PLEISTOCENE CLASSIFICATIONS.
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The very important evidences from the cave of Sirgenstein (7),
in Wurtemberg, lend no support to the theory of a Mousterian
glaciation with post-Mousterian milder conditions. On the
contrary, the main accumulations of the remains of Arctic
rodents are found overlying the Upper Mousterian, and in the
Magdalenian relics beds.
In Northern France the important plant beds of Resson yield
an associated industry which, according to de Mortillet (8) is of
Mousterian date. Yet both flora and fauna indicate a temperate
climate, with warmer winters and less frost than is experienced
at the present day, although the summers were cooler. *
Archaeological culture stages like the Mousterian, are geo-
logically brief periods, and it is questionable if they give enough
time to include a glacial episode as well as climatic conditions
with less frost than now.
The lignites of Jarville include more alpine and northern
elements in the flora, and would appear to be intermediate both
in date and in climate between the Mousterian and the
Magdalenian.
In our own country, the Palaeolithic Floor of Stoke Newington
gives us a well-developed and distinctive Mousterian industry,
and again the flora is thoroughly temperate, although associated
with the northern migrating animals which I take to be the first
heralds of the advancing Arctic cold that culminated in the
Magdalenian (9).
The excavations at High Lodge proved that Boulder Clay
in situ underlies the Mousterian deposit ; that important
fact was clearly shown (10). The channel filled with Boulder
Clay overlying the deposit may be a re-distribution or trail of
the same Boulder Clay. These phenomena of surface trailing
are so usual that it is the contrary assumption (namely, that
there are two similar Boulder Clays of different date) which needs
to be proved.
Every field geologist is only too familiar with the misleading
difficulties which arise from these phenomena of surface trailing ;
true relative dating can be proved only by regional evidences.
I will take two published instances at random. H. Dewey (11),
refers to a case at Epsom where a mass of the mottled clay of
the Reading Beds, no less than 12 feet in thickness, overlies
Pleistocene gravel.
My second instance is that recorded by A. L. Leach (12).
The section showed some 12 feet of displaced beds in the fol-
lowing descending order (1) Pebbly surface soil, a wash from the
Shooters Hill gravel ; (2) London Clay; (3) Claygate beds, newer
than 2 although underlying it; (4) Shooter's Hill Gravel, much
newer than 2 and 3; (5) Claygate Beds again, but not in place ;
(6) London Clay in place.
* It is classed as a cold flora, but with the winters milder than now.