H. A. Baker- — Quartzite Pebbles of the OLdhaven Beds. 63 



latter question, the difficulty confronting the geologist is that since 

 the pebbles of the Oldhaven Beds consist (except for the quartzites) 

 entirely of rolled flints, and since, where pebble-beds occur in other 

 of the component members of phe Lower London Tertiaries, they 

 are always composed of flints, it is naturally inferred that the 

 Chalk was denuded to furnish the material for these strata, but 

 it is obvious that the Chalk alone could not have supplied the 

 arenaceous and argillaceous material composing them. The hope 

 has therefore lingered in the minds of geologists that, sooner or 

 later, the parent-mass of rock from which these quartzites were 

 derived would be located, and evidence concerning the source of 

 the material of the Lower Eocenes be thereby gained. 



Dr. Gr. J. Hinde, in the course of a paper on the Blackheath 

 Pebble Beds of the Addington Hills,^ referred to these quartzites 

 as follows : " The only exception to the prevalent flint-pebbles 

 which came under my notice were some cake-shaped pebbles of 

 a light-grey quartzite, in form and smoothness of surface very 

 much like the flints, from which, indeed, they could hardly be 

 distinguished until they were broken. These quartzites are very 

 hard and fine-grained. They appear to be rare. The largest 

 I found was about 4 J inches across by 2 inches in thickness (110 by 

 45 mm.). Judging by the character of the rock, they may have 

 been derived from Palaeozoic strata, and it is not easy to account 

 for their presence in these Tertiary pebble-beds, associated as they are 

 with Chalk-flint pebbles exclusively. I am not aware that similar 

 pebbles have been previously recorded in the Blackheath or Old- 

 haven series, but Professor Prestwich has lately stated that large 

 pebbles of white or light-coloured quartzite, now present in the 

 beds of Westleton shingle, may have been derived indirectly from 

 the shingle-beds of the Woolwich and Reading series, where he has 

 occasionally found them, or they may have come from the quartzites 

 of the Palaeozoic rocks of the Ardennes." 



In the discussion which has centred round these interesting 

 pebbles (based chiefly on the external characters presented by them), 

 opinion has been divided. Whilst some have been inclined to adopt 

 the view of Hinde and Prestwich, quoted above, that these quartzites 

 may have been derived from Palaeozoic rocks, others have considered 

 them to be " sarsens ". If it be granted that a sarsen is a rock 

 originally associated with, and derived from. Tertiary strata (not 

 necessarily of Upper Eocene age), then the present writer regards 

 these quartzite pebbles as sarsens, but it is not his intention at this 

 juncture to labour the point, or to embark upon a plenary defini- 

 tion of the term " sarsen ". It is here proposed simply to consider 

 these pebbles as pebbles occurring in the Oldhaven (Blackheath) 

 Beds. 



With regard to their occurrence, these pebbles are certainly rare, 



1 Hinde, Proc. Geol. Assoc, vol, xi, 1890, p. 467. 



