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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.
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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
NOTE: cross section is perpendicular to strike of strata w= true outcrop width δ t= true thickness
Cos = (w) / (w’) β * (w’) w = Cos β w’ = apparent outcrop width N β 40 w = true outcrop width 40
West East Scenario: slope and dip are inclined in opposite directions w West-facing slope 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
West East East-facing slope Scenario: slope and dip are 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 ( ) must be measured perpendicular to strike. σ
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 δ d = t / Cos( )