Sedimentary Rock
Chapter 10.3
Sedimentary Rock
1.Sedimentary Rocks
a.Sedimentary rocks are formed
when sediment deposits harden
after being compressed and
cemented together.
b.Two process that form sedimentary
rock are compaction and
cementation.
Sedimentary Rock
i. Compaction is when the weight of
overlying sediments causes pressure,
pushing the fragments together and
squeezing out air and water from the
fragments.
ii. Cementation is when water carries
dissolved minerals through the
sediments, the minerals are left between
the fragments of sediment and provide a
cement to hold the fragments together.
Compaction & Cementation
Sedimentary Rock Classification
a.Sedimentary rocks are classified
according to the kind and size of
sediments that form them.
i. Scientists have formed three classifications
of sedimentary rock: Clastic Sedimentary,
Chemical Sedimentary, & Organic
Sedimentary.
Clastic Sedimentary Rock
2. Clastic Sedimentary Rock
a.Clastic sedimentary rock forms when
rock fragments carried away from their
source by water, wind, or ice are left as
deposits and compacted or cemented
over time.
b.A conglomerate is a clastic sedimentary
rock composed of rounded gravel-sized
fragments, or pebbles that are
compacted or cemented together.
Conglomerates
Clastic Sedimentary Rock
c. Breccia is a clastic sedimentary rock
composed of angular, or rocks with sharp
corners, that are compacted or cemented
together.
d. Sandstone is made mainly of sand-sized
quartz grains that have been cemented
together, but have large enough pores
between the grains that water and crude oil
can flow.
e. Shale consists of flaky, clay-sized clay
particles cemented and compacted under
pressure.
Breccia, Shale, & Sandstone
Chemical Sedimentary Rock
3. Chemical Sedimentary Rock
a.Chemical sedimentary rock form from
minerals that were once dissolved in
water. These minerals can precipitate
(form a solid) out from water or settle
out of the water to form chemical
sedimentary rocks.
Chemical Sedimentary Rock
i. Chemical limestone forms when cool
currents lower the temperature of
warm ocean water, calcite
precipitates, settles, and solidifies on
the ocean floor.
Chemical Sedimentary Rock
b. Evaporates are dissolved minerals
that are left behind when water
evaporates and form rocks.
i. Gypsum and halite, or rock salt, are
two examples of rock formed from
rapid evaporation. A large evaporate
structure is the Bonneville Salt Flats
in Utah.
Bonneville Salt Flats
Organic Sedimentary Rock
4. Organic Sedimentary Rock
a. Organic sedimentary rocks are formed
from the remains of once living
creatures.
i. Coal and some limestone are examples of
organic sedimentary rock.
ii. An example of organic limestone is chalk,
which originally forms as mud on the floor
of an ocean.
iii.The white cliffs of Dover, England are
made up of chalk.
white cliffs of Dover, England
Sedimentary Rock Features
5. Sedimentary Rock Features
a.Sedimentary rocks have many
identifiable features which include
stratification, ripple marks, mud cracks,
fossils, and concretions.
i. Stratification is the layering of sedimentary
rocks that occurs when there is a change in
the kind of sediment being deposited.
Stratification
Sedimentary Rock Features
1.The strata, or layers, change for
many reasons such as changes in
river currents, sea level, and wind
deposits.
2.Graded bedding occurs when
various sizes and kinds of
materials are deposited within one
layer.
Graded Bedding
Sedimentary Rock Features
ii. Ripple marks are formed by the action of
wind or water on sand, and when the sand
becomes sand stone the ripples may be
preserved.
iii. Mud cracks result when muddy deposits
dry, shrink, and crack.
iv. Fossils are the remains or traces of ancient
plants and animals.
1. Fossils are usually preserved in sedimentary
rock, because of the way the sediments slowly
cover, compact, and cement the fossil.
Sedimentary Rock Features
v. Concretions form when minerals
precipitated from solutions build up
around an existing rock particle.
1.Concretions can be formed from
groundwater depositing dissolved quartz
or calcite inside cavities in sedimentary
rock leaving crystals behind. The crystal
cavities are called geodes.