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Geologic Time Scale

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Smith's Map of England. Paleozoic (Old Life) Brachiopods, Trilobites, Fish ... World Stress Map. Brittle Deformation. Extensile or Shear. Continuum of Joints ... – PowerPoint PPT presentation

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Title: Geologic Time Scale


1
Geologic Time Scale
  • Precambrian Minimal fossil record
  • Era, Period, Epoch
  • Based on major changes extinctions, mountain
    building events

2
Relative Time
  • Principle of Superposition
  • Fossil Evidence
  • Cross Cutting Relationships
  • Unconformities
  • Alteration
  • Fracture Termination

3
Siccar Point Unconformity
4
Angular Unconformity Santa Barbara
5
Cross-cutting relationship - dike
6
Smiths Map of England
7
(No Transcript)
8
Paleozoic (Old Life) Brachiopods, Trilobites,
Fish
  • Periods based on English Geology
  • Cambrian for Latin Wales
  • Ordovician and Silurian for ancient Welsh Tribes
  • Devonian for Devon
  • Carboniferous for Coal Measures (also
    Mississippian and Pennsylvanian in US)
  • Permian for Perm Basin in Ukraine

9
Mesozoic (Middle Life) Ammonites, Dinosaurs
  • Triassic based on distinctive three-layer
    stratigraphy in southern Germany
  • Jurassic based on Jura Mountains in France and
    Switzerland
  • Cretaceous (Latin for Chalk) based on chalk unit
    that forms Dovers cliffs

10
Cenozoic (Recent Life) Mammals, Modern marine
fauna (foraminifera)
  • Periods are Tertiary (before Ice Ages) and
    Quaternary (ice ages)
  • Primary and secondary have been long replaces
  • Rocks of western Washington are Tertiary and
    Quaternary

11
Age of the Earth
  • Kelvin and a basis in heat flow (set at 20
    million years)
  • Problem of fitting all of evolution in this time
  • Rutherford and the introduction radioactive decay
  • Added a head source, pushed ages back to 4.5
    billion years

12
Absolute Time
  • Basis on radiometric dating (see Rahn chapter 1)
  • Common dating tools
  • 14C, K-Ar, Rb-Sr,Uranium decay series

13
CEE 437 Structural Geology
  • World Stress
  • Brittle and Ductile Deformation
  • Faults and Joints
  • Folds

14
Representing a Plane
  • Strike and Dip
  • Quadrant Convention (N 60 E, 45 SE)
  • 360o Convention (120, 45)
  • Right hand rule dip 90o clockwise of strike)
  • Pole trend and plunge
  • Dip vector
  • does not discriminate strike of vertical planes

15
Brittle Versus Ductile Behavior
  • Strain Rate Dependence
  • Non-elastic Deformation Mechanisms
  • recrystallization
  • lattice dislocations
  • pressure solution and redeposition

16
World Stress Map
17
Brittle Deformation
  • Extensile or Shear
  • Continuum of Joints and Faults
  • Faults as Strain Concentrators
  • Internal Structure of Faults

18
In Situ Stress Measurement
  • Seismic data
  • First motions
  • Stress drops
  • Hydraulic Fracturing
  • Overcoring
  • Borehole Breakouts

19
Fault Types
  • Normal Extensile Deformation
  • Hanging Wall down
  • Horsts and Grabens
  • Reverse Compressive Deformation
  • Hanging Wall up
  • Thrust Faults
  • Strike-slip
  • Mostly transform faults

20
Fault Nomenclature
  • Hanging wall (overhead)
  • Footwall (underfoot)
  • Gouge
  • Damage Zone
  • Cataclasite
  • Mylonite

21
Normal Fault, Death Valley
22
http//darkwing.uoregon.edu/millerm/slides.html
23
Normal Fault, Canyonlands
24
http//www.geo.cornell.edu/geology/classes/RWA/GS_
326/photos/tf/DesertPk.jpg
25
Fault Gouge
http//darkwing.uoregon.edu/millerm/slides.html
26
Sevier Thrust
27
Keystone Thrust, Nevada
http//darkwing.uoregon.edu/millerm/slides.html
28
Strike Slip Faults, Nevada
http//darkwing.uoregon.edu/millerm/slides.html
29
Strike-Slip, San Andreas Fault, Carrizo Plain
30
Engineering Concerns of Faults
  • Planes of Weakness
  • Sources of Seismic Hazard if Active
  • Significant Water Courses
  • Significant as Groundwater Dams

31
Folds
  • Anticline
  • Concave down or oldest beds at core
  • Syncline
  • Concave up or youngest beds at core
  • Overturned and Recumbent Folds
  • Fold Terms
  • Hinge, Axis

32
Identifying Fold Types
  • Attitude of beds
  • Pattern of beds on geologic maps
  • Anticline oldest at core
  • Syncline youngest at core

33
Engineering Concerns of Folds
  • Means of Extrapolating Bed Locations
  • Fracturing related to folding
  • Favorable or non-favorable orientations of beds
    to engineered structures or slopes

34
Ramp Fault, B.C.
35
Recumbent Folds
http//darkwing.uoregon.edu/millerm/slides.html
36
Fine-Scale Folding
http//darkwing.uoregon.edu/millerm/slides.html
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