Sed Rocks GEO 1

  1. Sedimentary Rocks "Settling"
    • A.Sedimentary rocks form fromt he products of chemical and mechanical weathering
    • B.Detrital Sediment
    • 1.Particles derived primarily fromthe products of mechanical weathering
    • C. Chemical Sediment
    • 1. Ions and compounds in solution that derived from chemical weathering of rocks.
    • 2. These ions and compounds eventually crystallize from solution to become solid particles
    • D. Erosion
    • 1. Removal and transportation of sediment by running water, wind, glaciers, or currents
    • E. When the transporting agent loses energy, sediment is deposited
    • F. Importance of sedimentary rocks
    • 1. Oil and gas are trapped in sedimentary rocks
    • 2. Two types of coal are classifed as sedimentary rocks
    • 3.Sedimentary rocks preserve clues about ancient enviroments of deposition
    • 4. Fossils are commonly preserved in sedimentary rocks
  2. Lithification
    • A. The process of turning sediment into sedimentary rock
    • B. Lithification may include
    • 1. Compaction
    • a. Weight of overlying sediment causes grains to compact more closely together
    • 2. Cementation
    • a. Minerals precipitate from solution in the pores spaces(openings) between grains
    • b. Types of cements
    • i. Quartz
    • ii. Calcite
    • iii. Iron oxide
  3. Detrital Sedimentary Rocks
    • A. Form from the lithification of detital sediments
    • B. Classified primarily by grain size
    • C. Sorting
    • 1. Well sorted-
    • a. Grains that compose the rock are all about the same size
    • b. Running water and wind
    • 2. Poorly-sorted
    • a. Grains that compose the rock are different sizes
    • b. Glaciers
    • D. Degree of rounding
    • 1. Angular grains
    • a. Indicate a short distance of trasnport
    • 2. Well-rounded particles
    • a. Indicate a long distance of transport
    • E.Common minerals that compose detrital sedimentary rocks
    • 1. Quartz
    • 2. Feldspar
    • 3. Clay minearls (derived from chemical weathering of feldspar minerals)
    • F.Classification of Detrital Sedimentary
    • 1. Conglomerate
    • a. Composed of rounded, gravel sized grains
    • b. May be found where energy is high -river beds
    • 2. Breccia-composed of angular , gravel sized grains
    • 3. Quartz Sandstone
    • a. Composed of> 90 % quartz grains
    • b. May form from beach or sand dune deposits
    • 4. Arkose
    • a. Sandstone composed of > 25% feldspar grains
    • b.May form near granites that are weathering
    • 5. Shale
    • a. Composed of grains that are too small to see without magnification
    • b. Fissile-splits along flat planes that reflect arrangement of platy clay-sized minerals
  4. Chemical Sedimentary Rocks
    • A. Rocks formed as a result of lithification of chemical sediments
    • B. Classified according to composition and grain size
    • C. Classification of Chemical Sedimentary Rocks
    • 1. Limestones- composed of calcium carbonate
    • a. Travertine-limestone that is deposited in caves
    • b. Coquina- limestone composed of visible shells and shell fragments that have been cemented together
    • c. Chalk- limestone composed of microscopic calcareous (CaCO3) hard parts of marine plants and animals.
    • 2. Chert-composed of the microscopic siliceous (SiO2) hard parts of marine and plants
    • 3. Evaporites
    • a. Composed of minearls that precipitate when bodies of water evaporate
    • b. Rock salt-composed of halite
    • c. Rock gypsum- composed of gypsum
    • 4.Coal
    • a. composed of altered plant material
    • b. Coal forms in swampy enviroments where there is little / no oxygen in the water.
    • c. Plant material only partially decays and goe through stages of alteration
    • d. Peat
    • i. partially altered plant material
    • ii. Essentially the sediment stage of coal
    • e. Lignite Coal
    • i. When peat undergoes burial and compaction, it may alter to lignite coal
    • ii. Soft brown coal
    • f. Bituminous Coal
    • i. If lignite coal undergoes further burial and compaction it may form bituminous coal
    • ii. Soft black coal
    • g. Anthracite Coal
    • i. If bituminous coal undergoes metamorphism, it will alter to antracite coal
    • ii. Hard black coal
  5. Sedimentary Structures
    • A. Feature preserved in sedimentary rocks
    • B. Sedimentary rocks are deposited in layers or beds
    • C. Beds are separated by bedding planes
    • 1. Flat planes that indicate the end of one episode of deposition and the beginning of another period of deposition
    • D. Ripple Marks
    • 1. Ridges on the surface of sedimentary rocks
    • 2. Wave -formed ripples
    • a. Formed by back and forth movement of waves
    • b. Ripples are symmetrical in shape
    • 3. Current ripples
    • a. Formed by currents in rivers or oceans or by wind moving in one direction
    • b. Ripples are asymmetrical in shape
    • E. Cross-beds
    • 1. Inclined layers of sand within a larger bed of rock
    • 2. Sand dunes often exhibit cross-beds formed by changing wind directions
    • F. Mud cracks- Form when clay- rich sediment dries and shrinks
Card Set
Sed Rocks GEO 1
Sed Rocks GEO 1