62 H. A. Baker— Quartzite Pebbles of the Oldhaven Beds. 



from the general outcrop of Gault to the east and south-east. In 

 pre-GIacial times the high ground must have been capped by some 

 remnants of the basal Cenomanian bed, as shown by the fossiliferous 

 lenticles preserved at Harris's Pit beneath the inverted mass of 

 rostratus Gault. 



Prom the information obtained from .the sections above dealt 

 with, as well as from Mr. Lamplugh's published records showing the 

 former occurrence of the brachiopod-lenticles (bed D) in parts of 

 Chance's Pit and Garside's Pit, we can form some idea as to the 

 original size of the overturned mass of strata. A great part of it 

 has been destroyed in the course of the excavations, so that at the 

 present time the remnant is only accessible for study at Harris's 

 Pit. It may be roughly estimated that the mass formerly showed 

 a north and south extension of about 250 yards. The position of its 

 original eastern boundary is more uncertain, but was probably 

 about 150-200 yards distant from the present working face at Harris's 

 Pit (see Fig. 1). It is impossible to say how much further to the 

 west the limit of the mass in that direction might be proved to occur 

 if excavation were to be continued. It is probable that its westerly 

 margin will not be reached in Harris's Pit, a sand-working situated 

 in the slope of the hill with a thickening cover of clay. But the 

 purely local character of the inverted mass has already been 

 sufficiently demonstrated. 



[To be conchided.) 



On the Quartzite Pebbles of the Oldhaven (Blackheath) 

 Beds of the Southern Part of the London Basin, 



By Herbert Arthur Baker, M.Sc, F.G.S. 



(PLATE I.) 



TT is common knowledge to all geologists interested in the Lower 

 -*- Eocenes of the southern part of the London Basin that, in the 

 Oldhaven (Blackheath) Pebble Beds, pebbles of a brown quartzite 

 are often to be found on searching amongst the rounded flints of 

 which these beds are so largely composed. When geological parties 

 visit sections exposing the pebble-beds of the Lower London 

 Tertiaries, the search for these quartzites usually constitutes one 

 of the items of the field-work to be done. A considerable number 

 of these pebbles must, by this time, have been collected, but, 

 although their occurrence has given rise to a good deal of discussion 

 and speculation, nobody appears, so far, to have undertaken a 

 systematic examination of their characters and petrological affinities. 

 The view has been propounded that the study of these pebbles 

 would throw light on the question of the source of the material 

 composing the Lower London Tertiary beds. In dealing with the 



