The geology of Brazil includes very ancient craton basement rock from the Precambrian overlain by sedimentary rocks and intruded by igneous activity, as well as impacted by the rifting of the Atlantic Ocean.
Much of the rock underlying Brazil formed during the Precambrian, including the São Francisco Craton which outcrops in Minas Gerais and Bahia. In the Mesoproterozoic, the Rio de la Plata Craton (beneath southern Brazil), the vast Amazonia Craton, and the small São Luis Craton and sections of the Congo Craton which form the basement rock of much of Brazil were joined with Africa.
Earlier, during the Archean, the São Francisco Craton developed between 3.2 and 2.6 billion years ago and grew as microcontinents collided with it, forming a series of mobile belts. The rocks became a craton, a section of stable continental crust by the end of the Trans-amazonian orogeny 1.8 billion years ago. [1] The Borborema Province is beneath areas in the northeast, with Paleoproterozoic craton basement rock originally assembled around even older Archean rocks. It includes three zones. The Zona Transversal is in the central sub-province between the Pernambuco Shear Zone and the São Francisco Craton, displaying 2.2 billion year old gneiss, a suite of metavolcanic, metasedimentary and metaplutonic rocks as well as pluton formations from 640 to 540 million years ago. [2] Uranium-lead dating has revealed two periods of acid magmatism in central Brazil, which produced the Goias tin province in granite and rhyolite. [3]
The Pernambuco Shear Zone, or lineament, is a steeply-dipping ductile shear zone formed 600 million years ago during the Brasiliano orogeny. The zone has two 100 meter wide mylonite zones surrounding it. [4] The Brasiliano orogeny was a South American extension of the major Pan-African orogeny during a period when the two continents were joined. The proto-South Atlantic opened and then closed with subduction by around 750 million years ago in the Katangan episode. [5] High potassium feldspar granites, gabbro and diorite emplaced following the Pan-African orogeny 600 million years ago in Goias, in central Brazil. [6]
In the northeast, the Brasiliano-Pan-African orogeny period led to reverse-type metamorphism, similar to what is now found in the Himalayas and thrust nappe formations 150 kilometers to the west. [7]
In the southeast of the country, the remnants of two mountain belts record the collision between three sections of continental crust: the Brasilia, São Paulo and Vitoria plates. [8]
Convergent plate tectonics within the continent of Gondwana had a major influence in the Paleozoic. [9] The Maranhao intracratonic basin in Piaui and Maranhao, close to the mouth of the Amazon spans 600,000 square kilometers and filled with 2.5 kilometers of sandstone and shale from the Cambrian through the Devonian. The sequence is capped with Mississippian, continental, marine and fluvial sandstones. [10]
With South America and Africa still conjoined, glaciers advanced across the region in the late Paleozoic. Glacial grooves and erosion marks scored the igneous, metamorphic and sedimentary rocks in the Parana Basin. Diamictite and sandstone from this period are common in the southeast. [11] The Early Permian Rio Bonito Formation in the Parana Basin contains fossil charcoal left by wildfires. [12]
Drilling in the Parana Basin and sampling of dikes around São Paulo revealed that the Serra Geral basalts and Kaoko basalts in Namibia both formed at the same time—121 million years ago—marking the beginning of the rifting open of the South Atlantic. [13] Elsewhere, flood basalts and hypabyssal rocks from the Mesozoic mark the opening of the ocean in Maranha in the north. [14] The Pernambuco Shear Zone in the northeast reactivated during the breakup of the supercontinent Pangea in the Cretaceous. In the late Cretaceous, kimberlite, carbonatite, olivine melilitite and tuffaceous diatreme intruded the Sao Francisco Craton. [15] Magmatic activity also took place in the Borborema Province in the northeast through the Jurassic and Cretaceous. [16] For almost 50 million years after the region rifted apart from Africa, relatively little material eroded. But analysis of offshore sediments indicates a rapid increase at the boundary with Paleogene. [17]
Continued crustal extension tied to the opening of the Atlantic continued into the Cenozoic. Shear and extension related fractures control water well productivity in São Paulo. [18] Along the coastline of Rio de Janeiro, an alkaline igneous complex intruded older Precambrian rocks with nepheline syenite, gabbro, shonkinite and clinopyroxenite. [19] Alkali basalt erupted in Paraiba and Rio Grande do Norte. [20] Brittle deformation and dike swarms accompanied the formation of the Ponta Grossa Arch in the Parana Basin, within sandstone and siltstone of the Piramboia and Botucatu formations and the Serra Geral Formation tholeiitic basalt. [21] In the northeast, the 130 kilometer long Pereiro Massif was uplifted. [22]
In the Paleogene, and in the early and late Miocene, sea levels dropped, recorded in sedimentary rocks in Para in the northeast. [23] Simultaneously, turbidites flooded into the offshore Sao Tome deep sea basin. [24]
Within the Holocene, a short run climate change associated with the draining of a glacial lake is recorded in Brazilian stalagmites, indicating an intense South American summer monsoon. [25]
Formed between the Mesozoic and Cenozoic, Brazil has numerous offshore basins that contain oil, related to the rifting of the Atlantic Ocean. The Sergipe-Alagoas Basin is an example of Aptian age shale, conglomerate and sandstone deposited in the final phase of rifting, while the Miranga, Aracas, Dom Joao and Agua Grande fields reflect mid-Mesozoic lake-bed shales, with high oil-content Jurassic sandstones above them. [26]
The geology of the Appalachians dates back more than 1.1 billion years to the Mesoproterozoic era when two continental cratons collided to form the supercontinent Rodinia, 500 million years prior to the later development of the range during the formation of the supercontinent Pangea. The rocks exposed in today's Appalachian Mountains reveal elongate belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks and slivers of ancient ocean floor – strong evidence that these rocks were deformed during plate collision. The birth of the Appalachian ranges marks the first of several mountain building plate collisions that culminated in the construction of the supercontinent Pangea with the Appalachians and neighboring Anti-Atlas mountains near the center. These mountain ranges likely once reached elevations similar to those of the Alps and the Rocky Mountains before they were eroded.
Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although originally it also included the cratonic areas of Greenland and also the northwestern part of Scotland, known as the Hebridean Terrane. During other times in its past, Laurentia has been part of larger continents and supercontinents and itself consists of many smaller terranes assembled on a network of Early Proterozoic orogenic belts. Small microcontinents and oceanic islands collided with and sutured onto the ever-growing Laurentia, and together formed the stable Precambrian craton seen today.
The geology of Uruguay combines areas of Precambrian-aged shield units with a region of volcanic rock erupted during the Cretaceous and copious sedimentary facies the oldest of which date from the Devonian. Big events that have shaped the geology of Uruguay include the Transamazonian orogeny, the breakup of Rodinia and the opening of the South Atlantic.
The country of Paraguay lies geologically at the borderzone between several cratons. Due to thick Cenozoic sediment cover and regolith development few outcrops are available in Paraguay. East of Paraguay River Precambrian and Early Paleozoic crystalline basement crop out mainly in the heights of Caapucú and Apa. The geological processes that have shaped Paraguay's bedrock and sedimentary basins are diverse including rifting, marine sedimentation, metamorphism, eruption of flood basalts and alkaline potassic volcanism.
The Huangling Anticline or Complex represents a group of rock units that appear in the middle of the Yangtze Block in South China, distributed across Yixingshan, Zigui, Huangling, and Yichang counties. The group of rock involves nonconformity that sedimentary rocks overlie the metamorphic basement. It is a 73-km long, asymmetrical dome-shaped anticline with axial plane orientating in the north-south direction. It has a steeper west flank and a gentler east flank. Basically, there are three tectonic units from the anticline core to the rim, including Archean to Paleoproterozoic metamorphic basement, Neoproterozoic to Jurassic sedimentary rocks, and Cretaceous fluvial deposit sedimentary cover. The northern part of the core is mainly tonalite-trondhjemite-gneiss (TTG) and Cretaceous sedimentary rock called the Archean Kongling Complex. The middle of the core is mainly the Neoproterozoic granitoid. The southern part of the core is the Neoproterozoic potassium granite. Two basins are situated on the western and eastern flanks of the core, respectively, including the Zigui basin and Dangyang basin. Both basins are synforms while Zigui basin has a larger extent of folding. Yuanan Graben and Jingmen Graben are found within the Dangyang Basin area. The Huangling Anticline is an important area that helps unravel the tectonic history of the South China Craton because it has well-exposed layers of rock units from Archean basement rock to Cretaceous sedimentary rock cover due to the erosion of the anticline.
Hainan Island, located in the South China Sea off the Chinese coast and separated from mainland China by the Qiongzhou Strait, has a complex geological history that it has experienced multiple stages of metamorphism, volcanic and intrusive activities, tectonic drifting and more. The oldest rocks, the Proterozoic metamorphic basement, are not widely exposed, but mostly found in the western part of the Island.
The geology of the Democratic Republic of the Congo is extremely old, on the order of several billion years for many rocks. The country spans the Congo Craton: a stable section of ancient continental crust, deformed and influenced by several different mountain building orogeny events, sedimentation, volcanism and the geologically recent effects of the East Africa Rift System in the east. The country's complicated tectonic past have yielded large deposits of gold, diamonds, coltan and other valuable minerals.
The geology of Mozambique is primarily extremely old Precambrian metamorphic and igneous crystalline basement rock, formed in the Archean and Proterozoic, in some cases more than two billion years ago. Mozambique contains greenstone belts and spans the Zimbabwe Craton, a section of ancient stable crust. The region was impacted by major tectonic events, such as the mountain building Irumide orogeny, Pan-African orogeny and the Snowball Earth glaciation. Large basins that formed in the last half-billion years have filled with extensive continental and marine sedimentary rocks, including rocks of the extensive Karoo Supergroup which exist across Southern Africa. In some cases these units are capped by volcanic rocks. As a result of its complex and ancient geology, Mozambique has deposits of iron, coal, gold, mineral sands, bauxite, copper and other natural resources.
The geology of Tanzania began to form in the Precambrian, in the Archean and Proterozoic eons, in some cases more than 2.5 billion years ago. Igneous and metamorphic crystalline basement rock forms the Archean Tanzania Craton, which is surrounded by the Proterozoic Ubendian belt, Mozambique Belt and Karagwe-Ankole Belt. The region experienced downwarping of the crust during the Paleozoic and Mesozoic, as the massive Karoo Supergroup deposited. Within the past 100 million years, Tanzania has experienced marine sedimentary rock deposition along the coast and rift formation inland, which has produced large rift lakes. Tanzania has extensive, but poorly explored and exploited natural resources, including coal, gold, diamonds, graphite and clays.
The geology of South Sudan is founded on Precambrian igneous and metamorphic rocks, that cover 40 percent of the country's surface and underlie other rock units. The region was affected by the Pan-African orogeny in the Neoproterozoic and extensional tectonics in the Mesozoic that deposited very thick oil-bearing sedimentary sequences in rift basins. Younger basalts, sandstones and sediments formed in the last 66 million years of the Cenozoic. The discovery of oil in 1975 was a major factor in the Second Sudanese Civil War, leading up to independence in 2011. The country also has gold, copper, cobalt, zinc, iron, marble, limestone and dolomite.
The geology of Libya formed on top of deep and poorly understood Precambrian igneous and metamorphic crystalline basement rock. Most of the country is intra-craton basins, filled with thick layers of sediment. The region experienced long-running subsidence and terrestrial sedimentation during the Paleozoic, followed by phases of volcanism and intense folding in some areas, and widespread flooding in the Mesozoic and Cenozoic due to a long marine transgression. Libya has the largest hydrocarbon reserves in Africa, as well as deposits of evaporites.
The bedrock under the U.S. State of Colorado was assembled from island arcs accreted onto the edge of the ancient Wyoming Craton. The Sonoma orogeny uplifted the ancestral Rocky Mountains in parallel with the diversification of multicellular life. Shallow seas covered the regions, followed by the uplift current Rocky Mountains and intense volcanic activity. Colorado has thick sedimentary sequences with oil, gas and coal deposits, as well as base metals and other minerals.
The geology of Venezuela includes ancient Precambrian igneous and metamorphic basement rocks, layered with sedimentary rocks from the Paleozoic and Mesozoic and thick geologically recent Cenozoic sediments with extensive oil and gas.
The geology of Argentina includes ancient Precambrian basement rock affected by the Grenville orogeny, sediment filled basins from the Mesozoic and Cenozoic as well as newly uplifted areas in the Andes.
The geology of Peru includes ancient Proterozoic rocks, Paleozoic and Mesozoic volcanic and sedimentary rocks, and numerous basins and the Andes Mountains formed in the Cenozoic.
The geology of the Northwest Territories has been mapped in different quadrangles by the Canadian government. The region has some of the oldest rocks in the world and among the oldest in North America, formed from several sections of stable craton continental crust, including the Slave Craton, Rae Craton and Hearne Craton. These rocks form the Archean and Proterozoic Precambrian basement rock of the region and are the subject of extensive research to understand continental crust and tectonic conditions on the early Earth.
The geology of Newfoundland and Labrador includes basement rocks formed as part of the Grenville Province in the west and Labrador and the Avalonian microcontinent in the east. Extensive tectonic changes, metamorphism and volcanic activity have formed the region throughout Earth history.
The Parnaíba Basin is a large cratonic sedimentary basin located in the North and Northeast portion of Brazil. About 50% of its areal distribution occurs in the state of Maranhão, and the other 50% occurring in the state of Pará, Piauí, Tocantins, and Ceará. It is one of the largest Paleozoic basins in the South American Platform. The basin has a roughly ellipsoidal shape, occupies over 600,000 km2, and is composed of ~3.4 km of mainly Paleozoic sedimentary rock that overlies localized rifts.
The geology of the Kimberley, a region of Western Australia, is a rock record of early Proterozoic plate collision, orogeny and suturing between the Kimberley Craton and the Northern Australia Craton, followed by sedimentary basin formation from Proterozoic to Phanerozoic.