Table 19.9 Summary of Underlying Superficial Geology3 Stratum


Age Alluvium


River Valley Drift


Marine and Coastal Zone Deposits: Mud


Head


River Terrace Deposits (undifferentiated)


Quaternary, Holocene


Quaternary, Holocene


Quaternary, Pleistocene


Description Variably sandy, silty Clay


Mud, tidal flat, channel and salt marsh deposits (coastal & River Deben zone only)


Diamicton, stony sandy clay and clayey sand


Quaternary, Pleistocene Sand and gravel


Lowestoft Formation Quaternary, Pleistocene


Drift


Stony, sandy clay rich in chalk and flint pebbles (diamicton)


Glaciofluvial Deposits Quaternary, Pleistocene Sand and gravel


Kesgrave Catchment Subgroup


19.5.1.2 Bedrock Geology 45.


Quaternary, Pleistocene


Sand and gravel; sand with flint and quartzite pebbles representative of an historical braided river system.


Thickness Unknown Unknown Unknown Unknown 8-12m 0-8m 5–10m


The underlying bedrock geology beneath the onshore electrical transmission works changes as the route moves west, with the exception of the Chalk Group which is prevalent across the entire corridor at depth, outcropping near Claydon (approximate NGR 614000, 249000). In addition, the Lambeth Group and Thanet Sand Formation (undifferentiated) are likely to be prevalent at depth across the entire study area although the lateral extent of these strata may discontinue around Claydon.


46.


The bedrock appears at the surface near to the coastline with Red Crag and London Clay apparent in the sea cliffs. These formations, along with the Harwich Formation, overlie the chalk in the east but as the cable route moves west the London Clay and Harwich Formations disappear leaving the Red Crag or superficial drift deposits directly overlying the Chalk Group or the Lambeth Group and Thanet Sand Formation.


3 After BGS solid and drift geology sheets 207, 208, 225 and British Regional Geology, East Anglia and Adjoining areas


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm


Chapter 19 Soils, Geology and Ground Condition Page 22


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