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![3)Cementation - minerals
precipitated from sediment
pore fluids bind particles
common cements - calcite
(CaCO3) and quartz (SiO2),
dolomite [(CaMg)CO3], iron
oxides (Fe2O3) and hydroxides
[FeO(OH)]
Lithification](https://image.slidesharecdn.com/sedimentary-241122183815-8a7ef4de/75/Sedimentary-rock-s-geology-ppt-science-ppt-51-2048.jpg)
Sedimentary rock’s geology ppt science ppt
- 1.
- 33. J only 5%of Earth’s crust J cover about 75% of surface J raw material (sediment) of sedimentary rocks - weathering or erosion of pre-existing rock J basic sources: detrital non-detrital Sediments and Sedimentary Rocks
- 34. detrital - mineral/rockfragments detritus or clasts - produced by mechanical weathering or erosion detrital sedimentary rocks sandstone shale mudstone Sediments and Sedimentary Rocks
- 35. non-detrital - precipitatefrom solution (chemical weathering) inorganic or biochemical processes chemical sedimentary rocks limestone halite gypsum Sediments and Sedimentary Rocks
- 36. ... what’s involved inthe physical transport of sediment?
- 37. place of weatheringto place of deposition: angular particles become rounded sorted by size and composition agents of sediment transport water (primary mechanism), gravity, wind, and ice sediment deposition processes (sedimentation): loss of velocity, evaporation and/ or chemical interactions Transport and Deposition
- 38. carried in suspensionby: ice: any size particle water: small gravel and smaller size particles wind: sand and smaller sizes abrasion and rounding removes corners sorting separates like-sized particles Detrital Transport
- 39. deposition = decreasein energy or velocity settling rate depends on: particle size density Detrital Deposition
- 40.
- 41. results from saturation dueto: increase of available ions through oversupply or evaporation change in temperature or other chemical conditions Chemical Deposition
- 42. ... in what typesof environments is sediment deposited?
- 43. Deep Marine deep ocean- submarine fans (turbidites) Depositional Environments
- 44. Marine - shallowocean (continental shelf) lagoon reef barrier island Depositional Environments
- 45. Transitional Beach Delta DepositionalEnvironments
- 46. Depositional Environments Continental (terrestrial) fluvial(streams) eolian (deserts) lacustrine (lakes) glacial
- 47. ... how is sediment convertedinto solid rock?
- 48. conversion of sediment intorock results from: 1. Compaction 2. Desiccation 3. Cementation 4. Crystallization Lithification
- 49. 1) Compaction -sediment grains packed together through burial reduction in volume by up to 40% results from pressure or weight of overlying sediments Lithification
- 50. 2) Desiccation -loss of water from sediment pore spaces results from compaction and evaporation in air Lithification
- 51. 3)Cementation - minerals precipitatedfrom sediment pore fluids bind particles common cements - calcite (CaCO3) and quartz (SiO2), dolomite [(CaMg)CO3], iron oxides (Fe2O3) and hydroxides [FeO(OH)] Lithification
- 52. 4)Crystallization - formationof interlocking crystals in chemical sediments Lithification
- 53.
- 54. both detrital and chemicalsedimentary rocks can show fragmented texture separated by clast size Wentworth Scale of particle size commonly used: gravel > 2 mm sand 1/16 to 2 mm silt 1/256 to 1/16 mm clay < 1/256 mm Grain Sizes
- 55. degree to whichclast or particle sizes similar Sorting
- 56. occurs during transportwith particles separated by: a) grain size - largest particles settle first b) composition - densest minerals settle first Sorting
- 57. poorly-sorted - mixof particle sizes Sorting well-sorted - if primarily one particle size
- 58. angularity or roundnessdepends on how far rock transported: a) Roundness - degree of edge and corner removal b) Sphericity - degree to which fragment approaches spheroid shape Clast Shape
- 59. Non-clastic Textures subdivided accordingto crystal size : fine-grained (< 1 mm) medium-grained (1-5 mm) coarse-grained (> 5 mm) interlocking crystals shown only by chemical sedimentary rocks
- 60. ... what are thedifferent types of sedimentary rocks?
- 61.
- 62. conglomerate - gravel-sized roundedparticles (>2 mm) surrounded by fine-grained material: deposition in high-energy environment characteristic of streams and beaches Clastic Sedimentary Rocks
- 63.
- 64. material not transportedgreat distances sedimentary breccia - particles > 64 mm and angular: Clastic Sedimentary Rocks
- 65.
- 66. sandstones - sand-sizedparticles (0.06-2 mm): mainly quartz, some feldspar and rock fragments: 1) Quartz Sandstone - almost pure quartz 2) Arkose - quartz and more than 25% feldspar 3) Graywacke - “Dirty” sandstone containing quartz, feldspar, rock, and clay both arkose and graywacke lack of transport Clastic Sedimentary Rocks
- 67. Mudrocks - low-energyenvironment: 1) Siltstones silt-sized quartz and feldspar particles (≤ 0.06 mm) 2) Mudstones silt- and clay-sized particles (≤ 0.004 mm) clay, quartz, feldspar, calcite, and dolomite 3) Claystones - mostly clay 4) Shales most abundant detrital rock rock breaks into layers (parallel to bedding) Clastic Sedimentary Rocks
- 68. Rounded rock fragmentsConglomerate Angular rock fragments Breccia Quartz predominates Quartz sandstone Quartz with considerable feldspar Arkose Dark color, quartz with considerable feldspar, clay and rock fragments Graywacke Splits into thin layers Shale Breaks into clumps or blocks Mudstone Clastic Sedimentary Rocks
- 69. organic (biochemical) orinorganic activity 1) limestone/dolostone (carbonate rock) - biochemical or inorganic rock of calcite or dolomite 2) evaporite (rock salt, rock gypsum) - halite, sylvite, or gypsum inorganically precipitated 3) chert - microscopic quartz deposited by biochemical or inorganic processes 4) coal - biochemical material (land plants that grew in swamps) Chemical Sedimentary Rocks
- 70.
- 71. Clastic or non-clastic Calcite, CaCO3Limestone Clastic or non-clastic Dolomite, CaMg(CO3)2 Dolomite (dolostone) Inorganic Non-clastic Microcrystalline quartz, SiO2 Chert Non-clastic Halite, NaCl Rock salt Non-clastic Gypsum CaSO4•2H2O Rock gypsum Clastic or non-clastic Calcite, CaCO3 Limestone Biochemical Non-clastic Microcrystalline quartz, SiO2 Chert Non-clastic Altered plant remains Coal Chemical Sedimentary Rocks
- 72. ... what can sedimentary rockstell us anyway?
- 73. evidence preserved insedimentary rocks allows events and processes which formed them to be inferred specific depositional environment of ancient sedimentary rocks indicated by sedimentary structures Sedimentary Structures
- 74. Sedimentary Structures usually horizontal orsub-horizontal layering Bedding or Stratification
- 75. Laminated Bedding closely spacedparallel layering Sedimentary Structures
- 76. Graded Bedding progressive decrease in grainsize upward through bed rapid deposition top of bed indicator Sedimentary Structures
- 77. non- horizontal bedding Cross-Bedding wind or water currents indicatetop of bed and paleocurrent directions Sedimentary Structures
- 78. small waves onsurface of sediment caused by water or wind movement used as top of bed indicator two forms: a) wave-formed ripple marks b) current-formed ripple marks Sedimentary Structures Ripple Marks
- 79. symmetric ripples formedin surf zone Wave-formed Ripple Marks Sedimentary Structures
- 80. water or air movesin one direction current indicator Sedimentary Structures Current Ripple Marks
- 81. polygonal cracks contraction during desiccation of silt- andclay- sized sediment shallow water deposition top indicator Sedimentary Structures Mud Cracks
- 82. provide no cluesabout deposition: nodules concretions geodes Sedimentary Structures Secondary Structures form long after rock formation
- 83. parallel bedding irregular, knobby- surfaced mineralbody different composition than surroundings Sedimentary Structures Nodules
- 84. dehydration cracks filled by material ofdifferent composition Sedimentary Structures Septarian Nodules
- 85. Concretions usually spherical characterized by concentric layering composedof silicic material Sedimentary Structures
- 86. in limestoneand shale roughly spherical hollow structures pocket of water surrounded by silica deposition large quartz or calcite crystals grow inward Sedimentary Structures Geodes
- 87. preserved plant andanimal remains clues about ancient life, evolution, and depositional environment basis for constructing geologic calendar allow rocks to be correlated in time two types Fossils
- 88. most dissolved and replaced silicaand pyrite (e.g., petrified wood): mold - cavity cast - filled mold Fossils
- 89. …. so whatdo these structures tell us about how and where sediments are deposited?
- 90. different sedimentary rocksdeposited in different places at same time change in composition and nature laterally due to changes in depositional environment rock assemblages reflect particular depositional environment Sedimentary Facies
- 91. may result fromsea level fluctuations: 1) Marine Regressions sediment deposition during falling sea level deep marine deposits overlain by shallower marine and nearshore deposits 2) Marine Transgressions sediment deposition during sea level rise sandstone (nearshore) overlain by shale (shallow marine) and limestone (deeper marine) Sedimentary Facies
- 92. why are such variationsimportant and why worry about where sediments are deposited anyway?
- 93. Petroleum/ Natural Gas/ Oil Shales/ TarSands migrate upward until reach surface or trapped petroleum trap - permeable reservoir rock and impermeable cap rock Sedimentary Hosted Resources
- 94. Uranium ores occurin fluvial sandstones containing organic matter uranium transported in groundwater until reducing conditions cause precipitation Banded iron formations largest source of iron ore deposited in shallow seas iron precipitated from seawater by oxygen addition from algae (photosynthesis) or bacteria (respiration) Sedimentary Hosted Resources
- 95. other sediment orsedimentary rock derived resources: building materials sand and gravel - construction limestone - cement gypsum - wallboard and plaster clay - bricks quartz - glass Sedimentary Hosted Resources
- 96. halite - seasoningand preservative clay - ceramics and kitty litter phosphates - fertilizers, matches, and preservatives diatomite - filtration coal - energy and coke in steel production Sedimentary Hosted Resources other sediment or sedimentary rock derived resources: