420 CARTER : GLACIATION OF DON AND DEARNE VALLEYS. 
3. — Yellow marl . . . , . . . . 5 feet. 
4. — Magnesian Limestone 
5. — Coal Measure sandstone and shale 
Still further north the escarpment of the Magnesian Lime- 
stone from Went Bridge to Pontefract and Glass Houghton 
shows extensive denudation, and is covered with pebbles of 
Carboniferous sandstone. 
There is another series of gravel and clay beds in this area 
which seem to agree together and to be parallel with the lower 
clay of Staincross (Plate LX.). One mile west of Darfield* there 
is a patch of gravel containing pebbles of Carboniferous sand- 
stone, quartzite, chert, and Magnesian Limestone. At Wombwell, 
near the 310-foot contour, there is an angular block of ganister. 
At Park Hill, near Wombwell, in the valley of the Dearne, is a 
gravel with large boulders of Carboniferous sandstone. At 
Barbot Hill, near Parkgate, is a clay with quartz pebbles, sand- 
stone. Carboniferous Limestone, Oolitic rocks, and Magnesian 
Limestone, covering the hill at 200 feet above O.D. At Sit well 
Vale, south of Rotherham, is a patch of clay filling up the end 
of a little valley, with Carboniferous sandstone boulders. At 
Hooton Roberts there are four patches of gravel resting on Coal 
Measures from 200 feet to 250 feet above O.D., containing 
Carboniferous sandstone, quartz, quartzite. and black chert. 
I have ventured to link these deposits together as having 
a common origin, which I attribute to an earlier glacier bringing 
mostly Carboniferous rocks, and agreeing with the Pennine ice 
of the Vale of York. The rare pieces of oolite may be due to 
material carried by icebergs, and caught up by the glacier in 
passing, and the predominant Coal iVIeasure material and the 
Magnesian Limestone are probably due to the denudation of 
the Pontefract district as the glacier passed over the Aire. These 
patches appear to be the mere remnants of much more widely 
spread deposits, and I attribute the perfect preservation of 
the three boulder-clay deposits at Staincross. Balby. and Hampole 
to the fact that in the case of each of them the glacial detritus 
has filled up a little pre-Glacial valley which on the resumption 
* Memoir on the Yorkshire Coalfield, p. 777. 
