The BGS Lexicon of Named Rock Units — Result Details

Coralline Crag Formation

Computer Code: CCG Preferred Map Code: CCG
Status Code: Full
Age range: Pliocene Epoch (NP) — Gelasian Age (Q2G)
Lithological Description: Carbonate-rich skeletal sands. The acid-insoluble sand fraction is moderately- to poorly-sorted medium-grained sand, the mud content is low. Basal lag gravel rich in pebbles of phosphatic mudstone largely derived from the Thames Group.
Definition of Lower Boundary: Rests unconformably on the undulose, possibly tidally-scoured, surface of the Thames Group throughout its known distribution.
Definition of Upper Boundary: Overlain unconformably by rocks of the Norwich Crag Formation across most of its extent, but Red Crag Formation material is banked against a buried ridge of the Coralline Crag in some areas and thin Red Crag deposits overlie the Coralline Crag locally.
Thickness: c.25m maximum onshore.
Geographical Limits: Restricted to southeast Suffolk, around Orford and Aldeburgh, as far north as Thorpeness and just into the adjacent offshore area. There are isolated outliers at Ramsholt and Tattingstone.
Parent Unit: Crag Group (CRAG)
Previous Name(s): Coralline Crag (-3283)
Alternative Name(s): Sudbourne Member
Aldeburgh Member
Ramsholt Member
Type Area  Pits around Aldeburgh, Sulffolk. Balson et al., 1993. 
Balson, P S, Mathers, S J and Zalasiewicz, J A. 1993. The lithostratigraphy of the Coralline Crag (Pliocene) of Suffolk. Proceedings of the Geologists' Association, Vol.104, 59-70. 
Balson, P S. 1989. Tertiary phosphorites in the southern North Sea Basin: origin, evolution and stratigraphic correlation, 51-70 in Herriet, J P, and de Moor, G (editors), The Quaternary and Tertiary geology of he Southern Bight, North Sea. Ministry of Economic Affairs, Belgium Geological Society. 
Balson, P S. 1990. The Neogene of East Anglia - a field excursion report. Tertiary Research, Vol.11, 179-189. 
Balson, P S and Cameron, T D J. 1985. Quaternary mapping offshore East Anglia. Modern Geology, Vol.9, 221-239. 
Moorlock, B S, Hamblin, R J O, Morigi, A N, Booth, S J and Jeffery, D H. 2000. The geology of the country around Lowestoft and Saxmundham. Memoir of the British Geological Survey, sheets 176 and 191 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E224 E242 E208 E225 E191 E207