87 
THE rS'GLETONIAN SERIES OF WEST YORKSHIRE. 
BY R. H. RASTALL, M.A., F.G.S., 
FELLOW OF Christ's college, Cambridge. 
The true stratigraphical position of the group of rocks which 
are commonly spoken of as the " Ingleton Green Slates and 
Grits " has long been a matter of doubt. They have been 
considered by many writers to be the equivalents of the Borrow- 
dale Volcanic Series of tlie Lake District, and they are coloured 
as " Lower Silurian " in the one-inch maps of the Geological 
Survey (97, S.W.). But this correlation, as was pointed out 
by Dr. Marr* in 1892. rests on somewhat slender foundations. 
It is true that the rocks possess a prevaihng greenish tinge, 
somewhat like that of many of the Borrowdale lavas and ashes, 
and they certainly occur in juxtaposition with an undoubted 
representative of the Coniston Limestone, but the resemblance 
goes no further. There is nothing to show that the junction 
with the Coniston Limestone is a natural, conformable one, 
and the green rocks themselves, apart from their colour, are 
utterly unlike any of the members of the Borrowdale series. 
They are true sediments of a well-defined and peculiar type, 
and their constitution shows no resemblance to that of the 
great lava-flows, ashes, and agglomerates of the central part 
of the Lake District, or the thinner representatives of the same 
in the Cross Fell inlier. In the absence, therefore, of any direct 
stratigraphical evidence as to their age and relationships I 
propose to apply to the pre-Caradocian rocks of this district 
the purely local and territorial designation of the " Ingletonian 
Series." Some suggestions as to possible correlations will be 
made after their petrographical character has been described 
in detail, as this may be considered to throw some light on the 
source from which the material has been derived. 
* Geol. Mag., 1892, p. 104. 
