GY403 Structural Geology Lab Thickness and Depth Problems

Special Case: horizontal attitude Note: geological contacts will parallel topographic contour lines on map. 93 ft. 87 ft. T=93-87 = 6 ft. Thickness (t) = Elev. Upper contact – Elev. Lower contact

Special Case: vertical attitude Note: cross-section is perpendicular to strike of unit. Thickness = outcrop width in this case. w General Rule: If the dip (δ) of the unit is perpendicular to the ground surface then w = t. δ t

perpendicular to strike of strata NOTE: cross section is perpendicular to strike of strata w= true outcrop width δ t= true thickness

N β Cos β = (w) / (w’) w = Cos β * (w’) w’ = apparent outcrop width 40 w = true outcrop width 40

w σ δ t West East Scenario: slope and dip are inclined in opposite directions West-facing slope w σ δ t δ = true dip angle σ = slope angle Sin( δ + σ ) = t/w t = Sin( δ + σ ) * w Note: cross-section must be perpendicular to strike of bedding

w σ t δ δ - σ West East Scenario: slope and dip are East-facing slope inclined in same direction w δ = true dip angle δ - σ σ = slope angle σ t δ Sin( δ - σ ) = t/w t = Sin( δ - σ ) * w Note: cross-section must be perpendicular to strike of bedding, and slope angle ( σ ) must be measured perpendicular to strike.

perpendicular to strike of strata NOTE: cross section is perpendicular to strike of strata w= true outcrop width δ δ t d= depth in vertical drill hole Cos ( δ ) = t / d d = t / Cos( δ )