1 8 STRATIGRAPHICAL GEOLOGY. 



A formation, closely allied to this calcareo-Pxiicaceous Gaspe series, has 

 been termed the Coos group, in New Hampshire. It consists of mica 

 schists abounding in staurolite, hornblende rocks, and quartzite. Its area 

 lies along the east border of Connecticut river, and it may be 5000 or 

 6000 feet thick. In the subsequent portions of this volume, the relations 

 of this group will be fully discussed. It may not be confined to the Con- 

 necticut valley, as there are rocks of similar character in western Maine 

 and western New Brunswick. 



At Port Daniel, on the St. Lawrence gulf, and at Squam lake, in north- 

 ern Maine, are limestones and shales, abundantly fossiliferous. over 1000 

 feet thick, referable to the Niagara group, or, possibly, a little higher. 



The developments of the Lower Helderberg series in the east are very 

 great, far exceeding anything of the same age in other parts of the coun- 

 try. In the Connecticut valley these rocks occur in several places, suffi- 

 cient to indicate the former submergence of this area beneath the ocean. 

 These outcrops will be fully treated of in succeeding chapters. I need 

 now only to say that the Connecticut valley Helderberg series consists of 

 several thousand feet thickness of quartzites, limestones, slates, conglom- 

 erates, sandstones, flags, and probably hornblende schists. In northern 

 Maine the limestones are mostly wanting, the rocks being slaty. There 

 is some limestone in Eustis plantation, and near Masardis and Ashland. 

 The slates border and are interstratified with the Gaspe series. Near 

 Eastport, in Perry, Pembroke, Cutler, Lubec, etc., the sandy slates and 

 grits of this age are very abundant, and well filled with fossils. They 

 cross Passamaquoddy bay into New Brunswick, appearing in several local- 

 ities, particularly in a long, narrow strip crossing the St. John's river 

 above the city of St. John. Bailey and Matthew's section of this range 

 gives a thickness of about 5700 feet to the series. 



Similar rocks occur in Nova Scotia. A typical locality is at Arisaig, 

 which has been considerably explored by Dr. J. W, Dawson and Rev. Dr. 

 Honeyman. These and others represent in Nova Scotia the greater part 

 of the Upper Silurian of New York and England, possibly as low as the 

 Medina, certainly the Clinton group. 



This review of the Cambrian and Silurian strata of the St. Lawrence 

 valley and the hilly region to the east, will enable us to compare them 

 together, i. The former are mainly sea-beaches and oceanic calcareous 



