324 MR. A. J. JUKES-BK0WXE OX L^ U 8'- 1 9°4' 



on the Halclon Hills, we may reasonably conclude that the Eocene 

 deposits did cover this central area. There is indeed some positive 

 evidence, as will be mentioned on a future page, that this was the 

 case. 



As no patches of Chalk remain on the Blackdown or the llaldou 

 Hills, and as the Eocene gravels there rest directly upon the 

 Selbornian Sands, it is evident that most, if not all, of the Chalk 

 had been removed from this central area during Lower Eocene 

 time ; so that the Eocene deposits were laid clown partly on the 

 Greensand and partly on the older rocks to the westward, the 

 flints remaining from the destruction of the Chalk being spread out 

 as a basement-gravel below the Bovey and Bournemouth Beds. 



Here we are confronted with the difficulty created by the curious 

 position of the Bovey Beds. This position does not seem to be 

 explicable by faults. The beds have apparently been bent down 

 into a deep syncline by post-Eocene movements; and as the gravels 

 can be traced from the basin up the slopes towards the Haldon 

 Hills, it is evident, from the map of the Geological Survey, that they 

 here passed across the outcrops of the Selbornian and Permian on to 

 the complex of Carboniferous and Devonian rocks which borders the 

 granite of Dartmoor. 



This transgression appears to have taken place within so short 

 a space, that we can only suppose that the surface which is now a 

 downward slope was then either a level floor or had a slight upward 

 slope towards the west. Thus the space between the present 

 termination of the Eocene gravel on Great Haldon and the similar 

 gravel west of Ideford is only a mile, yet in this short distance the 

 gravel has passed across the Greensand and the Permian, descending 

 through a space of about 300 feet. It is the same on the western 

 side of Little Haldon, where the boundary of the gravel is at about 

 700 feet, and the lower edge of the patch of gravel at Lindridge 

 (resting there upon Devonian Limestone) is at about 370 feet, the 

 space between being about a mile. 



The gravel could not have overstepped the boundary of the 

 Permian on a level surface, unless the dip of the Permian rocks 

 was sufficient to bring in a thickness of more than 300 feet in a 

 mile. Now, along the southern base of Little Haldon, the base of 

 the Permian does fall through 250 feet in the space of a mile, so 

 that the dip favoured the transgression, but is not quite enough to 

 account for it. We must therefore assume, either that the gravel 

 thickened in this distance by the amount of 80 feet, or, as is more 

 probable, that there was a gentle upward slope where there is now 

 a downward slope : and if we take the difference between 330 

 and 250 feet (that is, 80 feet in a mile), the slope comes out as 

 1 in 66. 



Assuming this to have been the average slope of the ground 

 between the plain of the Haldon Hills and the granite-ridge by 

 Elsford, north-east of Lustleigh, a distance of 5| miles, we find 

 that in Eocene times this ridge would have been 440 feet higher 

 than the level at which gravel was being spread out over the 



