Kairbanks.] 



Geology of Point Sal. 



59 



In addition to the dikes which are of later date than the serpen- 

 tine, there appear at numerous spots along the ocean bands and 

 streaks of lighter color. They differ from the serpentine in contain- 

 ing augite and feldspar in addition to olivine, and might be termed 

 picrites, although some are almost gabbroitic in appearance. They 

 are not generally sharply differentiated from the serpentine, the 

 dark bands passing into it with apparently little change. These 

 feldspathic bands are sometimes intersected by dikes, two to three 

 inches in thickness, which do not differ greatly in appearance but 

 contain abundant hypersthene. 



The steep southern slope of the Lion's Head consists of a rock 

 quite similar to that forming the higher part of Point Morrito, 

 namely, diallage and olivine, the former frequently in large green 

 crystals. ' The section given along the first creek east of the Lion's 

 Head is quite similar to that wesfi. On the northern side of the 

 complex there is first 500 to 600 feet of diabase and gabbro. The 

 extreme edge is a dark, fine-grained diabase, containing coarse, irreg- 

 ular veins. The veins recur occasionally until the bridge is reached 

 at the mouth of the canon, where a dark, aphanitic serpentine 

 replaces all the feldspathic rock. In the serpentine near the con- 

 tact are bodies of coarse hornblende gabbro, while narrow dikes of 

 serpentine intrude the feldspathic rock. Toward the southern edge 

 the serpentine becomes coarser, with prominent pyroxene crystals. 

 A little above the beach there appears in it, as shown in the sides 

 of a shallow ravine, a broken dike of gabbro. The serpentine near 

 it is greatly sheared, while the banding of the gabbro is apparently 

 diagonal to the course of the dike. 



From a point opposite the Lion's Head the serpentines extend 

 only a half mile southward before disappearing beneath the Miocene. 

 The different rock types which appear here are numerous and inter- 

 esting. Beneath the Head where the road comes nearest to the 

 cliffs there are some irregular dikes of diabase, which have broken 

 through the serpentine and caught up fragments of it as shown in 

 the annexed sketch, taken from a photograph (Fig. 6). The cliff 

 section cuts diagonally across the serpentine to its southern side. 

 Following along the shore, from the point where the large dike 

 occurs, there are many small ones to be seen. These split up into 



