CHAPTEE VIII. 



TRIASSIC PERIOD. 



1. Stratigraphical Evidence. 



THE lie of the Triassic rocks is different from that of 

 any of the Palaeozoic systems. In England their out- 

 crop is nearly continuous from the southern to the northern 

 coasts ; in Gloucestershire it is very narrow, but it broadens 

 out over the Midland counties, and stretches northward 

 over tracts of considerable width on either side of the 

 Pennine range. The one tract meets the sea in Durham, 

 the other in Lancashire, but both must originally have ex- 

 tended much farther north, for detached areas of Trias 

 occur in Cumberland and Dumfries, also in the north-east 

 of Ireland, in the Inner Hebrides, and in the north-east of 

 Scotland on the Moray Firth. 



The Triassic strata are everywhere unconformable to the 

 rocks on which they rest ; they extend far and wide beyond 

 the edges of the Dyassic beds, and run up many of our 

 wider valleys as if the principal hill-ranges of England 

 were then already in existence, as indeed they doubtless 

 were. The Coal-measures and older Palaeozoic rocks had 

 been bent into troughs, basins, and ridges, and had suffered 

 enormously from erosion and detrition before the Triassic 

 beds were deposited upon them, so that in most parts of 

 the country these beds rest upon a surface of erosion which 

 had been previously formed across the tilted edges of the 

 Palaeozoic rocks. 



