Stratigraphic range: Plio-Pleistocene ~4.4–0.78 Ma
PreꞒ
Ꞓ
O
S
D
C
P
T
J
K
Pg
N
↓
Red Crag Formation at Bawdsey cliff, Suffolk
Type
Geologic group
Unit of
Great Britain Superficial Deposits Supergroup
Sub-units
Coralline, Red, Norwich & Wroxham Crag Formations
Underlies
Dunwich, Albion Glacigenic, Britannia Catchments & British Coastal Deposits Groups
Overlies
Unconformity with Chalk Group and London Clay Formation
Thickness
Up to 70 m (230 ft) offshore
Lithology
Primary
Sand
Other
Gravel, clay, silt, calcarenite
Location
Region
East Anglia
Country
UK
Extent
East Anglia & North Sea
Type section
Named by
R.C. Taylor
Year defined
1823
The Crag Group is a geological group outcropping in East Anglia, UK and adjacent areas of the North Sea. Its age ranges from approximately 4.4 to 0.478 million years BP, spanning the late Pliocene and early to middle Pleistocene epochs.[1][2] It comprises a range of marine and estuarine sands, gravels, silts and clays deposited in a relatively shallow-water, tidally-dominated marine embayment on the western margins of the North Sea basin. The sands are characteristically dark green from glauconite but weather bright orange, with haematite 'iron pans' forming. The lithology of the lower part of the Group is almost entirely flint. The highest formation in the Group, the Wroxham Crag, contains over 10% of far-travelled lithologies, notably quartzite and vein quartz from the Midlands, igneous rocks from Wales, and chert from the Upper Greensand of southeastern England. This exotic rock component was introduced by rivers such as the Bytham River and Proto-Thames.[3][4]
The constituent formations of the Crag Group are the Coralline Crag (mid to late Pliocene); the Red Crag (late Pliocene / early Pleistocene); the Norwich Crag (early Pleistocene) and the Wroxham Crag (early to Middle Pleistocene).[5] The sedimentary record is incomplete, leading to difficulties in correlating and dating sequences[6]
The term Crag was first used in a geological sense by R.C. Taylor in 1823, a word commonly used in Suffolk to designate any shelly sand or gravel.[7]
^Head, MJ (1988). Marine environmental change in the Pliocene and early Pleistocene of eastern England: the dinoflagellate evidence reviewed. In: van Kolfschoten, T and Gibbard, PL (eds): The Dawn of the Quaternary - proceedings of the SEQS-EuroMam Symposium : Kerkrade, 16–21 June 1996. Netherlands Institute of Applied Geoscience, 1998; fig.2. ISBN 9072869613.
^Mathers, SJ & Hamblin, RJO (2015). Late Pliocene and Pleistocene Marine Deposits. In: Lee, JR; Woods, MA; Moorlock, BSP, eds. British Regional Geology: East Anglia (5th Edition). British Geological Survey; fig.46. ISBN 978 085272 823 9
^The BGS Lexicon of Named Rock Units. British Geological Survey; online at http://www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=CRAG. Accessed October 2017
^Lee, JR; Woods, MA; Moorlock, BSP, eds. (2015). British Regional Geology: East Anglia (5th Edition). British Geological Survey; p.110. ISBN 978 085272 823 9.
^Lee, JR; Woods, MA; Moorlock, BSP, eds. (2015). British Regional Geology: East Anglia (5th Edition). British Geological Survey; p.111. ISBN 978 085272 823 9.
^Jones, RL & Keen, DH (1993). Pleistocene Environments of the British Isles. Chapman & Hall. ISBN 0 412 44190 X.
^Woodward, HB (1881): The Geology of the Country around Norwich. Memoirs of the Geological Survey of the United Kingdom; p.32
The CragGroup is a geological group outcropping in East Anglia, UK and adjacent areas of the North Sea. Its age ranges from approximately 4.4 to 0.478...
Look up crag in Wiktionary, the free dictionary. Crag may refer to: Crag (climbing), a cliff or group of cliffs, in any location, which is or may be suitable...
its iron-stained reddish colour and crag which is an East Anglian word for shells. It is part of the CragGroup, a series of notably marine strata which...
The Norwich Crag Formation is a stratigraphic unit of the British Pleistocene Epoch. It is the second youngest unit of the CragGroup, a sequence of four...
The Eurasian crag martin or just crag martin (Ptyonoprogne rupestris) is a small passerine bird in the swallow family. It is about 14 cm (5.5 in) long...
Temple Crag is a mountain peak in the Palisades group of peaks of the Sierra Nevada with an elevation of 12,982 feet (3,957 m). The peak lies east of the...
continuous core sample of late Pliocene and early Pleistocene sediments of the CragGroup was recovered. Analysis allowed biostratigraphic zonal schemes for fossil...
Crag Lough is an inland lake at the southern edge of Northumberland National Park, 2.5 miles (4.0 km) north of Bardon Mill, and 0.5 miles (0.8 km) north...
tooth and a right inner ear periotic bone from the English Red Crag Formation of the CragGroup, dating to the Early Pleistocene, was referred by English geologist...
Glacigenic Group and sometimes by those of the Britannia Catchments Group or British Coastal Deposits Group and interfingers in places with those of the Crag Group...
The Weybourne Crag Formation is a geologic formation in England. It preserves fossils. Earth sciences portal England portal Paleontology portal List of...
neighbours Scafell Pike. What are now known as Scafell Pike, Ill Crag, and Broad Crag were collectively called either the Pikes (peaks) or the Pikes of...
Group, Britannia Catchments Group, British Coastal Deposits Group, Caledonia Glacigenic Group, CragGroup, Dunwich Group and Residual Deposits Group....
The crag martins are four species of small passerine birds in the genus Ptyonoprogne of the swallow family. They are the Eurasian crag martin (P. rupestris)...
underlying Albion Glacigenic Group (in England and Wales), the Caledonia Glacigenic Group (in Scotland), the Dunwich Group, CragGroup or with older bedrock...
Dove Crag is a fell in the English Lake District. Situated in the Eastern Fells of the national park, seven kilometres south-south-west of Glenridding...
boundary of the Lake District National Park in Cumbria, and all but one (Castle Crag) are over 1,000 feet (304.8 m) in height. Over two million copies of the...
Britannia Catchments Group (with which they also interfinger), Albion Glacigenic Group, Caledonia Glacigenic Group, Dunwich Group, CragGroup or earlier bedrock...
The Coralline Crag Formation is a geological formation in England. It is a series of marine deposits found near the North Sea coast of Suffolk and characterised...
The Crag Hotel, Penang is an abandoned hotel and former school building on the north edge of Penang Hill. The original site was first occupied by a Mr...
breccia; and rhyolitic lava-like tuff. The altitude places Loft Crag and Gimmer Crag within sightlines to east-southeast while Bowfell is three kilometres...
The dusky crag martin (Ptyonoprogne concolor) is a small passerine bird in the swallow family. It is about 13 cm (5 in) long with a broad body and wings...
Creswell Crags is an enclosed limestone gorge on the border between Derbyshire and Nottinghamshire, England, near the villages of Creswell and Whitwell...
Tarbuck Crag (68°35′S 78°12′E / 68.583°S 78.200°E / -68.583; 78.200) is one of a group of three high points about 0.75 nautical miles (1.4 km) southwest...
groups of mountains and subsidiary summits and tops in the Lake District, England. Allen Crags Angletarn Pikes Ard Crags Armboth Fell Arnison Crag Arthur's...
St Sunday Crag is a fell in the English Lake District, part of the Fairfield group in the Eastern Fells. It is a prominent feature in the Patterdale skyline...
The pale crag martin (Ptyonoprogne obsoleta) is a small passerine bird in the swallow family that is resident in Northern Africa and in Southwestern Asia...
Mundlauga Crags (71°57′S 8°24′E / 71.950°S 8.400°E / -71.950; 8.400) is a group of 2,455 m (8,054 ft) high rock crags that form the south end of Fenriskjeften...
Chaos Crags is the youngest group of lava domes in Lassen Volcanic National Park, California. They formed as six dacite domes 1,100-1,000 years ago, one...