Sedimentary Rocks
deposition
Origin of Sedimentary Rocks
• Most common rocks
on the earth are
igneous.
• 2nd common
sedimentary
Sedimentary Rock
• Rocks formed from
sediments
– 1. Sediments cemented
together (detrital)
– 2. Fall out of solution
as a precipitate
(chemical)
– 3. plant material
pressed together
(organic)
Sediments are:
•
•
•
•
Pieces of minerals
Pieces of rock
Pieces of organic matter
Minerals dissolved in water – in solution
Detrital Sedimentary Rocks
• Also known as clastic sedimentary rocks
• From Greek klastos, broken;
• Detrital or clastic sedimentary rocks are
rocks made from broken pieces of other
rock that have been cemented together to
form a new rock
Sizes of sediment designation
kind of rock formed
(copy chart in notebook)
How sedimentary rocks are
formed
Strata –
layers of rock
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•
•
•
Millions of years have gone by and
there are many layers of deposited
sediment now.
Some of the sediment granules
have been cemented together by
minerals that were dissolved in the
water.
They have turned into layers of
rock.
Compaction
• Pressure from the upper layers of sediments
squeeze out water.
• Reduce the spaces between the particles
• They become packed together more tightly.
• New rock formed
Cementation
• Water soaks through soil
• Dissolves minerals such as
•
Calcite, hematite, limonite are •
Kinds of cement.
•
•
calcite, hematite and
limonite (kinds of cement)
Solution moves through
open spaces between
sediment and fills spaces
Minerals fall out of
solution (precipitate –
solid left from solution)
“cement” the sediment
together.
New rock formed
Classification of Sedimentary
Rocks
• `1. Detrital Sedimentary
Rocks – Clastic
• Lt. Detritus – to wear
away
• Made from broken
fragments of other rocks.
Compacted and cemented
together.
• Clastic Gr.klastos –
broken
conglomerate
• Rounded gravel sized
sediments cemented
together
Breccia
• Angular sediments
that are cemented.
• Found at talus slopes
Talus slope
Sandstone
• Sand sized sediment
cemented together
Shale
• Clay sized sediment
held together by
compaction.
Coquina
• Beach pebbles, shells
and animal bodies
cemented together
• Found along shores
Chemical Sedimentary Rocks
• 2. chemical
sedimentary rocks
• Minerals precipitated
out of a solution.
– (falls out of solution
when water
evaporates)
• Calcite in caves
• Halite – salt mines
ancient salt seas
Limestone
• Calcium carbonate
(CaCO3) carried in
ocean water dissolved
from animal shells.
• Deposited on sea or
ocean floors
• Precipitates out of
solution.
• Precipitate – any
solid that comes out of
solution
Rock salt
• Found in evaporated
salt water lakes or
seas.
• Precipitates out when
water is evaporated
Fossiliferous limestone
• Limestone with
fossils.
• Found in old salt water
lakes, bays, seas
Chalk
• Smashed microscopic
shell bodies of sea
animals.
• compacted
Coal
• Decayed organic
matter that had been
compacted to form a
rock.