Guaporé Shiled partly due to the 2000 millions years old "Transamazonian Tectono-Thermal Event" that affected parts of South America. Low grade metamorphic rocks occur as well. The Guaporé Shield is believed to extend beneath a the Phanerozoic
Phanerozoic
The Phanerozoic Eon is the current eon in the geologic timescale, and the one during which abundant animal life has existed. It covers roughly 542 million years and goes back to the time when diverse hard-shelled animals first appeared...
Tarija-Chaco and Beni Basin
Beni River
The Beni River is a river in the north of Bolivia.It rises north of La Paz and flows northeast through the pampas. One of the tributary rivers is Tuichi River in the Madidi National Park. Tuichi River joins the Beni River upstream from the town Rurrenabaque. South of Rurrenabaque, Río Beni runs...
sediments into the Andes. Weakenses in the Guaporé Shield have been suggested to be responsible for the formation of the Arica Elbow. The East-West Río Mercedes Line in the Guaporé Shield host several 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"...
diabase
Diabase
Diabase or dolerite is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. In North American usage, the term diabase refers to the fresh rock, whilst elsewhere the term dolerite is used for the fresh rock and diabase refers to altered material...
intrusion
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
s. As of 1985 the rocks of Guaporé Shiled were considered to be poorly known. Near the Brazilian border the iron deposit of El Mutún
El Mutún
El Cerro Mutún is the world's largest iron ore deposit. Located in the Germán Busch Province in the Santa Cruz Department of Bolivia, near Puerto Suárez, it extends across the border into Brazil, where it is called the Serrania de Jacadigo. Also known as the "Serrania Mutún", it has an area of...
stands out as the world's largest iron ore deposit. Its located in the Serranía de El Mutún, also called Cerro Mutún or Serranía de Jacadigo 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...
. The shield also underlies Serrania Caparuch or Huanchaca which is the inspiration for the Lost World of Conan Doyle
Conan Doyle
Conan Doyle is a rugby player. His club is Garryowen. His usual position is inside centre, but he also plays out-half. He has made two appearances for Munster Rugby in the Magners League, but was released by Munster at the end of the 2008/2009 season. While at Munster he was selected for the...
Proyecto Precambrico, an Anglo-Bolivian Technical cooperation project, explored the area between 1976 and 1986. There are a series of published 1;250 000 scale maps of the area with accompanying bilingual reports, along with more detailed 1;100 000 maps of regions of economic interest. There is a published geochemical atlas. Most of this data is summarised in the overseas memoir