14,755,211 (Canada)
109-493: Traverse Bay may refer to a number of articles relating to the geography of the Great Lakes region : Lake Michigan Lake Superior Great Lakes region The Great Lakes region of Northern America is a binational Canadian – American region centered around the Great Lakes that includes the U.S. states of Illinois , Indiana , Michigan , Minnesota , New York , Ohio , Pennsylvania , and Wisconsin and
218-455: A Mohs hardness of 2 to 4, dense limestone can have a crushing strength of up to 180 MPa . For comparison, concrete typically has a crushing strength of about 40 MPa. Although limestones show little variability in mineral composition, they show great diversity in texture. However, most limestone consists of sand-sized grains in a carbonate mud matrix. Because limestones are often of biological origin and are usually composed of sediment that
327-463: A bloom of cyanobacteria or microalgae . However, stable isotope ratios in modern carbonate mud appear to be inconsistent with either of these mechanisms, and abrasion of carbonate grains in high-energy environments has been put forward as a third possibility. Formation of limestone has likely been dominated by biological processes throughout the Phanerozoic , the last 540 million years of
436-400: A Palaeozoic cover. The visible part was the last part of the primeval continent to sink under the advancing Palaeozoic seas. This district may be considered an ancient coastal plain. The weaker layers are worn down in sub-parallel belts of lower land between the upland and the belts of more resistant strata, which rise in uplands . Illustrations of this type of forms are found in the district of
545-434: A carbonate rock outcrop can be estimated in the field by etching the surface with dilute hydrochloric acid. This etches away the calcite and aragonite, leaving behind any silica or dolomite grains. The latter can be identified by their rhombohedral shape. Crystals of calcite, quartz , dolomite or barite may line small cavities ( vugs ) in the rock. Vugs are a form of secondary porosity, formed in existing limestone by
654-616: A central quartz grain or carbonate mineral fragment. These likely form by direct precipitation of calcium carbonate onto the ooid. Pisoliths are similar to ooids, but they are larger than 2 mm in diameter and tend to be more irregular in shape. Limestone composed mostly of ooids is called an oolite or sometimes an oolitic limestone . Ooids form in high-energy environments, such as the Bahama platform, and oolites typically show crossbedding and other features associated with deposition in strong currents. Oncoliths resemble ooids but show
763-449: A change in environment that increases the solubility of calcite. Dense, massive limestone is sometimes described as "marble". For example, the famous Portoro "marble" of Italy is actually a dense black limestone. True marble is produced by recrystallization of limestone during regional metamorphism that accompanies the mountain building process ( orogeny ). It is distinguished from dense limestone by its coarse crystalline texture and
872-949: A composition reflecting the organisms that produced them and the environment in which they were produced. Low-magnesium calcite skeletal grains are typical of articulate brachiopods , planktonic (free-floating) foraminifera, and coccoliths . High-magnesium calcite skeletal grains are typical of benthic (bottom-dwelling) foraminifera, echinoderms , and coralline algae . Aragonite skeletal grains are typical of molluscs , calcareous green algae , stromatoporoids , corals , and tube worms . The skeletal grains also reflect specific geological periods and environments. For example, coral grains are more common in high-energy environments (characterized by strong currents and turbulence) while bryozoan grains are more common in low-energy environments (characterized by quiet water). Ooids (sometimes called ooliths) are sand-sized grains (less than 2mm in diameter) consisting of one or more layers of calcite or aragonite around
981-1146: A concentration of economic power , industrial workers organized the Congress of Industrial Organizations , a coherent agricultural cooperative movement, and the Progressive politics led by Wisconsin's Governor and Senator Robert M. La Follette . State universities, professional social work, and unemployment and workers' compensation were some of the region's permanent contributions to American social policy. The Great Lakes region has produced globally influential breakthroughs in agricultural technology, transportation and building construction. Cyrus McCormick 's reaper, John Deere 's steel plow, Joseph Dart ( Dart's Elevator ), and George Washington Snow's balloon-frame construction are some of innovations that made significant, global impact. The University of Chicago and Case Western Reserve University figured prominently in developing nuclear power . Automobile manufacture developed simultaneously in Ohio and Indiana and became centered in
1090-412: A considerable fraction of the limestone bed. At depths greater than 1 km (0.62 miles), burial cementation completes the lithification process. Burial cementation does not produce stylolites. When overlying beds are eroded, bringing limestone closer to the surface, the final stage of diagenesis takes place. This produces secondary porosity as some of the cement is dissolved by rainwater infiltrating
1199-483: A drop of dilute hydrochloric acid is dropped on it. Dolomite is also soft but reacts only feebly with dilute hydrochloric acid, and it usually weathers to a characteristic dull yellow-brown color due to the presence of ferrous iron. This is released and oxidized as the dolomite weathers. Impurities (such as clay , sand, organic remains, iron oxide , and other materials) will cause limestones to exhibit different colors, especially with weathered surfaces. The makeup of
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#17327831049931308-637: A few million years, as this is the most stable form of calcium carbonate. Ancient carbonate formations of the Precambrian and Paleozoic contain abundant dolomite, but limestone dominates the carbonate beds of the Mesozoic and Cenozoic . Modern dolomite is quite rare. There is evidence that, while the modern ocean favors precipitation of aragonite, the oceans of the Paleozoic and middle to late Cenozoic favored precipitation of calcite. This may indicate
1417-455: A few thousand years. As rainwater mixes with groundwater, aragonite and high-magnesium calcite are converted to low-calcium calcite. Cementing of thick carbonate deposits by rainwater may commence even before the retreat of the sea, as rainwater can infiltrate over 100 km (60 miles) into sediments beneath the continental shelf. As carbonate sediments are increasingly deeply buried under younger sediments, chemical and mechanical compaction of
1526-490: A high percentage of the mineral dolomite , CaMg(CO 3 ) 2 . Magnesian limestone is an obsolete and poorly-defined term used variously for dolomite, for limestone containing significant dolomite ( dolomitic limestone ), or for any other limestone containing a significant percentage of magnesium . Most limestone was formed in shallow marine environments, such as continental shelves or platforms , though smaller amounts were formed in many other environments. Much dolomite
1635-435: A limestone sample except in thin section and are less common in ancient limestones, possibly because compaction of carbonate sediments disrupts them. Limeclasts are fragments of existing limestone or partially lithified carbonate sediments. Intraclasts are limeclasts that originate close to where they are deposited in limestone, while extraclasts come from outside the depositional area. Intraclasts include grapestone , which
1744-471: A lower Mg/Ca ratio in the ocean water of those times. This magnesium depletion may be a consequence of more rapid sea floor spreading , which removes magnesium from ocean water. The modern ocean and the ocean of the Mesozoic have been described as "aragonite seas". Most limestone was formed in shallow marine environments, such as continental shelves or platforms . Such environments form only about 5% of
1853-525: A lower diversity of organisms and a greater fraction of silica and clay minerals characteristic of marls . The Green River Formation is an example of a prominent freshwater sedimentary formation containing numerous limestone beds. Freshwater limestone is typically micritic. Fossils of charophyte (stonewort), a form of freshwater green algae, are characteristic of these environments, where the charophytes produce and trap carbonates. Limestones may also form in evaporite depositional environments . Calcite
1962-523: A mechanism for dolomitization, with one 2004 review paper describing it bluntly as "a myth". Ordinary seawater is capable of converting calcite to dolomite, if the seawater is regularly flushed through the rock, as by the ebb and flow of tides (tidal pumping). Once dolomitization begins, it proceeds rapidly, so that there is very little carbonate rock containing mixed calcite and dolomite. Carbonate rock tends to be either almost all calcite/aragonite or almost all dolomite. About 20% to 25% of sedimentary rock
2071-448: A plausible source of mud. Another possibility is direct precipitation from the water. A phenomenon known as whitings occurs in shallow waters, in which white streaks containing dispersed micrite appear on the surface of the water. It is uncertain whether this is freshly precipitated aragonite or simply material stirred up from the bottom, but there is some evidence that whitings are caused by biological precipitation of aragonite as part of
2180-449: A radial rather than layered internal structure, indicating that they were formed by algae in a normal marine environment. Peloids are structureless grains of microcrystalline carbonate likely produced by a variety of processes. Many are thought to be fecal pellets produced by marine organisms. Others may be produced by endolithic (boring) algae or other microorganisms or through breakdown of mollusc shells. They are difficult to see in
2289-554: A result of industrialization, the population became more concentrated into urban areas. In part to balance democratic representation against the economic and political power of these corporations, the region hosted industrial labor organization, consolidated agricultural cooperatives and state educational systems. The Big Ten Conference memorializes the nation's first region in which every state sponsored major research, technical-agricultural, and teacher-training colleges and universities. The Congress of Industrial Organizations grew out of
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#17327831049932398-672: A strong, established Lutheran tradition (as established by populations from Nordic and Germanic countries), but this tradition has become more diversified in recent years. Large professional sports leagues such as the National Football League (NFL), the Canadian Football League (CFL), Major League Baseball (MLB), National Basketball Association (NBA), Women's National Basketball Association (WNBA), National Hockey League (NHL) and Major League Soccer (MLS) have team franchises in several cities in
2507-416: Is a type of carbonate sedimentary rock which is the main source of the material lime . It is composed mostly of the minerals calcite and aragonite , which are different crystal forms of CaCO 3 . Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as
2616-560: Is also favored on the seaward margin of shelves and platforms, where there is upwelling deep ocean water rich in nutrients that increase organic productivity. Reefs are common here, but when lacking, ooid shoals are found instead. Finer sediments are deposited close to shore. The lack of deep sea limestones is due in part to rapid subduction of oceanic crust, but is more a result of dissolution of calcium carbonate at depth. The solubility of calcium carbonate increases with pressure and even more with higher concentrations of carbon dioxide, which
2725-518: Is an ancient monadnock having been preserved from destructive attacks of weather by burial under sea-floor deposits. It has been recently re-exposed through the erosion of its cover. The occurrence of the lake basins in the lowland belts on either side of the Niagara escarpment is an abnormal feature. Glacial erosion has formed them through the glacial drift obstructing the normal outlet valleys and to crustal warping in connection with or independent of
2834-482: Is an uncommon mineral in limestone, and siderite or other carbonate minerals are rare. However, the calcite in limestone often contains a few percent of magnesium . Calcite in limestone is divided into low-magnesium and high-magnesium calcite, with the dividing line placed at a composition of 4% magnesium. High-magnesium calcite retains the calcite mineral structure, which is distinct from dolomite. Aragonite does not usually contain significant magnesium. Most limestone
2943-402: Is carbonate rock, and most of this is limestone. Limestone is found in sedimentary sequences as old as 2.7 billion years. However, the compositions of carbonate rocks show an uneven distribution in time in the geologic record. About 95% of modern carbonates are composed of high-magnesium calcite and aragonite. The aragonite needles in carbonate mud are converted to low-magnesium calcite within
3052-474: Is clusters of peloids cemented together by organic material or mineral cement. Extraclasts are uncommon, are usually accompanied by other clastic sediments, and indicate deposition in a tectonically active area or as part of a turbidity current . The grains of most limestones are embedded in a matrix of carbonate mud. This is typically the largest fraction of an ancient carbonate rock. Mud consisting of individual crystals less than 5 μm (0.20 mils) in length
3161-416: Is commonly white to gray in color. Limestone that is unusually rich in organic matter can be almost black in color, while traces of iron or manganese can give limestone an off-white to yellow to red color. The density of limestone depends on its porosity, which varies from 0.1% for the densest limestone to 40% for chalk. The density correspondingly ranges from 1.5 to 2.7 g/cm . Although relatively soft, with
3270-420: Is controlled largely by the amount of dissolved carbon dioxide ( CO 2 ) in the water. This is summarized in the reaction: Increases in temperature or decreases in pressure tend to reduce the amount of dissolved CO 2 and precipitate CaCO 3 . Reduction in salinity also reduces the solubility of CaCO 3 , by several orders of magnitude for fresh water versus seawater. Near-surface water of
3379-545: Is converted to low-magnesium calcite. Diagenesis is the likely origin of pisoliths , concentrically layered particles ranging from 1 to 10 mm (0.039 to 0.394 inches) in diameter found in some limestones. Pisoliths superficially resemble ooids but have no nucleus of foreign matter, fit together tightly, and show other signs that they formed after the original deposition of the sediments. Silicification occurs early in diagenesis, at low pH and temperature, and contributes to fossil preservation. Silicification takes place through
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3488-503: Is deposited close to where it formed, classification of limestone is usually based on its grain type and mud content. Most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera . These organisms secrete structures made of aragonite or calcite, and leave these structures behind when they die. Other carbonate grains composing limestones are ooids , peloids , and limeclasts ( intraclasts and extraclasts [ ca ] ). Skeletal grains have
3597-460: Is described as coquinite . Chalk is a soft, earthy, fine-textured limestone composed of the tests of planktonic microorganisms such as foraminifera, while marl is an earthy mixture of carbonates and silicate sediments. Limestone forms when calcite or aragonite precipitate out of water containing dissolved calcium, which can take place through both biological and nonbiological processes. The solubility of calcium carbonate ( CaCO 3 )
3706-617: Is described as micrite . In fresh carbonate mud, micrite is mostly small aragonite needles, which may precipitate directly from seawater, be secreted by algae, or be produced by abrasion of carbonate grains in a high-energy environment. This is converted to calcite within a few million years of deposition. Further recrystallization of micrite produces microspar , with grains from 5 to 15 μm (0.20 to 0.59 mils) in diameter. Limestone often contains larger crystals of calcite, ranging in size from 0.02 to 0.1 mm (0.79 to 3.94 mils), that are described as sparry calcite or sparite . Sparite
3815-462: Is distinguished from micrite by a grain size of over 20 μm (0.79 mils) and because sparite stands out under a hand lens or in thin section as white or transparent crystals. Sparite is distinguished from carbonate grains by its lack of internal structure and its characteristic crystal shapes. Geologists are careful to distinguish between sparite deposited as cement and sparite formed by recrystallization of micrite or carbonate grains. Sparite cement
3924-539: Is generally small. Its continuity and its contrast with the associated lowlands on the underlying and overlying weak strata make it an important feature. The escarpment would lie straight east–west if the slant of the strata were uniformly to the south. However, the strata are somewhat warped and so the escarpment's course is strongly convex to the north in the middle, gently convex to the south at either end. The escarpment begins where its determining limestone / dolomite begins, in west-central New York . There, it separates
4033-560: Is one of the first minerals to precipitate in marine evaporites. Most limestone is formed by the activities of living organisms near reefs, but the organisms responsible for reef formation have changed over geologic time. For example, stromatolites are mound-shaped structures in ancient limestones, interpreted as colonies of cyanobacteria that accumulated carbonate sediments, but stromatolites are rare in younger limestones. Organisms precipitate limestone both directly as part of their skeletons, and indirectly by removing carbon dioxide from
4142-473: Is otherwise chemically fairly pure, with clastic sediments (mainly fine-grained quartz and clay minerals ) making up less than 5% to 10% of the composition. Organic matter typically makes up around 0.2% of a limestone and rarely exceeds 1%. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragments (such as sponge spicules, diatoms , or radiolarians ). Fossils are also common in limestone. Limestone
4251-472: Is produced by decaying organic matter settling into the deep ocean that is not removed by photosynthesis in the dark depths. As a result, there is a fairly sharp transition from water saturated with calcium carbonate to water unsaturated with calcium carbonate, the lysocline , which occurs at the calcite compensation depth of 4,000 to 7,000 m (13,000 to 23,000 feet). Below this depth, foraminifera tests and other skeletal particles rapidly dissolve, and
4360-518: Is secondary dolomite, formed by chemical alteration of limestone. Limestone is exposed over large regions of the Earth's surface, and because limestone is slightly soluble in rainwater, these exposures often are eroded to become karst landscapes. Most cave systems are found in limestone bedrock. Limestone has numerous uses: as a chemical feedstock for the production of lime used for cement (an essential component of concrete ), as aggregate for
4469-499: Is served by Interstate 94 , Interstate 75 , Ontario Highway 401 , Amtrak Lake Shore Limited and VIA rail services. The three largest international airports in the Great Lake region are Chicago O'Hare , Toronto Pearson , and Detroit Metro Airport . All three airports are major airline hubs that provide nonstop connectivity to other regions and continents. Limestone Limestone ( calcium carbonate CaCO 3 )
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4578-652: The Canadian province of Ontario . Canada's Quebec province is at times included as part of the region because the St. Lawrence River watershed is part of the continuous hydrologic system. The region forms a distinctive historical, economic, and cultural identity. A portion of the region also encompasses the Great Lakes megalopolis . State and provincial governments are represented in the Conference of Great Lakes and St. Lawrence Governors and Premiers , which also serves as
4687-1012: The Chicago Board Options Exchange (CBOE), and the Chicago Mercantile Exchange (the "Merc"), which is owned, along with the Chicago Board of Trade (CBOT) by Chicago's CME Group . The CME Group, in addition, owns the New York Mercantile Exchange (NYMEX), the Commodities Exchange Inc. (COMEX), and the Dow Jones Indexes ., as well as headquarters of the Federal Reserve Bank of Chicago (the Seventh District of
4796-512: The Detroit area of Michigan . Henry Ford 's movable assembly line drew on regional experience in meat processing , agricultural machinery manufacture, and the industrial engineering of steel in revolutionizing the modern era of mass production manufacturing. Chicago -based Montgomery Ward and Sears Roebuck companies complemented mass manufactures with mass retail distribution. Chicago , Detroit , and Cleveland carry important roles in
4905-481: The Great Lakes . The chief upland belt or escarpment is formed by the firm Niagara limestone/dolomite , which takes its name from the gorge and falls cut through the upland by the Niagara River . The Niagara Escarpment has a relatively strong slope or enfacing escarpment on the side towards the upland, and a long gentle slope on the other side. Its relief is seldom more than 200 or 300 feet (91 m) and
5014-579: The Gulf of Saint Lawrence on the north and to the Gulf of Mexico on the south. The three lakes of the middle group: Lake Michigan, Lake Huron and Lake Erie stand at practically the same level. Lake Michigan and Lake Huron are connected by the Straits of Mackinac with the Mackinac Bridge spanning the straits. Lake Huron and Lake Erie are connected by the St. Clair River and Detroit River , with
5123-644: The Treaty of Paris (1763) that ended The Seven Years' War , known in America as the French and Indian War ceded the entire region to the victor. Indian Reserve is the historical term for this largely uncolonized area set aside in the Royal Proclamation of 1763 for use by Native Americans , who already inhabited it. The British government had contemplated establishing an Indian barrier state in
5232-1019: The original thirteen . Five states evolved from its provisions: Ohio, Indiana, Michigan, Illinois, and Wisconsin. The northeastern section of Minnesota, from the Mississippi to St. Croix River , also fell under ordinance jurisdiction and extended the constitution and culture of the Old Northwest to the Dakotas . The surge of settlement generated tension culminating in the Battle of Fallen Timbers in 1794. Britain, fearing that fast American settlement could lead to annexation of its western provinces, countered with The Constitution Act of 1791 , granting limited self-government to Canadian provinces and creating two new provinces out of Canada: Lower Canada (today's Quebec) and Upper Canada (Ontario). Settlement and economic expansion on both sides accelerated after
5341-538: The 1825 opening of The Erie Canal , an astonishingly successful public venture that effectively integrated markets and commerce between the Atlantic seaboard and the region. The region on both sides of the border became a vast research and design laboratory for agricultural machinery and techniques. Owner-operator family farms transformed both demographics and ecology into a vast terrain of farmlands, producing primarily wheat and corn. In western New York and northeast Ohio,
5450-485: The American Revolution, the region was contested between Britain and rebellious American colonies. Hoping for favorable claims of territorial control in an eventual peace treaty with Britain, American adventurers led by Kentucky militia leader George Rogers Clark briefly occupied village settlements, including Cahokia, Kaskaskia and Vincennes unopposed, with passive support from Francophone inhabitants. In
5559-1112: The Big Five, have their global operational headquarters in Toronto. Outside of Chicago and Toronto, many other cities are host to financial centers as well. Major bank headquarters are located in Ohio including Huntington Bancshares in Columbus, Fifth Third Bank in Cincinnati, and KeyCorp in Cleveland. Insurance companies such as Anthem in Indianapolis, Nationwide Insurance in Columbus, American Family Insurance in Madison, Wisconsin, State Farm Insurance in Bloomington, Illinois, and Progressive Insurance and Medical Mutual of Ohio in Cleveland. The Great Lakes region has
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#17327831049935668-496: The Earth's history. Limestone may have been deposited by microorganisms in the Precambrian , prior to 540 million years ago, but inorganic processes were probably more important and likely took place in an ocean more highly oversaturated in calcium carbonate than the modern ocean. Diagenesis is the process in which sediments are compacted and turned into solid rock . During diagenesis of carbonate sediments, significant chemical and textural changes take place. For example, aragonite
5777-556: The Federal Reserve). Toronto is an international centre for business and finance. Generally considered the financial capital of Canada, Toronto has a high concentration of banks and brokerage firms on Bay Street, in the Financial District. The Toronto Stock Exchange (TSX) is the world's seventh-largest stock exchange by market capitalization. The five largest financial institutions of Canada, collectively known as
5886-793: The Great Lakes, the British continued to supply not only their own troops but a wide alliance of Native American nations through Detroit, Fort Niagara , Fort Michilimackinac , and so on, until these posts were turned over to the United States following the Jay Treaty (1794). During the Confederacy Period of 1781–1789, the Continental Congress passed three ordinances whose authority was unclear regarding
5995-536: The Indian population. The ordinance prohibited the establishment of state religion and established civic rights that foreshadowed the United States Bill of Rights . Civil rights included freedom from cruel and unusual punishment , trial by jury , and exemption from unreasonable search and seizure . States were authorized to organize constitutional conventions and petition for admission as states equal to
6104-586: The Peace of Paris (1784) Britain ceded what became known as the Northwest Territory , the area bounded by Great Lakes, Mississippi and Ohio rivers, and the eastern colonies of New York and Pennsylvania, to the fledgling United States. Britain, which may have entertained ambitions to repossess the area if America failed to govern it, retained control over its forts and licensed fur trade for fifteen years. By well-established trade and military routes across
6213-780: The Secretariat to the Great Lakes St. Lawrence Compact and the Great Lakes–Saint Lawrence River Basin Sustainable Water Resources Agreement . The Great Lakes region takes its name from the corresponding geological formation of the Great Lakes Basin , a narrow watershed encompassing the Great Lakes, bounded by watersheds to the region's north by the Hudson Bay , to the west by the Mississippi , and to
6322-836: The St. Lawrence, Mohawk, and Hudson rivers provided outlets for commercial corn and wheat, while The Ohio River let agricultural products from western Pennsylvania and southern Ohio, Indiana and Illinois journey downstream to New Orleans. Mining, primarily soft metals of copper, zinc, and lead; and timber to supply rapidly expanding sawmills that supplied lumber for new settlements. Agricultural and industrial production generated distinctive political and social cultures of independent republican producers, who consolidated an ideology of personal liberty, free markets, and great social visions, often expressed in religious terms and enthusiasms. The region's alliance of antislavery with free soil movements contributed troops and agricultural goods that proved critical in
6431-477: The Union's victory. The Homestead and Morrill Acts , donating federal land to extend the agrarian economic franchise, and support state universities, modeled western expansion and education for all future states. The British-Canadian London Conference of 1866 , and subsequent Constitution Act of 1867 analogously derived from political, and some military, turmoil in the former jurisdiction of Upper Canada , which
6540-430: The accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life. About 20% to 25% of sedimentary rock is carbonate rock, and most of this is limestone. The remaining carbonate rock is mostly dolomite , a closely related rock, which contains
6649-434: The base of roads, as white pigment or filler in products such as toothpaste or paint, as a soil conditioner , and as a popular decorative addition to rock gardens . Limestone formations contain about 30% of the world's petroleum reservoirs . Limestone is composed mostly of the minerals calcite and aragonite , which are different crystal forms of calcium carbonate ( CaCO 3 ). Dolomite , CaMg(CO 3 ) 2 ,
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#17327831049936758-657: The beds. This may include the formation of vugs , which are crystal-lined cavities within the limestone. Diagenesis may include conversion of limestone to dolomite by magnesium-rich fluids. There is considerable evidence of replacement of limestone by dolomite, including sharp replacement boundaries that cut across bedding. The process of dolomitization remains an area of active research, but possible mechanisms include exposure to concentrated brines in hot environments ( evaporative reflux ) or exposure to diluted seawater in delta or estuary environments ( Dorag dolomitization ). However, Dorag dolomitization has fallen into disfavor as
6867-466: The depositional fabric of carbonate rocks. Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles, based on criteria such as whether the grains were originally in mutual contact, and therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats. Unlike the Folk scheme, Dunham deals with the original porosity of
6976-469: The deposits are highly porous, so that they have a spongelike texture, they are typically described as tufa . Secondary calcite deposited by supersaturated meteoric waters ( groundwater ) in caves is also sometimes described as travertine. This produces speleothems , such as stalagmites and stalactites . Coquina is a poorly consolidated limestone composed of abraded pieces of coral , shells , or other fossil debris. When better consolidated, it
7085-406: The earth's oceans are oversaturated with CaCO 3 by a factor of more than six. The failure of CaCO 3 to rapidly precipitate out of these waters is likely due to interference by dissolved magnesium ions with nucleation of calcite crystals, the necessary first step in precipitation. Precipitation of aragonite may be suppressed by the presence of naturally occurring organic phosphates in
7194-513: The east and south by the Ohio . To the east, the rivers of St. Lawrence , Richelieu , Hudson , Mohawk and Susquehanna form an arc of watersheds east to the Atlantic . The Great Lakes region, as distinct from the Great Lakes Basin , defines a unit of sub-national political entities defined by the U.S. states and the Canadian province of Ontario encompassing the Great Lakes watershed, and
7303-461: The establishment of their brand names as purveyors of consumer goods. The region's natural features, cultural institutions, and resorts make it a popular destination for tourism. Advantages of accessible waterways, highly developed transportation infrastructure, finance, and a prosperous market base make the region the global leader in automobile production and a global business location. Henry Ford 's movable assembly line and integrated production set
7412-744: The field of architecture. Chicago pioneered the world's first skyscraper, the Home Insurance Building designed by William LeBaron Jenney . Engineering innovation established Chicago from that time on to become one of the world's most influential epicenters of contemporary urban and commercial architecture. Equally influential was the 1832 invention of balloon- framing in Chicago which replaced heavy timber construction requiring massive beams and great woodworking skill with pre-cut timber. This new lumber could be nailed together by farmers and settlers who used it to build homes and barns throughout
7521-460: The first permanent European settlements in the early seventeenth century, all these nation-peoples developed an extensive fur trade with French, Dutch, and English merchants in the St. Lawrence, Hudson and Mohawk Valleys, and Hudson's Bay, respectively. The prospects of fur monopolies and discovery of a fabled Northwest Passage to Asia generated sporadic but intense competition among the three most powerful northwest Europe imperial nations to control
7630-399: The first refers to the grains and the second to the cement. For example, a limestone consisting mainly of ooids, with a crystalline matrix, would be termed an oosparite. It is helpful to have a petrographic microscope when using the Folk scheme, because it is easier to determine the components present in each sample. Robert J. Dunham published his system for limestone in 1962. It focuses on
7739-572: The formation of distinctive minerals from the silica and clay present in the original limestone. Two major classification schemes, the Folk and Dunham, are used for identifying the types of carbonate rocks collectively known as limestone. Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks . Based on composition, there are three main components: allochems (grains), matrix (mostly micrite), and cement (sparite). The Folk system uses two-part names;
7848-429: The geologic record are called bioherms . Many are rich in fossils, but most lack any connected organic framework like that seen in modern reefs. The fossil remains are present as separate fragments embedded in ample mud matrix. Much of the sedimentation shows indications of occurring in the intertidal or supratidal zones, suggesting sediments rapidly fill available accommodation space in the shelf or platform. Deposition
7957-400: The glacial sheet. Lake Superior is unlike the other lakes. The greater part of its basin occupies a depression in the upland area, independent of the overlap of Palaeozoic strata. The western half of the basin occupies a trough of synclinal structure. The Great Lakes receive the drainage of a small peripheral land area, enclosed by a water-parting from the rivers that run to Hudson Bay or
8066-773: The largest city in Canada and the fourth largest city proper in North America behind Mexico City , New York City and Los Angeles. Cities along the Great Lakes have access to the Atlantic Ocean through the St. Lawrence Seaway , making them international ports. Chicago is the largest economic and financial center. Chicago was named the fourth most important business center in the world in the MasterCard Worldwide Centers of Commerce Index. The 2017 Global Financial Centres Index ranked Chicago as
8175-601: The largest economic units on Earth (with a $ 6-trillion gross regional product). This region also contains what area urban planners call the Great Lakes Megalopolis , which has an estimated 59 million people. Chicago is emerging as the third megacity in the United States , after the New York City and Los Angeles metropolitan areas, with a metro population approaching ten million. Toronto is
8284-469: The limestone and is hardly traceable across the Mississippi River . The arrangement of the Great Lakes closely matches the course of the lowlands worn on the two belts of weaker strata on either side of the Niagara escarpment. Lake Ontario, Georgian Bay and Green Bay occupy depressions in the lowland on the inner side of the escarpment. Lake Erie, Lake Huron and Lake Michigan lie in depressions in
8393-534: The lowland on the outer side. When the two lowlands are traced eastward, they become confluent after the Niagara limestone has faded away in central New York, and the single lowland is continued under the name of the Mohawk Valley . This is an east–west longitudinal depression that has been eroded on a belt of relatively weak strata between the resistant crystalline rocks of the Adirondacks on the north and
8502-525: The lowlands that separate Lake Ontario from Lake Erie . It curves to the northwest through the Ontario province to the island belt that divides the Georgian Bay from Lake Huron . From there, it heads westward through the land-arm between Lake Superior and Lake Michigan and southwestward into the narrow points dividing Green Bay from Lake Michigan. Finally, it fades away with the thinning out of
8611-510: The model and standard for major car manufactures. The Detroit area emerged as the world's automotive center, with facilities throughout the region. Akron, Ohio became the global leader in rubber production, driven by the demand for tires. Over 200 million tons of cargo are shipped annually through the Great Lakes. According to the Brookings Institution , if it stood alone as a country, the Great Lakes economy would be one of
8720-401: The nineteenth century Grange , which in turn generated the agricultural cooperatives that defined much of rural political economy and culture throughout the region. Fraternal , ethnic, and civic organizations extended cooperatives and supported local ventures from insurance companies to orphanages and hospitals. The region was the political base, and provided much leadership political parties in
8829-548: The northern escarpment of the Appalachian Plateau ( Catskills - Helderbergs ) on the south. Early in U.S. history, this provided a vital economic route between the Atlantic seaports and the U.S. interior. In Wisconsin , the inner lowland is a knob of resistant quartzites, known as Baraboo Ridge, rising from the buried upland floor through the partly denuded cover of lower Palaeozoic strata. This knob or ridge can be thought of as an ancient physiographic fossil, as it
8938-410: The ocean basins, but limestone is rarely preserved in continental slope and deep sea environments. The best environments for deposition are warm waters, which have both a high organic productivity and increased saturation of calcium carbonate due to lower concentrations of dissolved carbon dioxide. Modern limestone deposits are almost always in areas with very little silica-rich sedimentation, reflected in
9047-453: The pattern of American centralized industrial consolidation and eventual global dominance. The region hosted the world's greatest concentrations of production for oil, coal, steel, automobiles, synthetic rubber, agricultural machinery, and heavy transport equipment. Agronomy industrialized as well, in meat processing, packaged cereal products, and processed dairy products. In response to disruptions and imbalances of power resulting from so vast
9156-690: The political protocols by which American states south of the lakes would enter the union as political equals with the original thirteen colonies. The ordinance, adopted in its final form just before the writing of the United States Constitution , was a sweeping, visionary proposal to create what was at the time a radical experiment in democratic governance and economy. The Northwest Ordinance of 1787 prohibited slavery , restricted primogeniture , mandated universal public education , provided for affordable farm land to people who settled and improved it, and required peaceful, lawful treatment of
9265-661: The portion of the reserve west of the Appalachian Mountains , and bounded by the Ohio and Mississippi rivers and the Great Lakes . Britain's claims were intensely disputed by a confederation of Indians during Pontiac's Rebellion , which induced major concessions to still sovereign Indian nations; and by the Iroquois Confederacy , whose six member nations- Mohawk , Oneida , Onondaga , Cayuga , Seneca and Tuscarora -never conceded sovereignty to either Britain or, later, The United States. During
9374-426: The reaction: Fossils are often preserved in exquisite detail as chert. Cementing takes place rapidly in carbonate sediments, typically within less than a million years of deposition. Some cementing occurs while the sediments are still under water, forming hardgrounds . Cementing accelerates after the retreat of the sea from the depositional environment, as rainwater infiltrates the sediment beds, often within just
9483-500: The region became the global epicenter of motorized land vehicles, including cars, trucks and jeeps, as well as a major supplier of engine, transmission, and electrical components to the wartime aeronautics industry. Despite extreme labor shortages, the region increased mechanization, and absorbed large numbers of women and immigrant labor, to increase its food production. Navigable terrain, waterways, and ports spurred an unprecedented construction of transportation infrastructure throughout
9592-493: The region's coal and iron mines; steel, automobile and rubber industries; and breakthrough strikes and contracts of Ohio, Indiana, and Michigan. The role of government also grew during the early 20th century. In the rural areas, most people obtained food and manufactured goods from neighbors and other people they knew personally. As industry and commerce grew, goods such as food, materials, and medicines were no longer made by neighbors, but by large companies. During World War II ,
9701-623: The region's governance on the American side. The Land Ordinance of 1784 established the broad outlines of future governance. The territory would be divided into six states, which would be given broad powers of constitutional instituting, and admitted to the nation as equal members. The Land Ordinance of 1785 specified the manner in which land would be distributed in the Territory, favoring sale in small parcels to settlers who would work their own farms. The Northwest Ordinance of 1787 defined
9810-511: The region. Blue collar industry traditionally represent in the Great Lakes region. In the United States, it is a stronghold of the Democratic Party although in recent years many states in Great Lakes region have become swing states . In Ontario , it has long been divided between rural and urban districts, with many rural ridings voted more conservative, and larger urban and Suburban areas voting Liberal or NDP. The Great Lake region
9919-439: The region. The region's greatest institutional contributions were major corporate, labor, educational and cooperative organizations. It hosted some of the most influential national and international corporations of the late nineteenth and early twentieth century monopoly age, including John Deere Plow, McCormack Reaper, New York Central and Erie railroads, Carnegie Steel, U.S. Steel, International Harvester and Standard Oil. As
10028-626: The region. The region is a global leader in advanced manufacturing and research and development, with significant innovations in both production processes and business organization. John D. Rockefeller's Standard Oil set precedents for centralized pricing, uniform distribution, and controlled product standards through Standard Oil, which started as a consolidated refinery in Cleveland. Cyrus McCormick 's Reaper and other manufacturers of agricultural machinery consolidated into International Harvester in Chicago. Andrew Carnegie 's steel production integrated large-scale open-hearth and Bessemer processes into
10137-482: The relative purity of most limestones. Reef organisms are destroyed by muddy, brackish river water, and carbonate grains are ground down by much harder silicate grains. Unlike clastic sedimentary rock, limestone is produced almost entirely from sediments originating at or near the place of deposition. Limestone formations tend to show abrupt changes in thickness. Large moundlike features in a limestone formation are interpreted as ancient reefs , which when they appear in
10246-460: The rock. The Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample. A revised classification was proposed by Wright (1992). It adds some diagenetic patterns to the classification scheme. Travertine is a term applied to calcium carbonate deposits formed in freshwater environments, particularly waterfalls , cascades and hot springs . Such deposits are typically massive, dense, and banded. When
10355-479: The sediments increases. Chemical compaction takes place by pressure solution of the sediments. This process dissolves minerals from points of contact between grains and redeposits it in pore space, reducing the porosity of the limestone from an initial high value of 40% to 80% to less than 10%. Pressure solution produces distinctive stylolites , irregular surfaces within the limestone at which silica-rich sediments accumulate. These may reflect dissolution and loss of
10464-662: The sediments of the ocean floor abruptly transition from carbonate ooze rich in foraminifera and coccolith remains ( Globigerina ooze) to silicic mud lacking carbonates. In rare cases, turbidites or other silica-rich sediments bury and preserve benthic (deep ocean) carbonate deposits. Ancient benthic limestones are microcrystalline and are identified by their tectonic setting. Fossils typically are foraminifera and coccoliths. No pre-Jurassic benthic limestones are known, probably because carbonate-shelled plankton had not yet evolved. Limestones also form in freshwater environments. These limestones are not unlike marine limestone, but have
10573-407: The small Lake St. Clair between them. The land northeast of the rivers is undergoing a slow elevation. The Niagara River connecting Lake Erie and Lake Ontario, with a fall of 326 feet (99 m) (160 feet (49 m) at the cataract) in 30 miles (48 km), is thought to have been of recent origin, as an older river would have a mature valley. The original valley that is thought to have connected
10682-470: The states and province bordering one or more of the Great Lakes. The Palaeozoic strata are parts of a great area of similar layers hundreds of feet in thickness. These strata decline gently southward from the great upland of the Laurentian Highlands of eastern Canada. The visible upland area of today was a small part of the primeval continent with the remainder of it still buried under
10791-662: The territory. A century and a half of naval and land wars among France, The Netherlands and Britain resulted finally in British control of the region, from the Ohio River to the Arctic, and from the Atlantic to the Mississippi. Beyond the region, North American claims remained disputed among Britain, France, Spain and Russia. Britain defeated France decisively at the Battle of the Plains of Abraham near Quebec City in 1759, and
10900-473: The twenty-fourth most competitive city in the world, behind Toronto, also in the Great Lakes region, at seventh. The Chicago Board of Trade (established 1848) listed the first ever standardized "exchange traded" forward contracts, which were called futures contracts . As a world financial center it is home to major financial and futures exchanges , including the Chicago Stock Exchange ,
11009-565: The two depressions through the Niagara Escarpment is thought to have been at the present route of the Welland Canal , and to have been completely filled with glacial drift . The same is true for the St. Lawrence , where there may not have been an original valley. The Ontarian River that was a precursor to Lake Ontario is thought to have drained westward, and the St. Lawrence drainage to have been created by subsidence due to
11118-533: The water by photosynthesis and thereby decreasing the solubility of calcium carbonate. Limestone shows the same range of sedimentary structures found in other sedimentary rocks. However, finer structures, such as lamination , are often destroyed by the burrowing activities of organisms ( bioturbation ). Fine lamination is characteristic of limestone formed in playa lakes , which lack the burrowing organisms. Limestones also show distinctive features such as geopetal structures , which form when curved shells settle to
11227-553: The water. Although ooids likely form through purely inorganic processes, the bulk of CaCO 3 precipitation in the oceans is the result of biological activity. Much of this takes place on carbonate platforms . The origin of carbonate mud, and the processes by which it is converted to micrite, continue to be a subject of research. Modern carbonate mud is composed mostly of aragonite needles around 5 μm (0.20 mils) in length. Needles of this shape and composition are produced by calcareous algae such as Penicillus , making this
11336-648: The weight of the ice sheet. Paleo-Indian cultures were the earliest in North America, with a presence in the Great Plains and Great Lakes areas from about 12,000 BCE to around 8,000 BCE. Prior to European settlement, Iroquoian people lived around Lakes Erie and Ontario , Algonquian peoples around most of the rest, and a variety of other indigenous nation-peoples including the Menominee , Ojibwa , Illinois , Pottawatmie , Huron , Shawnee , Erie , Fox , Miami , Meskwaki and Ho-Chunk (Winnebago). With
11445-551: The western prairies and plains. Wisconsin-born, Chicago-trained Sullivan apprentice Frank Lloyd Wright designed prototypes for architectural designs from the commercial skylight atrium to suburban ranch house. German-born Pennsylvania immigrant John A. Roebling invented steel wire rope, a pivotal part of suspension bridges he designed and whose construction he supervised in Pittsburgh, Cincinnati and Buffalo, based on earlier successful canal aqueducts. His most famous project
11554-466: The world's most efficient and profitable mills. The largest, most comprehensive monopoly in the world, United States Steel , consolidated steel production throughout the region. Many of the world's largest employers began in the Great Lakes region. Mass marketing in the modern sense was born in the region. Two competing Chicago retailers— Montgomery Ward and Sears Roebuck —developed mass marketing and sales through catalogues, mail-order distribution, and
11663-416: Was likely deposited in pore space between grains, suggesting a high-energy depositional environment that removed carbonate mud. Recrystallized sparite is not diagnostic of depositional environment. Limestone outcrops are recognized in the field by their softness (calcite and aragonite both have a Mohs hardness of less than 4, well below common silicate minerals) and because limestone bubbles vigorously when
11772-505: Was renamed and organized in the new dominion as the province of Ontario . Like the provisions of the ordinance, Ontario prohibited slavery, made provisions for land distribution to farmers who owned their own land, and mandated universal public education . Industrial production, organization, and technology have made the region among the world's most productive manufacturing centers. Nineteenth-century monopolies such as International Harvester, Standard Oil, and United States Steel established
11881-584: Was the Brooklyn Bridge . Contributions to modern transportation include the Wright brothers ' early airplanes, designed and perfected in their Dayton, Ohio mechanics' workshops; distinctive Great Lakes freighters , and railroad beds constructed of wooden ties and steel rails. The early nineteenth century Erie Canal and mid-twentieth century St. Lawrence Seaway expanded the scale and capacity of massive water-born freight. Agricultural associations joined
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