112 DEPARTMENT OF THE NAVAL SERVICE 
7 GEORGE V, A. 1917 
referred to the Upper Devonian. From the fact that they are almost continuously 
exposed from a point not far above Brandy cove to the hghthouse in Passamaquoddy 
bay, and are tilted at a considerable angle, it is evident that they must possess con- 
siderable thickness, but they are undoubtedly faulted in places, and hence no definite 
or reliable estimate of that thickness can be made. At many points, especially towards 
their base, they are penetrated by intrusive voleanic rocks, dolerite, diabase and 
amygdaloid, occurring apparently both as dykes and sills. They are well exposed at 
the Biological Station, which is pertly built upon one of them, and another has no 
doubt determined the promontory of Joes point, as well as the “ Bar,” connecting the 
mainland with Minister’s or Van Horne’s island. They are, of course, of later origin 
than the rocks which they penetrate. 
As regards the relation of the geology to the present topography of the region, it 
may, in conclusion be said, that the position and general outline of Passamquoddy 
bay were determined by disturbance and upheavals antedating the opening of the 
Cambrian era, fixing at least the northern, southern, and eastern sides of the basin 
by ridges, such as the Boecabee hills on the north of those of Deer island and Campo 
Bello on the south, both converging eastwardly to and beyond St. George. 
Of the conditions characterizing the Cambrian era itself we know nothing. In 
the Silurian age the basin was evidently in existence and occupied by shallow waters 
in which accumulated sand and mud beds, now more or less filled with marine fossils, 
over which were spread the rhyolites, porphyries and ash beds, which now constitute 
such eminences as Chamcook mountain, Mt. Blair and Pendleton’s island. In the 
Devonian age were produced the granitic extrusions which now form the western side 
of the basin from Devil’s Head to the lower part of Robbinston; and somewhat later 
the coarse rocks of the Perry group, marking at this time considerable subsidences, and 
the operation of powerful marine currents, as well as the extrusion of igneous masses. 
No rocks of later age are met with; but evidences of extensive glaciation during the 
Quaternary era abound. The estuarine portion of the St. Croix river and the channels 
at either end of Deer island were probably fixed at this time. 
