Geoscience Reference
In-Depth Information
Figure 12.9 Marine sedimentary envi-
ronments and rock formation. This
generalized diagram illustrates how clastic
marine sediments ultimately become rock:
(1) sediments erode from continents;
(2) sediments are transported by streams
into the ocean; (3) sediments settle to the
ocean bottom; (4) the deposited sediments
are buried and slowly lithify to become rock;
and (5) the lithified sediments eventually
uplift as new rock layers.
1) Sediments erode from continent
2) Transport of sediment
by streams
3) Sediments settle
on sea floor
4) Burial and lithification
Different kinds of
sediment accumulate
in distinct layers
5) Eventual uplift
of rock layers
T A b L E 1 2 . 1
Some Common Types of Sedimentary RocksT
Class
Rock Type
Composition
Clastic : Formed
from rock or mineral
fragments
Conglomerate
Coarse-grained sandstone that contains rocks and pebbles of different sizes
Sandstone
Sand grains cemented by minerals
Siltstone
Silt particles cemented by minerals
Claystone
Clay particles cemented by minerals
Shale
Fine-grained particles that often contain fossils; most abundant sedimentary rocks;
forms layers along which rock can split
Limestone
Calcium carbonate, including that from animals and
microorganisms; forms rock layers
Chemical : Formed
from mineral precipi-
tates from seawater
or salty lakes
Dolomite
Magnesium carbonates, mostly formed by chemical replacement in
limestone
Evaporites
Minerals (gypsum, rock salt, calcite) left in deposits after
evaporation of water
Chert or flint
Extremely fine grains of silica (quartz) formed in layers or nodules
within limestone
Organic : Formed
from carbon-based
organic matter
Coal
Carbon-based materials lithified by heat and pressure
Oil (petroleum)
Liquid hydrocarbon trapped in sedimentary deposits; important
fossil fuel
Natural gas
Gaseous hydrocarbon trapped above oil in sedimentary deposits;
important fossil fuel
 
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