SITES
Name: Tavistock Railway Cutting, St Johns Avenue
Car Park and Tavistock Building Stones
Parish: Tavistock
Local Authority: West Devon
National Grid Ref: Railway cutting: SX47227413 – 47887450
OS Sheets: 1:50k - 201; 1:25k – Explorer 108; 1:10k – SW47SE; GS 1:50k – 348.
Locality Description: Includes rock faces around a public car park (St Johns
Avenue Car Park, exposures in the sides of a disused railway cutting (Tavistock
Railway Cutting) and local building stones visible in Tavistock Town centre.
Nature and Status of Site: Tavistock Railway Cutting and St Johns Avenue car
park are County Geological Sites (www.devonrigs.org.uk) and the former is also a
Local Nature Reserve (LNR). Tavistock Centre lies within the Cortnwall and West
Devon Mining Landscapes World Heritage Site.
Summary of Geological / Geomorphological Interest:
Tavistock Railway Cutting: The site shows one of the most important and extensive
exposures within the Upper Devonian–Lower Carboniferous sequences of West
Devon. It includes key fossiliferous sections in the Brendon and Burraton formations,
which yield conodont-ostrocod faunas crucial to the dating of these units. There is
also established public access thereby facilitating educational use.
St. John’s Avenue Car Park: A remarkably accessible locality showing a range of
structural features in Lower Carboniferous St. Mellion Formation (formerly assigned
to the Brendon Formation, and later the Cotehele Sandstone Formation).
Tavistock Town Centre: Tavistock includes a multitude of geological exposures,
mainly roadside cuttings showing slates and occasionally sandstones of Upper
Devonian and Carboniferous age. Exposures of volcanic rocks including gas
bubbles (‘vesicles’) are also present including on the east side of Drake Road south
of the Viaduct. Crucially, two of these exposures are sufficiently large and instructive
to merit County Geological Site Status, St. John’s Avenue Car Park and Tavistock
Railway Cutting (see above).
More obvious to the general visitor, however, are the impressive buildings of central
Tavistock, many of which are constructed of the local ‘Hurdwick Stone’, a Lower
Carboniferous volcanic ash full of spectacular lava ‘bombs’ (Fig. 31). Many other
types of geological materials have also been used, including local slate for rough
walling and Dartmoor granite for kerbs and sills. Another local speciality is
‘Roborough Stone’, a felsite much used in the Middle Ages for columns and other
carved features in ecclesiastical buildings – until the source was exhausted.
[Modified from Macadam and Page 2004]
Safety Considerations: The cutting has steep sides and locally the uncontrolled
growth of trees has the potential to destabilise rock faces. The use of safety helmets
when examining rock exposures is therefore advisable. Similarly, the use of safety
Educational Register of Geological Sites
helmets is a normal precaution when standing close to the rock faces in St. John’s
Avenue Car park. Due to traffic movement, group visits to the latter car park and
Tavistock Town centre should be well managed.
Educational Age Groups: Primary and Secondary Schools, 6th Form/College,
University Undergraduate Research, Professional or Amateur geologists, General
Public.
Parking and Access: The LNR is accessible from Crease Lane Bridge and from a
path leading westwards on the south side of Launceston New Road Bridge, in the
west, and from Grenville Road at its eastern end. Limited road-side parking is
available close to these areas. An off road cycle route runs through the railway
cutting and the site can therefore be accessed on bicycle. St Johns Avenue Car Park
is a public car park and provides a useful starting place for a geological visit to the
town. A large car park is also available close to the canal quay area.
For bus and train timetables, visit www.traveline.org.uk
References:
BULL. B.W. 1982. Geology and Mineralogy of an area around Tavistock, SW
England. Unpublished PhD thesis, University of Exeter.
MACADAM, J. and PAGE, K.N. 2004. Geodiversity Audit and interpretative review of
the mining districts of the Tamar and Tavy rivers in West Devon: Part 2 - ‘Rolling
back millions of years’ - interpreting the geology of West Devon. Report to Devon
County Council, 61pp.
PAGE, K.N. 2004. Geodiversity Audit and interpretative review of the mining districts
of the Tamar and Tavy rivers in West Devon: Part 1 – Geodiversity Audit and
selection of County Geological Sites. Report to Devon County Council, 92pp.
REID, C., BARROW, G., SHERLOCK, R.L., MACALLISTER, D.A. and DEWEY, H.
1911. Geology of the country around Tavistock and Launceston (Sheet 337).
Memoirs of the Geological Survey, England and Wales.
STEWART, I.J. 1981. Structure stratigraphy and conodont biostratigraphy of the NE
margin of Bodmin Moor. Unpublished PhD thesis. University of Exeter, 1981, p.150,
221-222.
TURNER, P.J. 1982. Aspects of the evolution of the Hercynides in central south-west
England. Unpublished PhD thesis, University of Exeter
WHITELEY, M.J. 1983. The geology of the St. Mellion outcrop, Cornwall and its
regional setting. Unpublished PhD thesis, University of Exeter.
Online References:
The Cornwall and West Devon Mining Landscape World Heritage Site (online)
available at www.cornishmining.org.uk
Educational Register of Geological Sites
Detailed Geology and historical review:
Tavistock Railway Cutting (SX47227413 – 47887450): The cutting reveals a key
regional section through three major units within the West Devon, Upper Devonian –
Lower Carboniferous succession, specifically the Tavy, Burraton and Brendon
formations. The Tavy Formation comprises greenish grey slates and is exposed at
the south-west end of the cutting for around 77 m (from c. SX47227413). It is faulted
against a wedge of Burraton Formation at around SX47507432, the latter dominated
by grey slates and black mudstones, which have yielded an important fauna at
SX47507432 from nodular dark grey and black slates, including conodonts
(Polygnathus, Bispathodes), ostrocods (Richterina spp.), small bivalves and crinoid
fragments, indicating the hemispherica-dichotoma [ostrocod] Biozone and the
costatus [conodont] Biozone of theUpper Devonian.
The Burraton Formation is exposed for around 175 m before a second faulted
contact brings in the Brendon Formation, which includes black slates, locally with
diagenetic pyrite, interbedded with laminated micaceous sandstone and quartz
sandstone. The latter formation is exposed for around 310 m from SX 47627439 to
SX 47887456 and contains a level with calcareous nodules yielding conodonts at
SX47807453, including Gnathodus spp., indicating the texanus Biozone of the Lower
Carboniferous. At this latter point typical Brendon Formation lithologies pass into a
sequence with volcanic rocks, including amygdaloidal lavas and tuffs intercalated
with mudstones, the latter containing some calcareous nodules up to 30 cm across.
St. John’s Avenue Car Park (SX48077409): The site reveals remarkable vertical
sections, at least 100 m long, in the local Lower Carboniferous succession, cut in two
orientations at 90º to each other. Dominated by micaceous siltstones with some finegrained sandstones and thin quartz veins, these sections show F1, S1 and S2
structures, and a third cleavage is also developed. Originally assigned to the
Brendon Formation, the unit is mapped as Cotehele Sandstone Formation on the
published BGS map (Sheet 337). The latter unit has now, however, been included
within the St. Mellion Formation.
Tavistock Town Centre:
History: Tavistock Abbey was founded in 974 and for five and half centuries the
Benedictines led the life of the locality socially and economically. However, the
dissolution of the monasteries in 1539 by King Henry VIII saw the grant of the lands
and property to John Russell who founded the dynasty of the Earls and Dukes of
Bedford and became so completely involved in the prosperity of Tavistock and its
neighbourhood.
The Town was linked with the extraction of minerals long before it became one of the
four Stannary Towns, strategically placed to control and administer the tin industry
from as early as 1305. Together with Plympton, Chagford and Ashburton, it became
the centre to which the produce of the tin-rich valleys of Dartmoor was brought for
assessing the tax payable to the Crown which depended upon the quality of the ore.
Its status also entitled it to elect 24 tinners to attend the Stannary parliament as part
of the 96 who met on windy Crocken Tor until it was abolished in 1896. The powers
for fining, seizure of property and even imprisonment at its own infamous gaol at
Lydford were used often. Buyers from the Continent as well as all parts of England
were attracted to the sales and there seems to have been a ready desire by many to
risk investment in obviously questionable mining ventures.
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The current layout of the Town centre owes almost everything to the 7th Duke of
Bedford and, in no small degree, to his well-respected steward John Benson, who
channelled an impressive proportion of the Duke’s vast profits from mining and
ancillary interests to the redesign and improvement of the Town and conditions for
the workers. Key features of interest include: Abbey Chapel – formerly the Great Hall
of the Abbey, also Betsy Gimbal’s Tower – the West Gatehouse, and Still House and
other remains of the Abbey which date from around 974; St. Eustachius Church was
dedicated in 1318 although much of the present building was constructed in the mid
fifteenth century; Tavistock Bank was built in 1791 and Tavistock Savings Bank in
1816 making it the second oldest savings bank in the country.
The Duke of Bedford’s re-planning early in 1800’s used the distinctive green volcanic
stone from Hurdwick Quarry (around a mile N of the Town) extensively and buildings
included the Cornmarket (1835), Guildhall (1863), Pannier Market (1860) - paved
with granite from Pew Tor on Dartmoor- and new shops and other buildings along the
widened road now known as Duke Street. The Bedford Hotel had been remodelled
from the Bedford Steward’s House in 1822-29. This rock, from the Lower
Carboniferous, Milton Abbot Formation, which gives the town centre its character, is
a remarkable material, full of spectacular lava ‘bombs.
Many other types of geological materials have also been used in the construction iof
the town and at different periods, including local slate for rough walling and Dartmoor
granite for kerbs and sills. Another local speciality is ‘Roborough Stone’, a felsite
much used in the Middle Ages for columns and other carved features in ecclesiastical
buildings – until the source was exhausted.
The straight “½ mile boulevard” between the statues of Tavistock’s greatest son, Sir
Francis Drake, who stands forever a few miles from his birthplace at Crowndale
Farm, and the 7th Duke, in the midst of his creations at the other end, was provided
with suitably imposing residences for professional and merchant classes. Workers
were not forgotten, however, and Bedford Cottages in Dolvin Road were built 1845
using brick and were followed by others in 1856 and 1859 in Parkwood Road using
local rubble stone. Two elementary schools were also provided and even forms of
health care and pension introduced - certainly unusual for mid 19th century! Fitzford
Church (1865-67), however, originally built for local mining families, is now
Tavistock’s Roman Catholic Church as many miners preferred their own nonconformist chapels.
1889 saw the completion of the railway viaduct of granite construction but with
arches of moulded concrete blocks – a very early use of this material in a heavy loadbearing situation. In 1890 Drake Road was constructed to serve the new railway
station.
Industry: Although upwards of 80 mines of varying sizes and success have been
recorded around Tavistock, probably only two were within the old town limits –
Crelake Mine was started in 1857 and extended around 1.6 km east of the River
Tavy, from around 110 m south-east of West Bridge. In 1862, 270 people were
employed decreasing to 120 in 1870 and a few years later working ceased. The site
is now a small industrial estate and the mine captain’s house is the Market Inn. In
the same general area was Wheal Pixon, but which seems to have been
unsuccessful.
The area surrounding Tavistock, however, had always been predominantly
agricultural and much of its needs were covered by relatively few businesses, but
Educational Register of Geological Sites
when the mining boom of the 19th century took over many left poorly paid land jobs to
join the hard working – but better paid – miners. This meant that more shops and
services were needed in the Town to serve both the increasingly affluent ‘upper and
middle classes’ and progressively more demanding working population.
One of the most notable developments was the design and construction of the
Tavistock Canal through the leadership of John Taylor which connected Tavistock to
Morwellham Quay and enabled minerals to be delivered at a fraction of the cost of
land transportation.
Other industrial features surviving in Tavistock include:
• Foundries: Including Gill & Rundle/Gill & Bray, Parkham Road; Mount
Foundry Iron Works (1805) which became Tavistock Iron Works and its Clock
Tower can still be seen; Tavy Iron Foundry (1850); Bedford Iron Works
(Nicholls, Williams and Mather) (1848) which still stands in Bannawell Street.
•
Rope Works: Tavistock Rope Works.
•
Warehousing: Canal Quayside.
•
Ore Collection Area: Quayside car park.
•
Granaries: Canal Quay and elsewhere.
•
Quarries: Hurdwick, Wallabrook, Mill Hill, Lower Deerpark, etc.
•
Gas Works: Callington Road – moved to Westbridge in 1906
•
Railways: Launceston and South Devon Railway Company (1865), later GWR
from station in Whitchurch Road; London & South Western Railway (1890)
from Tavistock North (Drake Road).
[adapted from Page, R.E. in Macadam and Page, K.N. 2004]
Educational Register of Geological Sites
LOCATION PLAN
TAVISTOCK RAILWAY CUTTING, ST JOHNS
AVENUE CAR PARK AND TAVISTOCK
BUILDING STONES
TAVISTOCK, WEST DEVON
National Grid Reference:
© Crown copyright. All rights reserved. Devon County Council Licence No. 100019783 2008
3
1
2
Scale 1:28000
1. Tavistock Railway
Cutting
2. St. John’s Avenue Car
park
3. Tavistock Town centre
Parking and Access
• An off road cycle route runs through the railway cutting and
the site can therefore be accessed on bicycle. There is some
on-road parking adjacent to the site
• There is parking available at St Johns Avenue Car Park and
adjacent to the canal quay. .
Educational Register of Geological Sites
SITE 1
TAVISTOCK RAILWAY CUTTING
National Grid Ref: SX47227413 – 47887450
© Crown copyright. All rights reserved. Devon County Council Licence No. 100019783 2008
Scale 1:4500
Approx. extent of site
Main points of interest
•
Key exposures in local Upper Devonian to Lower
Carboniferous succession, specifically the Tavy, Burraton
and Brendon formations.
Educational Register of Geological Sites
SITE 2
ST JOHNS AVENUE CAR PARK
© Crown copyright. All rights reserved. Devon County Council Licence No. 100019783 2008
Scale 1:5100
Site locality
Main points of interest
• Very accessible exposure showing a range of structural
features in Lower Carboniferous St. Mellion Formation.
Educational Register of Geological Sites
TAVISTOCK RAILWAY CUTTING
Burraton Formation (dark slaty mudrocks) in Tavistock railway cutting (from Page 2004)
Faulted contact of Tavy Formation greenish slates and Burraton Formation
marked by masonry (from Page 2004)
Educational Register of Geological Sites
Tavy Formation, near New Launceston Road Bridge (from Page 2004)
Brendon Formation exposures, west of Old Launceston Road Bridge (from Page 2004)
Educational Register of Geological Sites
ST JOHNS AVENUE CAR PARK
General views of St John’s Avenue Car Park showing sections in the Lower Carboniferous, St
Mellion Formation (from Page 2004)
Educational Register of Geological Sites
Crenulation cleavage in the NW corner of St John’s Avenue Car Park (from Page 2004)
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TAVISTOCK TOWN CENTRE
Lava bomb in ‘Hurdwick Stone’ in Tavistock Town Hall – note gas bubbles and ‘teardrop’
shape (from Macadam and Page 2004)
Educational Register of Geological Sites