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)