Sedimentary rock notes File

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First found May 22, 2018

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Entry task
 What
 How
are the agents of erosion?
are sedimentary rocks
formed?
Sand Sources
Beach





Far from source rock
Tumbled by water
Well rounded and
well sorted
In temperate climates: mostly quartz
In tropics: partly shells
Mountain stream

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Wide variety of sizes: poorly sorted
Not far from source rock
Not very rounded, many sharp edges
Limited weathering
Variety of minerals and color
Dunes

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Moved by wind in a dry environment
Frosted appearance from collision with
other grains
Well sorted
Some flat sides
Sedimentary Rock
Made from sediments


Sediments are
formed from the
breaking up of a
parent rock.
The size of the
sediment tells how
and where that rock
was created.
Sedimentary Rock Formation
Step 1: Derive a sediment via weathering or
erosion from a parent rock.
Step 2: Lithify the sediment
You have a sedimentary rock!
Two Stages of Lithification
Compaction
 grains
are compressed together
due to an overlying weight
Cementation
 minerals
invade pore spaces
between sediments and solidify
Three types of sedimentary
rocks

1. Clastic ~ from sediments
(sandstone)
2. Organic ~ from organisms
(fossil limestone)

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3. Chemical ~ from minerals left by
evaporation (halite)
Depositional Environment
Depositional Environment: A locality in
which sediment is deposited by a
depositional agent, including wind, water,
ice, and gravity
•
•
Deposit characteristics will be determined
by the environment of deposition.
Observations of these environments in the
rock record can used to identify ancient
conditions
Detrital Sedimentary Rocks

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Clastic sediments =
loose fragments of
pre-existing rocks or
minerals formed
weathering
Classified by grain
size, shape, sorting,
and composition
Chemical Sedimentary Rocks

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Minerals precipitate
out of solution
May appear
crystalline
Classified by
composition
Rock Salt
Biochemical Limestone
Review Questions


What are the three types of sedimentary
rocks?
What is the difference between
compacting and cementing?
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