1. Physical Geology Review
TXESS Revolution - Summer Institute A, 2010
Physical Geology Review
the expanse of material is vast!
Jon Olson

2. Internal Structure of the Earth granitic/basaltic
crust = 0-40 km; mantle = km;
outer core (liquid) = km; inner core = km
from:

3. Guidelines for Structural Analysis
reference frame
law of original horizontality (rocks deposited on nominally horizontal surfaces)
law of superposition (deposition of new layers are on top of old layers)
stratigraphic continuity (deposits tend to be continuous laterally, or discontinuous strata that lie in the same plane are equivalent in time)
nature of contacts
stratigraphic (bedding or unconformities)
intrusive (igneous or sedimentary)
tectonic (fractures/faults)

4. Basic Principles principle of superposition
younger rocks are deposited on top of older rocks

5. Basic Principles law of original horizontality
all sediments originally laid down in horizontal layers
Grand Canyon, Arizona

6. Basic Principles law of original horizontality
non-horizontal bedding implies some sort of deformation
The Alps of Sisteron, France

7. Interpreting Field Data
strike and dip measurements
topography following geologic structure
geologic cross-sections

8. “Undeformed”, horizontal rock
Cedar Point, UT

9. Horizontal Bedding in Sedimentary Rocks younger original horizontality
older
original horizontality
lateral continuity
superposition

10. Strike and Dip

11. Looking in strike direction, dip is angle from horizontal
arrow pointing down dip

12. Interpreting Field Data
strike and dip = attitude of planes (beds, fractures, ...)
strike is intersection of plane with horizontal
dip is angle between plane and horizontal

13. Vertical Beds Miocene Monterey Fm
Vertical Beds Miocene Monterey Fm., California coast Laminated bedding with selective dolomitization (yellow beds)
1 meter

14. Orientation of Planes (strike)
Horizontal is reference frame
3d block diagram
Strike is intersection between plane and horizontal
North is reference direction

15. Orientation of Planes (dip)
vertical cross-section view
strike
dip angle
Dip is inclination of plane from horizontal, measured in vertical plane perpendicular to strike

16. Folds and Faults - folds are evidence of ductile rock deformation
- faults represent brittle rock deformation

17. Monocline on the San Juan River, Utah

18. Lateral Continuity (or lack thereof!)

19. Faults Fault vertical cross-section view dip angle Hanging Wall
Footwall

20. Faults
3d block diagram
Fault
Hanging Wall
Footwall

21. Dip-Slip (Normal)
Footwall
Hanging Wall

22. horizontal stretching = extension
Dip-Slip (Normal)
Footwall
Hanging Wall
horizontal stretching = extension
vertical thinning

23. Dip-Slip (Reverse)
Footwall
Hanging Wall

24. horizontal shortening = contraction,
Dip-Slip (Reverse)
Hanging Wall
Footwall
horizontal shortening = contraction,
vertical thickening

25. Strike-Slip strike-slip faults are typically vertical,
Footwall
Hanging Wall
strike-slip faults are typically vertical,
but they can be dipping like this one

26. Strike-Slip (right-lateral)
Footwall
Hanging Wall
as you step across the fault,
the block you are stepping onto moves to the right

27. Strike-Slip (left-lateral)
Hanging Wall
Footwall
as you step across the fault,
the block you are stepping onto moves to the left

28. Oblique-Slip
Footwall
Hanging Wall

29. Oblique-Slip
Footwall
Hanging Wall
both strike-slip and dip-slip

30. Normal Fault with Basin Shaped Fold in Hanging Wall
shear sense = normal
Foot
Wall
Fault
Plane
Hanging Wall
Bedding
Slip vector

31. Fault drag & shale smear

32. Strike-slip fault and Drag folding

33. Slickensides = shear

34. Reverse Fault in Core

35. Geologic Cross-section
Map view A B A B
Cross-section view

36. Fracture Types shear failure – faults
relative displacement is parallel to fracture face = shearing mode
tensile failure – joints, veins, dikes
a fracture with relative displacement perpendicular to fracture face = opening mode

37. Joint are “just” cracks…. (looking at dip slopes)
orientation changes from bed to bed

38. Joints (looking at bed scarps)

39. A Joint filled with minerals = vein
Bristol Channel, UK
Ouachita Mtns., Arkansas

40. A “Joint” filled with magma = dike
Mt. Moran, Grand Tetons, WY

41. Famous Fractures in the Movies
The Middle East?
hardly!
from Transformers

42. Volcanic Neck and Igneous Dike: Shiprock dike
How about New Mexico?
propagating dike
volcanic source
curving path to line up with earth stresses
Volcanic Neck and Igneous Dike: Shiprock dike
volcanicsource

43. Igneous Rock Features
from Press and Siever, Understanding Earth

44. Other Geomorphic Features

45. Glacial Moraine & U-shaped Valley

46. Glacial Moraine

47. Immature River – Steep, V-shaped Canyons
Yellowstone River
Immature River – Steep, V-shaped Canyons

48. Mature, meandering river (Yellowstone River)

49. High energy rivers – heavy sediment load
channel cut & fill,
graded bedding
braided stream

50. Alluvial fan

51. Unconformities represent non-deposition or erosion
often indicate tectonic events or global sea level change, laterally very continuous
types
disconformity (parallel sed layers above and below, missing some time)
nonconformity (sed rocks on top of igneous/metamorphic basement)
angular unconformity (rocks above and below have different orientation)

52. Angular Unconformity

53. Disconformity

54. Cambrian Flathead ss on top of Precambrian granite
Nonconformity
Cambrian Flathead ss on top of Precambrian granite