Vol. 53.] MR. F. CHAPMAN ON THE BARGATE BEDS OF SURREY. 685 



well preserved, and quartz-grains rarely occurring. Foraminifera, 

 such as Lagma Iceuis (Mont.) and Nodosaria radicula (Linn.), are 

 frequent in the fragments of oolite. 



After a careful examination of these oolitic Bargate limestones 

 there remains no doubt whatever as to the detrital character of 

 the grains, especially as they occur associated with other rocks 

 evidently remnants of beds of the same age, possessing the brecciated 

 character. Moreover, the derived fragments and particles appear 

 to have been deposited gently, and quickly following their disin- 

 tegration, leaving the calcareous grains nearly as perfect as when 

 they formed part of the parent rock. The source of the derived 

 fragments was not, perhaps, very distant from the spot where these 

 beds are now found. 



,The occurrence of these detrital oolitic grains raises some question 

 as to the contenrnoraneity of the microscopic fossils found in the 

 clays of the Bargate series. Judging from the somewhat mixed 

 character of the facies, we probablv have, in the assemblage 

 collected, a few Jurassic forms (derived), mingled with other species 

 indigenous to the Lower Greensand. 



Prof. Judd, who has kindly examined my specimens, has called 

 my attention to the similarity of these rocks with those from the 

 Richmond well-boring, at a depth of between 1141' 6" and 1151' 6". 

 The material of the 10-ft. band at Richmond ' is manifestly derived 

 from the disintegration of Great Oolite rocks, some of which were 

 found lower down in the boring. Since the 10-ft. baud contains 

 oolite grains and some ostracoda, which are common to this and the 

 Bargate Beds of Surrey, there is good reason to suppose that we 

 have a thinned-out extension of the Bargate Beds represented in 

 the series beneath Richmond. 



The sections of the Richmond rocks from the 10-ft. band all 

 more or less resemble those of the Bargate limestone, and especially 

 one slide, marked with the depth of 1151 ft. 6 in., which shows 

 great similarity to the Bargate oolitic rock, excepting that the colour 

 of the Richmond rock is grey-black instead of yellow or brown (see 

 fig. 3, p. 686). 



It seems reasonable to conclude that the ridge of Great Oolite rocks 

 may have been situated immediately north of the Lower Greensand 

 outcrop in East Surrey, forming a subordinate axis, lying upon the 

 great Palaeozoic axis which underlies London. To allow for this 

 proximity of the Jurassic Beds it would be necessary to believe in 

 a sudden thinning-out in Surrey of the Wealden Beds, and also 

 of the members of the Lower Greensand older than the Bargate 

 Beds, to admit of the junction of the former with the Oolites ; or, 

 as Prof. Judd suggests, there is possibly a fault bringing up the 

 Oolitic rocks against the Lower Greensand. 



Above the Bargate Stone Beds at St. Martha's Hill are some 

 pebble-beds passing upwards into true, reddish-coloured Folkestone 

 Sands with quartz-pebbles. Farther up the lane very good exposures 



1 ' On the Nature and Relations of the Jurassic Deposits which underlie 

 London,' Quart. Journ. Geol. Soo. vol. xl. (1884) p. 738. 



