TIIK TRIASSIC SVSTKM 359 



Thougli overlapped by the Keuper marls in the valley of the 

 Trent east and south-east of Derby, the Banter is probably con- 

 tinuous as a narrow strip beneath them, since it recurs near 

 Nottingham and extends northward for a considerable distance. 

 Tin- Upper Mottled sandstone, however, is absent throughout this 

 eastern area. Near Nottingham the Lower sandstone has the 

 usual bright-red and yellow tints, but is there only 25 to 30 feet 

 thk-k ; northward, it thickens to about 100 feet at Mansfield. As 

 in the western area, it seems to occupy a tract of limited width, 

 and to be overlapped eastward by the Pebble Beds, which are the 

 lowest recognisable Triassic deposits in deep borings at South 

 Scarle near Newark, and at Haxey in North Lines. 



The Pebble Beds form the rock on which Nottingham Castle 

 stands, where they are about 200 feet thick, and consist of a coarse 

 yellowish sandstone full of quartzite pebbles. They range north- 

 ward through Sherwood Forest by Worksop, Tickhill, and 

 Doncaster. Along this tract the thickness of the Bunter is about 

 450 feet, and in a boring near Selby it is 620 feet ; but beyond 

 this place the pebbles disappear, and the whole Bunter division is 

 supposed to thin out near Knaresborough, though it may extend 

 en-tward underground beneath South Yorkshire. 



There is a similar disappearance of the pebbles on the western 

 side of the Pennine Anticline in North Lancashire, but the 

 combined Bunter sandstones persist and are about 1000 feet thick 

 near Preston and Garstang. They recur in the promontory of 

 Furness on the western side of Morecambe Bay, and extend along 

 the western side of Cumberland to St. Bees (see map, Fig. 39, 

 p. 1 30), where they are known as the St. Bees' sandstone. 



This St. Bees' sandstone is the sole representative of the Bunter 

 in the Carlisle basin, and along the valley of the Eden, unless the 

 underlying gypsiferous marls are included in the Trias (see p. 337). 

 These latter vary in thickness from 100 to 300 feet, and pass up 

 into the overlying sandstone by intercalations of sandstones and 

 marls. The St. Bees' sandstone is sometimes variegated in the 

 lower part, but most of it is of a dull, uniform, brick-red colour. 

 It contains some bands of pebbly sandstone, and its thickness is 

 estimated at over 1000 feet.- 



A similar sandstone has been found by borings in the northern 

 part of the Isle of Man 8 ; and again in Ireland, near Belfast, where 

 the Keuper is underlain by about 800 feet of soft red and yellow 

 sandstones with some beds of grey and buff shale. 



Rocks of Triassic age occur again in the Isle of Arran, occupying 

 much of the central and southern part of that island. The lower 

 portion of them is coloured as "Lower Trias" on the recent map 



