Physical Features 15 



Kimeridge Clay, Boar's Hill, Horspath, Bagley. 

 Portland Beds (Sands and Clay), Shotover, Garsington. 

 Purbeck Beds (Limestone and Sand). 



Wealden, Shotover Sands with Clay and Ironstone, Garsington Hill. 

 Lower Greensand, Boar's Hill, Cumnor Hurst. 

 Gault, Clay, Cumnor Hurst, traces only. 

 To a much more recent age belong : 

 (C) Plateau Gravel, Boar's Hill, Bagley. 

 Valley Gravel, Oxford City. 

 Brick Earth and Alluvium. 



as the expression of the debris of the ' Glacial Epoch ', and the enormous 

 denudation following it, in the cutting of the present river-beds with their 

 gravel ' terraces ' and present alluvial and winter-flood area. 



In the restricted Oxford district, series (C) remain only as casual 

 deposits, with little reference to the subjacent primary construction ; though 

 significant from the local standpoint of surface-soils. Series (B) are left 

 residual on the surrounding hills, and are denuded to the clay over a greater 

 portion of the plain-area. Series (A) are not exposed within local range, 

 nearer than Islip, but may be found by boring ; just as Palaeozoic rocks of 

 the Coal Measures are indicated at a depth of possibly 1,000 ft. (said to be 

 1,200 ft. at Burford) ; though no coal or plant-remains have been so far 

 recorded. 



Plant-remains of higher beds may occur in estuarine deposits, as the 

 sites may have been connected with great continental river out-flow ; but, 

 also, have not been recorded. The outstanding feature of the whole story 

 is the prevalence in all older times of a warm climate, warm seas with coral- 

 reefs, gigantic estuarine formations implying forest-land, with the ground 

 rising or falling over long periods of elevation and depression, or wholly 

 changed locally with the lateral deflection of the estuarine deposits, following 

 presumably alterations in the formation of adjacent predominant land- 

 masses. 



The Corallian Series : Of the surface of the Oxford Clay beneath the 

 later deposits little is known ; the soft material shows little bedding, and it 

 is not clear whether it was elevated and in part denuded before again sinking 

 in the Coral Sea of the Middle Oolite. Probably it was thoroughly denuded, 

 hummocked, pitted, and dried, as tundra-like formation, giving shrinkage 

 cracks to be filled later with sand-debris, which may become utilized as 

 channels for subterranean streams. 



The next beds show mixtures of sands and stone, as Calcareous Grit 

 of Lower Corallian, ranging 20-60 ft. thick, with characteristic Corals, large 

 Ammonites, and Mollusca. These again express a sinking coast, with in- 

 shore deposits as sand-bank formations in clean water. In places the beds 

 become shelly, and at Headington a layer of pebbles (8 in. thick), with rolled 

 material and shells, indicates an ancient beach ; so that land was exposed 

 close at hand. In other parts there is no appreciable break in the sea- 

 deposits. The most characteristic exposure is the deep bed of sand in the 

 railway-cutting near Littlemore Station, 8 ft. thick, with massive septaria 

 concretions, excavated for nests by sand-martins, and utilized for foundry- 

 castings by the railway company. Sandy soils, cultivated as arable land, 

 are characteristic of higher ground at 300 ft. at Hill Top, Headington, and 

 also at Cowley, Littlemore ; but in these the lime is commonly deficient, 

 having been leached out. The woodland area of Tubney is on soil of the 

 same nature. 



Later deposits of Coral Rag (Upper Corallian) do not rest conformably 

 on the preceding, nor necessarily conformably among themselves ; the 

 boundary between the two series may be ill-defined. Corals were particu- 



