Misplaced Pages

#876123

47-622: About 150,000 people live in the drainage area of this river. The L'Assomption River watershed overlaps two natural environments, the Laurentian Mountains and the St-Lawrence lowlands, which cover about a third of the watershed area. Its relief is a uniform plain with some hills—from 0 to 100 metres (0 to 328 ft)—dominated by agricultural lands. The texture of the soil is rather fine and rests on an impermeable argillaceous (clay) base. The Laurentian Mountains form part of

94-677: A massive dome of Proterozoic rock on the New York-Canada border. Both the Elzevirian (c. 1250–1190 Ma) and Ottawan (c. 1080–1020 Ma) orogenic pulses are recorded in the Adirondacks, producing high-grade metamorphic rock. A northwest-trending high-strain shear zone separates the dome into the highlands to the southeast and the lowlands to the northwest. It is believed that the shear zone (the Carthage-Colton)

141-474: A surface area larger than 1 square kilometre (250 acres). Most of the lakes are in the Laurentian highlands. The water quality of the L'Assomption River is seriously affected by the area's social-economic conditions. Since 1950, the situation has been complicated by the urbanization of the river banks, by diversified agriculture , and by industrialisation along the southern portion of the river. Although

188-493: Is a prominent orogenic belt which spans a significant portion of the North American continent, from Labrador to Mexico , as well as to Scotland . Grenville orogenic crust of mid-late Mesoproterozoic age ( c. 1250—980 Ma ) is found worldwide, but generally only events which occurred on the southern and eastern margins of Laurentia are recognized under the "Grenville" name. These orogenic events are also known as

235-487: Is a subdivision of the Canadian Shield, and in this area, the oldest rocks of this geologic region are found. These rocks represent a chain of mountains that formed between 1,500 and 900 million years ago. During that time, Laurentia , the geologic core of the Canadian Shield, collided with other continents that were dragged by moving tectonic plates . The Laurentian Mountains contain dense boreal forests . It

282-532: Is composed of meta-igneous gneisses including anorthosite massifs. Anorthosites form in plutons and are composed mostly of plagioclase. The rocks of the Grenville Province in Canada are included in this category. The oldest magmatism known in this area dates to 1.32 Ga approximately. Granulite facies metamorphism began around 1.15 Ga and continued for about 150 Ma after the onset, however the continuity of

329-669: Is difficult to control because it has a multitude of sources throughout the whole region. Yet without a solution to this problem the water quality of the river will never have the desired quality. Download coordinates as: Laurentian Mountains The Laurentian Mountains , also known as the Laurentians or Laurentides , are a mountain range in Canada . The range is 1,448 km (900 mi) long and ranges in height from 500 m (1,640 ft) with peaks over 1,000 m (3,280 ft). The Laurentian Mountains extend across Labrador and Quebec within

376-933: Is dynamic. The cyclic compression and extension history of this area is similar to the Wilson Cycle . In this area of the world the Wilson Cycle would be creating the basin for the Iapetus Ocean . Today, the Grenville orogen is marked by northwest verging fold-and-thrust belts and high pressure metamorphic regimes, as well as distinctive AMCG suite magmatism. Metamorphism is commonly of amphibolite and granulite facies , that is, medium to high temperature and pressure alteration. Eclogitized metagabbros (very high pressure ultramafic metamorphic rocks) are found in some localities and likely represent areas of deepest burial and/or most intense collision. Throughout

423-434: Is home to some deciduous trees, such as sugar maple , beech , but are rarely found past the northern boundary of the range. The Laurentian region is also rich in walnut , ash , cherry , linden , and oak . The range also contains bogs . The boreal ecosystem is represented by mixed forests , dominated by black spruce and balsam fir to the south, including areas of white birch . Laurentides Wildlife Reserve , which

470-615: Is itself derived from the St. Lawrence River . François-Xavier Garneau , author of Histoire de Canada , was first to use the term "Laurentien" when he coined the name of the mountains in 1845. Early geologists adopted the name for the complex of metamorphic and igneous rocks in this area, with the terms further being applied to the Laurentide Ice Sheet and the Laurentian Shield ( Canadian Shield ). Garneau applied

517-579: Is located in the range, contains mammals such as black bears , bobcats , raccoons, grey wolves , otters , moose , white-tailed deer and caribou , with birds such as the barred owl , American kestrel , and osprey . The Laurentian Mountains are a popular recreational destination in Quebec. The first ski lift in North America was built in the mountain range in 1931, and by the late 1930s, "snow trains" had brought tens of thousands of skiers to

SECTION 10

#1732793715877

564-637: Is predominantly sedimentary and volcanic rocks which have undergone greenschist to granulite facies metamorphism. Subdivisions of this belt include the Bancroft, Elzevir, Sharbot Lake, and Frontenac Domains and the Adirondack Lowlands. In this belt magmatism is known to have occurred between 1.42 and 1.04 Ga depending on location. As with the Gneiss Belt, metamorphism is believed to have occurred at approximately 1.16 Ga. The Granulite Terrane

611-546: Is suggested that the regime of subduction under the Laurentian margin (currently in Texas, north of the accreted Mexican terrane ) ended around 1230 Ma, and that subduction polarity reversed to bring the colliding continent north, since the Llano Uplift , which records the history of the Grenville in Texas, bears no evidence of arc magmatism after this time. The Appalachian Mountains contain small, isolated exposures of

658-414: Is the formation of sedimentary basins which means the margin was quiescent enough that sediments could accumulate. However, in some areas from 1.16 to 1.13 Ga, coeval with extension, there is evidence there was still thrusting and emplacement of terranes occurring. According to one model, westward thrusting occurred from 1.12 to 1.09 Ga and then extension was the primary tectonic activity until 1.05 Ga. It

705-532: The Canadian Shield . They are separated from the lowlands by a well-defined escarpment that rises about 150 metres (490 ft). This escarpment has many waterfalls. The Laurentians Mountains have an average height of 230 metres (750 ft) in the south and 460 metres (1,510 ft) in the north. And there are even mountains of over 600 metres (2,000 ft) in the Mont Tremblant massif where

752-522: The East Coast to the Great Lakes . The forests reached heights of 30 to 85 meters high. While the exports of logging grew, it eventually became a wasteful practice, with the felling of trees leaving huge portions of land vulnerable to erosion . Intensive forestry has not entirely ceased in the region. Public and private forests in Quebec have now been entirely mapped, with information such as

799-788: The Grenville orogeny , in which the Grenville Province formed, a subdivision of the Canadian Shield . During that time, Laurentia , the geologic core of the Canadian Shield, collided with other continents and formed Precambrian rocks which extend across the range. The mountain range is located around other related geographic features, such as the Monteregian Hills and the Adirondack Mountains . The Laurentian Mountains are home to vast extents of boreal ecosystems and mixed forests . The southern areas of

846-662: The Kibaran orogeny in Africa and the Dalslandian orogeny in Western Europe . The problem of timing the Grenville orogeny is an area of some contention. The timescale outlined by Toby Rivers in 2002 is derived from the well-preserved Grenville Province and represents one of the most detailed records of the orogeny. This classification considers the classical Grenville designation to cover two separate orogenic cycles;

893-977: The Laurentian Upland , which extends as far west as Lake Huron , with foothills extending into northeastern Ontario . Sub-ranges in the upland are the Opeongo Hills , Misquah Hills , Huron Mountains , and the Porcupine Mountains . This region is extensively forested and contains nearly untouched wilderness, with it not being suited for agriculture. One of Quebec's official regions is called Laurentides . The mountain range runs through four other regions; Capitale-Nationale , Outaouais , Lanaudière , and Mauricie . The elevation generally ranges from around 500 m (1,640 ft) to 1,000 m (3,280 ft) with Mont Raoul-Blanchard being its highest peak, at 1,166 m (3,825 ft). Mont Tremblant , Mont Bleu, and Mont des Conscrits are other prominent peaks in

940-527: The Laurentian Upland , which contains foothills in northeastern Ontario . The range is located near the rivers of Ottawa , St. Lawrence , and Saguenay . The Laurentian Mountains primarily stretch across multiple regions in Quebec, with geologic formations such as the Jacques-Cartier Massif located within the range. The Laurentians Mountains are one of the oldest mountain ranges on earth. The range formed around one billion years ago during

987-469: The country rock . Polarities of subduction (which plate overrode which) vary by region and time. Some island arc remnants were emplaced on the Laurentian margin, and some were accreted during orogeny. Timing of these events is constrained by cross-cutting relations observed in the field as well as SHRIMP ( sensitive high-resolution ion microprobe ) and TIMS ( thermal ionization mass spectrometry ) uranium-lead dating . The first period of tectonic activity

SECTION 20

#1732793715877

1034-547: The Grenville Province prior to opening of the Iapetus Ocean, the two share largely the same history. Texas and Mexico represent the southern margin of Laurentia and likely collided with a different continent than that involved in the eastern collision. The Zapotecan orogeny of Mexico is coeval with the later stages of the Grenville orogeny, and they are generally considered to be one and the same. Mesoproterozoic igneous protoliths (metamorphosed to granulite facies during

1081-834: The Grenville orogen. The largest of these, the Long Range Inlier, comprises the Long Range Mountains of Newfoundland. Other exposures include the Shenandoah and French Broad massifs , which comprise the Blue Ridge province of Virginia. Blue Ridge rocks consist of various gneisses of upper amphibolite and granulite facies, intruded by charnockite and granitoid rocks. These igneous rocks were intruded in three intervals: c. 1160–1140  Ma, c. 1112 Ma, and c. 1080–1050 Ma, and are massive to weakly foliated in texture. This region consists of

1128-422: The L'Assomption River forms. From north to south the average slope of the river decreases. The steeper slopes of the highlands create a fast current whereas the lowland flats produces a slower flow. Moreover, the river meanders a lot which is especially evident at the town of L'Assomption , almost completely surrounded by a large loop of the river. The L'Assomption River watershed has 490 lakes of which 24 have

1175-617: The Rigolet, Ottawan and Shawingian orogenies compose the Grenville Cycle, and the Elzevirian orogeny stands on its own. Due to the great size of the area affected by Grenville events, there is some variance in timing across the orogenic belt . Ages are approximated from the magmatic activity associated with the individual cycles of the orogeny. The gaps in the ages of the compression cycles and isotope analysis of hornblende , biotite , and potassium feldspar suggest that extension

1222-573: The Shawinigan occurs from 1190 to 1140 Ma and is no longer part of the Grenville cycle, the Ottawan (now 1090–1020 Ma) and Rigolet (still 1010–980 Ma) become phases which are grouped into the Grenvillian orogeny. Reconstruction of the events of the orogeny is ongoing, but the generally accepted view is that the eastern and southern margins of Laurentia were active convergent margins until

1269-544: The beginning of continental collision . This type of subduction (B-type) tends to emplace magmatic arcs on or near the edge of the overriding plate in modern subduction zones, and evidence of contemporary (c. 1300–1200 Ma) island arcs can be found throughout the Grenville orogen. The Andes of South America are considered a modern analogue. From about c. 1190–980 Ma (the actual timing varies by locality) two separate continental blocks collided with Laurentia. Both of these collision events are thought to be analogous to

1316-517: The bottom portion of the lithosphere is stripped off. Both models have been proposed for the Grenville orogeny. The Grenville orogeny can be categorized into three sections based on structure, lithology, and thermochronology. The three sections, respectively called the Gneiss Belt, Metasedimentary Belt, and the Granulite terrane are all separated by shear zones. The Gneiss Belt is made up of felsic gneisses and amphibolites that were metamorphosed in

1363-493: The collision driving modern-day growth of the Himalaya range. For some time one of the blocks was believed to be the continent of Amazonia, but paleomagnetic evidence has now proven that this is not the case. These periods of thrusting and metamorphism were not continuous but were interrupted by comparatively quiet periods, during which AMCG ( anorthosite / mangerite / charnockite / granite ) plutons were intruded into

1410-495: The continental crust was already taking place and thickening the lithosphere . By 1.19 Ga the Elzevir back arc basin was closing. From 1.18 to 1.14 Ga extension was occurring in the area. Whether from lithospheric cooling, also known as thermal subsidence, or the compressional activity in the area reactivated some extensional faults. The extension is marked by the isotopic ages of the previously mentioned rocks. Additionally there

1457-422: The environment's contamination. Agriculture has a dominant position along the river: in 1995 there were 1,305 producers with 60,221 hectares (148,810 acres) under cultivation and possessing 73,563 animals. Agricultural pollution takes several forms: direct pollution (discharge of manure directly in the rivers) and diffused pollution (infiltration of fertilizer products in the groundwater ). Diffused pollution

L'Assomption River - Misplaced Pages Continue

1504-622: The metamorphism cannot be determined. It is important to separate local from large-scale tectonic history of the orogenic belt in order to understand the orogeny. For this purpose, the Grenville orogen is generally broken into four localities: the southern extent in Texas and Mexico, the Appalachians , the Adirondacks , and the Grenville Province . A portion of the orogen can be found in Scotland, but because of Scotland's proximity to

1551-475: The mountain range. Jacques-Cartier National Park is located in this mountain range, which is north of Quebec City , residing in the Jacques-Cartier Massif . The Adirondack Mountains , which are located in northeastern New York , have great similarity to the Laurentian Mountains, consisting of the same type of rocks that are part of the Canadian Shield. The Laurentian Mountains are one of

1598-612: The new term to the whole range north of the St. Lawrence River. While the region has been popularly referred to as the Laurentians and Les Laurentides , it was officially adopted in 1987 as the territory was defined. The Laurentian Mountains extend from Quebec to Labrador over a distance of 1,448 kilometers (900 miles ). They are partially bounded by the Ottawa , St. Lawrence , and Saguenay River . The Laurentian Mountains reside in

1645-472: The oldest mountain ranges in the world, being of Precambrian age, with some regions dating to over one billion years old. The mountain range is between other related geologic features, such as the Monteregian Hills and the older Oka Hills. The mountain range is located within the Grenville orogeny . The rocks of the Laurentian Mountains contain deformation and metamorphic structures that show long periods of tectonic activity occurred. The Grenville Province

1692-507: The orogen, these sequences of high pressure metamorphic rocks are cut by intrusive AMCG suite plutons, generally interpreted as syn- or post-tectonic. AMCG plutonism is generally associated with asthenospheric upwelling under thinned lithosphere . This is derived from the theory that AMCG plutonism is driven by ponding of olivine tholeiite basalt at the base of the continental crust during tectonic extension. The lithosphere may be thinned either convectively or by delamination , in which

1739-458: The orogeny) fall into two age groups in Mexico; c. 1235–1115 Ma and c. 1035–1010 Ma. Rocks of the former group bear geochemical signatures implying island arc and back-arc basin provenance. The latter group represents AMCG magmatism. These AMCG rocks are somewhat anomalous throughout the Grenville orogen, there is no known orogenic event which immediately predates their emplacement. It

1786-450: The population by about 45,000 people during the vacation season. The majority of the municipalities take their drinking water from the river and provide it to more than 100,000 people. The drinking water supply to other residences and country cottages, distributed over approximately 90 percent of the watershed area, comes from water wells . Besides the urban and industrial pollution, agricultural pollution also contributes greatly to

1833-440: The range are dominated by black spruce and balsam fir , with areas of white birch . The range is home to various wildlife species. The Laurentian Mountains are an important part of the economy of Quebec, as they have been historically been used for forestry and provide access to tourism and outdoor recreation for people in the region. The namesake of the mountains is derived from the term "Laurentide" or "Laurentian", which

1880-479: The range. In the area, there is skiing, snowboarding , dog sledding , ice climbing , and snowmobiling during winter at Mont-Tremblant, with rafting , kayaking , hiking, camping, and golf through the region during spring, summer, and fall. The Laurentian Mountains have been historically used for logging . During the European colonization of North America, colonists were met with a woodland that stretched from

1927-425: The soil, terrain, and waterways, and the species and the age of the trees available. With this data, the chief forester calculates the amount of wood that can be harvested, ensuring the forest is not cut down faster than it can grow back. Grenville orogeny The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia . Its record

L'Assomption River - Misplaced Pages Continue

1974-432: The source of pollution has changed since 1950, because of strict environmental laws and the use of water purification equipment, water pollution is still not fully curbed. Over 150,000 people live in the river's watershed in 43 municipalities, of which the most important are Repentigny, Joliette , Le Gardeur , and L'Assomption. In addition, the northern portion of the river's watershed is a popular vacation area, swelling

2021-538: The upper amphibolite to granulite facies. Thrusting in this section was low angle but would have the potential to increase and rotate as it continued and evolved. Shear in this area is referred to as ductile shear meaning the material was cooling and becoming solid, but still behaving viscously or plasticly. The age of this belt is approximately 1.8 to 1.18 Ga. Regional metamorphism is believed to have deformed this area at approximately 1.4 Ga and metamorphic thrusting at approximately 1.16 to 1.12 Ga. The Metasedimentary Belt

2068-417: Was a transpressional boundary during the Ottawan, when the highlands were thrust over the lowlands. The Grenville province is named for Grenville , Quebec, and constitutes the youngest portion of the Canadian Shield . Since the area has not undergone any regional metamorphic overprinting since the orogeny, it is considered an ideal study area for Grenville and pre-Grenville age tectonics. Hence, most of what

2115-497: Was at this point that the Central Granulite Terrane was exhumed and minor magmatism occurred. The reason for change from compression to extension is unknown but may be the result of gravitational collapse, mantle delamination, the formation of a plume underneath a supercontinent , changes in far-field drivers on the distribution of stress, or any combination of reasons originating from the fact that our planet

2162-400: Was occurring when compression had momentarily ceased. Rivers' 2008 paper examines the timing of the different periods of the orogeny and reconstructs the timeline based on the spatial and temporal metamorphism of the rocks present. According to this newer version of the timeline which is a composite of Rivers 1997 and Gower and Krogh 2002, the Elzevirian orogeny occurs from 1240 to 1220 Ma,

2209-471: Was the accretion of an island arc at some point during the Elzevirian Orogeny. Before the accretion of the island arc took place, subduction between a continental plate and presumably an oceanic plate was taking place. Slab pull and far-field drivers such as ridge push were aiding in closing the distance between the island arc and the continent. Depending on the angle of subduction, deformation of

#876123