Retreat of the Late Pliocene and Lower Pleistocene Crag sea
Table 4. Pre-Anglian Thames: typical clast lithologies
'Colchester Formation'
U. Thames M. Thames C. Essex/
Suffolk
Hint 13% 19% 78-82%
Quartz + q'ite 98.4 18.4 14-19
Qtz (32.8) (13.1) ( 7-10)
Q'ite (65.6) ( 5.3) ( 7-10)
Chert 0.3 2.1 2.6
O'sandcht* - - (0.6-0.7)
art. cht* - - (1.4-2.0)
Acid volcanics 0.0 0.2 0.3-1.0
*Wivenhoe and Lower St Osyth Members only (Bridgland, 1994)
'Sudbury Formation'
U. Thames M. Thames C. Essex/
Suffolk
Hint 1- 5% 54-61% 66-75%
Quartz + q'ite 93-96 36-45 23-31
OB (38-58) (27-32) (15-20)
Q'ite (35-58) (10-12) ( 7-14)
Chert 0.0-2.4 0.8-1.5 1.7-3.0
G'sandcht* (0) ( 0-1.5)
Carb. cht* ( 0-2.4) ( 0-0.3)
Acid volcanics 0.0-0.5 0.2-0.5 0.0-0.8
* 8-32 mm (Gibbard, 1985)
Nettlebed Gravel
Angular flint 15-20%
Rounded flint 65-80
Quartz 5-10
Quartzite