Download Metamorphism and Metamorphic Rocks (Con`t.)

Colorado River, AZ
Mary Beth Dougherty
Sedona, AZ
Ryan Conlon
Red Rock Canyon, CA
Hilary Neff
SEDIMENTATION AND SEDIMENTARY ROCKS
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.
SEDIMENTATION AND SEDIMENTARY ROCKS
GRAIN-SIZE
Usually dependent upon energy and nature of the
transporting medium.
Also related to the medium’s ability to carry them.
Hopewell Rocks
Provincial Park
New Brunswick
Courtesy of
Warren Poulin
SEDIMENTATION AND SEDIMENTARY ROCKS
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.
SEDIMENTATION AND SEDIMENTARY ROCKS
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.
SEDIMENTATION AND SEDIMENTARY ROCKS
SORTING
SEDIMENTATION AND SEDIMENTARY ROCKS
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.
SEDIMENTATION AND SEDIMENTARY ROCKS
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.
SEDIMENTATION AND SEDIMENTARY ROCKS
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.
SEDIMENTATION AND SEDIMENTARY ROCKS
SEDIMENTARY STRUCTURES
Cape Liptrap, Australia
Courtesy of Lorraine Beane
SEDIMENTATION AND SEDIMENTARY ROCKS
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.
SEDIMENTATION AND SEDIMENTARY ROCKS
SEDIMENTARY STRUCTURES
GRADED BEDDING
SEDIMENTATION AND SEDIMENTARY ROCKS
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.
SEDIMENTATION AND SEDIMENTARY ROCKS
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.
SEDIMENTATION AND SEDIMENTARY ROCKS
SEDIMENTARY STRUCTURES
CROSS-BEDDING
Consists of sedimentary layers deposited at an angle to
the underlying set of beds.
Navajo Sandstone
Utah
Coconino Sandstone
Arizona