754

THE COLLIERY GUARDIAN.

April 9, 1915.

positions. Thus its position is defined within very
narrow limits. The outcrop of the Wernffraith seam,
about 1J miles to the north, as shown on the map,
proves that the fault must have intersected the
Rhydding fault to the south of that outcrop, therefore
its course is clearly defined. It is highly improbable
that a sudden alteration in the line of level course
between the workings in Court-Herbert Colliery and
the workings in Court-Sart Pit exists so as to account
for the 170 yds. difference of level above described.

Whitworth Colliery.—This sinking has been completed
since the publication of Part II. Its depth agre- s with
the borehole section above mentioned, but the details of
the strata, which were given to the writer by the colliery
official<, differ from those of the pit, the latter are,
presumably, the more correct. The seams intersected
at 491 yds. 11 in. and 503yds. Ilin, are respectively the
Field Vein and the Wernddu, or No. 2 Rhondda.

Ynyscorrwg Colliery.—This pit also has been sunk to
No. 2 Rhondda seam since the publication of Part II.
The exact site of the pit is 492 yds. due south of the
goods station at Glyncorrwg which is shown on the
above Geological Sheet. From this pit the No. 2
Rhondda is worked to the rise—south-east—instead of
to the dip as was previously done from the same com-
pany’s pits, in the Afan Valley—2,250 yds. distant
to the south-east—which are shown on Geological
Sheet XVII., S. W., as “Glyncorrwg Pits 315 yds. to
No. 2 Rhondda.” It may be well to state that this depth
is inaccurate, as No. 2—owing to a local “wash-out "—
was not identified in the pit, the total depth of which is
only about 315 ft. The exact position at which the
seam should have been found is stated by Mr. Trevor F.
Thomas to be 88 yds., as ascertained by the colliery
workings.

The Ynyscorrwg Pit section is interesting as it differs
considerably from the Whitworth Colliery section.
No. 1 Rhondda seam proves at 126 yds. 1 ft. 9 in., but it
is a little thinner than at Glyncastle Colliery and at the
Old Clyne Colliery in the Vale of Neath. At a distance
of 17 yds. beneath No. 1 Rhondda a seam, 2 ft. 2 in.
thick, occurs, which has been worked 1^ miles to the
north-east and is of fair quality. Neither this seam nor
No. 1 Rhondda occurs at the Whitworth Pit. It seems
to be probable that the upper portion of the No. 2 seam
at Ynyscorrwg, with coal 1ft. 3 in., holing 6 in., and
clod 8 in., represents the Field seam, the distance
between which and the Wernddu varies considerably.
If this surmise be untenable, then the Field seam does
not occur in Glyncorrwg district, although it does at
Cymmer, nearly 2 miles distant to the south-west.

about 11 degs., and the slip was filled with gravel and
water. In driving the headings in No. 2 Rhondda seam
to the east, downthrow faults to the east, of 2 yards and
8 yards, were met with, and 35 yards, beyond another
downthrow to the east was found. Its throw was proved
to exceed 18 yards, and Mr. J. W. Hutchinson considers
that the indications are that its throw is fully 45 yards.

Its direction is north-west and south-east, conse-
quently it crosses Mynydd-y-gwair pointing to Llandy-
fodwg, and it is highly probable that this is the
downcast east fault which the writer proved in his
little colliery, a quarter of a mile to the south of
Llandyfodwg in ’1873, and which in his 1876 paper is
called “ Church Fault,” and shown on its accompanying
map to continue to the south-east' in the direction of
Capel-Llanbad, or “ St. Peters in Ruins,” as it is called
on the recent Ordnance Survey map. The position of
this fault has been proved by the workings of South-
Rhondda Colliery to be close to the south side of that
old ruin. Its course to the north-west as far as the top
of the Garw Valley was correctly shown in the writer’s
above-mentioned map in 1876.

On the west side of Catherine pit a series of
downthrow-west faults was met with, but not of big
throw, and beyond these the workings have not extended
far. Thus it appears that this pit was sunk on a ridge
of elevated strata—an anticline of faults.

Llewelyn Pit. — The writer is indebted to Mr.
Leonard W. Llewelyn for this remarkable section. The
pit-top is but a short distance to the north of the
surface position of the axis of the great anticline which
traverses the coal field westward to Swansea Bay. The
strata in the pit were regular to a depth of 369 yds.
2 ft. 9 in. where disturbances commenced, the strata
dipping in various directions, the coal attaining remark-
able thickness and ultimately the strata revealed
extraordinary deformation. Between 386 yds. 1 ft. 8 in.
and 407 yds. 1 ft. 3 in. from the surface a thickness of
no less than 62 ft. 7 in. of coal was intersected on one
side of the pit, and 50 ft. 6 in. on the other, and, 5 yds.
beneath, another bed 20 ft. 6in. thick on one side of the
pit and 18 ft. on the other was reached. Thus a
thickness of 71 ft. of coal occurs in a pit depth of 95 ft.

The writer is not aware that a similar thickness has
been found elsewhere in the coal field, but he remembers
being told in 1873 that at Tondu the Fawr seam was
found to be 30 ft. thick in limited are«s, its normal
thickness being about 15 ft.

The great thickness of coal above-mentioned is
doubtless due to the stupendous thrust from the south
which gave the steep dips to the south-crop seams, and

due to the same reason that the two other seams
received the same name. The analysis of the Metros
band of “ Lantern Coal ” is given in Part I., p. 78.

The next lower “ Lantern Vein ” is the seam named
“ Victoria” in the writer’s 1876 paper. In recent years
it has been worked in Bryn-chwyth, South Rhondda
and Metros collieries, but neither this seam nor the
former represents the original Lantern seam of Tondu.

The lowest of the three “ Lantern ” seams is that
which was intersected in South Llanharan Colliery
about the year 1872, where it is 118 yds., or thereabouts,
beneath the Victoria “ Lantern ” and in South Llanharan
pit is 85 yds. above the Bodwr-fach seam, as compared
with 50 yds. at Tondu.

The writer considers the seam at 262 yds. 1ft. 7^ in.
to be the Bodwr-fach, and the seam at 288 yds. 2 ft. 8 in.
to be the Bodwr-fawr. If corrected for the 20 degs.
dip these distances will respectively be 246 and 271 yards,
and if to each of these 67 yds. be added it will show
their depths beneath the Rock-fawr to be 313 and
338 yards respectively.

Bryn-chwyth Colliery.—The slope of this colliery
commenced at the outcrop of the Victoria “ Lantern ”
seam. It was driven to the north for a considerable
distance, and large quantities of coal have been obtained
from it. ,

The Rock-fawr and the Malthouse seams have also
been worked, and the true distances between these
three seams have now been proved by accurate colliery
surveys. It may be of interest if these distances be
compared with those shown in the vertical section of
the above-mentioned 1876 paper.

Distances between No. 2 Rhondda and Victokia
“ Lantern” Seams.

No. 2 to No. 3 Rhondda
(= Malthouse to Rock-fawr).

Yds.

T/n-y-waun............ —

Bryn-chwyth ......... 95

Writer’s 1876 Paper... 94

South Rhondda ....... 88

Meiros............... 90

No. 3 Rhondda to
Victoria.

Yds.

Ty’n-y-vTaun ........ 158

Bryn-chwyth ......... 145

Writer’s 1876 Paper.. 137

South Rhondda........ 110

Meiros .............. 108

It may be mentioned that Bryn-chwyth and South
Rhondda collieries were not in existence in 1874, and
the writer’s horizontal section passed between the
positions they now occupy.

The above figures show that a marked attenuation in
an easterly direction exists between Ty’n-y-waun and
Meiros, and later on it will be shown that the lower
strata also attenuate toward the Ely Valley.

Fig. 4.—Tydraw Colliery, Rhondda Valley, Yard Seam.
Section of Barrack’s Heading.

Clod

COAL

$

£

The Glyncorrwg Fault.—This fault gave rise to con-
siderable debate in the old days of the institute, when
practically all the mining authorities were of the
opinion that from Blaen-corrwg the fault ran in a
direction slightly to the west of south and continued into
the Garw Valley, but the writer who had examined the
district showed that the fault could not run in that
direction, and, in 1875, he gave a small plan which
showed the fault to run to the east of south, and thus
to traverse the upper part of the Ogmore Valley.

Since those days pits have been sunk near Blaen-
corrwg to No. 2 Rhondda and the steam coal seams, and
the colliery workings prove that the fault has divided
into two branches. Three years ago, through the courtesy
of Mr. Trevor F. Thomas—a member of the council of
this institute—the writer examined the colliery plans,
and the information thus gained enabled a measurement
to be made of the more westerly branch of the fault.
It is a downthrow to the west of 225 yards, and its
course is a little to the east of south, passing 100 yards
to the west of Lletty-Dafydd where it is marked on the
sheet “fault touched.” In the opposite direction the
fault curves in a northerly direction up Cwm-corrwg-
fechan, past the waterfalls which are shown near the
north margin of the sheet, and it seems to be probable
that near this position it unites again with the eastern
branch.

Gibb's Navigation Colliery, Cymmer.—This new
colliery is is situated on the west side of the South
Wales Mineral Railway 1 mile north of Cymmer, and
380 yards south-west of Nant-tewlath. It reached the
No. 2 Rhondda seam in September 1914.

The coals between the depths 206 yards 1 ft. and
211 yards 5 in. are doubtless the Field seam and No. 2
Rhondda in close proximity. The seam 2 ft. 2 in. thick,
which was noticed in Ynyscorrwg section, occurs in this
pit 10 yards only beneath No. 1 Rhondda. It is a
persistent seam over Glyncorrwg district, but lower
down the valley it was not recognisable in Whitworth
pit. This section does not differ materially from the
Ynyscorrwg section.

Rhondda Main Collieries: Catherine Pit.—This pit
has been sunk since Part I. was published. It is
situated on the east side of Ogmore Valley Branch
Railway, about three-quarters of a mile south of
Ogmore Vale Station. A fault was met with in the
pit at 23 yards 2 ft. 11 in. from the surface, and the
slip, or fracture plane, crossed the shaft and disappeared
at 60 yards 1 ft. 10 in. Its hade is therefore very steep,

formed the anticline, and caused a sliding movement
over some of the thicker coalseams—of which they bear
evidence—which resulted in their being doubled, or
trebled, in thickness for a limited distance in the line of
thrust.

The anticline has attained its greatest development
from Glyn westward to Gilfach-goch, and then it
becomes less pronounced westward to Maesteg, the
steep dips of 30 degs. and 45 degs between the syncline
at Hendre-forgan and the anticline at Gilfach-goch
being greatly less in the Ogmore, Garw, and Llynvi
valleys, in corresponding positions. This is due to the
‘Moel-gilau fault, which originates about 2 J miles to the
south-west of Gilfach-goch—or dies out there, according
to the point of view from which it is regarded—and
increases in its throw rapidly as it goes west.

The Moel-gilau fault will be further referred to a little
later on.

In the Rhondda Valley, also, disturbances occur in
some of the lowest seams beneath higher seams which
are not affected. An interesting disturbance in Tydraw
Colliery is shown in the accompanying section (fig. 4).
It shows that the bending of the strata has caused the
roof to slide over the seam , pushing the coal outwards
from the axis of the syncline in each direction.

Ty n-y-waun Old Pit.—About a mile to the east of
Bryncethin Colliery, which was sunk by the Barrow
Steel Company in the years 1872-5, is Ty’n-y-waun Pit,
which also was sunk by that company a year or two
later.

The identity of the seams intersected by the pit was
not ascertained, but Mr. Dillwyn considers the vein at
102 yds. 9 in. to be the same as that which in recent
years has been worked at Bryn-chwyth, South Rhondda
and Meiros collieries, farther to the east, and called
“Lantern Vein,” and the distance betweenit and the
Rock-fawr, corrected for the 20 degs. dip, is 158 yds. at
Ty’n-y-waun, but this lessens eastward, as will be
shown.

This correlation is no doubt correct, and it enables
the identity of some of the lower seams in the pit to be
established with probable accuracy. It is, however,
necessary to point out that in Pencoed district three
seams of coal—each of which is separated by more than
100 yds. of strata—have been called “Lantern Vein,”
and confusion consequently exists. The uppermost of
these is the Rock-fawr, which at Meiros Colliery has
been called “ Lantern Vein ” owing to its having a band
of cannel coal on the top of the seam. It is, no doubt,

A fault was met with in Bryn-chwyth Colliery which
commenced at Melin Raglan and extended northwards
with a rapid increase of throw. In the workings of the
Malthouse seam (No. 2 Rhondda), less than half-a-mile
to the north, the fault is a downthrow to the west of
60 yards and apparently is increasing in its throw. It
probably continues its course past Caner-mawr to at
least as far as the writer’s supposed position of the
Moel-gilau fault near the Little Ogmore branch of the
Great Western Railway.

The throw and direction of the latter fault were con-
sidered in the 1.876 paper with a diagrammatic section,
and the opinion was expressed that the fault has died
out in Mynydd-y-gaer.

The recently-published (1907) 6 in. geological map
(Glam. Sheet XXXV., N.W.), shows the fault to termi-
nate at the Little Ogmore Branch Railway, near
Ynys-y-bwt, but 2 miles farther to the east a fault is
shown on the same sheet which is called “supposed
continuation of Moel-gilau Fault,” and this is not shown
to have any connection with the known position of the
fault at Ynys-y-bwt, a little to the east of Blackmill;
on the contrary, it is shown to run to the north-west
from Mynydd-y-gaer to the Ogwr-fach river, near
Llwyn-helig, and pointing to the outcrop of the Tydu
Vein (No. 3 Llantwit) 180 yards distant. This is
certainly untenable, for in 1873 the writer worked
this seam at the above position and no downthrow
fault to the south-west exists there, for the crop
runs regularly westward as shown on the Geological
Sheet, therefore one of two things—either the fault
that is shown to run from Mynydd-y-gaer to Llwyn-
helig does not exist, or if it do<-s it must have died
out before reaching the crop of the Tydu Vein, and
consequently could have .no connection with the Moel-
gilau Fault.

The writer considers that this fault continues to the
south-south-east from Ynys-y-bwt—where in 1876 he
estimated its throw to be about 100 yds.—possibly as
far as Gelli-feddgaer Wood, at the 500 ft. contour line,
and to die out somewhere near that position; but this’
is somewhat questionable, for it will depend in a large
degree upon the Melin Raglan Fault above mentioned,
for if this stops at its point of intersection with the
Moel-gilau fault the throw of the latter would be
reduced eastward by the throw of the former—60 yards,
or probably more—and in this case the Melin Raglan
fault would be a potent factor in the disappearance of
the Moel-gilau Fault.