The Bristol Coalfield is a geologically complex coalfield

Coalfield

A coalfield is an area of certain uniform characteristics where coal is mined. The criteria for determining the approximate boundary of a coalfield are geographical and cultural, in addition to geological...

 in the west of England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. Comprising the coal-bearing rocks arranged around the Coalpit Heath Syncline and Kingsdown Anticline, it extends beneath the eastern parts of the city of Bristol

Bristol

Bristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...

 and northwards through southern Gloucestershire

Gloucestershire

Gloucestershire is a county in South West England. The county comprises part of the Cotswold Hills, part of the flat fertile valley of the River Severn, and the entire Forest of Dean....

. The coalfield is sometimes referred to together with the Somerset Coalfield

Somerset coalfield

The Somerset Coalfield included pits in the North Somerset, England, area where coal was mined from the 15th century until 1973.It is part of a wider coalfield which covered northern Somerset and southern Gloucestershire. It stretched from Cromhall in the north to the Mendip Hills in the south, and...

, which lies to its south, as the Bristol and Somerset Coalfield. There are also two outlying coal-mining areas, the Severn Coalfield and the Nailsea Basin which are described below.

Several coal seams are named in the sequence in the Bristol Coalfield. The seams are listed stratigraphically with the uppermost (youngest) at the head of the list and the lowermost (oldest) at the foot. Not all seams are named, nor are all seams present at any one location.

Upper Coal Measures

• Pensford No 1
• Pensford No 2
• Pensford No 3
• Bromley No 4
• Bromley No 5
• Rock Vein of Brislington
• Salridge
• Mangotsfield (?Salridge)
• Stinking
• Corston
• Cock (?=Millgrit & Rag)
• Coke
• Chick (?=Buff)
• Hen (?=Parrot)
• Coking

Lower and Middle Coal Measures

• New Smith's (?Yate Little, Warmley)
• ?Yate Hard
• Lower Five
• Kingswood & Bedminster Great
• Giller Inn
• Kingswood Little
• Soundwell Hard Venture
• Ashton Great
• Ashton Little

Severn Coalfield

Within the Upper Coal Measures of the outlying 'Avonmouth

Avonmouth

Avonmouth is a port and suburb of Bristol, England, located on the Severn Estuary, at the mouth of the River Avon.The council ward of Avonmouth also includes Shirehampton and the western end of Lawrence Weston.- Geography :...

 Basin' are the Avonmouth No 1 and No 2 coals. This is sometimes known as the Severn Coalfield. It lies several miles to the west of the main Bristol Coalfield and extends under the Severn Estuary

Severn Estuary

The Severn Estuary is the estuary of the River Severn, the longest river in Great Britain. Its high tidal range means it has been at the centre of discussions in the UK regarding renewable energy.-Geography:...

 as far as Portskewett

Portskewett

Portskewett is a village in Monmouthshire, south east Wales. It is located four miles south west of Chepstow and one mile east of Caldicot, in an archaeologically sensitive part of the Caldicot Levels on the Welsh shore of the Severn Estuary...

. It is also largely obscured by thick deposits of estuarine alluvium. Coal was also worked on a very small scale in the rocks of the Clapton-in-Gordano inlier

Inliers and outliers (geology)

An inlier is an area of older rocks surrounded by younger rocks. Inliers are typically formed by the erosion of overlying younger rocks to reveal a limited exposure of the older underlying rocks. Faulting or folding may also contribute to the observed outcrop pattern...

 just to the south of the Severn Coalfield.

Nailsea Basin

In the small 'Nailsea

Nailsea

Nailsea is a town in the unitary authority of North Somerset within the ceremonial county of Somerset, England, approximately to the southwest of Bristol and about to the northeast of the seaside resort of Weston-super-Mare. The nearest village is Backwell, which lies south of Nailsea on the...

 Basin' 7 miles / 12km to the west of Bristol, a sequence of Coal Measures rocks are preserved within a syncline

Syncline

In structural geology, a syncline is a fold, with younger layers closer to the center of the structure. A synclinorium is a large syncline with superimposed smaller folds. Synclines are typically a downward fold, termed a synformal syncline In structural geology, a syncline is a fold, with younger...

. These rocks are connected at depth with those of the Somerset Coalfield; though it lies close to the main body of the Bristol Coalfield, it is not connected with it. Two seams are known from the upper Coal Measures and twelve from the Lower and Middle Coal Measures within this 'basin'. Only those indicated thus - w - were worked to any great extent:

Upper Coal Measures

• Grace's (0.9m) w

Lower and Middle Coal Measures

• White's Top (1.1m) w
• Golden Valley
• Backwell Little
• Dog (0.9m) w