1914.] NATURAL SCIENCES OF PHILADELPHIA. 3 



NOTES ON SOME IGNEOUS ROCKS AT OGUNQUIT, MAINE, AND PIGEON 



COVE, MASS. 



BY FRANK J. KEELEY. 



It would probably be difficult to find a more remarkable display of 

 igneous rocks than that along the coast of Maine south of Ogunquit. 

 Here for a couple of miles the shale, dipping nearly vertically, is 

 penetrated by almost innumerable dikes, varying from a few inches 

 to over fifty feet in thickness and showing great variety in color and 

 texture. 



The shale itself, as the result of these numerous intrusions, has 

 been metamorphosed and indurated until it is frequently as hard 

 as the igneous dikes. Fresh fractures are usually gray with faint 

 indications of differently constituted lamina, but on the weathered 

 surfaces the various layers assume different colors, often producing 

 a decidedly striped appearance resembling banded jasper, Ijecoming 

 particularly noticeable in the rounded pebbles occasionally lining 

 the shore. Numerous ramifying veins of white and yellow quartz 

 further characterize the shales, and the extremely rugged character 

 of the coast line, with several coves and an overhanging cliff exceeding 

 fifty feet in height, together with the almost unlimited variation 

 in color due to weathering of the shale and its igneous intrusives, has 

 resulted in this section becoming a favorite haunt of artists. From 

 early times it has likewise attracted the attention of geologists, and 

 in the first geological survey of Maine, published in 1838, Charles T. 

 Jackson gives considerable space to the description of the features 

 of this district and calls attention to the manner in which some of 

 the dikes intersect each other, as indicating that the igneous intru- 

 sions can be referred to at least three periods. 



During the past summer, with the view of becoming better 

 acquainted with the petrographical character of these rocks, I 

 collected a number of specimens, from which I have since prepared 

 sections and studied them microscopically. The locality receiving 

 particular attention was a small cove on Israel's Head, between the 

 mouth of the Ogunquit River and Lobster Point. Here a patch of 

 sand beach, used by the guests of the Ontio and Lookout Hotels 

 as a bathing place, is surrounded by the usual shales of the region, 



