Map Patterns of Tilted Lithostratigraphic Units and Unconformities GEOL 3000

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

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

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

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)

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

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)

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

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’

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

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