July 21, 1916.

THE COLLIERY GUARDIAN

113

written on this point as follows : “ The Keele group,
being regarded as the base of the upper coal measures,
is excluded from the Staffordian series, and placed in
the group to which the name Radstockian series was
given. That the Radstockian series is part of the upper
coal measures, or Stephanian of the Continent, is proved
by the fossil flora of the Radstock series, which has
given origin to the term.” From this statement the
present author concluded that Dr. Kidston now regarded
our upper coal measures (his Radstockian series) as part
of the Stephanian, and as equivalent in part to1 the beds
termed upper coal measures (terrain houiller superieur)
in France.	1

Dr. Arber was not in agreement with that opinion.
So far as he was aware, there was no evidence of any
true Stephanian flora from British rocks, though that
fact did not of course rule out the possibility of
Stephanian deposits occurring in this country. At
present that was an entirely open question. It is quite
possible, as was shown here, that the red beds, termed
the Enville series, would eventually prove to be a desert
iacies of Stephanian age, and thus a new type. But, be
this as it might, his point was that, so far, neither these
nor any other rocks in Britain had yielded a flora which
is botanically Stephanian. There was thus obviously a
difference of opinion as to what constituted a true
Stephanian flora. All our recorded coal measure floras
were Westphalian in affinity, the highest, that of the
upper coal measures, being a true transition or inter-
mediate stage to the Stephanian, as Zeiller pointed out,
though still essentially Westphalian in character. This
horizon should therefore be grouped with the West-
phalian.

Turning next to the Halesowen series, which was very
unfossiliferous, a few fossil plants had been recently
made known from these beds, but these were not suffi-
cient to indicate the horizon. This, however, was only
a minor gap in our knowledge of the fossil floras of
South Staffordshire, since the horizon of the beds below
and above was now known. There was thus little doubt
that the horizon was transition coal measures—a conclu-
sion which the larger flora obtained by Mr. Vernon from
the corresponding beds in Warwickshire (the Haunch-
wood sandstones) tended to confirm. Recent discoveries
by Mr. Kay, Dr. Kidston, and also by the present
author, confirmed the conclusion that the horizon of the
productive measures was the middle coal measures, and
that there was no trace of any lower coal measure in
South Staffordshire.

The Lithological Succession in the Warwickshire Coal Field.

In the sequence of sediments in the Warwickshire
coal field, Mr. Vernon found a close parallelism with that
of South Staffordshire.

(a)	The Enville Series.—Mr. Vernon had shown that
the unproductive measures of Warwickshire were excep-
tionally complete. With his conclusions Dr. Arber was
in general agreement, except on two points, both of
which relate to the difficult question of the so-called
” permians.” Mr. Vernon had concluded that “ until
definite palaeontological evidence to the contrary is forth-
coming the Corley conglomerates and Kenilworth sand-
stones must be regarded as of permian age.” The
author’s view was that, even on the present evidence,
they were much more accurately described as upper
carboniferous than as permian rocks. Secondly, Mr.
Vernon, as the result of his mapping of this coal field,
had concluded that the so-called permians overlie the
Keele series unconformably. The Geological Survey,
who were at present surveying the Warwickshire field,
liad, however, shown that there wras no evidence of any
such unconformity, and with this view the author
agreed.

It may thus be concluded that in Warwickshire, as
in South Staffordshire, the unproductives formed a per-
fectly conformable series.

The original correlation of the Enville series with the
permian appeared to have been founded purely on litho-
logical similarity. There was no doubt that these beds
did resemble in many respects the Rothliegende of Ger-
many, but palaeontological studies had shown that such
resemblances were often entirely deceptive. Red rocks,
representing the prevalence of either temporary or pro-
longed periods of desert conditions, might, and did,
occur on almost any horizon in the upper carboniferous.
One standard instance would suffice. The Whitehaven
sandstone of the Cumberland coal field was so “ per-
mian ” in aspect, that Sidgwick had had no hesitation
in declaring it to be of equivalent age to the lower
Rothliegende of Germany. Yet when the plants were
examined, it was found that these beds were in reality
middle coal measures, belonging to the very same
horizon as the productive beds below. Thus such litho-
logical resemblances, unless supported by palaeonto-
logical evidence, were quite misleading.

These Stephanian rocks of Warwickshire (the Corley
and Kenilworth beds) represented the lower part of the
knville series, which originally was continuously and
widely spread over almost the whole of the Midlands,
Miough with some local variations in thickness and
lithology.

(b)	The Keele and Other Series.—The Keele series of
Warwickshire appeared to agree closely with that of
South Staffordshire. The flora of these beds in the
former field was more scanty than that known from the
latter, but it included Pecopteris arborescens (Schl.) &
P. polymorpha (Brongn.), and there was thus little
doubt that it should also be attributed to the upper coal
measures.

The Haunchwood sandstones of Warwickshire were
thinner than the Halesowen group of South Stafford-
shire. From the similarity in position which these sedi-
ments occupied in the lithological sequence in both coal
fields, there could hardly be a doubt that they belonged
to the same epoch of coal measure time. The Nuneaton
days of Warwickshire appeared to be the same beds as
the much thicker red clay group (Old Hill) marls of

South Staffordshire, though whether the two iseries were
or were not continuous laterally remained to be proved.
They both, however, lay undoubtedly on the same
stratigraphical horizon.

The productive measures of Warwickshire at first sight
appeared to possess a strong likeness to those of South
Staffordshire, and in certain respects this was
undoubtedly the case. There was a thick coal in the
southern portion of each field, which split into com-
ponent seams to the northward. These measures also
thinned towards the southern limits of both fields.
Further, all the productives belonged to the middle coal
measures, and both the lower coal measures and mill-
stone grit of the Pennine fields were absent. The pro-
ductives rested on Cambrian rocks in Warwickshire and
on silurian, for the most part, in South Staffordshire.

The fossil floras of the productives, as recorded by
Vernon in the case of Warwickshire and by Dr. Kidston
and the author as regards South Staffordshire, agreed
closely, especially if the large number of very rare and
in many cases unique types, known only from one or
two localities in the latter field, were omitted.

Apart from these similarities, however, there were
several important points of difference between the pro-
ductives of the two coal fields. Chief among these was
the succession of coal seams and ironstones which
could not be correlated in the two areas. Even if we
assumed that the thick coal of Warwickshire was iden-
tical with that of South Staffordshire, we had still to
explain how it was that the greater number of the coals
and ironstones of the western field were absent in the
eastern.

Dr. Arber thus concluded that the productive measures
of the two fields were not, and never had been, con-
tinuous, and in this view he was entirely in agreement
with the opinion which Ramsay and Jukes had long ago
expressed on this point. No doubt these measures had
been laid down at about the same time and under the
same conditions in adjoining but independent depres-
sions in the old palaeozoic floor of the Midlands. It
might be well imagined that the conditions of deposition,
and the results of deposition in two adjacent areas had
been very similar, especially if both districts had
been subject to the same set of oscillations of uplift and
depression. This appeared to have been the case. In
Dr. Arber’s opinion it was not necessary to assume that
the two areas were continuous. On the contrary, the
dissimilarity in the sequence of the productive deposits
pointed strongly to the conclusion that they had been
originally isolated, though no doubt continuity had been
established between the two fields at a much later period
when some part of the unproductive series was being
deposited.

The Lithological Succession in the Wyre Forest—
Coalbrookdale Coal Fields.

Dr. Arber had already entered so fully into a consider-
ation of the grey and red-grey measures of the Wyre
Forest and Coalbrookdale in a former paper, that only
a very brief mention of these beds was necessary here.
The interpretation there offered was that there were in
these districts at least four coal fields of different ages,
some of them in part, but only in part, overlapping one
another. It had been shown that the lower productive
measures of Coalbrookdale and the lower series of the
Wyre Forest were distinct areas, quite dissimilar litho-
logically, though both belonging to the same palaeo-
botatiical horizon. The former consisted of grey
measures; the latter of red-grey sediments. They were
both overlain unconformably and in part by a third coal
field, consisting of red-grey sediments belonging to the
transition coal measures. A fourth and similar field
also existed further south in the Wyre Forest, resting
directly on old red sandstone. As the author pointed
out then, there was no question but that the lower fields
of the Wyre Forest were quite distinct from anything
met with in South Staffordshire on this horizon. On
the other hand, the Coalbrookdale lower series was
similar lithologically to the productives of the latter
field, though, in his view, these measures had been
deposited on a basin quite apart from that of South
Staffordshire. The succession of the beds of the lower
productive series of Coalbrookdale was just as different
from that of South Staffordshire as was the correspond-
ing series in Warwickshire. In view of these facts,
the author had little doubt that we were dealing with
areas which had been ab initio independent, though the
sequence of subsequent events might have been very
similar in each case, and thus the products to some
extent might resemble one another.

The red-grey measures of the higher (transition) coal
fields of the Wyre Forest-Coalbrookdale areas (the
sulphur coal series) likewise presented some resem-
blances to the red-grey unproductives of South Stafford-
shire. They were, however, productive in part, and
Dr. Arber was inclined, for this and other reasons, to
regard them as a distinct series. At any rate, an alter-
nating series of red-grey unproductives, similar to that
occurring in the South Staffordshire field, had not been
recognised so far in the Welsh borderland coal fields,
though the same horizons were there represented. Thus,
in regard to this horizon also, there was at present little
evidence that the beds were continuous from one coal
field to the other. In the case, however, of the Keele
and Enville series, so far as the author had examined
them, he saw no reason to doubt that these measures
were continuous over the South Midland area. The
Keele and Enville group he regarded as the one red
link between these two districts.

The Geological History of the South Staffordshire Field,
with Special Reference to the Concealed Areas.

Dr. Arber pointed out that there was this important
difference between the southern and the northern limits
of the visible field. In the former direction the trias
overlay the Enville series; in the latter it concealed
the productive measures, and sometimes the lowest
beds of that division of the coal measures. We had

now reached a discussion of the oft-debated question :
What do these mesozoic rocks conceal? Our answer
would primarily depend on our interpretation of the
structure of the field, as it was to-day, and of the
sequence of past events in the area.

The structure of the visible field as it stood at the
present time was exceedingly complicated, both by fold-
ing, faulting, fracture, and denudation. The visible coal
field was said to occur “ on the crest of a denuded
arch.” The essential structure was described as due to
the South Staffordshire anticline, which “ enters the
Midlands from the south, and is prolonged northwards
in its turn almost to the centre of the Midland region.
The arch splits the southern parts of the South Stafford-
shire basin into two long bays or troughs—the Wolver-
hampton sub-basin and the Birmingham sub-basin.”

As the author understood, the current interpretation
of the South Staffordshire coal field, the visible coal field
was the dominant anticline of the field. There were,
however, several considerations which had led Dr.
Arber to interpret the 'South Staffordshire coal field in
quite a different manner. The exposed productives had
not a general anticlinal ’form. There was no one anti-
cline dominant over the whole of this field. Everyone
would agree that the strike of this coal field was nearly
north and south. The author’s interpretation of the
dip, however, was that it is towards the centre of the
field, except where it was interfered with by secondary
folds, both anticlines and synclines, such as the Nether-
ton and Dudley crests, all of which, as we should see,
were on his view later embellishments, and not primary
structural features. The visible coal field was unmis-
takably a syncline and not an anticline. It differed in
no respect, except in the degree of complexity, from
many other eoal fields, where one or more anticlinal
folds had been superposed upon an original synclinal
structure. The coal field of South Wales and the Notts
and Derby fields were typical examples of districts in
which a prolonged dominant fold, parallel to the strike
of the beds, was an outstanding feature. In South
Staffordshire, instead of a single elongated anticline, we
found a large number of short anticlinal crests, some-
times so crowded together as to obscure, and even in
some districts to obliterate, the original syncline.

These marked features of the field naturally attracted
immediate attention, wheras the synclinal form of other
districts, such as that between Coseley and Wednes-
bury, and between Cannock and Brownhills, unaffected
by secondary folds, escaped observation.

A

Fontt
Butin



Bi

t

;»S;

rs:





S,',

'S’

FUU BuunJtus
FutU

Fig. 1.—Diagrammatic Sections, Illustrating
the Original and Present Conditions of
the South Midland, Especially the South
Staffordshire) Coalfields.

S =Pre-carboniferous floor I P=Productive measures
N=Non-productive measures | T=Trias

A.	Original condition, at the close of the Stepbanian
period, of the Wyre Forest, South Staffordshire and
Warwickshire basins; the productive measures (P) filling
previously-formed hollows in the lower palaeozoic floor
(silurian, etc.. S). The non-productives (N), however.hada
regional distribution.

B.	The condition of affairs in South Staffordshire, and in
Warwickshire, at the clo-e of triassic times, illustrating
the pre-triassic horsts, ami the accumulation of triassic
sediments (T) in the sunken areas between and around the
horsts. The presence of minor (pre-triassic) local folds in
the coal measures of the present visible field is indicated in
the case of South Staffordshire, though for rhe sake of
clearness these are omitted in the case of the Warwickshire
horst.

C.	Present conditions of the denuded horst and concealed
areas of South Staffordshire, showing the local alteration in
the dips of the syncline of the productive measures pro-
duced by minor folds imposed in pre-triassic times on the
visible area. (The non-productives (N) should here be the
same thickness as in B).

Next to the syncline, the other great cardinal feature^
of the field, as it at present existed (especially in any
consideration of the concealed areas) were the great east
and west boundary faults. These lines of fracture, of
displacement through a vertical range of between 1,000
and 2,000 ft., or perhaps more, were of much greater
importance than any of the other lines of movement to
which the term fault was applied elsewhere in the field.

The author’s interpretation of the visible field was
that it was part of the original syncline left elevated as
a great horst, standing between 1,000 and 2,000 ft. above
the level of the surrounding country, by the subsidence
of the rest of the syncline to the east and west along
the two great sag lines, the boundary faults. (Text
fig. 1, B and C.) Since then, of course, the horst had