Colorado River, AZ

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Colorado River, AZ Mary Beth Dougherty
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Sedona, AZ Ryan Conlon
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Red Rock Canyon, CA Hilary Neff
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SEDIMENT TRANSPORT AND TEXTURE
Most sediment is clastic. Individual grains are
called CLASTS. Produced by mechanical weathering
and erosion. During transport, clasts move from
high elevation to low, generally by influence
of gravity. Gravity is assisted by a transport
medium, water, wind, or ice. Clasts are
deposited when transporting medium loses energy.
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GRAIN-SIZE
Usually dependent upon energy and nature of
the transporting medium. Also related to the
mediums ability to carry them.
Hopewell Rocks Provincial Park New
Brunswick Courtesy of Warren Poulin
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SORTING
Process by which a transport medium selects
particles of different sizes, shapes and
densities. Wind is most selective. Produces well
sorted sediment. Glacial ice and flooding rivers
are unselective. Produce poorly sorted sediments.
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SORTING
Sorting provides evidence as to what medium
transported the sediment. Heaviest particles
are usually deposited first, close
to source. Lightest particles are carried
further away from source.
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SORTING
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GRAIN SHAPE
Clastic particles usually start out
angular. Abrasion through transport rounds
particles. Rivers are effective at rounding
particles. Greater abrasive activity, the more
rounding occurs. Softer minerals tend to round
faster than hard minerals.
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SEDIMENTARY STRUCTURES
Clastic sediments often contain
SEDIMENTARY STRUCTURES. SEDIMENTARY STRUCTURES
are physical indicators, preserved in the rocks
that provide information as to how the the
particles were deposited and what type of
environment it was.
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SEDIMENTARY STRUCTURES
BEDDING OR STRATIFICATION
Deposition of sediments is arranged into distinct
layers of different composition or
grain-size. These layers are called BEDS or
STRATA. One bed is a STRATUM, two are
STRATA. Layers are separated by BEDDING
PLANES. BEDDING PLANES usually indicate changes
in sediment type or environment.
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SEDIMENTARY STRUCTURES
Cape Liptrap, Australia Courtesy of Lorraine Beane
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SEDIMENTARY STRUCTURES
GRADED BEDDING
Results in rapid deposition of particles of
varying sizes in still water. Different sized
particles settle out at different
rates. Generally largest first at the base and
then get smaller. Produces GRADED BEDS.
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SEDIMENTARY STRUCTURES
GRADED BEDDING
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SEDIMENTARY STRUCTURES
GRADED BEDDING
Graded bedding is usually found on ocean floors
as SUBMARINE LANDSLIDES. Sediment is carried to
the continental shelf and deposited as an
unstable mass. When dislodged (earthquake) a
TURBIDITY CURRENT is produced.
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SEDIMENTARY STRUCTURES
TURBIDITY CURRENTS
Are a dense mixture of sea water and
sediment. Cascade down the continental
slope. Lose energy when they reach the
ocean floor and velocity decreases and sediment
is deposited rapidly. Also produced by lahars and
mudflows.
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SEDIMENTARY STRUCTURES
CROSS-BEDDING
Consists of sedimentary layers deposited at an
angle to the underlying set of beds.
Navajo Sandstone Utah
Coconino Sandstone Arizona