Algoman orogeny

Last updated

The Minnesota River Valley subprovince collided with and overrode the Superior province. Orogenic wedge.jpg
The Minnesota River Valley subprovince collided with and overrode the Superior province.

The Algoman orogeny, known as the Kenoran orogeny in Canada, was an episode of mountain-building (orogeny) during the Late Archean Eon that involved repeated episodes of continental collisions, compressions and subductions. The Superior province and the Minnesota River Valley terrane collided about 2,700 to 2,500 million years ago. The collision folded the Earth's crust and produced enough heat and pressure to metamorphose the rock. Blocks were added to the Superior province along a 1,200 km (750 mi) boundary that stretches from present-day eastern South Dakota into the Lake Huron area. The Algoman orogeny brought the Archean Eon to a close, about 2,500 million years ago; it lasted less than 100 million years and marks a major change in the development of the Earth's crust.

Contents

The Canadian shield contains belts of metavolcanic and metasedimentary rocks formed by the action of metamorphism on volcanic and sedimentary rock. The areas between individual belts consist of granites or granitic gneisses that form fault zones. These two types of belts can be seen in the Wabigoon, Quetico and Wawa subprovinces; the Wabigoon and Wawa are of volcanic origin and the Quetico is of sedimentary origin. These three subprovinces lie linearly in southwestern- to northeastern-oriented belts about 140 km (90 mi) wide on the southern portion of the Superior Province.

The Slave province and portions of the Nain province were also affected. Between about 2,000 and 1,700  million years ago these combined with the Sask and Wyoming cratons to form the first supercontinent, the Kenorland supercontinent. [1]

Overview

Through most of the Archean Eon, the Earth had a heat production at least twice that of the present. The timing of initiation of plate tectonics is still debated, but if modern-day tectonics were operative in the Archean, higher heat fluxes might have caused tectonic processes to be more active. As a result, plates and continents may have been smaller. No broad blocks as old as 3 Ga are found in Precambrian shields. Toward the end of the Archean, however, some of these blocks or terranes came together to form larger blocks welded together by greenstone belts. [2]

Two such terranes that now form part of the Canadian shield collided about 2,700 to 2,500 million years ago. These were the Superior province and the large Minnesota River Valley terrane, the former composed mainly of granite and the latter of gneiss. [3] This led to the mountain-building episode known as the Algoman orogeny in the U. S. (named for Algoma, Kewaunee County, Wisconsin), [4] : 5  and the Kenoran orogeny in Canada. [5] : 32  [6] Its duration is estimated at 50 to 100 million years. [5] : 32  The current boundary between these terranes is known as the Great Lakes tectonic zone (GLTZ). This zone is 50 km (30 mi) wide and extends in a line roughly 1,200 kilometers long from the middle of South Dakota, east through the middle of the Upper Peninsula of Michigan, into the Sudbury, Ontario region. The region remains slightly active today. [5] : 214–215  Rifting in the GLTZ began about 2,500  million years ago at the end of the Algoman orogeny.

The orogeny affected adjacent regions of northern Minnesota and Ontario in the Superior province [7] [8] : 157  as well as the Slave and the eastern part of the Nain province, a far wider region of influence than in subsequent orogenies. [8] : 158  It is the earliest datable orogeny in North America [9] : 1  and brought the Archean Eon to a close. [8] : 152  The end of the Archean Eon marks a major change in the development of the Earth's crust: the crust was essentially formed and achieved thicknesses of about 40 km (25 mi) under the continents. [8] : 158 

Tectonics

The collision between terranes folded the Earth's crust, and produced enough heat and pressure to metamorphose then-existing rock. Repeated continental collisions, compression along a north–south axis, and subduction resulted in the uprising of the Algoman Mountains. [6] This was followed by intrusions of granite plutons [10] and batholithic domes within the gneisses [11] about 2,700  million years ago; [12] two examples are the Sacred Heart granite of southwestern Minnesota and the Watersmeet Domes metagabbros (metamorphosed gabbros) that straddle the border of Wisconsin and Michigan's Upper Peninsula. After the intrusions solidified, new stresses on the greenstone belt caused movement horizontally along several faults and moved huge blocks of the crust vertically relative to adjacent blocks. [12] This combination of folding, intrusion and faulting built mountain ranges throughout northern Minnesota, northern Wisconsin, Michigan's Upper Peninsula and southernmost Ontario. [12] Igneous and high-grade metamorphic rocks are associated with the orogeny. [13]

By extrapolating the now-eroded and tilted beds upward, geologists have determined that these mountains were several kilometers high. Similar projections of the tilted beds downward, coupled with geophysical measurements on the greenstone belts in Canada, suggest the metavolcanic and metasedimentary rocks of the belts project downward at least a few kilometers. [5] : 32 

Greenstone

The action of metamorphism on the border between granite and gneiss bodies produces a succession of metamorphosed volcanic and sedimentary rocks called greenstone belts. [5] : 31  Most Archean volcanic rocks are concentrated within greenstone belts; [14] : 45  the green color comes from minerals, such as chlorite, epidote and actinolite that formed during metamorphism. [9] : 1  After metamorphism occurred, these rocks were folded and faulted into a system of mountains by the Algoman orogeny. [7]

The volcanic beds are 8 to 9 km (26,000 to 30,000 ft) thick. [4] : 5  About 2,700  million years ago the greenstone belt was subjected to new stresses that caused movement along several faults. Faulting on both small and large scales is typical of greenstone belt deformation. [15] : 37  These faults show both vertical and horizontal movement relative to adjacent blocks. [5] : 31  Large-scale faults typically occur along the margins of the greenstone belts where they are in contact with enclosed granitic rocks. [15] : 38  Vertical movement may be thousands of meters and horizontal movements of many kilometers occur along some fault zones. [15] : 38 

Some time before 2,600  million years ago, masses of magma intruded under and within the igneous and sedimentary rocks, heating and pressing the rocks to metamorphose them into hard greenish greenstones. [4] : 6  They began with fissure eruptions of basalt, continued with intermediate and felsic rocks erupted from volcanic centers and ended with deposition of sediments from the erosion of the volcanic pile. [8] : 158  The rising magma was extruded under a shallow ancient sea where it cooled to form pillowed greenstones. [11] Some of Minnesota's pillows probably cooled at depths as great as 1,000 m (3,300 ft) and contain no gas cavities or vesicles. [5] : 26 

Most greenstone belts, with all of their components, have been folded into troughlike synclines; the original basaltic rock, which was on the bottom, occurs on the outer margins of the trough. [15] : 36  The overlying, younger rock units – rhyolites and greywackes – occur closer to the center of the syncline. [15] : 36  The rocks are so intensely folded that most have been tilted nearly 90°, with the tops of layers on one side of the synclinal belt facing those on the other side; the rock sequences are in effect lying on their sides. [15] : 37  The folding can be so complex that a single layer may be exposed at the surface many times by subsequent erosion. [15] : 37 

Volcanic activity

As the greenstone belts were forming, volcanoes ejected tephra into the air which settled as sediments to become compacted into the greywackes and mudstones of the Knife Lake and Lake Vermilion formations. [4] : 5  Greywackes are poorly sorted mixtures of clay, mica and quartz that may be derived from the decomposition of pyroclastic debris; the presence of this debris suggests that some explosive volcanic activity had occurred in the area earlier. [9] : 2  The volcanism took place on the surface and the other deformations took place at various depths. [5] : 32  Numerous earthquakes accompanied the volcanism and faulting. [5] : 32 

Superior province

Wawa, Quetico and Wabigoon subprovinces Wawa, Quetico & Wabigoon Subprovinces of southern Superior Province.PNG
Wawa, Quetico and Wabigoon subprovinces

The Superior province forms the core of both the North American continent and the Canadian shield, and has a thickness of at least 250 km (160 mi). Its granites date from 2,700 to 2,500 million years ago. [5] : 24  It was formed by the welding together of many small terranes, [16] : 102  the ages of which decrease away from the nucleus. [8] : 165  This progression is illustrated by the age of the Wabigoon, Quetico and Wawa subprovinces, discussed in their individual sections. Later terranes docked on the periphery of continental masses with geosynclines developing between the fused nuclei and oceanic crust. [8] : 165  In general the Superior province consists of east–west-trending belts of predominately volcanic rocks alternating with belts of sedimentary and gneissic rocks. [17]

Due to down warping along elongate zones, each belt is essentially a large downfold or downfaulted block. [5] : 25  The areas between individual belts are fault zones consisting of granite or granitic gneiss. [5] : 25  Its western part contains a regional pattern of east–west-trending 100 to 200 km (60 to 120 mi) wide granitic greenstone and metasedimentary belts (subprovinces). [18] Western Superior province's mantle has remained intact since the 2,700-million-year-ago accretion of the subprovinces. [18]

Both folding and faulting can be seen in the Wabigoon, Quetico and Wawa subprovinces. [6] These three subprovinces lie linearly in southwestern- to northeastern-oriented belts of about 140 km (90 mi) wide (see figure on right). The northernmost and widest province is the Wabigoon. It begins in north-central Minnesota and continues northeasterly into central Ontario; it is partially interrupted by the Southern province. [19] Immediately to the south, the Quetico subprovince extends as far west in north-central Minnesota, and extends further to the northeast. It is completely interrupted by a narrow band of the 1,100- to 1,550-million-year-old Southern province to the northeast of Thunder Bay. [19] The Wawa subprovince is the most southerly of the three; it begins in central Minnesota, continues northeast to Thunder Bay, Ontario, Canada, (where its southern border just skims north Thunder Bay) and then extends east beyond Lake Superior. The northern boundary continues in a roughly northeasterly heading, while the southern border dips south to follow the northeast shore of Lake Superior. [19]

Fault zones

The three subprovinces are separated by steeply dipping shear zones caused by continued compression that occurred during the Algoman orogeny. [19] These boundaries are major fault zones. [6]

The boundary between the Wabigoon and Quetico subprovinces seems to have been also controlled by colliding plates and subsequent transpressions. [20] This Rainy Lake – Seine River fault zone is a major northeast–southwest trending strike-slip fault zone; it trends N80°E to cut through the northwest part of Voyageurs National Park in Minnesota and extends westward to near International Falls, Minnesota and Fort Frances, Ontario. The fault has transported rocks in the greenstone belt a considerable distance from their origin. The greenstone belt is 2 to 3 km (0 to 0 mi) wide at the Seven Sisters Islands; to the west the greenstone interfingers with pods of anorthositic gabbro. [9] : 1  Radiometric dating from the Rainy Lake area in Ontario show an age of about 2,700 million years old, which favors a moving tectonic plate model for the formation of the boundary. [20]

The largest fault is the Vermilion fault [4] : 6  separating the Quetico and Wawa subprovinces. [6] It has a N40°E trend [21] and was caused by the introduction of masses of magma. [4] : 6  The Vermilion fault can be traced westward to North Dakota. [5] : 33  It has had a 19 km (12 mi) horizontal movement with the northern block moving eastward and upward relative to the southern block. [5] : 33  The junction between the Quetico and Wawa subprovinces has a zone of biotite-rich migmatite, a rock that has characteristics of both igneous and metamorphic processes; [9] : 1  this indicates a zone of partial melting which is possible only under high temperature and pressure conditions. [22] It is visible as a 500 m (1,600 ft) wide belt. [21] Most of the flattened large crystals in the fault indicate a simple compression rather than a wrenching, shearing or rotational event as the two subprovinces docked. [22] This provides evidence that the Quetico and Wawa subprovinces were joined by the collision of two continental plates, [22] about 2,690 million years ago. [23] Structures in the migmatite include folds and foliations; the foliations cut across both limbs of earlier-phase folds. [21] These cross-cutting foliations indicate that the migmatite has undergone at least two periods of ductile deformation. [21]

Wabigoon subprovince

Precambrian rock in Voyageurs National park, which straddles the Wabigoon and Quetico subprovinces. Voyageur Fig4.png
Precambrian rock in Voyageurs National park, which straddles the Wabigoon and Quetico subprovinces.

The Wabigoon subprovince is a formerly active volcanic island chain, [6] made up of metavolcanic-metasedimentary intrusions. [24] These metamorphosed rocks are volcanically derived greenstone belts, and are surrounded and cut by granitic plutons and batholiths. [19] The subprovince's greenstone belts consist of felsic volcanics, felsic batholiths and felsic plutons aged from 3,000 to 2,670 million years old. [19]

Quetico subprovince

The Quetico gneiss belt extends some 970 km (600 mi) across Ontario and parts of Minnesota. The dominant rocks within the belt are schists and gneisses produced by intense metamorphism of greywackes and minor amounts of other sedimentary rocks. The sediments, alkalic plutons and felsic plutons are aged from 2,690 to 2,680 million years. [19] The metamorphism is relatively low-grade on the margins and high-grade in the center. The low-grade components of the greywackes were derived primarily from volcanic rocks; the high-grade rocks are coarser-grained and contain minerals that reflect higher temperatures. The granitic intrusions within the high-grade metasediments were produced by subduction of the ocean crust and partial melting of metasedimentary rocks. Immediately south of Voyageurs National Park and extending to the Vermilion fault is a broad transition zone that contains migmatite. [15] : 46–47 

The Quetico gneiss belt represents an accretionary wedge that formed in a trench during the collision of several island arcs (greenstone belts). Boundaries between the gneiss belt and the flanking greenstone belts to the north and south are major fault zones, the Vermilion and Rainy Lake – Seine River fault zones. [15] : 47 

Wawa subprovince

The Wawa subprovince is a formerly active volcanic island chain, [6] consisting of metamorphosed greenstone belts which are surrounded by and cut by granitic plutons and batholiths. [19] These greenstone belts consist of felsic volcanics, felsic batholiths, felsic plutons and sediments aged from 2,700 to 2,670 million years old. [19]

The predominant rock type is a white, coarse-grained, foliated hornblende tonalite. [21] Minerals in the tonalite are quartz, plagioclase, alkali feldspar and hornblende. [21]

Slave province

This shows the location of the Slave province to the northwest and the Nain province to the northeast. North American provinces and orogens.PNG
This shows the location of the Slave province to the northwest and the Nain province to the northeast.

In extensive regions of the Slave province of northern Canada, the magma that later became batholiths heated the surrounding rock to create metamorphic regions called aureoles about 2,575 million years ago. These regions are typically 10 to 15 km (6 to 9 mi) wide. The creation of aureoles was a continuous process, but three recognizable metamorphic phases can be correlated with established deformational phases. The cycle began with a deformation phase unaccompanied by metamorphism. This evolved into the second phase accompanied by broad regional metamorphism as thermal doming began. With continued updoming of the isotherms, the third phase produced minor folding but caused major metamorphic recrystallization, resulting in the emplacement of granite at the core of the thermal dome. This phase occurred at lower pressure because of erosional unloading, but the temperatures were more extreme, ranging up to about 700 °C (1,300 °F). With deformation complete, the thermal dome decayed; minor mineralogical changes occurred during this decay phase. The region has since been effectively stable. [25]

Geochronology of several Archean rock units establishes a sequence of events, approximately 75 million years in duration, leading to the formation of a new crustal segment. The oldest rocks, at 2,650 million years old, are basic metavolcanics with largely calc-alkaline characteristics. Radiometric dating indicates ages of 2,640 to 2,620 million years are recorded for the syn-kinematic quartz diorite batholiths and 2,590 to 2,100 million years for the major late-kinematic bodies. Pegmatitic adamellites, at 2,575±25 million years, are the youngest plutonic units. [26]

Metagreywackes and metapelites from two areas traversing one of these aureoles near Yellowknife have been studied. [25] Most of the Slave province rocks are granitic with metamorphosed Yellowknife metasedimentary and volcanic rocks. Isotopic ages of these rocks is around 2,500 million years ago, the time of the Kenoran orogeny. Rocks comprising the Slave province represent a high grade of metamorphism, intrusion and basement remobilization typical of Archean terranes. Migmatites, batholithic intrusive and granulitic metamorphic rocks show foliation and compositional banding; the rocks are uniformly hard and so thoroughly deformed that little foliation exists. Most Yellowknife Supergroup metasediments are tightly folded (isoclinal) or occur in plunging anticlines. [14] : 37 

Nain province

The Archean rocks forming the Nain province of northeastern Canada and Greenland are separated from the Superior terrane by a narrow band of remobilized rocks. [16] : 102  Greenland separated from North America less than 100 million years ago and its Precambrian terranes align with Canada's on the opposite side of Baffin Bay. [16] : 102  The southern tip of Greenland is part of the Nain Province, this means it was connected to North America at the end of the Kenoran orogen. [16] : 102 

See also

Related Research Articles

The Yilgarn Craton is a large craton that constitutes the bulk of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts. Zircon grains in the Jack Hills, Narryer Terrane have been dated at ~4.27 Ga, with one detrital zircon dated as old as 4.4 Ga.

Slave Craton Archaean craton in the north-western Canadian Shield, in Northwest Territories and Nunavut

The Slave Craton is an Archaean craton in the north-western Canadian Shield, in Northwest Territories and Nunavut. The Slave Craton includes the 4.03 Ga-old Acasta Gneiss which is one of the oldest dated rocks on Earth. Covering about 300,000 km2 (120,000 sq mi), it is a relatively small but well-exposed craton dominated by ~2.73–2.63 Ga greenstones and turbidite sequences and ~2.72–2.58 Ga plutonic rocks, with large parts of the craton underlain by older gneiss and granitoid units. The Slave Craton is one of the blocks that compose the Precambrian core of North America, also known as the palaeocontinent Laurentia.

Kaapvaal Craton Archaean craton, possibly part of the Vaalbara supercontinent

The Kaapvaal Craton, along with the Pilbara Craton of Western Australia, are the only remaining areas of pristine 3.6–2.5 Ga crust on Earth. Similarities of rock records from both these cratons, especially of the overlying late Archean sequences, suggest that they were once part of the Vaalbara supercontinent.

Trans-Hudson orogeny Mountain-building event in North America

The Trans-Hudson orogeny or Trans-Hudsonian orogeny was the major mountain building event (orogeny) that formed the Precambrian Canadian Shield and the North American Craton, forging the initial North American continent. It gave rise to the Trans-Hudson orogen (THO), or Trans-Hudson Orogen Transect (THOT), which is the largest Paleoproterozoic orogenic belt in the world. It consists of a network of belts that were formed by Proterozoic crustal accretion and the collision of pre-existing Archean continents. The event occurred 2.0–1.8 billion years ago.

Wyoming Craton Craton in the west-central United States and western Canada

The Wyoming Craton is a craton in the west-central United States and western Canada – more specifically, in Montana, Wyoming, southern Alberta, southern Saskatchewan, and parts of northern Utah. Also called the Wyoming Province, it is the initial core of the continental crust of North America.

The Great Lakes tectonic zone (GLTZ) is bounded by South Dakota at its tip and heads northeast to south of Duluth, Minnesota, then heads east through northern Wisconsin, Marquette, Michigan, and then trends more northeasterly to skim the northernmost shores of lakes.

Geology of Massachusetts

The geology of Massachusetts includes numerous units of volcanic, intrusive igneous, metamorphic and sedimentary rocks formed within the last 1.2 billion years. The oldest formations are gneiss rocks in the Berkshires, which were metamorphosed from older rocks during the Proterozoic Grenville orogeny as the proto-North American continent Laurentia collided against proto-South America. Throughout the Paleozoic, overlapping the rapid diversification of multi-cellular life, a series of six island arcs collided with the Laurentian continental margin. Also termed continental terranes, these sections of continental rock typically formed offshore or onshore of the proto-African continent Gondwana and in many cases had experienced volcanic events and faulting before joining the Laurentian continent. These sequential collisions metamorphosed new rocks from sediments, created uplands and faults and resulted in widespread volcanic activity. Simultaneously, the collisions raised the Appalachian Mountains to the height of the current day Himalayas.

Geology of North America Overview of the geology of North America

The geology of North America is a subject of regional geology and covers the North American continent, the third-largest in the world. Geologic units and processes are investigated on a large scale to reach a synthesized picture of the geological development of the continent.

Eastern Pilbara Craton

The Eastern Pilbara Craton is the eastern portion of the Pilbara Craton located in Western Australia. This region contains variably metamorphosed mafic and ultramafic greenstone belt rocks, intrusive granitic dome structures, and volcanic sedimentary rocks. These greenstone belts worldwide are thought to be the remnants of ancient volcanic belts, and are subject to much debate in today's scientific community. Areas such as Isua and Barberton which have similar lithologies and ages as Pilbara have been argued to be subduction accretion arcs, while others suggest that they are the result of vertical tectonics. This debate is crucial to investigating when/how plate tectonics began on Earth. The Pilbara Craton along with the Kaapvaal Craton are the only remaining areas of the Earth with pristine 3.6–2.5 Ga crust. The extremely old and rare nature of this crustal region makes it a valuable resource in the understanding of the evolution of the Archean Earth.

Eoarchean geology

Eoarchean geology is the study of the oldest preserved crustal fragments of Earth during the Eoarchean era from 4 to 3.6 billion years ago. Major well-preserved rock units dated Eoarchean are known from three localities, the Isua Greenstone Belt in Southwest Greenland, the Acasta Gneiss in the Slave Craton in Canada, and the Nuvvuagittuq Greenstone Belt in the eastern coast of Hudson Bay in Quebec. From the dating of rocks in these three regions scientists suggest that plate tectonics could go back as early as Eoarchean.

Geology of the Democratic Republic of the Congo

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.

Geology of Ivory Coast

The geology of Ivory Coast is almost entirely extremely ancient metamorphic and igneous crystalline basement rock between 2.1 and more than 3.5 billion years old, comprising part of the stable continental crust of the West African Craton. Near the surface, these ancient rocks have weathered into sediments and soils 20 to 45 meters thick on average, which holds much of Ivory Coast's groundwater. More recent sedimentary rocks are found along the coast. The country has extensive mineral resources such as gold, diamonds, nickel and bauxite as well as offshore oil and gas.

Geology of Sierra Leone

The geology of Sierra Leone is primarily very ancient Precambrian Archean and Proterozoic crystalline igneous and metamorphic basement rock, in many cases more than 2.5 billion years old. Throughout Earth history, Sierra Leone was impacted by major tectonic and climatic events, such as the Leonean, Liberian and Pan-African orogeny mountain building events, the Neoproterozoic Snowball Earth and millions of years of weathering, which has produced thick layers of regolith across much of the country's surface.

Archean felsic volcanic rocks Felsic volcanic rocks formed in the Archean Eon

Archean felsic volcanic rocks are felsic volcanic rocks that were formed in the Archean Eon. The term "felsic" means that the rocks have silica content of 62–78%. Given that the Earth formed at ~4.5 billion year ago, Archean felsic volcanic rocks provide clues on the Earth's first volcanic activities on the Earth's surface started 500 million years after the Earth's formation.

The geology of Nunavut began to form nearly three billion years ago in the Archean and the territory preserves some of the world's oldest rock units.

The Grenville Province is a tectonically complex region, in Eastern Canada, that contains many different aged accreted terranes from various origins. It exists southeast of the Grenville Front and extends from Labrador southwestern to Lake Huron. It is bounded by the St. Lawrence River/Seaway to the southeast.

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.

Eastern Block of the North China Craton

The Eastern Block of the North China Craton is one of the Earth's oldest pieces of continent. It is separated from the Western Block by the Trans-North China Orogen. It is situated in northeastern China and North Korea. The Block contains rock exposures older than 2.5 billion years. It serves as an ideal place to study how the crust was formed in the past and the related tectonic settings.

The Superior Craton is a stable crustal block covering Quebec, Ontario, and southeast Manitoba in Canada, and northern Minnesota in the United States. It is the biggest craton among those formed during the Archean period. A craton is a large part of the Earth's crust that has been stable and subjected to very little geological changes over a long time. The size of Superior Craton is about 1,572,000 km2. The craton underwent a series of events from 4.3 to 2.57 Ga. These events included the growth, drifting and deformation of both oceanic and continental crusts.

Dharwar Craton Part of the Indian Shield in south India

The Dharwar Craton is an Archean continental crust craton formed between 3.6-2.5 billion years ago (Ga), which is located in southern India and considered as the oldest part of the Indian peninsula.

References

  1. ↑ Aspler, Lawrence B.; Wisotzek, Ira E.; Chiarenzelli, Jeffrey R.; Losonczy, Miklos F.; Cousens, Brian L.; McNicoll Vicki J.; Davis, William J. (June 1, 2001). "Paleoproterozoic intracratonic basin processes, from breakup of Kenorland to assembly of Laurentia: Hurwitz Basin, Nunavut, Canada". Sedimentary Geology. 141–142: 287. Bibcode:2001SedG..141..287A. doi:10.1016/S0037-0738(01)00080-X.
  2. ↑ Stanley, Steven M. (2005). Earth system history (2nd ed.). New York: Freeman. pp. 258–261. ISBN   978-0-7167-3907-4.
  3. ↑ Davis, Peter (1998). The Big Picture, Early Penokean Orogeny: From Rifting to Iron Formations, and The Penokean Collisions (Thesis). University of Minnesota-Duluth. Archived from the original on May 16, 2008. Retrieved April 10, 2010.
  4. 1 2 3 4 5 6 Bray, Edmund C (1977). Billions of Years in Minnesota, The Geological Story of the State. Library of Congress Card Number: 77:80265.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Ojakangas, Richard W; Matsch, Charles L (1982). Minnesota's Geology. University of Minnesota Press. ISBN   978-0-8166-0950-5.
  6. 1 2 3 4 5 6 7 8 "Voyageurs National Park, Geologic History". National Park Service. p. 1. Retrieved March 8, 2010.
  7. 1 2 Schwartz, George M; Theil, George A (1963). Minnesota's Rocks and Waters, A Geological Story. pp. 109 & 244. Library of Congress Library Card Number: 54:6370.
  8. 1 2 3 4 5 6 7 Stearn, Colin W; Carroll, Robert L; Clark, Thomas H (1979). Geologic Evolution of North America . ISBN   978-0-471-07252-2.
  9. 1 2 3 4 5 "Voyageurs National Park, Geologic Features & Processes". National Park Service. Retrieved March 3, 2010.
  10. ↑ Voyageurs National Park, Geologic Resource Evaluation Report (PDF). National Park Service, U.S. Department of the Interior. June 2007. p. 3. Natural Resource Report NPS/NRPC/GRD/NRR—2007/007. Archived from the original (PDF) on May 28, 2010. Retrieved March 25, 2010.
  11. 1 2 "Minnesota Prehistory, Prehistoric Minnesota Geology an Overview". mnsu.edu. p. 1. Archived from the original on October 9, 2010. Retrieved March 8, 2010.
  12. 1 2 3 Minnesota Department of Transportation, Geotechnical Section (PDF). Minnesota Department of Transportation. May 30, 2008. p. 9. Archived (PDF) from the original on 16 February 2010. Retrieved March 24, 2010.
  13. ↑ Walker, Erin. U-PB Detrital Zircon Provenance of the Proterozoic Nopeming and Puckwunge Formations Northeastern Minnesota (PDF) (Report). 19th Annual Keck Symposium. Retrieved April 10, 2010.
  14. 1 2 Condie, KC, ed. (1994). Archean Crustal Evolution, Developments in Precambrian Geology 11 (PDF). ISBN   978-0-444-81621-4 . Retrieved March 22, 2010.[ permanent dead link ]
  15. 1 2 3 4 5 6 7 8 9 LaBerge, Gene L (1994). Geology of the Lake Superior Region. Geoscience Press, Inc. ISBN   978-0-945005-15-5.
  16. 1 2 3 4 Yadav, P.R. (2004). Prehistoric Life. Discovery Publishing House of New Delhi. ISBN   978-81-7141-778-0.
  17. ↑ "Geology of the Porcupine Area". Porcupine Prospectors and Developers Association. p. 1. Archived from the original on 2010-07-19. Retrieved March 20, 2010.
  18. 1 2 Ferguson, I.J.; Craven, J.A.; Kurtz, R.D.; Boerner, D.E.; Bailey, R.C.; Wu, X.; Orellana, M.R.; Spratt, J.; et al. (2005). "Geoelectric response of Archean lithosphere in the western Superior Province, central Canada". Physics of the Earth and Planetary Interiors. 150 (1–3, Special Issue): 123. Bibcode:2005PEPI..150..123F. doi:10.1016/j.pepi.2004.08.025.
  19. 1 2 3 4 5 6 7 8 9 "Geology of the Thunder Bay South District". Ontario Ministry of Northern Development, Mines and Forestry, Resident Geologist Program. pp. 1, 2 and 3. Archived from the original on January 19, 2010. Retrieved March 14, 2010.
  20. 1 2 Davis, DW; Poulsen, KH; Kamo, SL (July 1989). "New Insights into Archean Crustal Development From Geochronology in the Rainy Lake Area, Superior Province, Canada". The Journal of Geology. 97 (4): 379–398. Bibcode:1989JG.....97..379D. doi:10.1086/629318. JSTOR   30078346.
  21. 1 2 3 4 5 6 Chastain, Lynne Marie; Kolinski, Amy. "Character of Megascopic Ductile Structures at the Wawa Subprovince and Quetico Subprovince Junction in Quetico Provincial Park, Ontario, Canada" (PDF). pp. 76 & 79. Retrieved March 14, 2010.
  22. 1 2 3 Gupta, Anupma; Weng, Kevin. "Docking Mechanism of the Quetico-Wawa Junction as Indicated by Structural Mapping and Analysis of Augen Zones in Quetico Provincial Park, Canada" (PDF). pp. 80 & 81. Retrieved March 14, 2010.
  23. ↑ Fralick, Phillip; Purdon, RH; Davis, DW (July 1, 2006). "Neoarchean trans-subprovince sediment transport in southwestern Superior Province: sedimentological, geochemical, and geochronological evidence". Canadian Journal of Earth Sciences. NRC Research Press. 43 (7): 1055. Bibcode:2006CaJES..43.1055F. doi:10.1139/E06-059.
  24. ↑ "Chapter 2, Watershed Description, 2.2 The Physical Description, 2.2.1 Bedrock Geology" (PDF). Lakehead Source Protection Area Watershed Characterization Report, Lakehead Region Conservation Authority, Draft Report for Consideration of the Lakehead Source Protection Committee – March 2008. p. 20 of 219. Retrieved March 14, 2010.
  25. 1 2 Ramsay, CR; Kamineni, DC (1977). "Petrology and Evolution of an Archaean Metamorphic Aureole in the Slave Craton, Canada". Journal of Petrology. Oxford University Press. 18 (3): 460. Bibcode:1977JPet...18..460R. doi:10.1093/petrology/18.3.460.
  26. ↑ Green, DC; Baadsgaard, H (1971). "Temporal Evolution and Petrogenesis of an Archaean Crustal Segment at Yellowknife, N.W.T., Canada". Journal of Petrology. Oxford University Press. 12 (1): 177. Bibcode:1971JPet...12..177G. doi:10.1093/petrology/12.1.177.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.