GEOLOGY 



northern Europe similar to that of central Asia at the present day. 

 The Triassic deposits were then laid down, the Bunter apparently in 

 desert lakes subject to desiccation, into which periodical streams swept 

 sand and pebbles from the neighbouring uplands ; the Keuper in a 

 much more extensive lake or inland sea, into which the ocean at last 

 broke and introduced the marine fauna of the Rha;tic. 



In Warwickshire the following subdivisions of the Triassic rocks 

 occur : 



Rhaetic 



j,. f Keuper Marls with Upper Keuper Sandstone. 



I Lower Keuper Sandstone. 



(Upper Sandstone. 

 Pebble Beds. 

 (Lower Sandstone ?) 



The Lower Bunter Sandstone which to the west of our district is 

 so well developed in the Severn valley dies out when followed thence to 

 the east, and has generally been thought to be absent east of the South 

 Staffordshire coalfield ; but in 1890 Mr. J. Landon l called attention to 

 the occurrence of beds of yellow sandstone below the Pebble Beds near 

 Barr Beacon, and concluded that the Lower Bunter Sandstone is there 

 present in force. 



The Pebble Beds are well developed at Sutton Park and west of 

 Birmingham, while a small area occurs to the east of Polesworth. The 

 rocks consist of pebbly red coarse sandstone and impersistent beds of 

 pebbles. These are well rounded by water action, and are chiefly of 

 yellow, brown, and liver-coloured quartzite, white quartz, and grey 

 crinoidal Carboniferous limestone and chert. Where two or more 

 pebbles are in contact they have generally pressed into each other and 

 produced a characteristic crush-mark. The source and mode of origin 

 of these pebbles is still a matter of dispute, but the opinion of those 

 most familiar with them is that they were derived from rocky ridges of 

 high land which stood as islands in or formed the margins of the Triassic 

 lake basins. Of parts of these old ridges we see the worn-down relics 

 in the Wrekin and Caradoc districts of Shropshire, the Malvern-Abberley 

 and Lickey ranges in Worcestershire, and the Nuneaton and Charnwood 

 hills in Warwickshire and Leicestershire. Buckland long ago recognized 

 that the Bunter pebbles are in many instances agreeable in substance 

 with the quartz rock of the Lickey, and was of opinion that an exten- 

 sive outcrop of this latter rock was the source of much of the Bunter 

 material. 



Exposures of the Bunter pebble beds may be seen in Sutton Park, 

 notably in a gravel pit near Blackroot Pool. They are to be seen also 

 on the east of the Warwickshire coalfield in a railway cutting east of 

 Polesworth. The rock being more resistent to the weather than those 

 above and below, generally forms a well-marked escarpment, as at 

 Barr Beacon ; the soil is generally poor and exceedingly pebbly, and is 



1 Proc. Birm. Phil. Soc. vii. 113. 

 15 



