Portsmouth Basin, Me. and N. H. 143 



granite which outcrops less than 2000 feet distant from 

 the exposures of Gonic schist. The formation has, in 

 general, a gentle northwesterly dip, but departures from 

 the normal dip and strike are abundant. The thickness 

 of the formation is unknown. 



Berwick Gneiss. — This formation is typically devel- 

 oped at the falls of the Salmon Falls River in Berwick, 

 Maine. Dynamic and static metamorphism have entirely 

 obscured the original texture and composition of the 

 rocks which now consist of thin bands of mica schist 

 alternating with well banded paragneiss. The formation 

 appears to have been derived from an argillaceous sand- 

 stone or a graywacke. Because of metamorphism some 

 of the bands are now characterized by giaucophane. 

 Associated with the amphibole are feldspar, quartz, 

 biotite, chlorite, pyrite, and titanite. Quartz veins vary- 

 ing in width from mere stringers up to masses two feet 

 in thickness frequently cut the formation. Although 

 some of the veins are developed parallel to the foliation 

 of the gneiss, the general tendency is for them to occur 

 in cross-cutting relationships. The thickness could not 

 be determined. Departures from the general north- 

 westerly dip of the foliation, which in rather limited 

 areas may undergo wide variations, suggest that the 

 formation is compressed into several tight folds which 

 have been overturned to the southeast. Little can be 

 said of the position of this formation in relation to its 

 neighbors. 



Rye Gneiss. — The Rye gneiss has been so called from 

 the typical exposures that occur along the Rye coast of 

 New Hampshire. The most northerly outcrops of rock 

 belonging to this formation are found on Gerrish's 

 Island, Kittery, Maine. From this locality the rocks 

 have been traced south and southwest into Portsmouth, 

 Rye, North Hampton and Hampton, New Hampshire. 

 At Hampton Falls the country becomes drift-covered 

 and for a space of six miles westward across the towns 

 of Kensington and East Kensington no outcrops are to 

 be seen. In the town of Kingston gneisses outcrop at 

 Rock Rimmon Hill. 



At the type-locality the gneiss is well banded, consist- 

 ing of alternations of light feldspathic layers, which 

 become pegmatitic with dark-fine biotite-rich bands that 



A.m. Jour. Sci.— Fifth Series, Vol. IV, No. 20.— August, 1922. 

 10 



