Coastal geomorphology in the Devensian Bristol Channel

 Cliffs of Pleistocene deposits, near Sheringham, Norfolk.  As the sediment cliffs retreat, the storm beach is fed with material derived from landslides / cliff falls.  There is so much redeposited material that the bulk of the cliff face is hidden.

Coastal erosion near Happisburg, Norfolk

Cliffs near Sheringham, Norfolk

What did the Bristol Channel coast look like during the Devensian, when RSL (relative sea level) was low and when ice rafted boulders might have been moved through St Georges Channel following discharge on a floating glacier terminus?

In one of the most wide-ranging and comprehensive studies of high-latitude coastal geomorphology ever published, David Sugden and I attempted to identify the processes at work currently in the polar regions -- and hence the processes that will have operated in the mid latitudes at times of maximum Quaternary glaciation. It was published in the "Progress in Geomorphology" series in 1975.

https://www.researchgate.net/publication/262414487_Coastal_Geomorphology_of_High_Latitudes

Types of ice affecting the landmasses and maritime zones in the polar regions. During glacial episodes these zones are expanded and redistributed.

In our review we described the different types of floating ice, making it clear that sea ice (including pack ice and ice floes) is very different from floating glacier ice in icebergs and bergy bits.  In general, sea ice forms on a freezing sea or lake surface and does not carry large erratics and glacial debris.  In icebergs and bergy bits there may be substantial quantities of far-travelled debris  -- indeed, some icebergs incorporating ice from the bed of a glacier may be spectacularly "dirty".  Icebergs tend to "run deep" -- and they generally waste away -- and dump their debris loads -- in deeper water or far out on tidal mud flats.  In contrast, although ice floes may have deep "keels" formed in the same way as surface pressure ridges, they generally float flat, and therefore regularly ride up onto shorelines where they may be incorporated into an ice foot.  In storms they can be driven by a moving mass of floating ice to positions 5m or more above HWM.  Waves generated by iceberg collapse or rolling can also lift and deposit ice masses of all types and deposit them hundreds of metres inland on low relief coasts such as the tidal estuaries of East Greenland or Arctic Canada.

The meaning of all this?  Please don't let me hear any more about large erratics being deposited on rocky coasts by "ice floes"...........

Grounded icebergs in Nordostbugt, East Greenland.  They are stranded in shallow water, but may move again at HWST if there is a change in wind direction.  These are glacier fragments -- some carrying glacial debris including boulders. 

An overturned tabular berg displaying its debris-rich underside

We found this nice little erratic In Kjove Land in 1962.  My mate David Sugden shows the scale.  The boulder was probably dumped by melting ice -- the sea played no role in its transport.

Broken seasonal pack ice (ice floes) in Scoresbysund.  This is a Greenpeace image purportedly showing "glacier ice" and I suppose linked to a climate change agenda -- but they should be more careful with their labelling.

Because, for the whole of the Devensian cold stage, the shoreline was far to the west of the cliff rampart of the Devon and Cornwall coasts, the coastline of the time probably looked much like that of North Norfolk -- with easily eroded cliff faces made of unconsolidated marine, estuarine and glacial sediments constantly changing with minor shifts of sea level, storm surges.  The tidal range will have been smaller than that of the Severn Estuary of today, and there will have been constant inputs of ice-rafted debris.

Was this a permafrost coast with masses of ground ice like those of the coast of Siberia? I doubt that, since in this westerly location the meteorological conditions may well have been too dynamic and changeable.  I know that the BRITICE team have been devoting some thought to this.

 There is a huge variety of sea-floor sediments in the Bristol Channel today, but I am not sure whether it is yet possible to see a coherent sequence of glacial and interglacial sediments.  Watch this space........