192 



DR. C. T. TRECHMANST OX IXTERGLACIAL [vol. lxXV, 



had abandoned the coastal region and had been diverted down the 

 Yale of York. 



A fragment of earlier Boulder- Clay has thus been preserved in 

 the Preglacial depression at Hartlepool. It is clear that a corre- 

 sponding lobe was projected at about the same time through the 

 Tyne Gap, and reached the coastal region. I know of no lower 

 clays having been preserved in hollows (or by any other means) in 

 the region of the mouth of the Tyne, such as might contain only 

 western erratics corresponding with the lower clay at Hartlepool. 

 South of a certain point in Northumberland, however, the Drift 

 of the latest ice-stream that flowed southwards past the Cheviots is 

 very rich in Lake-District rocks, which in the Durham coastal Drifts 

 are often nearly or quite as plentiful as the Cheviot erratics. 



It is clear that, unless there are previously existing hollows lying 

 in the way ready to receive samples of the earlier Drifts, the 

 material tends to become incorporated and merged in that derived 

 from the next ice- sheet that flowed over it. especially if the ice- sheet 

 passed over a rather elevated area, 

 stone region of Eastern Durham. 



such as the Magnesian Lime- 



VIII. Sequence of Episodes in the Glacial History 

 oe East Durham. 



The Glacial beds of the Durham coastal area prove to be of so 

 varied and interesting a character that it is possible, tentatively 

 and with the aid of evidence of the Glacial deposits of the adjacent 

 counties, to construct a fairly-accurate mental picture of the 

 sequence of events which caused their deposition. 



I have also added a correlation with the Glacial events of the 

 Continent, though it must be understood that this is of a suggestive 

 rather than of an assertive nature. 



Submerged peat-bed at Hartlepool and Poker (near \ 

 Sunderland), resting on the Cheviot Drift. J 



Postglacial gorges cut. "^ 



Finely-laminated clays enclosing rafted erratics, distri- 

 buted over a limited area around the mouths of the Tees 

 and Tyne, probably deposited in lakes held up by a portion 

 of the Cheviot ice- sheet still occupying the North Sea. 



Dry watercourse at Ferryhill, eroded by water held up by 

 ice, probably occupying the Tees valley and draining into 

 the watershed of the Wear. 



Drumlins and gravel-spreads in various parts of the area. 



Gravelly moraine -heaps deposited on the retreat of the 

 Cheviot ice and the ice coming through the Tyne Gap. The 

 group that I called the Sheraton Kaims is aligned roughly 

 north and south, and east and west. Those aligned north 

 and south mark roughly the line of demarcation between 

 the two ice-streams, and indicate the western limit of the 

 region where material from the Cheviots is plentiful. 



The gravels associated with the Cheviot Drift contain 

 fragments of marine shells, flints, etc. torn up from a shore- 

 line. 



Neolithic 



? 



Eetreat 

 Phase. 



