FORM AND RELATION OF THE AREA 393 



330 to 420 meters above the sea. This part is largely covered with allu- 

 vial deposits. Surrounding this and generally concentric with the outline 

 of the area is the " Ridge," which reaches an elevation of 650 meters on 

 the west, 590 on the south, and 570 on the east. On the north it is 

 lower, being cut through by Cove creek. This ridge slopes down, occa- 

 sionally steeply, to the surrounding shales. The cove is drained by 

 Cove creek, which, catting through at the north, flows through the west- 

 ern part of the basin, cuts the ridge again at the southwest, in a narrow 

 valley, and goes off to the south. A small stream, known as Stone 

 Quarry creek, flows south in the outer part of the igneous area. 



Outside of the main igneous area occurrences of igneous rock of any 

 size are rare. There is a small patch of " basic eleolite syenite," which 

 lies just northeast of the main mass. A large number of dikes, mostly 

 small, are found in the surrounding shales and novaculites, as well as 

 in the main area. These have in general, but by no means always, a 

 more or less east-and-west trend. The rocks immediately about the 

 mass are shales and sandstones, while beyond these are the novaculite 

 ridges. 



Relation to surrounding shales. — These shales are very much folded, the 

 disturbance having taken place prior to the igneous intrusion. The 

 conditions therefore are not favorable for the observation of one of the 

 most characteristic features of a laccolith, namely, the upbending of the 

 surrounding strata on all sides by the magma. Notwithstanding this, 

 evidences of such upturning have been observed at several places, both 

 by Williams and myself. The best of these is the contact shown at 

 Diamond Jo quarry, described and figured by Williams.* This, by the 

 way, is still preserved. The shales here have been bent upward, dip- 

 ping about 55 degrees to the south, and are highly metamorphosed at 

 the contact. 



Other places in which similar relations have been observed by Wil- 

 liams or myself are near the mouth of Neusch's gully, another point a 

 little farther up Cove creek, near J. M. Henry number 5, and near D. R. 

 Rutherford number 2. At none of these, however, is the bending up of 

 the shales as well shown as at Diamond Jo quarry, though at each the 

 dip of the upturned strata is in a general way away from the igneous 

 complex — that is, quaquaversal. 



The surrounding shales are highly metamorphosed at or near the con- 

 tact where this is visible, as has been described by Williams. Similarly 

 the sandstone near W. W. Brown, at the extreme west end of the area, 

 is reddened, baked, and much shattered. 



* Williams : Op. cit., p. 298, pi. 18. 



