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Op ch07 lecture_earth3, sedimentary rocks

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Sedimentary rocks are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause ...

Sedimentary rocks are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles (detritus) to settle and accumulate or minerals to precipitate from a solution. Particles that form a sedimentary rock by accumulating are called sediment. Before being deposited, sediment was formed by weathering and erosion in a source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers which are called agents

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Op ch07 lecture_earth3, sedimentary rocks Presentation Transcript

  • 1. Chapter 7 A Surface Veneer: Sediments, Soils, and Sedimentary Rocks LECTURE OUTLINE earth Portrait of a Planet Third Edition ©2008 W. W. Norton & Company, Inc. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 2. A Surface Veneer: Sediments, Soils, and Sedimentary Rocks Prepared by Ron Parker Earlham College Department of Geosciences Richmond, Indiana
  • 3. Sediments  The Nile flows over a canyon filled by thick sediments.  The size of Grand Canyon.  The canyon was carved by the Nile.  Indicates the Mediterranean has evaporated and re-filled.  Sediment:  Rock and mineral fragments.  Shells.  Mineral precipitates.  Cemented into rocks. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 4. Sedimentary Cover  Earth is covered by a thin “veneer” of sediment.  The veneer caps igneous and metamorphic “basement.”  Sediment cover varies in thickness from 0 to 20 km.  Thinner (or missing) where ig and meta rocks outcrop.  Thicker in sedimentary basins. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 5. Weathering  Processes that break up rock to create sediment.  Physical - Mechanical breakage and disintegration.  Chemical - Decomposition by reaction with water.  Weathering processes occur at Earth’s surface.  Rocks react with hydrosphere, atmosphere, and biosphere.  Low temperature and pressure. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 6. Physical Weathering  Mechanical breakup; doesn’t change mineral makeup.  Creates broken fragments or “detritus.”  Detrital fragments classified by size.  Coarse-grained – Boulders, cobbles, and pebbles.  Medium-grained – Sand-sized.  Fine-grained – Silt and clay (mud). Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 7. Physical Weathering  Types of physical weathering.  Jointing.  Frost wedging.  Root wedging.  Salt wedging.  Thermal expansion.  Animal activity.  Physically weathered rock fragments move by gravity.  Large blocks often accumulate as talus below a cliff.  Smaller fragments are carried away by water and wind. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 8. Jointing  Deep crustal rocks are hot and under high pressure.  Erosion removes material; deep rocks become exposed.  At the surface, crustal rocks cool and expand.  This causes through-going fractures called joints.  Joints may exhibit a variety of geometries. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 9. Jointing  Igneous plutons crack in onionlike “exfoliation” layers.  These layers break off as sheets that slide off of a pluton.  Over time, this process creates domed remnants.  Examples: Half-Dome (Ca.) and Stone Mountain (Ga.). W. W. Norton Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 10. Chemical Weathering  Reaction with water disintegrates many minerals.  Water is the universal solvent.  Maximized under warm and wet conditions. Tropical weathering is intensive. Turns rock into heavily decomposed “saprolite.”  Chemical weathering is virtually absent in deserts. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 11. Chemical Weathering  Forms stable minerals from unstable precursors.  Common chemical weathering reactions include:  Dissolution.  Hydrolysis.  Oxidation.  Hydration. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 12. Chemical Weathering  Dissolution  Some minerals (halite, gypsum, calcite) dissolve. CaCO3 + H2CO3 +2H+ = 2H2O + 2CO2 +Ca2+ (calcite) + (carbonic acid) + (hydrogen ion) = (water) + (carbon dioxide) + (calcium ion)  Acidity (i.e. acid rain) enhances this effect. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 13. Hydrolysis  Water breaks cation bonds in silicate minerals. Yields…  Dissolved cations.  Alteration residues. Clay minerals. Iron oxides (rust). Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 14. Chemical Weathering  Oxidation  A reaction whereby a metal loses electrons.  Important process in mafic silicate decomposition.  Rusting is a familiar example.  Hydration  Absorption of water into a mineral structure.  Results in a volume increase (expansion).  Important processes in some clay minerals. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 15. Chemical Weathering  Minerals differ in their tendency to weather chemically.  Silicate weathering susceptibility predicted by stability.  Temperature (T) and pressure (P) are a dominant control. High T and P minerals tend to weather quickly at low T and P. Low T and P minerals are more stable at Earth’s surface. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 16. Biological Weathering  Organisms often important chemical weathering agents.  Plant roots.  Fungi.  Lichens.  Bacteria.  Organic acids attack minerals. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 17. Weathering Feedbacks  Weathering processes often work as a positive feedback.  Physical weathering speeds chemical weathering. How?  An increase in surface area accelerates chemical attack.  Chemical weakening increases surface area via breakage. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 18. Chemical Weathering Rate  Block geometry influences weathering.  Corners weather fastest; 3 sides of attack.  Edges weather at a moderate rate (2 sides).  Flat faces weather slowest (1 side).  Cube-shaped rocks develop “spheroidal weathering.” Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 19. Differential Weathering  Rates of weathering attack vary due to changes in…  Mineral stability.  Degree of compaction or cementation.  Subtle differences in texture, etc.  Major control on surficial expression. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 20. Soil  “Soil consists of rock and sediment that has been modified by physical and chemical interaction with organic material and rainwater, over time, to produce a substrate that can support the growth of plants.”  Soil-forming processes require long periods of time.  Soil may be easily destroyed by human activities.  Soil is a crucial natural resource in need of protection. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 21. The Soil Profile  Soil forms a vertical sequence of layers called a profile.  Profiles develop from the surface downward.  Weathering generates detritus.  Rainwater alters the detritus.  Individual layers are horizons.  The upper horizons form topsoil.  The only fertile part of the profile.  Easily removed by erosion.  1000s of years in the making. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 22. Soil-Forming Processes  Coffee is a direct analogue.  Zone of leaching – Upper soil profile.  Ions from chemical weathering  Fine silts and clays infiltrate.  Zone of accumulation – Lower soil profile. Ions form new minerals. Silts and clays clog pore spaces. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 23. Soil Horizons  Distinct horizons reflect soil- forming processes.  O Horizon – Dark organic matter-rich surface layer.  A Horizon – Organic and mineral matter.  E Horizon – Transitional layer leached by organic acids.  B Horizon – Organic-poor mineral rich layer.  C Horizon – Slightly altered bedrock. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 24. Soil-Forming Factors  Soil genesis influenced by a number of factors.  Climate – Amount of water and warmth.  Substrate composition – Soil parent minerals.  Slope steepness – Soils develop best on low slopes.  Drainage – Wet soils are more organic-rich.  Time – Older soils are more developed.  Vegetation – Controls type of organic matter added. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 25. Soil vs. Climate  Climate exerts a dominant control on soil development.  Latitude.  Elevation. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 26. Soil Use and Misuse  Human activities can make soil unproductive.  Crops can strip soil nutrients.  Topsoil erodes away when vegetation is removed.  Topsoil is sometimes mined and sold; usually a bad idea.  Soil quality is degraded by…  Overuse of pesticides.  Industrial contamination.  Salt build-up.  It is wise to protect soils. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 27. Sedimentary Rocks  Sediments are the building blocks of sedimentary rocks.  Sediments are diverse, as are the rocks made from them.  4 classes:  Clastic – Made from weathered rock fragments (clasts).  Biochemical – Cemented shells of organisms.  Organic – The carbon-rich remains of plants.  Chemical – Minerals that crystallize directly from water. Clastic Biochemical Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Organic Chemical Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 28. Clastic Sedimentary Rocks  Clastic sedimentary rocks reflect several processes.  Weathering – Generation of detritus via rock disintegration.  Erosion – Removal of sediment grains from rock.  Transportation – Dispersal by wind, water, and ice.  Deposition – Accumulation after transport stops.  Lithification – Transformation into solid rock. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 29. Clastic Sedimentary Rocks  Lithification – Transforms loose sediment into solid rock.  Burial – More sediment is added onto a previous layer.  Compaction – Overburden weight reduces pore space. Sand – 10-20% Clay – 50-80%  Cement – Minerals from groundwater that “glue” sediment. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 30. Clastic Sedimentary Rocks  Classified on the basis of texture and composition.  Clast (grain) size.  Clast composition.  Angularity and sphericity.  Sorting.  Character of cement.  These variables produce a diversity of clastic rocks. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 31. Clastic Sedimentary Rocks  Clast (grain) size – The average diameter of clasts.  Range from very coarse to very fine.  Boulder, cobble, pebble, and pea gravel.  Coarse, medium, and fine sand.  Coarse, medium, and fine silt.  Coarse and fine clay.  With increasing transport, average grain size decreases. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 32. Clastic Sedimentary Rocks  Clast composition – Mineral makeup of clasts.  May be individual minerals or rock fragments.  Mineral identity important. Stable end-products of weathering (quartz, Fe-oxides, clays). Unstable minerals signify special conditions (feldspars).  Composition helps to decipher depositional history. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 33. Clastic Sedimentary Rocks  Angularity and sphericity – Indicate degree of transport.  Fresh detritus is usually angular and non-spherical.  Grain roundness and sphericity increases with transport.  Well-rounded – Long transport distances.  Angular – Negligible transport. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 34. Clastic Sedimentary Rocks  Sorting – The uniformity of grain size.  Well-sorted – Uniform grain size.  Poorly sorted – Wide variety of grain sizes.  Sorting indicates the constancy of environmental energy.  Well-sorted – Uniform energy (i.e., a beach).  Poorly sorted – Variable energy (i.e., an alluvial fan). Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 35. Clastic Sedimentary Rocks  Cement – Minerals that fill sediment pores.  Fluids with dissolved solids flush through pore system.  Dissolved ions slowly crystallize in (and fill) pores.  Cementation varies in degree.  Weakly cemented (friable) – Grains easily pulled from rock.  Strongly cemented (indurated) – Grains hard to dislodge.  Common cements:  Quartz  Calcite  Hematite  Clay minerals Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 36. Clastic Sedimentary Rocks  Maturity – A measure of the degree of “processing.”  Textural maturity – Degree of roundness and sorting.  Mineral maturity – Degree of unstable mineral removal.  Time and transport causes sediment evolution.  Texture - Average grain size  ; roundness and sorting  .  Composition - Unstable minerals  ; Stable minerals  .  Maturity is used to reconstruct depositional conditions. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 37. Clastic Sedimentary Rocks  Coarse clastics - Composed of gravel-sized clasts.  Breccia – Comprised of angular clasts. Indicates lack of transport processing. Deposited close to source.  Conglomerate – Comprised of rounded clasts. Indicates processing by transport. Deposited away from source area. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 38. Biochemical and Organic Rocks  These are sediments derived from living organisms.  Biochemical limestone – Made from CaCO3 shell remains.  Carbonate grains accumulate in the “carbonate factory.” Warm (tropical and subtropical). Normal-salinity marine water. Wave-agitated. Oxygenated. Shallow. Clear. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 39. Biochemical and Organic Rocks  Organic rocks – Made from organic carbon.  Coal – Altered remains of fossil vegetation. Accumulates in lush tropical wetland settings. Requires deposition in the absence of oxygen.  Oil shale – Shale with heat-altered organic matter. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 40. Chemical Sedimentary Rocks  Comprised of minerals precipitated from water solution.  Evaporites – Created from evaporated seawater.  Evaporation triggers deposition of chemical precipitates.  Examples include halite (rock salt) and gypsum. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 41. Sedimentary Structures  Sedimentary rocks are usually layered or “stratified.”  Arranged in planar, horizontal “beds.”  Bedding is often laterally continuous for long distances.  Beds are often similar in composition, color, and texture. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 42. Sedimentary Structures  Bedding caused by changing conditions during deposition.  These can be changes in…  Energy conditions, and hence, grain size.  Disturbance by organisms.  Bedding may also reflect non-deposition or erosion. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 43. Sedimentary Structures  A series of beds are referred to as strata.  A sequence of strata that is sufficiently unique to be recognized on a regional scale is termed a formation.  The formation is the fundamental geologic mapping unit. Example: Note how the prominent white cliff-forming band of the Coconino Formation can be visibly traced across Grand Canyon. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 44. Sedimentary Structures  Water flowing over loose sediment creates bedforms.  Bedforms are linked to flow velocity and sediment size.  Ripples, cm-scale ridges, and troughs indicate flow. Asymmetric ripples – Unidirectional flow. Symmetric ripples – Wave oscillation. Ripples are commonly preserved in sedimentary rocks. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 45. Bedforms  Dunes – Similar to ripples except much larger.  Cross-bedding – Created by ripple and dune migration.  Sediment moves up the gentle side of a ripple or dune.  Sediment piles up, then slips down the steep face. The slip face continually moves downstream. Added sediment forms sloping “cross-bedded” layers. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 46. Bedforms  Graded Beds – Bedding layers that fine upward.  Transition from coarse to medium to fine grain sizes. Base of coarse sand and gravel. Mid-level sands. A fine silt and clay cap. Abrupt contact with overlying coarse base. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 47. Depositional Environments  Locations where sediment accumulates. They differ in…  Energy regime (mostly comes from the sun; gravitational and chemical potential energy)  Sediment delivery, transport and depositional conditions.  Chemical, physical and biological characteristics.  Environments range from continental to marine. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 48. Depositional Environments  Terrestrial environments – Deposited above sea level.  Glacial – Due to movement of ice. Ice carries and dumps every grain size. Creates glacial till; poorly sorted gravel, sand, silt, and clay. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 49. Depositional Environments  Terrestrial environments.  Mountain streams. Water carries large clasts during floods. During low flow, boulders are immobile. Course conglomerate is characteristic. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 50. Depositional Environments  Terrestrial environments.  Alluvial fan - Sediments that pile up at a mountain front. Rapid drop in stream velocity creates a cone-shaped wedge. Sediments are immature conglomerates and arkoses. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 51. Depositional Environments  Terrestrial environments.  Rivers – Channelized flow transports sediment. Sand and gravel fills concave-up channels. Fine sand, silt, and clay is deposited on flood plains. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 52. Depositional Environments  Marine environments – Deposited at or below sea-level.  Deltas – Sediments dropped where a river enters the sea. River flow halts at the ocean. Sediment carried by the river is dumped when velocity drops. Deltas grow over time, building out into the basin. Often develop a topset – foreset – bottomset geometry. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 53. Depositional Environments  Marine environments.  Shallow marine – Finer version of beach sediment. Fine silts and muds. Biologically active. Siltstone and mudstone. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 54. Depositional Environments  Marine environments.  Shallow water carbonates – Tropical. Skeletons of marine invertebrates. Born in the carbonate factory. Warm, clear, shallow, normal salinity marine water. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 55. Depositional Environments  Marine environments.  Deep marine – Fines predominate far from land sources. Skeletons of planktonic organisms make chalk or chert. Fine silts and clays turn to shale. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 56. Sedimentary Basins  Sediments vary in thickness across Earth’s surface.  Thin to a zero edge where non-sedimentary rocks outcrop.  Thicken to 10 to 20+ km where the surface has subsided.  Subsidence – Sinking of the land during sedimentation.  Due to crustal flexure and faulting.  Compounded by the weight of added sediments.  Basins are important locations for natural resources.  Coal  Petroleum  Natural gas  Uranium Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 57. Sedimentary Basins  Basins form where tectonic activity creates space.  Rift basins – Divergent (pull-apart) plate boundaries. Crust thins by stretching and rotational normal faulting. Thinned crust subsides. Sediment fills the down-dropped basin. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 58. Sedimentary Basins  Basins form where tectonic activity creates space.  Passive margins – Non-plate boundary continental edge. Underlain by crust thinned by previous rifting. Thinned crust subsides as it cools. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 59. Diagenesis  Physical, chemical, and biological changes to sediment.  Bioturbation (The stirring or mixing of sediment or soil by organisms)  Lithification.  Dissolution.  Mineral precipitation.  Pressure solution.  Temp range between burial and metamorphism (~300oC).  Integrates changes across the entire sediment history. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks
  • 60. This concludes the Chapter 7 A Surface Veneer: Sediments, Soils, and Sedimentary Rocks LECTURE OUTLINE earth Portrait of a Planet Third Edition ©2008 W. W. Norton & Company, Inc. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks