Geology Chp7

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Chp7!

Sedimentary rocks

products of mechanical and chemical weathering

Sedimentary rocks are important for economic considerations because

they may contain
Coal
Petroleum and natural gas
Sources of Fe, Al, and Mn

Detrital sedimentary rocks

transported sediment as solid particles

Chemical sedimentary rocks

sediment that was once in solution

Organic sedimentary rocks

-Coal

detrital rocks include

Clay minerals
Quartz
Feldspars
Micas

Shale

Mud-sized particles in thin layers that are called laminae
Parallel alignment of grains
Barrier to flow of water
Low energy environments of deposition
Most common sedimentary rock--can be shales, mudstones, siltstones

Sandstone

Rock composed mainly of sand-sized particles
Forms in a variety of environments
Described by
Sorting
Particle shape
Composition
Predominant mineral = quartz

Conglomerate consists largely of

rounded gravels

Breccia is composed mainly of large

angular particles

Inorganic processes

evaporation, chemical activity

Organic processes

-life processes of water-dwelling organisms

Limestone

Most abundant chemical rock
Composed chiefly of the mineral calcite
Marine biochemical limestones form as coral reefs, coquina (broken shells), and chalk (microscopic organisms)
Inorganic limestones include travertine and oolitic limestone

Dolostone

Typically formed secondarily from limestone

Chert

Microcrystalline quartz
Varieties include flint, agate, and jasper

Evaporites

Evaporation triggers deposition of chemical precipitates

Coal

Different from other rocks because it is composed of organic material
1. Plant material
2. Peat
3. Lignite
4. Bituminous coal

Diagenesis

Chemical, physical, and biological changes that take place after sediments are deposited and lithified.
Occurs within the upper few kilometers of Earth's crust

Two major textures are used in the classification of sedimentary rocks

Clastic,Nonclastic

Clastic

Discrete fragments and particles
All detrital rocks have a clastic texture

Nonclastic

Pattern of interlocking crystals
May resemble an igneous rock

Types of Sedimentary Environments

Continental
Marine
Transitional

Marine Sedimentary Environments

Shallow ,Deep

Types of sedimentary structures

Graded beds
Ripple marks
Mud cracks
Fossils

A sedimentary facies is the sedimentary rock's ________.

environment of deposition

Which of the following sedimentary rocks would you expect to have originally been deposited by fast-moving streams?

conglomerate

Oolitic limestone is most likely to form in what type of depositional environment?

shallow, clear marine waters with vigorous current activity

If shale is such a common rock in the sedimentary rock world, why isn't it as prominently exposed at the surface as sandstone?

Shale crumbles easily, causing increased mechanical weathering, whereas sandstone resists weathering more effectively.

Which of the following is a feasible explanation as to why quartz sandstone is an excellent use of "uniformitarianism"

Layers of sand-size quartz-rich sediment found today at the beach are virtually identical to layers in a 10-million-year-old sandstone, thus suggesting the location of the sandstone was the location of a beach 10 million years ago.

Many limestones are ________.

biogenic

Which are sedimentary rocks?

Conglomerate and mudstone

How do you classify sedimentary rocks?

Texture and grain size

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