208 Tertiary. 



large portion of the series of ridges between the Gavilan, on the one 

 side, and the Monte Diablo Range on the other. At the first exposure, 

 about two miles beyond Tres Pinos, the stratified detritus forms a 

 steep bluff about 400 feet above the creek. The gravel is made up of 

 pebbles of granite, red and green jaspers, and silicious slate and other 

 metamorphic materials. At a point a tew miles below Bookers the 

 strata are worn into precipitous canons, with bare bluff banks or al- 

 most perpendicular walls, regularly stratified, and var^'ing in fineness 

 from a coarse gravel to fine sand, with here and there a thin band of 

 consolidated materials, the remainder entire)}^ in the original condition 

 in which it was deposited, as far as being held together by any cement 

 is concerned. The thickness of these deposits is enormous; one hill 

 was found to be 1,274 feet above the valley, and another 1,800 feet. 

 Both these hills are entirely made up of these unconsolidated materials. 

 This region gives one a most vivid idea of how recently geological 

 changes of magnitude have taken place in this part of the State, and 

 furnishes most impressive testimony to add to that obtained in other 

 places, in relation to the lateness of the geological epoch, during which 

 this portion of the chain was elevated. It would appear that the basin, 

 in which these strata were deposited, was drained of the water at suc- 

 cessive intervals, by the elevation of the basin itself, judging from the. 

 disturbed position of the strata it contains, and not by the gradual 

 wearing away of a barrier at its lower end. 



Prof. J. W. Dawson* described the Post-pliocene deposits in the 

 country around Cacouna and Riviere-du-Loup. The depressions be- 

 tween the ridges are occupied by these deposits resting upon the 

 Quebec Group of rocks. The oldest member of the deposit, is a tough 

 marine bowlder clay, its cement formed of gray or reddish mud, de- 

 rived from the waste of the shales of the Quebec Group, and the stones 

 and bowlders with which it is filled, partly derived from the harder 

 members of that Group, and partly from the Laurentian hills, on the 

 opposite or northern side of the I'iver, more than twenty miles distant. 

 The thickness of the bowlder clay is variable, but at He Vert'C, it forms 

 a terrace 50 feet in height. The bowlder clay at Cacouna, is a deep- 

 water deposit. Its most abundant shells are Leda trmicata, Nucida 

 tenuis^ and Tellina proxima, and these are imbedded in the clay with 

 the valves closed, and in as perfect condition as if the animals still in- 

 habited them. The bowlder clay is also fossiliferous at Murra}' bay, 

 St. Nicholas, and Cape Elizabeth. 



* Can. Nat. aud Geol. new ser., vol. ii. 



