﻿4:6 JV. S. Shaler — Geology of Cobscook Bay District, Me. 



portion of the old sea, in which the fossils of the Cobscook sec- 

 tion lived, was on the northeastern face of the old Appalachian 

 Island, and thus by their position were cut off from the warm 

 current which flowed from the southwest against the ancient 

 shores of Central New York. This same life-giving current of 

 warm water may have found its way along the western shores 

 of the Appalachian island to the region of the St. Lawrence. 



The action of the mountain-building forces on these sedi- 

 mentary deposits of Cobscook Bay has been great but ex- 

 tremely peculiar in its effects. Everywhere within the field of 

 my enquiry there are evidences of much pressure, except per- 

 haps in the southern part of Whiting or Orange Bay ; that the 

 rocks have been subjected to strong compressive action, is 

 shown by the general distortion of the fossils. This distortion 

 is very general ; it is doubtful if in any part of the basin the 

 rocks have entirely escaped it. The amount of the distortion 

 varies from an elongation which does not exceed one-twelfth 

 of the diameter to a very extreme condition, where it is as 

 much as one-half the diameter of the distorted object, i. e. 

 where a circle of an inch in diameter lying in the plane of the 

 movement would be changed to an ellipse having a length of 

 an inch and a half. Possibly one of the results of this com- 

 pression is the singularly close adhesion of the fossils and the 

 matrix. In the many thousand specimens of fossils observed, 

 none were found fairly separated from the rock in which they 

 were preserved. The pressure seems to have welded the walls 

 of the fossil to the matrix in a very perfect manner. 



10. 



Shales and trap south end of Shakford Head. 

 A, overlying trap. B, dark colored shales. C, intrusive trap. 



The most curious feature in the attitudes of these rocks is y 

 that few of their dislocations take the form of folds, only three 

 examples of folding meet the eye, in the hundred and fifty 

 miles of cliffs inspected. (These exceptional folds are shown 

 in figs. 10, 11 and 12.) In nearly all cases the dislocations were 

 effected by a system of principal faults extending in a general 

 north-northeast and south-southwest direction, cut more or less 

 nearly at right angles by less important transverse fractures. 



So far none of these fractures, except in a few unimportant 

 cases, have been observed in the form of simple faults; they 

 seem in nearly all cases to have been made the pathway for 

 extrusions of igneous matter thrown out at the time when the 



