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Sediment and
Sedimentary Rocks
Big rocks into pebbles,
Pebbles into sand.
I really hold a million, million
Rocks here in my hand.
Florence Parry Heide
Created from the
“scraps of old rocks
Sedimentary Rocks:
Terms
• Regolith: rock and mineral
fragments produced by
weathering
• Sediment: regolith that has
been transported by wind,
water or ice
• Soil: portion of regolith that
supports plant life
Sedimentary Rocks: Characteristics
• Loose, solid particles
– sediments
• Unconsolidated
• Classified based on size of individual
fragments
Four Fundamental Components of
Sedimentary Rocks
1. Grains/Clasts:
sand, gravel or
fossils
2. Matrix: fine grained
clay-sized sediment
3. Cement: chemically
precipitated mineral
material
4. Porosity: space
with no mineral
matter
Cement
Clasts, matrix and iron oxide cement
(reddish brown colour)
Types of Sedimentary Rocks
• 2 main types of sedimentary
rocks (based on composition) :
– Clastic:
• Inorganic sediments
• rocks made up of broken and
worn particles of rocks and
Breccia
minerals
– Non-Clastic:
• Organic sediments
• sediment precipitates from
solution in water originating
from chemical and organic
processes Chert from Will County, Illinois
Characteristics of Clastic Sediment
• Clastic sediment is divided into four main size
classes (based on texture as well):
– Gravel
Bedrock outcrop
– Sand
– Silt
River gravel
Beach sand
– Clay
Marine clay
Clayey silt
Properties of Clastic Sedimentary Rock
• Processes:
– Lithification / Diagenisis
• Compaction:
– Pressure from recent, overlying sediment
• Cementation
• Hardening
– Stratification
• Layering
How Clastic Sedimentary Rock Form
• Clastic sedimentary rocks originate because of:
– Weathering
– Erosion/Transportation
– Deposition/Burial
– Lithification / Diagenesis
Weathering
• Destroying rock
The rocks that make high ridges are
much more resistant to weathering
than the surrounding rocks
Erosion and Transport
• Sediments on the
move
This stream carries sediment that has weathered from nearby
mountains at Polychrome Pass, Alaska
Deposition/Burial
• Sediments settling down
These pebbles were deposited in a stream that once flowed over this
area in Indiana, USA thousands of years ago. Now they are part of a
clastic sedimentary rock called conglomerate