Sedimentary Geology

Chapter 6 section 1 Formation of
Sedimentary Rocks

Weathering and Erosion

• Sedimentary rock would not exist without …
• Weathering: the break-up of rock physically or chemically
• Erosion: the transport of weathered material by running

water, wind, gravity, and glaciers

Multiple Choice

Which process is the first stage of creating a sedimentary rock?

• depostion

• erosion

• weathering

• lithification

Multiple Choice

Another term used for transportation of sediment would be

• deposition

• erosion

• weathering

• transpiration

Deposition
• The opposite of

erosion…

• Sediment comes to rest

in many different
environments
depending on its size

• The smallest of

sediment is generally
found in lake bottoms
and seas

• MOVING WATER AND

WIND SORT SEDIMENT

Multiple Choice

The smallest sediments are deposited

• close to shore in a lake or sea

• far from shore in a lake or sea

• on a river bend

• by a glacier

• Lithification = the formation of

sedimentary rock from fragments of
material (sediment)

• What causes lithification?
• Compaction – the squeezing of

sediment by overlying sediments

• Cementation – sediment can be

held together by different natural
cements, like…calcite, iron oxide
and silica

Drag and Drop

Following the deposition of sediments, ​

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is the process where the sediment become layered and then ​

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by overlying new layers and eventually ​

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by various minerals in the soil and groundwater to create ​

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rocks.

Drag these tiles and drop them in the correct blank above

lithification

compacted

cemented together

sedimentary

Sedimentary Rock Features and Structures

• Stratification

• Crossbedding

• Ripple marks

• Mud cracks

• Fossils

• Concretions

• Graded Bedding

Stratification

• Visible parallel layers in

sedimentary beds of varying color

• The layering is known as Bedding
• There are different types of

bedding…

Graded Bedding

• This is the type of bedding

in which particle size
becomes progressively
larger toward the bottom
layers

Multiple Choice

In a graded bed

• sediments range from smaller at the top to larger at the bottom

• sediments range from larger at the top to smaller at the bottom

• sediments are randomly arranged

Multiple Choice

Which would be FALSE based on the stream channel deposition diagram

• Large grained sediments are deposited on the outside bends of river channels

• Small grained sediments are deposited on the inside bends of river channels

• Old river channels created graded beds

• Deposition of grain size is not effected by bends in river channels.

Sorting and Rounding

• As sediment is

transported collisions
cause material to chip
off angular edges

• As a result mature

sediments will have
particles that are more
rounded and softer
minerals are gone

Multiple Choice

Which of the following minerals tends to round instead of dissolve with distance from its parent rock

• feldspar

• mica

• quartz

• gypsum

Crossbedding

• Cross-beds show

direction of past
stream flow or
prevailing wind
direction.

• Size of cross-beds helps

to determine stream
volume and velocity

Ripple Marks

• Fossilized stream bed or beach

deposits.

• Enables scientists to interpret

past environments

• Symmetrical?
• Asymmetrical?

Mud Cracks
• Created when clayey materials that are wet

begin to dry and contract (bottom of muddy pond)

• Can become fossilized

Multiple Choice

Which of the following sedimentary structures is essentially a fossilized beach?

• ripple-mark sandstone

• mudcracks

• crossbedding

• sc

VARVES

Fossils

• Caused by the replacement of

bone material, and sometimes
skin with minerals
(permineralization)

• Insects, birds, fish and other

softer bodied creatures can leave
imprints in mudstone

Nodules

• Lump of material within a body

of rock with different
composition than surrounding
rock

• Locally “sand balls” are iron-

stone concretions

• Geode = special concretion

​Ammonite fossils are common fossil in the sedimentary rocks of Eastern MT.

​Oil and Gas come from sedimentary structures.

Open Ended

Give at least two examples of fossils from sedimentary rocks found locally.