Sediments and Sedimentary Rocks n Rock Cycle Definitions

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Sediments and Sedimentary Rocks n Rock Cycle

Sediments and Sedimentary Rocks n Rock Cycle

Definitions n Sediments: Solid fragmental material transported and n Lithification: The conversion of a

Definitions n Sediments: Solid fragmental material transported and n Lithification: The conversion of a newly deposited n Diagenesis: All the changes (chemical, physical, or deposited by wind, water, or ice, chemically precipitated from solution, secreted by organism, and that forms in layers in loose unconsolidated form. sediment into a solid rock involving processes such as cementation, compaction, and crystallization. biological) undergone by a sediment after its initial deposition, exclusive of weathering and metamorphism. Definitions from Dictionary of Geologic Terms

Diagenesis n n Compaction: occurs when the weight of the overlying sediments pushes down

Diagenesis n n Compaction: occurs when the weight of the overlying sediments pushes down on sediments; compaction is accompanied by the expulsion of water from these sediments Cementation: Occurs when solution “crystallizes” around sediment n Common elements in sedimentary rocks n n Silica (Si. O 2) Calcite (Ca. CO 3) Iron (Fe 2 O 3) Recrystallization (pressure solution): Occurs when sediments are exposed to very high pressures; as a result, the melting points of the constituent minerals are lowered and liquification occurs.

Environmental Clues in Sedimentary Rocks n Fossils Salt Water - Corals, Echinoderms n Fresh

Environmental Clues in Sedimentary Rocks n Fossils Salt Water - Corals, Echinoderms n Fresh Water - Insects, Amphibians n Terrestrial - Leaves, Land Animals n n Color And Chemistry Red Beds - Often Terrestrial n Black Shale - Oxygen Poor, Often Deep Water n Evaporites – Arid Climates n

Bedding or Stratification n n Almost Always Present in Sedimentary Rocks Originally Horizontal Tilting

Bedding or Stratification n n Almost Always Present in Sedimentary Rocks Originally Horizontal Tilting by Earth Forces Later Variations in Conditions of Deposition Size of Beds (Thickness) n Usually 1 -100 Cm n Can Range From Microscopic to 50 m

Sedimentary Rocks Clastic Rocks n Made of Fragmentary Material n Deposited by n Water

Sedimentary Rocks Clastic Rocks n Made of Fragmentary Material n Deposited by n Water (Most Common) n Wind n Glacial Action n Gravity Biochemical Sedimentary Rocks n Evaporation n Precipitation n Biogenic Sediments

Clastic Rocks Classified by: n Grain Size n Grain Composition n Texture

Clastic Rocks Classified by: n Grain Size n Grain Composition n Texture

Sediment Sizes and Clastic Rock Types Rock Type Sediment Grain Size Shale Clay less

Sediment Sizes and Clastic Rock Types Rock Type Sediment Grain Size Shale Clay less than 0. 001 mm Siltstone Silt . 001 -0. 1 mm Sandstone Sand . 01 -1 mm Conglomerate Gravel 1 mm + Sedimentary rocks made of silt- and claysized particles are collectively called mudrocks, and are the most abundant sedimentary rocks.

Range of Clast Size in Sediments Coarse Medium Fine Boulder > 256 mm Boulder

Range of Clast Size in Sediments Coarse Medium Fine Boulder > 256 mm Boulder >28 mm 64 mm < Cobble < 256 mm 26 mm < Cobble < 28 mm 2 mm < Pebble < 64 mm 21 mm < Pebble < 26 mm 1/16 mm < Sand < 2 mm 2 -4 mm < Sand < 21 mm 1/256 mm < Silt < 1/16 mm 2 -8 mm < Silt < 2 -4 mm Mud < 1/256 mm Mud < 2 -8 mm

Chemical Sediments Evaporites -Water Soluble n Halite n Gypsum n Calcite Precipitates Gypsum n

Chemical Sediments Evaporites -Water Soluble n Halite n Gypsum n Calcite Precipitates Gypsum n Limestone n Iron Formations Alteration After Deposition n Dolomite Biogenic Sediments n Limestone - Shells, Reefs, Etc. Organic Remains n Coal n Petroleum

Coal Seams, Utah

Coal Seams, Utah

Sedimentary Structures

Sedimentary Structures

Sedimentary Structures

Sedimentary Structures

Ea. ES 350 -3 23

Ea. ES 350 -3 23

Ea. ES 350 -3 24

Ea. ES 350 -3 24

Sedimentary Structures

Sedimentary Structures

Utah sandstone

Utah sandstone

Patch Reefs

Patch Reefs

Sediments and Sedimentary Rocks n Sedimentary Structures (cont’d) n Ripple marks - small ridges

Sediments and Sedimentary Rocks n Sedimentary Structures (cont’d) n Ripple marks - small ridges formed on the surface sediment layer by moving wind or water n Wave generated ripple marks are symmetric n Current generated ripple marks are asymmetric

Sediments and Sedimentary Rocks n Sedimentary Structures (cont’d) n Fossils - traces of plants

Sediments and Sedimentary Rocks n Sedimentary Structures (cont’d) n Fossils - traces of plants or animals preserved in sedimentary rock; includes replacement by calcite or silica, voids spaces or molds reflecting the former shape, filling in the molds to form casts, flat carbon imprints. footprints, trails, and burrows

Differential Weathering

Differential Weathering

Sedimentary Rocks

Sedimentary Rocks