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Report Contents
Section 1
Section 1 Description
Section 1 Interpretation
Section 2
Section 2 Description
Section 2 Interpretation
Site Interpretation

Betteshanger - Relic Cliff

Summary of Surfaces Cleared as at 12 March 2006
(Notes recorded by Dr Peter Allen)

Section 1

Section 1 Description of Beds

For a sketch of the beds in section 1, prepared by Andy Oxford, see Figure 4 below

1. Soil/spoil
    
2. Clayey sandy silt ('brickearth'), structureless,(Munsell colour chart 10YR5/4 yellowish brown)
    

3. Fining upwards sequence, from basal flints (up to 8 cm) and chalk pebbles and granules in a sandy silty matrix to silts, silts + fine sands, clay lenses forming a laminated sequence; laminae in upper part disrupted, chalk granules frequent, sub-angular flints scattered throughout, (10YR6/4, 6/5, 6/6, light yellowish brown to brownish yellow) (see Figure 2, upper part)
    
4. Silt and silty fine sand (10YR6/6, brownish yellow) with boudins of chalky silt (10YR7/4, very pale brown) and frequent chalk granules and small pebbles (see Figure 2, lower part)
    

5. Silt and sandy silt with many chalk granules and sub-angular flints, (10YR6/6, brownish yellow)
    
6. Fine sands, sandy silts, silts, silty clays, becoming more clayey with depth, horizontally laminated, possible occasional troughs of ripples (see Figure 3, right)

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Section 1 Interpretation

Bed 6
The horizontal nature of the laminae, with possible ripples, could indicate a variety of quiet water depositional environments, including tidal flats which would be in keeping with the inshore marine environment suggested by Shephard-Thorn (1988). As the sedimentological evidence is equivocal, a resolution of the environment and of the time of deposition is more likely via bio-environmental investigation

Beds 5
The poor sorting of this bed with large sub-angular flint clasts indicates solifluctional deposition in a cold environment

Bed 4
The poor sorting of this bed suggests a lower energy solifluction deposit. Within the sequence a chalky silt has become attenuated, the stretching causing it to thin or even part in places, forming boudins (an analogy being a string of sausages; from Fr. boudin)

Bed 3
This fining upwards sequence is coarse and poorly sorted in its basal part, suggesting solifluction, becoming finer-grained and laminated in its upper part, though still with flint pebbles, suggesting slopewash (colluvium). The uppermost laminae are disrupted, possibly due to desiccation or to freezing

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Bed 2
This brown sandy silt is typical of the brickearth of the area. Its massive fine-grained nature is suggestive of an aeolian origin, but the occasional bedding seen in places (not seen at this site yet) indicates reworking by water

Section 2

Section 2 Description of Beds

1. Soil/spoil
    
2. Clayey sandy silt ('brickearth')
    
3. Coombe rock - small clasts of sub-angular to sub-rounded chalk set in a chalk matrix (see Figure 6, right).

The boundary between Beds 3 and 2 is very irregular, comprising rounded concavities where Bed 2 intrudes downwards into Bed 3, separated to narrow irregular or deformed inverted 'V' structures where Bed 3 has injected upwards into Bed 2.

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Section 2 Interpretation

Bed 3
Coombe rock is chalk-rich solifluction deposit.

Bed 2
'Brickearth' - as for Section 1.

The boundary between the two beds is indicative of loading, where the coombe rock, when saturated, has been unable to bear the weight of the overlying 'brickearth'. Consequently the 'brickearth' has sunk into the coombe rock, which to compensate has injected upwards.

Site Interpretation

Section 1 indicates an initial phase of deposition of laminated deposits (Bed 6), possibly representing a tidal flat and indicating a higher sea-level than at present. As the sedimentological evidence is equivocal, bio-environmental investigations are required to confirm a near-shore marine environment and support an Ipswichian (MIS 5e) age as suggested by Shephard-Thorn (1988)

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In Section 1, the sequence continues with a series of slope deposits (Beds 5 to 3) varying from high-energy coarse solifluction deposits to low-energy colluvial slope-wash. These are characterised by frequent sub-angular flints and chalk pebbles and granules, the source of which is likely to be the coombe rock (Bed 3) of Section 2

The Pleistocene sequence finishes with 'brickearth', Bed 2 in both sections. The origin of this is subject to debate. The high percentage of silt in it suggests an aeolian origin, but banding and occasional fluvial bedding seen in it at other locations suggest a more complex history that involves reworking by slopewash or running water

Highly unstable, saturated conditions are indicated by the load structures in Section 2.

Beds 5 to 2 and the loading structures are all in keeping with deposition and deformation in cold, periglacial conditions. As such, these Beds are likely to have been deposited during the Devensian

The coombe rock occurs at a higher altitude in Section 2 than most of the deposits in Section 1, where it is absent. This suggests that the in situ Chalk rises in the direction of Section 2 and it would be worth further investigation to establish whether a fossil Chalk cliff exists, as suggested by Shephard-Thorn (1988). The extant evidence suggests that this is likely