158 GEOLOGICAL AND 



some hundreds of feet ; but the great amount of denuda- 

 tion from various causes, particularly through the agency 

 of the ice sheet which covered this region during the 

 glacial period, together with the frequent faulting of the 

 strata, makes it nearly impossible to give the exact depth 

 of these beds. They have been distorted and crumpled 

 into anticlinal and synclinal folds accompanied by, and 

 perhaps causally connected with, the intrusion of the gran- 

 ite, diorite, syenite and felsite eruptive rocks. The 

 elaeolite-syenite of Naugus Head, on the Marblehead shore, 

 and at Woodbury's point, on the Beverly shore, are seen 

 to cut these sediments and, being also later cut bygabbros 

 and quartz felsites, the contact metamorphism is so com- 

 plete that the old crystalline sediments are now found as 

 hornblende and mica schists. The diorite areas of Mar- 

 blehead proper, Salem, Danvers and Ipswich often contain 

 fragments and masses of these metamorphosed crystalline 

 sediments. One large area in Danvers and the adjoining 

 towns occupies almost the entire valley from Locustdale, 

 West Peabody, through Danvers Centre to Putnamville 

 and Wenham. The trend is E. 40 N. to S. W. At Lo- 

 custdale it is seen as a hornblende schist interstratified 

 with schistose argillite shales. At Danvers Centre these 

 beds are a true gneiss and in Putnamville and Wenham 

 the area is all amphibolite schists. Mining shafts and 

 trenches for water mains have opened these rock masses 

 in several places showing the actual contact. In digging 

 a well at Tapleyville, Danvers, on the bank of Tapley's 

 brook a bed of typical argillaceous shale was revealed. 

 This brook occupies the valley between the granite areas 

 of Peabody on the south and the main mass of the diorite 

 on the west and north and the contact of these eruptive 

 rocks with the crystalline sediments is probably so distant 

 that the metamorphism in them is less complete. In the 



