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132 Cards in this Set
- Front
- Back
How does the volume of sedimentary rocks in earth's crust compare to the volume of igneous and metamorphic rocks? |
Most of the earth consists of igneous and metamorphic rocks they make up 90 to 95% of the outer crust. However about 75% of the land area are covered by sedimentary rocks. Meaning sedimentary rock are only on the surface |
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List two ways in which sedimentary rocks are important |
They contain fossils, and Sedimentary rocks are also the primary reservoir of groundwater |
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mass wasting |
Solid particles move downslope by gravity often affected by water |
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changes that take place after sediments are deposited during and after lithification |
Diagenesis |
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Rocks that form from the accumulation of materials that originate and are transported as solid particles from weathering |
detrital sedimentary rocks |
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Chemical sedimentary rocks |
rocks that form by precipitation of minerals from water by either organic or inorganic means |
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when dissolved materials come out of water. For example: Take a glass of water and pour some salt (halite) into it. The salt will dissolve into the water. |
Precipitation |
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Organic sedimentary rocks |
form from the accumulation and lithification of organic debris, such as leaves, roots, and other plant or animal material. OR Sedimentary rock composed of organic carbon from the remains of plants that died and accumulated on the floor of a swamp. Coal is the primary example. |
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List three basic sedimentary rock categories |
Organic, detrital, and chemical sedimentary rocks |
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What minerals are most abundant in detrital sedimentary rocks |
Clay minerals (feldspar) and quartz |
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detritus |
Loose particles or grains formed by the disintegration of rocks |
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What is the primary basis for distinguishing detrital rocks |
particle size |
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The formation of sedimentary rock requires |
weathering and erosion of pre-existing rocks |
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sedimentary rock composed of solid masses of intergrown crystals |
rock salt |
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You find a sedimentary rock that has all its flat particles aligned in parallel. From this you can infer that _____ |
The particles have been compacted |
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flat particles are aligned parallel in a sedimentary rock are |
compacted |
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compaction |
A type of lithification in which the weight of an overlaying material compresses more deeply buried sediment |
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cementation |
A type of lithification. As percolating water coats the water with mineral matter, and gradually cements the particles together |
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Name the 2 types of lithification |
compaction and cementation |
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A fine grained sedimentary rock consisting of silt and clay size particles |
Shale |
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Name the 5 types of detrital rocks |
conglomerate, breccia, sandstone, shale, mudstone, and siltstone |
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As silt and clay accumulate they tend to form thin layer called what |
laminae |
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Fissility |
capable of being split or divided; cleavable (often refers to shale) |
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mudstone |
a dark sedimentary rock formed from consolidated mud and lacking the laminations of shale. |
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siltstone |
fine-grained sedimentary rock consisting of consolidated silt |
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the most common sedimentary rock |
shale |
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Sandstone |
Sedimentary rock in which sand size grains predominate (after shale sandstone is the most abundant sedimentary rock) |
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Sorting |
Refers to the degree of similarity in particle size in a sedimentary rock |
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Sedimentary rocks that exhibit the intergrowth of crystal masses are generally formed from the products of ___ |
chemical weathering (Chemical weathering produces extremely small particles that can later precipitate to produce intergrown crystal masses.) |
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If all the particles in a detrital sedimentary rock are nearly the same size, it is _______ |
very well sorted |
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A smooth grain shaped like a cigar is __________ and shows _________ |
well-rounded; low sphericity |
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Wind-blown sand deposits would most likely be __________ and __________. |
very well-sorted; well-rounded |
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what correlate to transport distance |
grain size and rounding |
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A conglomerate is poorly sorted with well-rounded grains. This rock was likely formed in what depositional environment |
mountain stream |
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What is the most abundant chemical sedimentary rock in Earth’s crust? |
limestone |
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Working in the field, you find a rock that contains rounded fragments that are greater than 2 mm in diameter. What would you call this rock |
conglomerate |
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The geologic laboratory where you work received a sample for analysis that is composed of calcite that includes many microscopic fossils of marine organisms and reacts with acid. What name would identify this rock? |
chalk (Chalk is a biochemical sedimentary rock composed of calcite and contains many microscopic fossils of marine organisms.) |
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Name the progression of coal types with increased heat and pressure from burial |
peat, lignite, bituminous, anthracite |
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Abundant plant material accumulating in a swampy environment with __________ is required for peat to form. |
low oxygen levels |
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What coal is soft, black in color, and produces soot upon handling |
bituminous |
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How is anthracite produced from bituminous coal |
metamorphism |
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In the United States, the most common type of coal is __________ and the largest producing state is __________. |
sub-bituminous; Wyoming |
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The common sediment name for particles bigger than 2mm are called |
gravel |
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conglomerate |
a coarse-grained sedimentary rock composed of rounded fragments (> 2 mm) within a matrix of finer grained material. |
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breccia |
rock consisting of angular fragments cemented together |
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arkose |
Sandstone containing 25% or more feldspar |
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name the 3 types of sandstone |
Arkose, quartz sandstone, and graywacke |
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graywacke |
sandstone containing both quartz and feldspar and is dark colored (abundant rock fragments) |
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Turbidity currents |
an underwater current flowing swiftly downslope owing to the weight of sediment it carries. |
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biochemical sedimentary rocks |
consist of fragments of particles produced by precipitation from once living organisms. Most of these rocks are limestones and cherts |
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coquina |
a cooars rock composed of poorly cemented shells and ssh fragments |
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chalk |
a soft porous rock made up almost entirely of the hard parts of microscopic marine organisms |
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travertine |
a type of inorganic limestone commonly seen in caves |
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oolitic limestone |
a rock composed of small spherical grains (ooids) |
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Ooids |
are small (2 mm in diameter), spheroidal, "coated" (layered) sedimentary grains, usually composed of calcium carbonate, but sometimes made up of iron- or phosphate-based minerals. |
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Dolostone |
Closely related to limestone, a rock composed of the calcium-magnesium carbonate mineral dolomite (doesn't react to acid [easy way to tell apart from limestone]) |
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Chert |
a hard, dark, very well compacted rock composed of silica and quartz with an fine-grained texture. It occurs in nodules or bedded cherts |
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Name the 4 different varietys of chert |
Petrified wood, Flint, Jasper, and Agate |
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Evaporites |
A sedimentary rock formed of material deposited from solution by evaporation of the water |
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name two examples of evaporites |
halite and gypsum |
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salt flats |
A white crust on the ground that is produced when water evaporates and leaves behind its dissolved materials. |
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how do evaporites form |
from crystals that precipitate during evaporation of water (water with dissolved material in it), such as in a drying lake bed. |
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Define Coal |
fossilized organic plant matter (organic) |
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PEAT |
Partially altered plant material |
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lignite |
soft brown coal |
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bituminous |
soft black coal |
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Anthracite |
Hard black coal or metamorphism of bituminous coal |
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How does PEAT form |
The partial decomposition of plant remains in a an oxygen poor swamp |
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Clastic texture |
A sedimentary rock texture consisting of broken fragments of preexisting rock. |
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compaction |
A type of lithification in which the weight of overlying material compresses more deeply buried sediment. It is most important in the fine-grained sedimentary rocks such as shale. |
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Environment of deposition |
A geographic setting where sediment accumulates. Each site is characterized by a particular combination of geologic processes and environmental conditions. |
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mud crack |
A feature in some sedimentary rocks that forms when wet mud dries out, shrinks, and cracks. |
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Fissility |
The property of splitting easily into thin layers along closely spaced, parallel surfaces, such as bedding planes in shale. |
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graded beds |
A sedimentary layer that most characterizes rapid deposition from water containing sediment of varying sizes. Also the layer gradually changes from coarse to fine within the one layer |
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nonclastic rocks |
A term for the texture of sedimentary rocks in which the minerals form a pattern of interlocking crystals. |
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Bedding Plane |
A nearly flat surface that separates two beds of sedimentary rock. Each bedding plane marks the end of one deposit and the beginning of another having different characteristics. |
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Facies |
A portion (layer) of a rock unit that possesses a distinctive set of characteristics that distinguishes it from other parts of the same unit. |
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Ripple marks |
Small waves of sand that develop on the surface of a sediment layer by the action of moving water or air. |
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cross-bedding |
A structure in which relatively thin layers are inclined at an angle to the main bedding. Cross-bedding is formed by currents of wind or water. |
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talus slope |
a debris pile up on the base of a mountain |
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Limestones originated as what |
coral reefs |
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evaporite rock rich in halite |
Rock salt |
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another name for strata is |
beds |
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What property of detrital sedimentary rocks can be indicative of the energy of sediment transport |
grain size (Grain size in a detrital sedimentary rock typically indicates the amount of energy associated with the transport of the sediment. High-energy transport can move much larger grains than low-energy transport.) |
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For a detrital sedimentary rock that contains mudcracks, you could be confident that the environment in which it formed was _____ |
alternately wet and dry |
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In your field area you find a quartz sandstone unit with cross-bedding in it that is on the order of 2 m high. In what environment would you deduce this rock formed? |
sand dunes (Quartz sandstone with 2-meter-scale cross-bedding would be typical of sand dunes) |
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In another field area you find a detrital sedimentary rock that contains particles larger than 264 mm that are rounded and surrounded by finer-grained particles. In what environment might you think these sediments were deposited |
glacial moraine |
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List 3 common cements |
Calcite, silica, and iron oxide |
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What is the primary basis for distinguishing different chemical sedimentary rocks? |
the mineral composition |
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What is the primary basis for distinguishing different detrital sedimentary rocks? |
Particle size |
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All detrital rocks have what kind of texture |
clastic texture |
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alluvial fan |
a fan-shaped mass of alluvium deposited as the flow of a river decreases in velocity. |
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eolian |
The work of wind and its resulting deposits (named after the greek god of wind) |
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playa lakes |
a lake in an arid or semiarid region that evaporates during the drier months to leave a playa |
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tidal flats |
coastal wetlands that form when mud is deposited by tides or rivers. They are found in sheltered areas such as bays, bayous, lagoons, and estuaries. |
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deltas |
An accumulation of sediment formed where a stream enters a lake or an ocean. |
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spit |
An elongate ridge of sand that projects from the land into the mouth of an adjacent bay. |
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barrier island |
A low, elongate ridge of sand that parallels the coast. |
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What are the three broad categories of sedimentary environments |
Marine, Transitional, and Continental environments |
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What consists of transitional sedimentary environments |
beaches, tidal flats, spits, bars, barrier islands, lagoons, and deltas |
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What consists of continental sedimentary environments |
Streams, floodplains, alluvial fan, eolian, dunes, playa lakes |
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What consists of Marine sedimentary environments |
They are divided at depth Deep marine: all the floors of the deep ocean and sediment that deposits at the floor Shallow Marine: Coral reefs and Skeletal debris of carbonate secreting organisms |
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bedding planes |
relatively flat surfaces along which rocks tend to separate or break (often separating the strata) |
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What can create bedding planes |
changes in the grain size or the composition of the sediment being deposited can create bedding planes |
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What is the single most characteristic feature of sedimentary rocks |
Layers called strata or beds |
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Formed when they were exposed to alternating wet and dry environments |
Mud cracks |
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Describe how chemical weathering and the formation of biochemical sediment remove carbon from the atmosphere and store it in the geosphere |
Atmospheric carbon combines with water to form a weak acid—carbonic acid—that falls to the surface in rain. The acid dissolves rocks—a process called chemical weathering—and releases calcium, magnesium, potassium, sodium ions. Then gets buried in the geosphere |
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Provide 3 examples by which carbon moves from the geosphere to the atmosphere |
Volcanic activity, burning and decay of biomass, and burning of fossil fuels |
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list the correct sequence in the formation of a sedimentary rock? |
Weathering, erosion, deposition, lithification |
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The term __________ is a collective term for all of the chemical, physical, and biological changes that take place after sediments are deposited, and during and after lithification. |
diagenesis |
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What are the chief constituents in most detrital sedimentary rocks? |
Quartz and clay minerals |
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what is the particle size for a Boulder |
Particle size > 256 mm |
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what is the particle size for Cobble |
64–256 mm particle size range |
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what is the particle size for Gravel |
Common name for sediments with particle size > 2 mm |
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what is the particle size for Sand |
1/16 to 2 mm particle size range |
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what is the particle size for Silt |
1/256 to 1/16 particle size range |
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what is the particle size for Clay |
Particle size < 1/256 mm |
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Coquina and chalk |
Biochemical limestone in which shell fragments are poorly cemented together |
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Coral reef |
Formed by relatively simple invertebrate animals that secrete a calcareous skeleton and grow together |
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Travertine |
Formed when groundwater droplets become exposed to the air in a cavern causing calcium carbonate concentrations to the point of precipitation |
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Inorganic |
Formed when chemical changes or high water temperatures increase calcium carbonate concentrations to the point of precipitation |
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Oolitic |
Composed of small spherical grains–commonly small shell fragments–coated with precipitated calcium carbonate |
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Turbidity currents are generally associated with what sedimentary feature? |
Graded beds |
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When a body of seawater evaporates, minerals precipitate in a certain order. What determines this order? |
Mineral solubility—less soluble minerals precipitate first; more soluble minerals precipitate later. |
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Coal that has the lowest volatile content and highest percentage of fixed carbon is called _________ |
Anthracite |
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A diagenetic change that involves the crystallization of minerals among individual sediment grains is called _______ |
cementation |
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_________ is an important diagenetic process in fine-grained sediments that results in the reduction of pore space and the expulsion of water. |
Compaction |
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_______ is the term that describes deposits that result from the work of wind. |
Eolian |
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Compaction and cementation are examples of this process. |
lithification |
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The most common minerals in detrital sedimentary rocks are __________. |
clay and quartz |
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What accumulation of sediment would most likely exhibit good cross-bedding? |
windblown sand (sand dune) |
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What sedimentary rock consists of materials that originated and were transported as solid particles? (sandstone or travertine limestone) |
sandstone |