Chapter 6: Sedimentary Rocks Review

Origins of a Sedimentary Rock

- Erosion, transportation, deposition, and subsequent lithification of pre-existing rocks near, or at, surface of earth - Inorganic or organic chemical reactions - From lithified accumulations of organic debris

Conglomerate

- Grain sizes more than 2mm in diameter (size of pebbles)

Clastic (detrital) Sedimentary Rocks

- Origin is from erosion, transportation, deposition, and subsequent lithification of pre-existing rocks near, or at, surface of earth - Shale, sandstone, siltstone

Limestone

-Composed of the mineral calcite; can be chemical or biochemical

Coal

Accumulation of organic material composed primarily of carbon along with smaller variable quantities of sulfur, hydrogen, oxygen, and nitrogen

How are clastic sedimentary rocks subdivided

Based on size of grains (clast) glued (lithified) together to make rock

In order from shallowest depth of burial to deepest depth of burial and exposure to highest temperatures, the correct order for coal is: a. peat, bituminous, anthracite, lignite b. lignite, peat, bituminous, anthracite c. peat, lignite, bituminous, anthracite d. peat, lignite, anthracite, bituminous

C

How are limestones formed?

Can be formed by organic (involving life processes) or inorganic chemical reactions; when these organisms die, shells (with fecal fish pellets) sink to the bottom of ocean floor-eventually forming limestone

What are the three dominant sedimentary rock types found in the Earth's crust?

Clastic, Chemical, Biochemical

What are the major sedimentary depositional environments?

Coastal: Glacial, Alluvial Fan, Fluvial, Delta, Eolian Marine: Beach, Tidal Flat, Barrier Island, Reef, Shallow Marine, Deep Marine

Breccia

Conglomerate in which clasts are angular in shape

What general types of sedimentary deposits/rocks are found at each of the major sedimentary depositional environments?

Continental: sand and gravel, Coastal: coarser grained clasts, sandstone, shale, conglomerates Marine: finer grained, limestone, corals, muds, some sands, chert

Evaporite

Form by the precipitation of salts left behind by the evaporation of sea-water - Inorganic chemical reaction

How is coal formed?

Forms in anoxic (oxygen-poor) environments when there isn't enough oxygen present to decay carbon into carbon dioxide - swamps, marches, bottom of inland seas

Sandstone

Grain sizes between 2mm & 1/16th mm in diameter (size of sand particles)

Chert

Made up of microcrystalline quartz

Chemical Sedimentary Rocks

Rocks formed by chemical reactions occurring at/near earth's surface; subdivided based primarily on composition

Biochemical Sedimentary Rocks

The end product of chemical weathering and whose formation is aided by the action of organisms

Shale

Type of mudstone that is thinly layered and tends to spilt along those layers, grain sizes less than 1/256th mm in diameter (size of clay particles)

Siltstone

Very fine-grained between 1/16th & 1/256th mm in diameter (size of silt particles)