2.3 Sedimentary Processes and Structures

  • Created by: 11pha
  • Created on: 02-03-17 09:31
the in situ chemical alteration and mechanical and biological breakdown of rocks by exposure to the atmosphere, water and organic matter
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the reation between carbonic acid and minerals
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the reation between minerals and water causing the minerals to decompose
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occurs when sheets of rock split off due to differential expansion and contraction of minerals during diurnal heating and cooling
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Frost shattering
caused by the expansion of freezing water in fractures which forces rocks apart
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Pressure release
the expansion and fracturing of rock due to removal of overlying rocks
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Root action
causes the mechanical and chemical weathering of rocks by the wedging action of plant roots
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by invertebrate and vertebrate animals mixes and brings to the surface rock and soil particles. This facilitates weathering at greater depth, by providing access for atmospheric gases and water
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the wearing away of the land surface and removal of sediment by means of transport
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wearing away of the Earth's surface by the wind, water or ice dragging sediment over or hurling it at a surface
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wearing down of sedimentary grains due to collisions with other grains during transport
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transport of ions dissolved in water
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the transport of material in water or air, without it touching the Earth's surface
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the transport of material by bouncing
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the transport of material by rolling and sliding along a surface
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defines the relationship of the outline of a grain to a circle. A grain with few sharp corners has a high degree of roundness
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the relationship of a grain to a sphere, rod, disc or blade
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Phi Scale
expresses the grain size of a logarithmic scale. Phi values increase arithmetically as the grain size decreases geometrically
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Grain Size
the average diameter of the grains of sediment being studied
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the degree to which particles are the same size
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a rock fragment or grain resulting from the breakdown of larger rocks
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fragment of rock from a volcanic explosion
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a biologically formed sedimentary rock composed of fragmented organic material
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Mechanically Formed
the erosion, transport and deposition of clasts are by mechanical processes
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Chemically Formed
the weathering transport and deposition of these rocks is by chemical processes
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Biologically formed
organisms such as sea creatures or trees extract ions that are in solution in sea water or groundwater and turn them into organic tissue, such as shells or wood
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the remains of an organism that lived more than 10000 years ago including skeletons, tracks, impressions, trails, borings and clasts
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sedimentary rocks are those in which the grain size of clasts is greater than 2 mm
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sedimentary rocks are those in which the grain size of clasts is 0.0625 to 2 mm
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sedimentary rocks are those in which the grain size of casts is less than 0.0625 mm
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refers to the interrelationship of grains in a rock. Includes grain size, sorting, roundness, shape and packing of sedimentary grains
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Clay Minerals
a group of sub-microscopic platy aluminium silicates related to mica
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the ability of a materia to permanently change shape without fracturing
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refers to the tendency of a rock to split into thin layers
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the background material, consisting of small particles in which larger fragments occur
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a microcrystalline calcite, a depositional matrix of lime mud
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a coarse grained (>0.01 mm) crystalline calcite cement, formed after deposition
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a material that binds sedimentary grains together
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Paleocurrent indicator
a sedimentary structure that allows the direction of an ancient current to be deduced
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Palaeo-environment indicator
a sedimentary structure formed in specific environmental conditions in the ancient part
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Way Up Indicator
allows geologists to work out whether rocks are in their original orientation or whether they have been inverted by folding
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all changes that take place in sediments at low temperature and pressure, at or near the Earth's surface
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the process of changing unconsolidated sediment into rock
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the colume occupied by spaces in between sedimentary grains. A reduction in porosity squeezes fluids from pore spaces
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partly decomposed plant remains with high water content
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carbon-rich rock formed from fossil plant remains
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the ability of a rock to allow fluids such as water to pass through it
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a poorly sorted sediment ranging from boulders to clay size, deposited from ice and not reworked by water
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clasts of a different rock type from that found locally and therefore transported from another area
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Flucio-glacial deposits
sediments produced by meltwater streams flowing from a glacier
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fine grained banded deposits from glacial lakes containing coarses pale material deposited in summer and finer dark material deposited in winter
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Upward fining
describes a series of layers in whhich average grain size decreases upwards as energy decreases
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Channel Lag
coarse grained sediment deposit left in a channel after finer grained particles have been transported away
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Point Bar
a deposit of sand or coarser grained sediments on the inside of a meander bend
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Flood Plain
flat land adjacent to a river over which it spreads when in flood
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Flash Flood
a brief but very high energy flow of water over a surface or down a river channel, usually caused by heavy rain
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a river channel in a hot desert region in which flow may occur very occasionally
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Playa Lakes
a temporary lake formed by storm run-off in deserts having inland drainage
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sedimentart rocks resulting from the exaporation of saline water
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sedimentart rocks resulting from the exaporation of saline water
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the lowest horizontal layers of a delta, commonly consisting of shales
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represents layers repeated due to cyclic sedimentation
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the distance of sediment by the activities of organisms
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Seat Earth
a sandy or clay-rich fossil soil found beneath a coal seam. It represents the soil in which coal forming plants grew and frequently contains carbonised traces of plant roots
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a stream channel that takes water away from the main stream channel
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the uppermost horizontal layers of a delta commonly consisting of channel sandstones, coal and seat earth
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Spring Tides
the tides with the greates range, and occur about every two weeks
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Tidal range
the vertical difference in height between extreme high and extreme low water
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Littoral Zone
the area between extreme low and extreme high water of the spring tide
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Rip Current
a narrow fast current flowing seaward, away from the coastline
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occurs where the sea spreads over the land
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a green-coloured mineral formed on continental shelves
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occurs where the sea retreats from the land
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fossil large enough to be visible
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a fossil that is less than 1 mm and can only be seen with a lens or microscope
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describes fragments derived from the mechanical weathering of rocks
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mass of coarse rock fragments accumulating at the foot of a slope
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a solution that contains more dissolved substance than does a saturated solution
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a concentrated solution of salts formed by partial evaporation of sea water
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Barred Basin
a bay partly isolated from the open ocean by a bar
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Turbidity Current
a high velocity current that flows down a gentle gradients because the sediment dispersed within it makes it denser than sea water
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a upward fining deposit of greywacke deposited from a turbidity current
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Bourma Sequence
an idealised sequence of sediments and sedimentary structures seen in a trubidite deposit
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minute organisms living in the surface layers of the ocean, transported by currents
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a planktonic plant that secretes siliceous material
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planktonic animals with a siliceous test
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Calcareous ooze
pelagic clay containing >30% biogenic skeletal material made of calcite
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Siliceous ooze
pelagiv clay containing >30% biogenic skeletal material made of silica
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Carbonate compensation depth
the depth in the oceans at which the rate of solution of solid CaCO3 equals the rate of supply
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Card 2




the reation between carbonic acid and minerals

Card 3




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Card 4




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Card 5


Frost shattering


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