272 
CORRELATION AND FACIES OF THE UPPER AND MIDDLE OOLITES 
IN ENGLAND AND NORTH-WEST FRANCE. 
BY M. ODLING. M.A., B.SC. (OXON.), F.G.S. 
(Read November 18tli, 1914.) 
The Jurassic, probably better than any other System, emphasizes 
the fact of a gradual transition of one series into another by means of 
passage beds, represented locally by uncontormities,* and in spite of 
numerous local facies, the general sequence may be readily followed. 
The beds dealt with in this paper comprise a well-marked group of 
clays, sandstones and limestones, the " Tripartite Series " of Phillips,f 
commencing with the Cornbrash at the base and terminating with the 
Purbeck Beds at the top. 
These beds have been very fully dealt with, not only in the Memoirs 
of the Geological Survey, but also in numerous individual papers by 
Messrs. Blake, Hudleston and, more recently, Morley Davies.f 
In spite, however, of the attention that these beds have most 
deservedly received, there appears to be no readily accessible paper in 
which their general correlation can be found§. At Prof. Kendall's 
suggestion, therefore, I am venturing to attempt to supply this want. 
Perhaps the most remarkable feature of the whole series is the 
inclusion at various horizons of arenaceous and calcareous facies in 
what is as a general rule an argillaceous series of beds. As has been 
pointed out by Blake, Hudleston and others, these beds are to be re- 
garded as purely accidental, and the fauna is in every case transitional, 
the apparent sharp palseontological breaks being due to environment 
rather than to an actual change in a fauna by the extinction of a pre- 
vious one. We thus find, as we should expect, repetitions of fauna, 
which render exact correlation extremely difficult. More especially is 
* A recent school of geologists would probably prefer the term 
non -sequences," since the unconformity is only recognizable by the 
absence of beds, not by a marked change in dip. 
t Geology of Oxford, p. 392. 
% See Bibliography at the end. 
§ A correlation of the English and Weymouth sequence is given by 
Pellat, Proc. GeoL Assoc., Vol. IV., p. 20." 
