1. Map Patterns of Tilted Lithostratigraphic Units
and Unconformities
GEOL 3000

2. Simple Structures of Strata
Flat-lying
Monocline
Homocline
From Spencer (2000)

3. Flat-lying Strata of Fillmore County
Dendritic Map Pattern

4. Another Example of Flat-lying Strata
The Grand
Canyon

5. Orientation of Strata Strike and Dip North Hemisphere Method
N45E/40oSE
Right-hand Azimuth Method
45/40o

6. Map Patterns of Tilted Strata
Steeply Tilted Pattern-
Narrower and less affected by topography
ModeratelyTilted Pattern
From Bulter and Bell (1988)

7. Map Patterns of Tilted Strata in Valleys
Flat-lying strata -
contacts || to topography and V upstream
Strata tilted downslope steeper than slope - contacts V downstream
Vertical strata -
contacts straight across topography
Strata tilted upslope - contacts V upstream
Strata tilted downslope shallower than slope - contacts V upstream
From Spencer (2000)

8. Determining Thickness of Tilted Strata
On a Horizontal Surface
T = GD * sin A GD A T
From Bulter and Bell (1988)

9. Determining Thickness of Tilted Strata on a Sloping Surface
GD= W / cos(B)
Dip of Strata (A) is opposite direction of
ground slope (B) and B + A > 90o
T = GD cos(A+B-90)
and B + A < 90o
T = GD sin(A+B)
Dip of Strata (A) is same direction as
ground slope (B) and B < A
T = GD sin(A-B)
Dip of Strata (A) is same as ground slope (B)
and B > A
T = GD sin(B-A)

10. Topography of a Planar Surface
Structural Contours
Topography of a Planar Surface
For homoclinal strata, structural contours will be parallel and evenly spaced

11. Using Structural Contours to Predict the Location of Geologic Contacts
Outcrop of contact at 1600’
Measure strike at N-S and dip at 10o to the west
Outcrop
10o
Horizontal Spacing
1600’
Elevation
Spacing θ
Contact Surface
Land
Surface
1700’
HS=ES/tanθ
100/tan10°=100/0.176= 2835’

12. Determining the Strike and Dip of a Contact from Three Points of Elevation
tan(dip) = d/m
dip = tan-1 (d/m) m d

13. Map Patterns of Unconformities
Sed Rx
Sed Rx
Sed Rx
Sed Rx
Sed Rx
Ig/Meta Rx