N 



W- 



i^ 



Figure 25-6. Stereogram of the problem of two tilts solved by both cyclographic and 

 polar projection. 



circles. True dip is then measured on the W-E line as 40 degrees. When the 

 stereogram is oriented to N, the direction of dip is seen to be north 23 degrees 

 west. 



The Problem of Two Tilts (3) 



We have an angular unconformity, with the lower series of beds, A, dip- 

 ping 60 degrees on azimuth 230 degrees, while the upper series, B, dips 35 de- 

 grees on azimuth 125 degrees. We are required to find the dip and strike of 

 beds in series A during deposition of series B, presumably in a horizontal po- 

 sition. Solution of the problem requires the rotation of the entire system until 

 series B is horizontal, and then the determination of the new position of series 



537 



