Transcript STRUCTURAL GEOLOGY GEOL 4110 Advanced Earth Science for Teachers

GEOL 4110
Advanced Earth Science for Teachers
STRUCTURAL
GEOLOGY
Structural Geology
The study of how earth materials respond to largescale differential stresses in the Earth’s crust
TECTONIC DEFORMATION
Small Scale Response - Foliation
Characteristic of Convergent Zones
Accompanied by Metamorphism
TECTONIC DEFORMATION
Large-scale Response – Folding & Faulting
Elastic – Ductile –Brittle Behavior
Tensile
Strength
Point up to which strain is
entirely recoverable
(Brittle behavior)
(Ductile behavior)
(Deformation)
Effects of Temperature, Pressure
and Strain Rate
Ductile Behavior is
favored over brittle
behavior with:
Increased
Temperature
Increased Pressure
Decreased Strain Rate
Increasing Temperature 
Decreasing Tensile Strength
Orientation of Strata
Strike and Dip
Strike Line – the line traced by the intersection of the plane of interest with a horizontal
plane
Dip Line – tick mark drawn at 90° from strike line drawn on the side of the strike line
where the plane forms an acute angle with the horizontal plane = Fall Line
Dip Angle – degree angle between the horizontal and the plane of interest
Drawing a Strike and Dip Symbol
40o
Reporting the Strike and Dip
North Hemisphere Method
N45E/40oSE
Right-hand Azimuth Method
45/40o
Strike and Dip Symbology
US Geological Survey
Recommendations for Symbology
USGS Open-file Report 99-430
http://pubs.usgs.gov/of/1999
/of99-430/
Legend from the Duluth quad (Green & Miller, 2008)
Simple Structures of Strata
Flat-lying
Monocline
Homocline
From Spencer (2000)
Flat-lying
Strata of
Fillmore
County
Dendritic Map
Pattern
Another Example
of Flat-lying
Strata
The Grand
Canyon
Topographic Contour Lines
connects points of equal elevation
Rules:
• Lines never cross
•Lines never end
•Lines “V” upstream
•Lines encircle hills
and depressions
Reading Topography
Map Patterns
of Tilted Strata
in Valleys
Vertical strata contacts straight
across topography
Flat-lying strata contacts || to
topography and
V upstream
Strata tilted
downslope steeper
than slope contacts V
downstream
Strata tilted
upslope - contacts
V upstream
Strata tilted
downslope
shallower than
slope - contacts V
upstream
From Spencer (2000)
Map Patterns of Tilted Strata
Steeply Tilted PatternNarrower and less affected
by topography
ModeratelyTilted Pattern
From Bulter and Bell (1988)
Fold Terminology
Upright Fold
Recumbent Fold
Inclined Fold
Overturned Fold
Assymetrical
Symmetrical
Orientations of Folds
Based on Hinge Line (Fold Axis) and Axial Plane
Types of Folds
Horizontal Normal
Horizontal Inclined
Plunging Normal
Plunging Inclined
Vertical
From Spencer (2000)
Recumbent
Reclined
Fold Symbology
Longer arrow
on shallower
limb
Horizontal Fold Patterns
Symmetrical
Asymmetrical
Plunging
Fold Patterns
Domes and Basins
Elongate Basin or
Doubly Plunging
Syncline
Refolded Folds
Multiple Deformational Events
F1
F2
Types of Faults And Applied Stesses
Horizontal
Compression
Listric faults
Normal
Mid-Crustal
Horizontal
Compression
Horizontal
Extension
Horizontal
Shear
Thrust to Reversed
Horizontal
Compression
+ Shear
Horizontal
Extension
+ Shear
Terminology of Faults
FTP
FB
FP – Fault Plane
FPT – Trace of Fault Plane
FB – Footwall Block
HB – Hanging Wall Block
HB
Slickensides – Lineations on the fault
plane that record the direction of slip
FTP
Displacement Parameters
ad – Apparent Displacement
s – Slip (or dip) separation (measured on FP)
d – Stratigraphic displacement
u – Throw (vertical displacement)
FP
ad
FB
HB
HB
FB
Fault Symbology
Determining Type of Fault from Offset
of Lithostratigraphic Units
Hard to tell just from
one offset example
Normal
Left Lateral
Strike-slip
Oblique
(Left Lateral
+ Reversed)
Normal
Normal
Oblique
(Left Lateral
+ Normal)
Regional Fault Features
Divergent Tectonics
Convergent Tectonics Thrust Faulting
Thickening and Stacking Older Rocks on Younger Rocks
Mapping With Google Earth