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The geology of Missouri includes deep Precambrian basement rocks formed within the last two billion years and overlain by thick sequences of marine sedimentary rocks, interspersed with igneous rocks by periods of volcanic activity. Missouri is a leading producer of lead from minerals formed in Paleozoic dolomite. [1]
The oldest rocks in Missouri are igneous and metamorphic crystalline basement rocks formed during the Proterozoic through the accretion of volcanic island arcs to the southern shore of the proto-North American continent of Laurentia. Rocks formed from 1.7 to 1.6 billion years ago are primarily known from deep boreholes in the north of the state, but are universally deeply buried by thick layers of sedimentary rock. Younger igneous rocks formed from magma in the south between 1.5 and 1.4 billion years ago. In places, magma intruded preexisting basement rock and then erupted at the surface as volcanoes along the Laurentian coastline. Granite and lava flows remain in the St. Francois Mountains from this period. Middle Proterozoic basement rocks are cut by the Central Missouri Tectonic Zone and Grand River fault zone, both of which are hypothesized to be the remnants of boundaries between small plates. Magma often moves along these fault zones.
Between the two zones is the Missouri Gravity Low, or MGL, a mass of low density granite including the Missouri batholith up to 370 miles long and 60 miles wide, identified in gravity surveys. Igneous activity ended around 1.3 billion years ago, with the intrusion of numerous dikes and sills into newly crystallized rhyolite and granite.
Although not directly impacting the current boundaries of Missouri, the Midcontinent Rift System formed from 1.2 to one billion years ago as mafic lava erupted in a rift zone spanning Lake Superior through Iowa to Kansas. Laurentia was included in the supercontinent Rodinia from one billion to 539 million years ago and no new rock formation took place in Missouri. Failed rifting of the continent produced the Reelfoot Rift, which extends beneath the Mississippi Embayment to the southeast lowlands of the state and intersects the Missouri Gravity Low, creating the New Madrid Seismic Zone. [2]
Sloss sequences – long-running changes in sea level, described by American geologist Laurence L. Sloss – played an important role in sediment deposition during the Paleozoic. The Sauk sequence formed during the Cambrian, followed by the Tippecanoe in the Ordovician, the Kaskaskia between the full immersion of the Silurian and the early Mississippian. Finally, the Absaroka sequence emplaced into the early Pennsylvanian.
The Great Unconformity separates Proterozoic igneous rocks from the Lamotte Sandstone, the basal unit of the Sauk sequence which also includes the Bonneterre Dolomite, Davis Formation, Derby-Roe Run Dolomite, Potosi Dolomite and Eminence Dolomite from the Cambrian, and the Ordovician Gasconade Dolomite, Roubidoux Formation and Jefferson City Dolomite. The Tippecanoe comprises the St. Peter Sandstone, Joachim Dolomite, Plattin Limestone, Decorah Shale, Kimmswick Limestone, and an unconformity, followed by the Girardeau Limestone (only in the southeast), Maquoketa Shale and northeast Missouri Noix Limestone. Silurian Tippecanoe rocks include only two units: the Bainbridge Formation in the southeast and Bowling Green Dolomite in the northeast.
Devonian Kaskaskia rocks include the Chattanooga Shale in the southwest, Cedar Valley Limestone, split by an unconformity and separated from Mississippian rocks by a second unconformity, with numerous small shale and limestone units in the east. A complicated sequence of shale, sandstone and limestone follows from the Carboniferous.
Sedimentary petrologists have debated why dolomite is so prevalent in Missouri relative to limestone, even though marine conditions often favor limestone formation. Only a few dolomite beds formed after the Middle Ordovician and few are younger than the Joachim Dolomite. Fault fractures suggest that groundwater altered limestone to dolomite, replacing calcium with magnesium. [3]
The Zuñi sequence formed in the Mesozoic, during a fifth major marine transgression lasting from the Middle Jurassic into the Cretaceous. The Cretaceous geochronology of the state is unclear and debated, between some who believe the state experienced dryland conditions and others who suspect it was flooded. The only Cretaceous deposits are unconsolidated marine and delta sands together with clay in the Southeast Lowlands, beneath Pleistocene alluvium. Previously, small circular deposits of Cretaceous clay in the Ozarks were suspected to be the remains of sinkholes in Ordovician dolomite. However, recent fossil discoveries suggest possible small lakes and ponds. [4]
A final marine transgression called the Tejas sequence took place in the Cenozoic. Aside from clay and both delta and marine sandstone in the Crowley Ridge, deposited in the subsiding Mississippi Embayment, there are no Paleogene rocks in the state. The Midway Group deposited in the Paleocene, rich in bentonite, followed by the Eocene Wilcox Group, which contains terrestrial sandstone and clay laden with plant fossils.
In unglaciated parts of the state and beneath Quaternary deposits in the north is the Pliocene Mounds Gravel, unconformably atop older rocks and sediments. The Mounds Gravel remains as gravel alluvium from the Teays River, which once flowed north of current day St. Louis transporting sediments shed by the rising Rocky Mountains. Some geologists have suggested that the Mounds Gravel originated from erosion of the Central Highlands, when a large river flowed south through Kansas and Oklahoma to the Gulf of Mexico, until it was rechanneled to the present Mississippi River during the Illinoian glaciation. As Missouri experienced terrestrial erosion in the Pliocene, the Ozark Dome uplifted.
Missouri did experience the Pleistocene glaciations, with the most recent glacial till from 600,000 years ago. A small lobe of ice pushed across the Mississippi River in the vicinity of St. Louis 200,000 years ago. The route of the Ancestral Kansas River rapidly eroded and filled with sediment in the area of Kansas City during periods of glacial melting and outwash. Till in northern Missouri is up to several hundred feet thick, sometimes containing cobbles and boulders, with an overall tan to red-brown color. [5]
The Thirty-Eight Parallel Lineament is one of Missouri's unique structural features, a 10- to 20-mile wide area of folds, faults and shattered bedrock from the Kansas state line to Vernon County to the Mississippi River in Ste. Genevieve County. It contains the widespread Ste. Genevieve Fault and pockets of Paleozoic rock—particularly eight locations with broken, but rearranged groupings of igneous and sedimentary rocks together. Hypotheses suggest possible origins ranging from cryovolcanoes to pent up gas tearing through Paleozoic rocks and bringing up more ancient igneous rocks. [6]
Galena is the official state mineral of Missouri and lead mining began in the 1720s in Madison County, spearheaded by French miners. The state is the leading extractor of lead in the U.S., both from galena and sphalerite. The minerals are sourced from Mississippi Valley Type deposits, deposited through hydrothermal activity. The Old Lead Belt and Tri-State Area were mined significantly before World War II, with new deposits found since in the southeast. The new deposit is known as the Viburnum Trend and spans Iron County and Reynolds County, with secondary production of copper, cadmium and silver, housed in the Bonneterre Dolomite between 600 and 1500 feet deep. During the late Cambrian, stromatalite beds shielded carbonates forming below and created a permeable interface for mineralization. [7]
The main points that are discussed in the geology of Iran include the study of the geological and structural units or zones; stratigraphy; magmatism and igneous rocks; ophiolite series and ultramafic rocks; and orogenic events in Iran.
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 geological history of Zambia begins in the Proterozoic eon of the Precambrian. The igneous and metamorphic basement rocks tend to be highly metamorphosed and may have formed earlier in the Archean, but heat and pressure has destroyed evidence of earlier conditions. Major sedimentary and metamorphic groups formed in the mid-Proterozoic, followed by a series of glaciations in the Neoproterozoic and much of the Paleozoic which deposited glacial conglomerate as well as other sediments to form the Katanga Supergroup and rift-related Karoo Supergroup. Basalt eruptions blanketed the Karoo Supergroup in the Mesozoic and Zambia shifted to coal and sandstone formation. Geologically recent windblown sands from the Kalahari Desert and alluvial deposits near rivers play an important role in the modern surficial geology of Zambia. The country has extensive natural resources, particularly copper, but also cobalt, emeralds, other gemstones, uranium and coal.
The geology of Somaliland is very closely related to the geology of Somalia. Somaliland is a de facto independent country within the boundaries that the international community recognizes as Somalia. Because it encompasses the former territory of British Somaliland, the region is historically better researched than former Italian Somaliland. Somaliland is built on more than 700 million year old igneous and metamorphic crystalline basement rock.. These ancient units are covered in thick layers of sedimentary rock formed in the last 200 million years and influenced by the rifting apart of the Somali Plate and the Arabian Plate.
The geology of Morocco formed beginning up to two billion years ago, in the Paleoproterozoic and potentially even earlier. It was affected by the Pan-African orogeny, although the later Hercynian orogeny produced fewer changes and left the Maseta Domain, a large area of remnant Paleozoic massifs. During the Paleozoic, extensive sedimentary deposits preserved marine fossils. Throughout the Mesozoic, the rifting apart of Pangaea to form the Atlantic Ocean created basins and fault blocks, which were blanketed in terrestrial and marine sediments—particularly as a major marine transgression flooded much of the region. In the Cenozoic, a microcontinent covered in sedimentary rocks from the Triassic and Cretaceous collided with northern Morocco, forming the Rif region. Morocco has extensive phosphate and salt reserves, as well as resources such as lead, zinc, copper and silver.
The geology of Nigeria formed beginning in the Archean and Proterozoic eons of the Precambrian. The country forms the Nigerian Province and more than half of its surface is igneous and metamorphic crystalline basement rock from the Precambrian. Between 2.9 billion and 500 million years ago, Nigeria was affected by three major orogeny mountain-building events and related igneous intrusions. Following the Pan-African orogeny, in the Cambrian at the time that multi-cellular life proliferated, Nigeria began to experience regional sedimentation and witnessed new igneous intrusions. By the Cretaceous period of the late Mesozoic, massive sedimentation was underway in different basins, due to a large marine transgression. By the Eocene, in the Cenozoic, the region returned to terrestrial conditions.
The geology of Virginia began to form 1.8 billion years ago and potentially even earlier. The oldest rocks in the state were metamorphosed during the Grenville orogeny, a mountain building event beginning 1.2 billion years ago in the Proterozoic, which obscured older rocks. Throughout the Proterozoic and Paleozoic, Virginia experienced igneous intrusions, carbonate and sandstone deposition, and a series of other mountain building events which defined the terrain of the inland parts of the state. The closing of the Iapetus Ocean, to form the supercontinent Pangaea added additional small landmasses, some of which are now hidden beneath thick Atlantic Coastal Plain sediments. The region subsequently experienced the rifting open of the Atlantic Ocean in the Mesozoic, the development of the Coastal Plain, isolated volcanism and a series of marine transgressions that flooded much of the area. Virginia has extensive coal, deposits of oil and natural gas, as well as deposits of other minerals and metals, including vermiculite, kyanite and uranium.
The geology of Ohio formed beginning more than one billion years ago in the Proterozoic eon of the Precambrian. The igneous and metamorphic crystalline basement rock is poorly understood except through deep boreholes and does not outcrop at the surface. The basement rock is divided between the Grenville Province and Superior Province. When the Grenville Province crust collided with Proto-North America, it launched the Grenville orogeny, a major mountain building event. The Grenville mountains eroded, filling in rift basins and Ohio was flooded and periodically exposed as dry land throughout the Paleozoic. In addition to marine carbonates such as limestone and dolomite, large deposits of shale and sandstone formed as subsequent mountain building events such as the Taconic orogeny and Acadian orogeny led to additional sediment deposition. Ohio transitioned to dryland conditions in the Pennsylvanian, forming large coal swamps and the region has been dryland ever since. Until the Pleistocene glaciations erased these features, the landscape was cut with deep stream valleys, which scoured away hundreds of meters of rock leaving little trace of geologic history in the Mesozoic and Cenozoic.
The geology of Arizona began to form in the Precambrian. Igneous and metamorphic crystalline basement rock may have been much older, but was overwritten during the Yavapai and Mazatzal orogenies in the Proterozoic. The Grenville orogeny to the east caused Arizona to fill with sediments, shedding into a shallow sea. Limestone formed in the sea was metamorphosed by mafic intrusions. The Great Unconformity is a famous gap in the stratigraphic record, as Arizona experienced 900 million years of terrestrial conditions, except in isolated basins. The region oscillated between terrestrial and shallow ocean conditions during the Paleozoic as multi-cellular life became common and three major orogenies to the east shed sediments before North America became part of the supercontinent Pangaea. The breakup of Pangaea was accompanied by the subduction of the Farallon Plate, which drove volcanism during the Nevadan orogeny and the Sevier orogeny in the Mesozoic, which covered much of Arizona in volcanic debris and sediments. The Mid-Tertiary ignimbrite flare-up created smaller mountain ranges with extensive ash and lava in the Cenozoic, followed by the sinking of the Farallon slab in the mantle throughout the past 14 million years, which has created the Basin and Range Province. Arizona has extensive mineralization in veins, due to hydrothermal fluids and is notable for copper-gold porphyry, lead, zinc, rare minerals formed from copper enrichment and evaporites among other resources.
The geology of Mississippi includes some deep igneous and metamorphic crystalline basement rocks from the Precambrian known only from boreholes in the north, as well as sedimentary sequences from the Paleozoic. The region long experienced shallow marine conditions during the tectonic evolutions of the Mesozoic and Cenozoic, as coastal plain sediments accumulated up to 45,000 feet thick, including limestone, dolomite, marl, anhydrite and sandstone layers, with some oil and gas occurrences and the remnants of Cretaceous volcanic activity in some locations.
The geology of Wyoming includes some of the oldest Archean rocks in North America, overlain by thick marine and terrestrial sediments formed during the Paleozoic, Mesozoic and Cenozoic, including oil, gas and coal deposits. Throughout its geologic history, Wyoming has been uplifted several times during the formation of the Rocky Mountains, which produced complicated faulting that traps hydrocarbons.
The geology of Utah includes rocks formed at the edge of the proto-North American continent during the Precambrian. A shallow marine sedimentary environment covered the region for much of the Paleozoic and Mesozoic, followed by dryland conditions, volcanism and the formation of the basin and range terrain in the Cenozoic. Utah is a state in the western United States.
The geology of Wisconsin includes Precambrian crystalline basement rock over three billion years old. A widespread marine environment during the Paleozoic flooded the region, depositing sedimentary rocks which cover most of the center and south of the state.
The geology of the State of New York is made up of ancient Precambrian crystalline basement rock, forming the Adirondack Mountains and the bedrock of much of the state. These rocks experienced numerous deformations during mountain building events and much of the region was flooded by shallow seas depositing thick sequences of sedimentary rock during the Paleozoic. Fewer rocks have deposited since the Mesozoic as several kilometers of rock have eroded into the continental shelf and Atlantic coastal plain, although volcanic and sedimentary rocks in the Newark Basin are a prominent fossil-bearing feature near New York City from the Mesozoic rifting of the supercontinent Pangea.
The geology of North Dakota includes thick sequences oil and coal bearing sedimentary rocks formed in shallow seas in the Paleozoic and Mesozoic, as well as terrestrial deposits from the Cenozoic on top of ancient Precambrian crystalline basement rocks. The state has extensive oil and gas, sand and gravel, coal, groundwater and other natural resources.
The geology of Montana includes thick sequences of Paleozoic, Mesozoic and Cenozoic sedimentary rocks overlying ancient Archean and Proterozoic crystalline basement rock. Eastern Montana has considerable oil and gas resources, while the uplifted Rocky Mountains in the west, which resulted from the Laramide orogeny and other tectonic events have locations with metal ore.
The geology of Kazakhstan includes extensive basement rocks from the Precambrian and widespread Paleozoic rocks, as well as sediments formed in rift basins during the Mesozoic.
The geology of Afghanistan includes nearly one billion year old rocks from the Precambrian. The region experienced widespread marine transgressions and deposition during the Paleozoic and Mesozoic, that continued into the Cenozoic with the uplift of the Hindu Kush mountains.
The geology of Uzbekistan consists of two microcontinents and the remnants of oceanic crust, which fused together into a tectonically complex but resource rich land mass during the Paleozoic, before becoming draped in thick, primarily marine sedimentary units.
The geology of Yukon includes sections of ancient Precambrian Proterozoic rock from the western edge of the proto-North American continent Laurentia, with several different island arc terranes added through the Paleozoic, Mesozoic and Cenozoic, driving volcanism, pluton formation and sedimentation.
