EXPLANATION OF PLATE VI 

 CLEAVAGE IN SLATE 



The slate is of the Yakutat Series. The locality is on a slender 

 cape of Pogibshi Island, about a mile southwest of Kadiak village. 

 The view is toward the northeast, in the direction of the strike. The 

 dip is northwest, at about 60 degrees. Not far away the planes of 

 bedding show fossils. See page 51. 



The beds are argillaceous, with varying admixtures of sand. In the 

 purer argillite layers the cleavage is nearly vertical ; in the more aren- 

 aceous layers it departs widely from the vertical. The dip of cleavage 

 planes is here to the southeast, or opposite to the dip of bedding planes. 

 In the opposed limb of a local fold the bedding dips southeast and the 

 cleavage dips northwest. From a photograph by G. K. Gilbert. 



