wednesday february 15, 2012 (sedimentary rocks; ws – sedimentary rocks [part 1])
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Quiz 18 S5 2/3 2/3 2/3 2/17
WS – Igneous Rocks (Part 1) F 2/9 2/13
Quiz 19 S6 2/10 2/10 2/10 2/24
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Sedimentary Rocks Sedimentary rocks form from
sediment, which is the product of weathering.
Sedimentary rocks make up about 75% of all rock outcrops
on Earth’s continents.
These rocks are used to reconstruct much of Earth’s
history, as they provide clues to past environments and
sediment transport.
Sedimentary rocks often contain fossils.
Sedimentary Rocks Sedimentary rocks are
of tremendous economic importance
because they can contain fossil fuels:
coaloil
natural gas They are also sources
of iron and aluminum.
Sedimentary Rocks There are two classifications of sedimentary rocks based upon the source of the material in the rocks, detrital and
chemical.Materials accumulating as sediment have two principle
sources:Sediment may originate as solid particles from weathered
rocks, such as igneous rocks. These particles are called detritus, and the sedimentary rocks they form are called
detrital sedimentary rocks.In detrital rocks, the material is in solid particles, so
geologists use particle size to distinguish amoung detrital rocks.
Detrital Sedimentary Rocks
shale(very fine particles)
siltstone(fine particles)
sandstone(medium particles)
breccia(course, angular particles)
conglomerate(course, rounded
particles)
Chemical Sedimentary Rocks There are two classifications of sedimentary rocks based upon
the source of the material in the rocks.
Materials accumulating as sediment have two principle sources:
The second major source of sediment is solid material produced largely by chemical weathering. When these dissolved
substances are precipitated back as solids, they are called chemical sediments, and they form chemical sedimentary rocks.
Chemical sedimentary rocks are derived from material that was once in solution and precipitates to form sediment.
They are either directly precipitated as the result of physical processes, or deposited through life processes (biochemical
origin.)
Chemical Sedimentary Rocks fossiliferous limestone
coquina (shell fragments)
Chalk
Agate flint
jasper