T11K IM.KISTOCKNK SKKIKS 623 



3. Yorkshire and Lincolnshire 



\Vheit this northern ice reached the Cleveland Hills in Ka>t 

 Yorkshire the mass of it was diverted into the Vale of York and, 

 tvinl'oivetl liy contributions from the west, it spread out a confused 

 mass of clays and gravels over the Triassic plain as far south as 

 York and Escriok, where it has left some remarkable terminal 

 moraine?-. Another lobe of this ice passed down the eastern side 

 of tin- Cleveland Hills and along the coast to Flamborough Head. 



South of York there is a long and fairly broad area which is 

 almost free of boulder-clay, a fact which is not yet fully understood, 

 for there art- boulder-clays to the west of it about Wakefield, 

 Barnsley, and Doncaster, and one would have expected these to 

 extend into the plains west of the river Trent. 



Boulder-clays occur in East Yorkshire near the coast and over 

 the greater part of Lincolnshire, but they are of two different 

 types ; those found on the eastern side of the Chalk Wolds being 

 reddish and purple clays with intercalated marine deposits, while 

 those on the western side are grey and more or less chalky clays. 



The Chalky Boulder-clay covers the central parts of Lincolnshire, 

 spreading over the Jurassic Clays east of Lincoln by Tattershall, 

 Horncastle, Wragby, and Market Rasen ; and the increase in the 

 amount of chalky matter in the direction of the Chalk Wolds is 

 particularly noticeable, till near these hills it becomes a stony 

 Chalk-marl, and has been burnt for lime in some places. There is, 

 however, very little of it on the Wolds themselves, though its 

 occurrence at Kelstern, near Louth, proves that it originally spread 

 over all levels below 400 feet. 4 



It occurs also in South Lincolnshire, not only on the border of 

 the Fenland district, but on the higher ground to the west, and 

 appears to have formed a continuous mantle which covered even 

 the summit ridges of the Jurassic escarpment and passed southward 

 through Rutland, Northampton, and Huntingdon. The boulder- 

 clay of the high ground between Stamford and Grantham i> 

 remarkable for containing huge masses of Lias Marlstone and 

 Lincolnshire Limestone, which have been carried many miles from 

 the spots whence they were quarried by the ice. These blocks 

 appear to have come from the west and north-west. Carboniferous 

 rocks came from the north-west, and Chalk from the north-east, 

 so that several ice-currents seem to have met in this area. 



The boulder-clays of the eastern type occupy the area in 

 Yorkshire known as Holderness, and underlie the whole of the 

 eastern lowland of Lincolnshire. In both cases they and the 

 associated sands and gravels are banked up against an ancient 



