4 Weed and Pirsson — Hightvood Mts. Laccoliths. 



valley floor ; it is not an even regular sheet of detritus but is 

 carved down at rather regular intervals by rain-washed gulches 

 and raised at the points between by a more abundant supply 

 of materials, so that it presents the appearance of a rude series 

 of intersecting half cones or steep fans resting against the cliff 

 wall of the valley. The surface of these talus cones is gen- 

 erally grassed over, giving a rather smooth appearance, but 

 they are elsewhere covered with large blocks of rock from the 





Fig. 2. Cliff wall of Shonkia Sag- laccolith. Dissecting gulch to left over 

 standing figure. 



great columns of the cliff above, which have broken down and 

 whose pieces have rolled down the slopes. At the apices of 

 the cones the material reaches nearly or up to the foot of the 

 columns, and the sandstones of the laccolith floor are in places 

 nearly concealed, but in the intervening gulches a considerable 

 thickness of them is seen. On top of the laccolith are seen 

 resting the Cretaceous sandstones into which it is intruded in 

 horizontal, unbroken position. Their thickness is variable as 

 from each end of the cliff-wall it gradually diminishes until 

 about the middle, where the laccolith is cut by the intersecting 

 gulch, they disappear, leaving, especially on the eastern side, a 

 portion of the top of the laccolith bared. On the opposite side 

 of the gulch, however, a considerable thickness of them is seen 

 resting on top of the columns of igneous rock. 



