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Tippecanoe Sequence
The Tippecanoe sequence was the cratonic sequence--that is, the marine transgression--that followed the Sauk sequence; it extended from roughly the Middle Ordovician to the Early Devonian. Sedimentary characteristics After the regression of the Sauk Sea early in the Ordovician, the exposed craton for a time underwent vigorous erosion, due to being located in a tropical climate; indeed, at this point in the Paleozoic the North American continent roughly straddled the equator. The Tippecanoe transgression ended this period of erosion, beginning with the deposition of clean sandstones across the craton, followed by abundant carbonate deposition.Monroe and Wicander, pp. 534-5 In the east these carbonates gradually become shales, representing sediments eroded from highlands created in the Taconic orogeny. The Tippecanoe sequence may have been the deepest of the Paleozoic. At one point during the Silurian period, the Taconic highlands—which later became the Appalachian Mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cratonic Sequence
A cratonic sequence in geology is a very large-scale lithostratigraphic sequence in the rock record that represents a complete cycle of marine transgression and regression on a craton (block of continental crust) over geologic time. Cratonic sequences are also known as "megasequences", "stratigraphic sequences", "Sloss sequences", "supersequences" or simply "sequences". They are geologic evidence of relative sea level rising and then falling (transgressing and regressing), thereby depositing varying layers of sediment onto the craton, now expressed as sedimentary rock. Places such as the Grand Canyon are a good visual example of this process, demonstrating the changes between layers deposited over time as the ancient environment changed. Cratonic sequences were first proposed by Laurence L. Sloss in 1963. Each one represents a time when inland seas deposited sediments across the craton. The top and bottom edges of a sequence are each bounded by craton-wide unconformities (time ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonate Rock
Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3), and dolomite rock (also known as dolostone), which is composed of mineral dolomite (CaMg(CO3)2). Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases. When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. Karst topography and caves develop in carbonate rocks because of their solubility in dilute acidic groundwater. Cooling groundwater or mixing of different groundwaters will also create conditions suitable for cave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician United States
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The Ordovician, named after the Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian Perio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kaskaskia Sequence
The Kaskaskia sequence was a cratonic sequence that began in the mid- Devonian, peaked early in the Mississippian, and ended by mid-Mississippian time. A major unconformity separates it from the lower Tippecanoe sequence. The basal—that is, the lowest and oldest—units of the Kaskaskia consist of clean quartz sandstones eroded from the Appalachian orogenic belt to the east, the Ozark Dome in the center of the continent, and south from the Canadian Shield. These sandstones are followed by extensive carbonates, though these are often difficult to distinguish from preceding Tippecanoe carbonates. The Kaskaskia is well known for its widespread carbonate and evaporite strata, which in fact compose most of the rocks; the Williston Basin in Canada is a superb example of such evaporite deposits. Beginning in the late Devonian, black shales begin to dominate in the rocks, composed of detritus eroded from the uplifted Acadian highlands to the west; they also indicate widespread ano ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Michigan Basin
The Michigan Basin is a geologic basin centered on the Lower Peninsula of the U.S. state of Michigan. The feature is represented by a nearly circular pattern of geologic sedimentary strata in the area with a nearly uniform structural dip toward the center of the peninsula. Geology The basin is centered in Gladwin County where the Precambrian basement rocks are deep. Around the margins, such as under Mackinaw City, Michigan, the Precambrian surface is around below the surface. This contour on the bedrock clips the northern part of the Lower Peninsula and continues under Lake Michigan along the west. It crosses the southern counties of Michigan and continues to the north beneath Lake Huron. On the north in the Canadian Shield, which includes the western part of Michigan's Upper Peninsula, Precambrian rocks are exposed at the surface. The eastern margins of Wisconsin along Green Bay are along the margins of the basin, while Precambrian rocks crop out to the west in central Wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evaporite
An evaporite () is a water-soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean deposits, and non-marine, which are found in standing bodies of water such as lakes. Evaporites are considered sedimentary rocks and are formed by chemical sediments. Formation of evaporite rocks Although all water bodies on the surface and in aquifers contain dissolved salts, the water must evaporate into the atmosphere for the minerals to precipitate. For this to happen, the water body must enter a restricted environment where water input into this environment remains below the net rate of evaporation. This is usually an arid environment with a small basin fed by a limited input of water. When evaporation occurs, the remaining water is enriched in salts, and they precipitate when the water becomes supersaturated. Evaporite depositi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Appalachian Mountains
The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They once reached elevations similar to those of the Alps and the Rocky Mountains before experiencing natural erosion. The Appalachian chain is a barrier to east–west travel, as it forms a series of alternating ridgelines and valleys oriented in opposition to most highways and railroads running east–west. Definitions vary on the precise boundaries of the Appalachians. The United States Geological Survey (USGS) defines the ''Appalachian Highlands'' physiographic division as consisting of 13 provinces: the Atlantic Coast Uplands, Eastern Newfoundland Atlantic, Maritime Acadian Highlands, Maritime Plain, Notre Dame and Mégantic Mountains, Western Newfoundland Mountains, Piedmont, Blue Ridge, Valley and Ridge, St. Lawrence Valley, Appalac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out. One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods (myriapods, arachnids and hexapods) became fully terrestrialized. A significant evolutionary milestone during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taconic Orogeny
The Taconic orogeny was a mountain building period that ended 440 million years ago and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont of the East coast of the United States. As the mountain chain eroded in the Silurian and Devonian periods, sediments from the mountain chain spread throughout the present-day Appalachians and midcontinental North America. New England and Canada Beginning in Cambrian time, about 550 million years ago, the Iapetus Ocean began to close. The weight of accumulating sediments, in addition to compressional forces in the crust, forced the eastern edge of the North American continent to fold gradually downward. In this manner, shallow-water carbonate deposition that had persisted on the continental shelf margin through Late Cambrian into Early Ordovician time, gave way to fine-grained clastic deposition and deeper water conditions during the Middle Ordovician. In this period ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone (sedimentary rocks) through lithification. Sediments are most often transported by water (fluvial processes), but also wind (aeolian processes) and glaciers. Beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of aeolian transport and deposition. Glacial moraine deposits and till are ice-transported sediments. Classification Sediment can be classified based on its grain size, grain shape, and c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.Blatt, Harvey and Robert J. Tracy (1996) ''Petrology: Igneous, Sedimentary and Metamorphic'', 2nd ed., Freeman, pp. 281–292 Shale is characterized by its tendency to split into thin layers ( laminae) less than one centimeter in thickness. This property is called '' fissility''. Shale is the most common sedimentary rock. The term ''shale'' is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the more narrow sense of clay-rich fissile mudrock. Texture Shale typically exhibits varying degrees of fissility. Because of the parallel orientation of clay mineral flakes in shale, it breaks into thin layers, often splintery and usually parallel to the otherwise indistinguishable beddin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) because they are the most resistant minerals to weathering processes at the Earth's surface. Like uncemented sand, sandstone may be any color due to impurities within the minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colors of sandstone have been strongly identified with certain regions. Rock formations that are primarily composed of sandstone usually allow the percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Quartz-bearing sandstone can be changed into quartzite through metamorphism, usually related to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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