Torquay-- last interglacial and later deposits

It's good to remind ourselves now and again of the situation that applies in the "extra-glacial" parts of Britain -- or those areas assumed to have been outside the influence of glacial action. The above annotated pic comes from Ian West's great web site -- a treasure trove of  careful observations, cautious interpretations and invaluable teaching materials, mostly relating to the English Channel coasts.

Reference:  http://www.southampton.ac.uk/~imw/Torquay.htm

These images come from the Hope's Nose SSSI raised beach site, not far from Torquay.  At the base there is a layer of coarse rockfall debris.  Then comes the raised beach pebble beds, overlain by an oyster shell bed and then by a pebbly and sandy layer.    The pebble beds are not represented in all sections; this is not surprising, since beach dynamics change from place to place along a complex coastline. 

It's assumed by Ian West that the rockfall material dates from pre-Ipswichian times, and that the overlying beach materials all date from the last interglacial (Ipswichian /Eemian). Then comes cemented laminated sand -- which is referred to elsewhere as "sandrock."  And above that we see blown sand that might be of Holocene age.  Does the sandrock layer represent the whole of the Devensian?  That's a long period of time -- around 80,000 years -- with not much to show for it........

Unfortunately there is not much discussion of the significance of this site -- and I'm reluctant to speculate without having seen it.  There is an interesting paper by Derek Mottershead et al -- I'll revisit this issue when I have had a look at it.

PS.  The paper in question is this:

MOTIERSHEAD, D. N., D. D. GILBERTSON & D. H. KEEN 1987. The raised beaches and shore platforms of Tor Bay: are-evaluation. Proc. Geol. Ass. 98(3), 241-57.

It was published quite a while ago, and much has changed in the dating of glacial and interglacial episodes.  The site stratigraphy as recorded by these 3 authors is as shown on this diagram:

The sequence of events suggested by the authors is as follows:

7. Accumulation of Upper head (Unit 11).
6. Accumulation of Main Head (upper layer- Unit 10).
5. Weathering of dune sand to form reddened  layer (Unit 9).
4. Accumulation of dune sand (Unit 8).
3. Washing in of derived red silt and clay (Unit 6).
2. Accumulation of beach/shallow marine sediments (Units 2-4), contemporaneously with Main Head (lower layer-Unit 3).
2b. Partial erosion of Main Head (lower layer- Unit 1) and accumulation of beach/shallow marine sediments.
2a. Accumulation of Main Head (lower layer- Unit 1).
1. Erosion of platform and buried cliff by marine processes.

I'm not very convinced by this, and I cannot understand why the label "Main Head" is used for what appear to be two distinct layers of chaotic and tumbled rockfall deposits.    I think there is a degree of "forcing" here,  resulting from some rather dubious amino acid dating......

So I cannot see why rockfall layer 1 cannot simply have been contemporaneous with the accumulation of the beach -- rockfalls occur in association with beach formation all the time, where there are cliffs in the vicinity.     There does seem to be a break, represented by  the blown sand layer 8, before a fresh pile of rockfall debris accumulated close to the bedrock slope.  An apparent weathered layer (9) separates the two.  Rockfall layer no 10 may just represent the Devensian cold episode, while layer 11 may be equivalent to the "upper head" of many other locations, possibly coinciding with the final cold snaps of the Late Devensian, conventionally referred to as Older and Younger Dryas. This is the interpretation adopted by Keen on page 165 of the GCR volume on the Quaternary of SW England.  Keen prefers to refer to three head layers, namely Lower, Main and Upper.  But I don't like the use of the term "head" here because it is conventionally used for periglacial deposits which are brecciated and which have stratification or pseudo-stratification.