The American Geologist Volume 25 (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: A NEW LOWER CAMBRIAN FAUNA FROM EASTERN MASSACHUSETTS. By Hexhv T. Blur, Cambridge, Muss. There is, at North Weymouth, Massachusetts, an area of red slates and impure limestones, which have been generally regarded as of Cambrian age. The assignment of these rocks to the Cambrian has been based largely upon lithological and structural evidence. The country round about is deeply covered with drift so that rock exposures are relatively few. For this reason the structural relations of the Weymouth beds to sediments of known age are not clear. The nearest sedimentary rocks, however, are the Middle Cambrian slates of Hay word's creek and Wyman's hill (map localities, 2). On the south the red slate series is in contact with granitic rocks. According to Crosby these granites are intrusive into the slates. As the granites of the vicinity of Boston are not known to be intrusive into rocks of age later than Cambrian, this, in itself, is a strong indication that these beds are of that age. The red, sandy slates of this area are much like the red slates of Lower Cambrian age in the vicinity of North Attle- boro.t both in lithological character, and in the extent to which they have been affected by secondary alteration. The limestone beds resemble portions of the Lower Cambrian limestone at Nahant. The series, as a whole, is quite unlike anything in the rocks of supposed Carboniferous age, which lie to the north. Thus the Cambrian age of the beds is supported by lithological evidence. Various observers have found traces of organic remains,particularly in the more calcareous portions of these rocks. It is, no doubt, true that certain obscure markings in the limestone are of organic origin. They much resemble the more obscure of the pteropod remains found at Nahant. So far as is kn...