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Rocks
B. Sedimentary Rocks
What are sedimentary rocks formed
from?
Where do sedimentary rocks form?
How do you turn sediment into rock?
Sedimentary rocks are formed from sediments
What are sediments?
When the process called weathering attacks rocks near or at
the surface, the rocks are broken into fragments.
This fragmentary material is called sediment.
Sediments come in different shapes and sizes:
•Boulders
Silt
•Pebbles
mud
•Gravel
clay
•Sand
Depositional Environments for Sediments or
Where sediments are deposited after they are transported
Where sediments accumulate:
a- alluvial fans
h-deltas
b- Glaciers
i- tidal flats
c- rivers
j- continental shelf
d- dunes
k-continental slope
e- lakes
L-abyss
f- lagoons
m-reefs
g- estuaries
There are three major deposition settings: continental, marginal
marine, and marine
How do sediments become Sedimentary Rocks?
•form by the lithification of unconsolidated sediments.
•lithification is a process of compaction and cementation
What sediments produce what rocks?
Sediment
Rock
•
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•
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•Sandstone
•Mudstone
•Siltstone
•Shale
•Conglomerate
•Breccia
Sand
Mud
Silt
Clay
Rounded gravel
Angular gravel
These are called Detrital sedimentary rocks: because they are
made of detritus or solid particles of other rocks
Chemical Sedimentary Rocks
Sometimes material is dissolved in water as the rocks are
weathered.
This material is transported to lakes and oceans where it can reform
into minerals and rocks by:
• inorganic chemical reactions
•or the activities of organisms (organic).
these are often called biochemical sedimentary rocks
Chemical sedimentary Rocks (inorganic)
Sometimes when water evaporates, the dissolved chemical
precipitate out minerals.
e.g.
Rock salt ( NaCl )
Rock Gypsum ( CaSO4.2H2O )
Chert (SiO2) is a hard rock is is made of microscopic
crystals of quartz. (can also be bio-chemical)
It comes in several colored varieties
flint (Black)
jasper (brown/red)
novaculite (white)
agate (banded)
Rock salt
Rock
gypsum
Chert
Chemical Sedimentary Rocks
Coal
Bio-Chemical sedimentary Rocks (organic)
These are formed by living organisms
Chert can be made from the accumulations of silica shells
Coal is formed from woody land plant material
Limestone (fossilifereous) ( CaCO3) is formed from the
accumulation of seashells
Limestone (chalk) ( CaCO3) is formed from the
accumulation of microscopic shells
Bio-chemical Sedimentary Rocks
Limestone (fossiliferous)
Limestone (chalk)
Some common Sedimentary Rocks you will have to learn.
Sandstone*
Limestone (chalk)
Conglomerate*
Siltstone
Breccia*
Shale*
Mudstone*
Chert*
Coal*
Rock Salt
Limestone (fossiliferous)*
* = must know for test
Sedimentary Structures: Crossbedding
= desert sand dune
Sedimentary Structures:Ripple marks = streams, lake shores
Sedimentary Structures: Fossils = environment, age, comparison