﻿44 JV. & S holer — Geology of Cobscook Bay District, Me. 



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clearly less resisting to the glacial action than those of igneous 

 origin; they are not only softer, but their thin-bedded and 

 much-jointed condition caused them to break 

 up under the action of the ice or waves 

 much more readily than the compact igneous 

 deposits. 



The greater part of these sedimentary rocks 

 of the Cobscook series consist of very fine 

 grained sandstones, and dark blue and black- 

 ■ ish shales, which at certain points contain a 

 ijlf: "« J good deal of lime, but rarely are pure lime- 

 :::;H oH stones. At only two or three points are 

 Hi:tHa' m & these beds sufficiently calcareous to be used 

 *!§::: ^ ^ n making commercial lime, and even at the 

 '«*§ S'f best of these points, as in the beds exposed 

 : ^,-g in Eeynolds Cove, an effort to use them 

 §'~ for lime failed, for the reason that in the 

 _J greater part of the rock there was so much 

 o a silex that it was apt to melt in the kiln. 

 "I g The siliceous element in the rock is larger 

 , m © than in any equally extensive section of 

 g p these horizons known to me in this coun- 

 - w try, though at few points does it consist 

 g a of pebbly matter ; the only important ex- 

 S'8 ception being in certain conglomerates of a 

 |-§ reddish color, apparently belonging to about 

 j|s the horizon of the Medina sandstone. These 

 o £» beds have so far been found only in or near 

 ^J the basin known as Mine Cove, an inlet near 

 r| £ the head of great South Bay of Cobscook 

 "| m - Bay. At many other points there are strata 

 'g'g which contain small scattered fragments of 

 J2,£ hypogene rocks, presumably volcanic in their 

 g« origin. These are particularly well shown 

 *o 2 i n the extensive limestone section exposed 

 » ™ at the head of Denbo Bay, the shallow fjord 

 '■g^ lying to the west of Leighton's Point. 

 ;:f o |<T The fossiliferous rocks of the Cobscook 

 |||18 l)^*" district are mostly thin-bedded, even the im- 

 5 pure limestones, though sometimes appear- 

 ing in massive form, being on the whole 

 distinctly divided into strata of no great 

 thickness. The general absence of detrital 

 material derived from the land, as well as 

 the nature of the organic contents of these 

 rocks of the Cobscook series, favor the hypothesis that they 

 were formed at some distance from the shore. It is generally 



