Jncc coastal Directories Project Region 11 The Western Approaches

Subsequent uplift led to the removal, in the English Channel
and elsewhere, of much of the Jurassic sequence, and the
accumulation of thick Lower Cretaceous sediments.  An
overlying blanket of chalk (Upper Cretaceous) covers much
of the complex structure of the buried early Mesozoic
sequences (
Map 2.2.3
).  
The removal of much of the Jurassic sediment from the
English Channel Basin has greatly reduced its potential as a
hydrocarbons province.  The Celtic Sea Basin, which has salt
structures in the Jurassic sediments and a thick Cretaceous
cover, has greater potential.  The hydrocarbons potential of
the Bristol Channel is highest in the west, where the thick
and relatively complete Jurassic and Lower Cretaceous
succession is overlain by a thick Upper Cretaceous and
Tertiary blanket.
Tertiary (Palaeogene) sediments preserved in the Celtic
Sea Basin are largely of Oligocene or Eocene age.  Of interest
is the Stanley Bank Basin to the east of Lundy.  This basin,
containing sediments of Oligocene age, is formed along the
Sticklepath Fault, which is traceable north-westwards into
Dyfed and south-eastwards into Devon.   
The rocks making up the Lizard (see 
section 2.1.2
)
extend a short distance offshore, before becoming concealed
beneath Devonian and Permo-Triassic rocks.  At Land’s End,
Devonian rocks were intruded by a granite batholith during
the early Permian, and the coarse granite outcrops on the
sea bed.  
2.2.4  Further sources of information
A.  Maps
British Geological Survey.  1982.  Scilly. Sheet 49°N-08°W. Sea-bed
sediments.  1:250,000 series.  Keyworth, British Geological
Survey.
British Geological Survey.  1982.  Scilly. Sheet 49°N-08°W. Solid
geology.  1:250,000 series.  Keyworth, British Geological Survey.
British Geological Survey.  1983.  Land’s End. Sheet 50°N-06°W. Solid
geology.  1:250,000 series.  Keyworth, British Geological Survey.
British Geological Survey.  1983.  Lizard. Sheet 49°N-06°W. Sea-bed
sediments.  1:250,000 series.  Keyworth, British Geological
Survey.
British Geological Survey.  1983.  Lizard. Sheet 49°N-06°W. Solid
geology.  1:250,000 series.  Keyworth, British Geological Survey.
British Geological Survey.  1983.  Lundy. Sheet 51°N-06°W. Sea-bed
sediments.  1:250,000 series.  Keyworth, British Geological
Survey.
British Geological Survey.  1983.  Lundy. Sheet 51°N-06°W. Solid
geology.  1:250,000 series.  Keyworth, British Geological Survey.
British Geological Survey.  1985.  Land’s End. Sheet 50°N-06°W. Sea-
bed sediments.  1:250,000 series.  Keyworth, British Geological
Survey.
British Geological Survey.  1986.  Bristol Channel. Sheet 51°N-04°W.
Sea-bed sediments and Quaternary geology.  1:250,000 series.
Keyworth, British Geological Survey.
British Geological Survey.  1986.  Haig Fras. Sheet 50°N - 08°W. Sea
bed sediments.  1:250,000 series.  Keyworth, British Geological
Survey.
2.2  Offshore geology
25
k
pt
j
pt
B
k
j
pt
k
k
pt
d
Acid igneous intrusive
G
B
dc
G
G
dc
pt
pt
k
g
pt
pt
dc
dc
dc
g
k
j
k
k
B
g
k
j
k
j
t
dc
t
t
dc
j
t
dc
t
j
g
k
g
k
k
Palaeogene
Cretaceous
Jurassic
Triassic
Stratigraphy
j
k
t
g
Igneous rocks
Structures
Devonian–Carboniferous
Undivided
Permian–Triassic
B
dc
pt
Fault, tick on downthrow side
Map 2.2.3
Offshore solid (pre-Quaternary) geology.  Source: British Geological Survey (1991).

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British Geological Survey.  1987.  Haig Fras. Sheet 50°N - 08°W. Solid
geology.  1:250,000 series.  Keyworth, British Geological Survey.
British Geological Survey.  1988.  Bristol Channel. Sheet 51°N-04°W.
Solid geology.  1:250,000 series.  Keyworth, British Geological
Survey.
British Geological Survey.  1991.  North Celtic Sea sheet, Quaternary
geology.  1:250,000 series.  Keyworth, British Geological Survey.
B.  References cited
British Geological Survey.  1991.  Geology of the United Kingdom,
Ireland and the adjacent continental shelf.  1:1,000,000 scale.
Keyworth, British Geological Survey.
British Geological Survey.  1994.  Quaternary geology around the
United Kingdom (north & south sheets). Keyworth, British
Geological Survey.
Folk, R.L.  1954.  The distinction between grain-size and mineral
composition in sedimentary rock nomenclature.  Journal of
Geology, 62: 344-359.
Scourse, J.D., Bateman, R.M., Catt, J.A., Evans, C.D.R., Robinson,
J.E., & Young, J.R.  1990.  Sedimentology and
micropalaeontology of glacimarine sediments from the central
and south-western Celtic Sea.  In: Glacimarine sediments: processes
and sediments, ed. by J.A. Dowdeswell & J.D. Scourse, 329-347.
London, Geological Society.  (Special Publication No. 53.)
C.  Further reading
Evans, C.D.R.  1991.  The geology of the western English Channel and its
western approaches.  London, HMSO, for the British Geological
Survey.  (United Kingdom Offshore Regional Report.)
Hamblin, R.J.O., Crosby, A., Balson, P.S., Jones, S.M., Chadwick,
R.A., Penn, I.E., & Arthur, M.J.  1992.  The geology of the English
Channel.  London, HMSO, for the British Geological Survey.
(United Kingdom Offshore Regional Report.)
Pantin, H.M.  1991.  The sea bed sediments around the United Kingdom:
their bathymetric and physical environment, grain size, mineral
composition and associated bedforms. Keyworth, British Geological
Survey.  (BGS Research Report SB/90/1.) 
Tappin, D.R., Chadwick, R.A., Jackson, A., Wingfield., R.T.R., &
Smith, N.J.P.  1994.  The geology of Cardigan Bay and the Bristol
Channel.  London, HMSO, for the British Geological Survey.
(United Kingdom Offshore Regional Report.)  
Taylor, R.T., & Goode, A.J.J.  1987.  Late Pleistocene and Holocene
radiocarbon dates from the Penzance District, Cornwall.
Proceedings of the Ussher Society, 6: 559.
D.  Contact names and addresses
Type of information
Contact address and telephone no.
Geological information for 
Coastal Geology Group, British 
region and the whole of 
Geological Survey, Keyworth, 
Britain
Nottingham  NG12 5GG, 
tel: [phone]
UKDMAP 1992.  Version 2.  
*BODC, Birkenhead, 
United Kingdom digital 
tel: [phone]
marine atlas.  
Oceanographic maps
Region 11  Chapter 2  Geology and physical environment
26

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