Vol. 69.] BATHONIAN ROOKS OF THE OXFORD DISTRICT. 511 



On the Clypeus Grits and ^Northampton Sands lie a series of 

 beds, chiefly calcareous, forming the Chipping-Norton Limestone, 

 which have been exposed round Chipping Xorton, at Fawler, 

 Stonesfield, and in the Ardley section; and they probably also occur 

 ■under Oxford. This is followed by the Xeaaran Beds, predo- 

 minantly green clays containing wood as well as numerous dwarfed 

 ■oysters (Ostrea sowerhyi), and resembling the oyster-banks of the 

 Lower Fullonian near the Fleet, We3'tnouth. Upon these south 

 of the ridge were laid the Stonesfield-Slate beds, which probably 

 do not extend far east, north, or south of Stonesfield, nothing that 

 resembles them being recorded in any of the well-sections. 



The coarse oolitic nature of some of the beds, together with the 

 rolled fragments, suggests shallow water, and possibly the ridge 

 on the north continued to rise, thus cutting off mud from that 

 direction ; while proximity to land is suggested by the very large 

 percentage of angular quartz-grains and the perfect preservation 

 of delicate land-plants, as also by the abundance of insect-remains. 



The fact that the teeth of Pycnodont fishes are found embedded 

 in the rock in their natural relative positions shows that the 

 current cannot have been strong, although deposition must have been 

 rapid. Unfortunately, nothing is known of the Stonesfield Slates 

 in this district except from Stonesfield; and thus it is impossible to 

 trace their thinning-out, or to arrive at any conclusion as to where 

 the quartz came from. The beds seem to have been laid down in 

 shallow water not far from land, while the abundance of sand and 

 plant-remains suggests that the river which brought down the 

 material probably entered the sea not far off. 



The Rhynchonella-Inoceramus Beds (Beds 33-35 of the Ardiey 

 section) seem to have been deposited right over this ridge, and to 

 have been but slightly influenced by it. 



The thinning of the upper beds of the Great Oolite towards the 

 ■north-east is suggestive of a land-surface in that direction, an 

 inference which is further borne out by the apparent absence of 

 these beds north of Peterborough. 



Throughout the Great Oolite Period in the Oxford district, tho 

 beds were apparently deposited in water that was shallow, but still 

 •sufficiently deep to prevent them from accumulating under the 

 influence of shifting currents. 



The alternations of horizontal bedding with marked false bedding 

 in the Forest Marble seem to suggest violent oscillations of the 

 currents, possibly due to periodic changes in the level of the sea- 

 floor ; while the thinning of the Cornbrash towards the suggested 

 position of the ridge and its entire absence at Calvert, imply that, 

 for a time, the folding along the ridge reasserted itself. It should 

 be noticed that Mr. Buckman considers the absence of Cornbrash 

 in the Calvert boring to be due to the denudation of an anticlinal 

 fold previous to the faulting (see Q. J. G. S. vol. lxix, 1913, p. 341). 

 Personally, I consider that thinning-out of the Cornbrash (owing 

 to non-deposition on the axis of the fold), followed by subsequent 

 faulting, is a simpler explanation. 



