23. On the contour map below (Figure Q23) a coal seam was discovered at point A.

Question

23. On the contour map below (Figure Q23) a coal seam was discovered at point A. The seam appears to dip to the West at 14 degrees, however, the geologist is not sure. Assuming the geologist found the true dip: a. b. c. Name the strike and dip of the coal layer. Trace the outcrop pattern on the surface contours. What is the apparent dip in the direction S60°W, North 100 m 100 250 150 200 Note: contours are in meters Figure Q23. Contour Map of Coal Seam ' = arctan (cos0 x tan ); where, = actual dip Useful equations:

Explanation / Answer

a) Strike : North - South ( 0 degree -180 degree)

as dip is perpendicular to strike,   

Dip : 14 degree west (14degree/270degree)

b) ?

c) tan( apparent dip) = tan (true dip) x sin( angle between strike and cross section)

cross section is parallel to dip direction hence S60W means angle is 60 degree

= tan(14) x sin(60)

= 0.2493 x 0.8660

= 0.2159

= tan-1(0.2159)

= 12 degree

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