Inverted Mass of U'p'per Cretaceous Strata. 105 



of this boring. Near Wendover, also, we failed to see the basement- 

 bed of the Chalk. Finally, a visit was paid to the supposed outlier 

 of Chalk at Billington, where the whole hill was found to consist 

 of Gault Clay. 



We conclude that to the south-east and south of Shenley Hill 

 the basal bed of the Chalk was laid down in an area of deeper water 

 than that in which the lenticles of gritty brachiopod-limestone 

 of bed D at Harris's Pit were formed. This type of deposit must 

 have had origin in shallower water, agitated by stronger currents. 

 We must assume that these conditions prevailed in an area which 

 included Shenley Hill, but did not extend to the present location 

 of the outcrop ; and that owing to the recession of the Chalk 

 escarpment and the denudation of the outliers all traces of the bed 

 in its normal position have been removed. 



4. Interpretation op the Evidence. 

 The main points of our interpretation have already been stated 

 in the foregoing description of the evidence, but it may be well to 

 give a brief account of the succession of events which we believe 

 to be deducible from the study of the sections at Shenley Hill. 

 Our reading of the evidence may be conveniently considered under 

 two headings : events during Cretaceous time and events during 

 and since Glacial time. 



A. Events during Cretaceous Time. 



There is no reason to doubt that deposits of Lower Gault age at 

 one time extended over the area now occupied by Shenley Hill. 



Passage-beds from Lower Greensand to Gault, of tardefurcata 

 age, are the highest strata at present exposed in this immediate 

 neighbourhood, underlying the Upper Gault. Later beds became 

 denuded away before the deposition of the Upper Gault. The Upper 

 Gault rests discordantly upon these passage-beds and upon the 

 underlying Lower Greensand, showing a thin basement-bed of 

 mixed composition containing much coarse material. This debris 

 includes relics of the destruction of the tardefurcata bed, in the 

 shape of nodules and fossils. The active denudation accompanying 

 the overlap resulted in the sweeping together of other remains 

 from older strata then exposed, as may be inferred from some of 

 the fossils obtained by the late Mr. Walker at Harris's Pit from 

 rock-masses which comprised much material from this Upper 

 Gault basement-bed. 



During the progress of the transgression, deeper-water conditions 

 soon supervened, as shown by the clays overlying the basement- 

 bed. These were relatively unfossiliferous at first, and included 

 a deposit of finely brecciated clay, apparently formed of materials 

 derived from the destruction of some older clay. This passes up- 

 wards into marly clay containing the fauna characteristic of Bed IX 

 at Folkestone. These relations indicate that the overlap probably 

 coincides in date with the break marked by Bed VIII at Folkestone, 



