Fforest Fawr
UNESCO
Global Geopark
United Nations
Educational, Scientific and
Cultural Organization
Cribarth
Geotrail
Quarries and crags, folds
and fractures
GEOPARK
WALK
1
This is chert, a variety of silica not unlike flint, filling burrows
created by organisms when these rocks were still soft
sediments.
Return to the fence/wall
and follow it to the left for
100m as it starts to climb a
short bank. Halfway up the
bank you cross what looks like
a rough ditch running at right
angles to the fence.
Remains of rottenstone workings appear
as mounds beside a ‘ditch’.
These are abandoned mineral workings from the 19th century
where a layer of ‘limestone shale’ had weathered over millennia
to form rottenstone. This rock was so extensively quarried along
its outcrop for use as an industrial polish that no trace of it
remains today. The humps and hollows resulting from its
quarrying can be seen here and elsewhere on this walk.
Prominent beds of Twrch Sandstone dipping steeply NW to right
Immediately above these workings are scattered blocks and
bedrock outcrops of the
Twrch Sandstone
. At the top of the
bank, the remains of a
‘ty-un-nos’
, a hastily erected building,
are built into the wall. A prominent band of very steeply
dipping Twrch Sandstone extends away to the left.
Start by following the outcrop of this rock directly
away from the wall/fence, then continue walking
southwest along the crest of the broad ridge, passing a
shallow pool on your left after 250m as the ridge broadens.
Meet a rough track after a further 100m – the remains of
a half-finished tramroad.
4
Turn right, following the
twisting track for 100m as
it drops down into a gully which
cuts across its route.
The distant Old Red Sandstone peak
of Fan Gyhirych is seen down the gully
This gully is the result of 19th
century quarrying for ‘silica rock’
as the Twrch Sandstone or Basal Grit is sometimes known.
Normally a very hard rock, it has been shattered in this area by
movement along a geological fault which cuts NE-SW through
the area and left it easier to quarry with the hand-tools
available to our forebears.
Continue for another 100m beyond the gully to a stile
and gate in the fence/wall ahead.
From here you can follow the line of the unfinished tramroad with
your eye as it curves to the right. It was built to provide access to a
large area of ground where rottenstone was quarried though the
tramway was never completed. You can also see numerous
shakeholes, large and small, which reveal that limestone beneath
has been dissolving away.
Retracing your steps, go back across the gully to
the point at which you joined the tramroad (5).
Continue along it as it curves uphill to the right and then
back left.
Notice further rottenstone workings down to the left below the
tramroad before passing through a field of Twrch Sandstone
boulders scattered down the hill from the cairn-topped summit
above.
The unfinished tramroad flattens out before joining
another former tramroad coming in from the left.
Continue beyond the junction
of the two tramroads up a
further 50m into an
embayment immediately
beneath the rocky knoll which
forms Cribarth’s highest point
(428m above sea level).
Note the beds of limestone dipping in
the direction from which you have
come.
6
3
5
More information on the route can be found at www.fforestfawrgeopark.org.uk
2
START
Leave the car park and turn left along the main road.
Beware of traffic as you walk south for about 350m.
Across the road from a large layby on the left is a gate
leading to a broad track.
Once through the gate, stop to view rocks and drams on display.
Follow the concessionary route as it runs up
through privately owned woods for 90m. Do NOT
continue ahead to the old quarries with their hazardous
cliff faces; instead, turn sharp right up a narrower
footpath with steps in places.
Stop to enjoy the view up the Tawe valley at an open
area by a fence.
Continue up more steeply beside a fence to a ladder-stile.
The upper part of Cwm Tawe was carved through the Old Red Sandstone
by ice. Blocks of this rock can be seen along this path. Their chestnut-brown
colour contrasts with the grey Carboniferous Limestone which forms the
bedrock of this hillside.
Turn right to follow an often rough path beside the
wall/fence for over 400m. As you descend a couple
of rocky sections, notice that the beds of limestone dip
steeply to the northwest (see front cover photo).
Approaching a field gate on your right, venture about 50m
up the grassy slopes on your left to take a closer look at
the rocks.
Chert-filled burrows in limestone
Unlike the rocks you passed
earlier, the limestone here is
almost horizontal and contains
oddly shaped lumps of a
different rock type within it.
A 5.25km / 3.25 mile walking trail exploring the
rocky slopes of a spectacular hill rising above
Craig-y-nos Country Park in the upper Swansea
Valley (Cwm Tawe). This landscape has been
carved by water and ice from folded layers of
sandstone and limestone. A legacy of quarrying
adds detail and drama to the scene.
Start Craig-y-nos Country Park
(OS grid reference SN 839155) (postcode SA9 1GL)
Ascent About 250m / 800ft
Time Allow about 3.5 hours to fully enjoy the walk
Map Use OS Explorer map OL12 ‘BBNP western area’
The initial ascent (and later descent) through woodland
is steep. Several sections of the trail follow abandoned or
unfinished sections of 19th century industrial tramroad
which offer relatively easy walking.
Warning There are numerous areas of steep ground and
loose rock on Cribarth though this trail avoids these
difficulties. Some sections of path are wet. Both rocks
and grass slopes can be slippery particularly after rain –
beware! Unless you’re an expert, navigating Cribarth’s
complex terrain in mist or low cloud can be difficult –
save this walk for a good day!
Route Several sections follow abandoned or unfinished
sections of 19th century industrial tramroad which offer
relatively easy walking.
Getting there
From Brecon
Turn off the A40 at
Sennybridge and take
the A4067 towards
Swansea to reach Craig
y nos Country Park
after 19 miles/26 mins.
From junction 45,
M4 nr Swansea
Take the A4067
up the Swansea Valley
to reach
Craig y nos
Country Park
after 16 miles/26mins. Pay and display parking.
Information staff at the National Park Visitor Centre near
Brecon (and at other seasonal centres at Pontneddfechan
and Llandovery) can advise on purchasing detailed walking
maps of the area. Visit www.beacons-npa.gov.uk/shop
faith
n) /
andstone)
Carreg Laid Bishopston /
Bishopston Mudstone
Carreg Laid Bishopston /
Bishopston Mudstone
10
3
4
de-ddwyrain /
south-east
gogledd-orllewin /
north-west
prif grib Cribarth/
Cribarth main ridge
Tywodfaen Twrch /
Twrch Sandstone
Calchfaen Carbonifferaidd /
Carboniferous Limestone
Hen Dywodfaen Coch /
Old Red Sandstone
Tywodfaen Dil Mel /
Honeycombed Sandstone
pyllau garreg bwdr /
rottenstone pits
ty-un-nos
(adfail / ruin)
A
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423m
426m
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Craig-y-nos
Country Park
P
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Pentre
Cribarth
Craig-y-nos
Craig y
Rhiwarth
Pant-y-wal
A 4067
C
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Parc Gwledig
Craig-y-nos /
Castell Craig-y-nos
(gwesty) /
Craig-y-nos Castle
(hotel)
"ty-un-nos"
carn/cairn
carn /
cairn
Pwll-yr-cawr
piler triongli /
trig point
sticil ysgol /
ladder stile
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pwll / pool
llyn / lake
giat / gate
^
giat / gate
^
giat / gate
^
c
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428m
Man cychwyn
/ Starting point
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6
1
Tywodfaen Twrch /
Twrch Sandstone
Calchfaen Carbonifferaidd /
Carboniferous Limestone
chwarela carreg bwdr /
rottenstone workings
tywod, graean /
sand, gravel
pyllau carreg bwdr /
rottenstone workings
pyllau carreg bwdr /
rottenstone workings
>
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Gwybodaeth ddaearegol yn deillio o fapio gan Arolwg Daearegol Prydeinig © NERC 2018 Cedwir pob hawl
Map seiliedig ar fapio OS dihawlfraint / Map based upon out of copyright OS mapping
Geological information based on mapping by the British Geological Survey © NERC 2018 All rights reserved
0 milltir / mile 1/2
0 cilomedr / km 0.5
G/N
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P
Allwedd / Key
Llwybr Cribarth / Cribarth Trail
Llwybrau, traciau / paths, tracks
Esgyniadau serth / steep ascents
Ffyrdd & adeiladau / roads & buildings
Maes parcio (T&A) / car park (P&D)
Hen dramffyrdd / old tramroads
Coed, llyncdwll / woods, shakehole
Chwareli / quarries
Muriau, ffensys / walls, fences
Copa, pant llydan / summit, broad hollow
2
Mae’r croestoriad yma’n dangos y creigiau o dan eich traed wrth i chi ddringo’r inclên tua’r gogledd-ddwyrain o’r man cychwyn. Mae’r
graig hynaf a welir ar yr wyneb ar y daith yw’r Calchfaen Carbonifferaidd a ddyddodwyd oddeutu 350 miliwn o flynyddoedd yn ôl mewn
moroedd trofannol. Y rhai ieuengaf yw cerrig llaid a thywodfeini’r Cystradau Glo a ffurfiwyd mewn deltâu afonydd oddeutu 310 miliwn o
flynyddoedd yn ôl.
BELOW This cross-section shows the rocks under your feet as you ascend the incline northeast from the start. The oldest rock seen at the
surface on the walk is the Carboniferous Limestone laid down around 350 million years ago in tropical seas. The youngest are the Coal
Measures mudstones and sandstones formed in river deltas around 310 million years ago.
UCHOD 300 miliwn o flynyddoedd yn ôl, perodd pwysedd ochrol i haenau’r graig blygu a hollti. Golygai’r craciau hyn fod calchfeini’r Cribarth yn haws
eu cloddio na chreigiau gorweddol mewn mannau eraill.
LEFT Three hundred million years ago, lateral pressure caused rock layers to fold and crack. These cracks made Cribarth's limestones easier to quarry
than flat-lying rocks elsewhere.
A new simple geology map of Fforest Fawr Geopark is available from National Park information
centres to help you understand the landscape you're walking through.
Please follow
the Countryside Code
This land is grazed by sheep and horses – please
keep dogs on a short lead on the hill.
As you follow this tramroad note how the dip of the rock
strata has changed – you are now on the south-eastern
flank of the main Cribarth anticline. The rocks dip steeply
to the southeast in contrast to earlier stops where they
were dipping to the northwest.
The anticline is part of the Cribarth Disturbance, a set
of major geological faults and folds stretching from
Swansea Bay northeast up Cwm Tawe, through this hill
and on towards Brecon.
Continue beyond the quarry in the same direction
and, as you head down a grassy slope, the
wall/fence which you followed earlier, comes into view.
Head for the ladder-stile you crossed much earlier.
Retrace your steps carefully down the steep hillside to the
road. Beware if wet, it is more slippery going downhill!
Return to the Country Park, mindful of traffic on the road.
Facilities at Craig-y-nos Country Park include:
• Pay & display parking
• Toilets
• Café
• Walks
• Geopark and National Park displays
More information at
www.breconbeacons.org/craig-y-nos-country-park
Fforest Fawr Geopark is grateful to The National Showcaves
Centre for Wales for use of the permitted path through the
woodland.
Retrace your steps for 50m
and take the right fork
where the tramroads split,
continuing along this narrow
bench cut into the hillside for
400m to a small quarry set a
few metres back on the right.
The smooth back wall of the quarry
is a fault plane.
Continue behind the quarry and, with a larger
quarry to your left, drop down first to one minor
tramroad and then down to a second. Don’t go beyond
it – the grounds gets much steeper!
Originally horizontal, the rocks of Cribarth were folded
300 million years ago. They were heavily fractured in the
process, making them easier to quarry with hand tools.
Turn left along this second tramroad, following it
NE for about 500m before it ends in another quarry
At a couple of places, the tramroad passes through
shallow cuttings – look out for blocks of the
Honeycombed Sandstone, a thin bed of sandstone
within the limestone.
Honeycombed Sandstone in tramroad cutting
Mae map daeareg syml newydd o Geoparc y Fforest Fawr ar gael gan Ganolfannau
Gwybodaeth y Parc Cenedlaethol i’ch helpu i ddeall y dirwedd rydych yn cerdded drwyddi.
© Eleanor Flaherty
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Lluniau o'r awyr © Hawlfraint y Goron: Comisiwn Brenhinol Henebion
Cymru /Aerial images © Crown copyright: Royal Commission on the
Ancient & Historical Monuments of Wales.
