Fairlight Cove Geology

Cliff Section 2:

Between the Haddock’s Fault and the Fairlight Cove Fault (intersects cliff at approximately Cliff Way footpath)

The Middle Ashdown Beds are exposed and consist of alternating thin sandstone, sandy shales, silts and sandy clays. The beds are extremely variable. The strata are folded into a gentle anticline (hill) with its crest intersecting the cliff at Merrie Lands Cottage and running WNW to ESE. The clay layers within the cliffs in this section contain a perched water table (indicated by seeps) which is fed by infiltration of rain water.

The anticline brings a clay layer of variable thickness (0.7m-1.8m) to the face of the cliff at beach level. It runs for approximately 340m along this section. This layer plays an important role in the cliff failure of this section. The mechanism for failure is erosion of the clay layer by wave action and other weathering which undercuts blocks of sandstone/siltstone. The overlying sandstones and siltstones are well jointed (cracked) both vertically and horizontally along bedding and water can be observed to seep from the horizontal joints. The vertical joints run sub-parallel to the cliff face and are further widened by clay detritus which fills them and expands in the presence of water. The result is failure of the massive bedded sandstone and siltstone which topples onto the beach as blocks. This process of clay removal with bed instability above is seen throughout the vertical extent of the cliff at alternations between clay and slits/sands.

Alternations of sand and clay can be seen in the cliff face, with small scale block falls at the cliff base