Augering and test pitting have (like the excavation trenches) concentrated on The Common and the associated hills of the Grand Monceau. The main aims of the work are to:
1) identify the depth, thickness and extent of any buried land surfaces and palaeosols beneath the sand dune system, and
2) identify the nature of preservation of old land surfaces and palaeosols associated with the Neolithic monuments, concentrating on the Kendrick tombs 6 and 15, and Roberts Cross (tomb 12);
3) establish land-use sequences related to the Neolithic use of the northern part of Herm.
The old land surface on Herm
A consistent occurrence of old land surface/palaeosol has been identified during the auger survey of The Common area. It extends between The Bear's Beach on the west and Mouissonnière Beach on the north, and on the south up to the foot of the slopes of Le Petit Monceau and Le Grand Monceau. It was not evident within c.75m of the Shell Beach on the east in boreholes up to 3.4m in depth, where the old ground surface generally lies about 2.75-3.4m beneath the modern ground surface.
The range of palaeosols
investigated through auger survey and test pit excavation across the
northern half of Herm are now able to provide a composite soil and
landscape history throughout the Holocene period. First, there appears
to have been the widespread development of a woodland brown earth with a
strong wind-blown silt and very fine sand component derived from the
dry and cold conditions of the late glacial period on the weathered
granite geology of the island. Subsequently this soil was opened up, and
was much disturbed, probably by a combination of plough disturbance and
hillwash effects. Exactly when this occurred is a matter of some
speculation, but soil associations with the Robert’s Cross tomb suggests
that this had occurred by the time the tombs had been constructed or
within the early-middle part of the 4th millennium BC. In a
few places, subsequent use such as the Roman occupation in front of
Fisherman’s Cottage and the associated accumulation of midden material
has added a much needed organic ‘mulch’ to the soil, more or less
creating a ‘dark earth’ soil which would have been a valuable localised
resource for arable agriculture.
Nonetheless soil movement caused by ploughing and hillwash appears to have been widespread across the northern part of the island. These processes were often interrupted by brief accumulations of wind-blown fine-medium sand. Towards the later prehistoric period, the aggradation of wind-blown fine-medium sand deposits became widespread and of greater intensity, and these features in turn imply that changes were occurring to the coastal morphology of the island, with greater exposed areas of foreshore and possibly a greater intensity of storms. In the Roman period there was perhaps a return to a more stable local climatic and shoreline conditions with an intense period of ploughing, but with episodic but minor wind-blown sand accumulations still occurring. Subsequently there was a more major phase of wind-blown beach sand aggradation, with multiple standstill events marked by short-lived turf development. OSL dating suggests that this was certainly happening by post-AD 1000, and indeed dune accumulation and blow-outs are still occurring today. At the end of the sequence, it should be noted that most of the Common area was re-modelled to create a short-lived golf course in the 1930s.
Photographs copyright Professor Chris Scarre, and Dr Charles French