l60 OSCAR H. HERS HEY 



formation, must have been many times wider than the present 

 valley. Yet I think the old valley followed this course, but has 

 been carried up so high by uplift and deformation as to have 

 been completely destroyed by erosion. 



After passing the gabbro, the Trinity valley is wider again, 

 and low ridges near the river with the higher mountain ridges 

 some considerable distance back, suggest that the present small 

 valley is trenched beneath an older larger valley. I would not 

 be certain of the value of the evidence, had not Mr. Diller dis- 

 covered one of the Neocene remnants in this basin. ^ It contains 

 lignite and is otherwise similar to the Neocene deposits of Hay 

 Fork and Hyampom valleys. A short distance below Big Bar 

 the river enters a veritable gorge which it follows for about thirty 

 miles, nearly to Hawkin's Bar, and I am practically certain that 

 this is not the old course of the stream. The gorge widens 

 where it crosses the Paleozoic slates, but where it is trenched in 

 gabbro and allied Plutonic rocks, as it is through most of its 

 course, it is extremely narrow. In many places the slopes rise 

 directly from the river's edge on both sides and continue up as 

 steeply as the loose material will lie to the tops of the neighbor- 

 ing mountains, probably 3,000 feet above the river. Rock preci- 

 pices are common, and often the trail has to climb hundreds of 

 feet above the river to pass a rocky point. There are no shoulders 

 on the slopes of this valley, and nothing to indicate complexity 

 in its history. It is a simple Pleistocene valley of the gulch 

 type 3,000 feet in depth. 



I have some confidence that the Neocene valley followed the 

 present course of the river as far as Big Bar, but what was its 

 course beyond that point is a problem. It is probable that it 

 went more directly west for a few miles than does the present 

 river beyond this point and then turned to the southwest ; there 

 is some evidence of this, but it has not been studied in detail. 

 On the line between Big Bar and Hyampom valley there is a 

 depression among the mountain summits which may mark the 

 line of this old valley. Nearly midway is Corral valley, which is 

 described as a flat-bottomed, basin-like depression about a mile 



^Fourteenth Annual Report, U. S. Geol. Surv., Plate XLV, and p. 419. 



