Investigation of the Lower and Middle Wentlooge Formation, and further excavation of a later Romano-British farmstead at Henbury Level (Plot 5000, Western Approaches Distribution Park, Avonmouth, South Gloucestershire)

In 2007 Oxford Archaeology carried out a staged field investigation at Plot 5000 of
the Avonmouth Western Approaches Distribution Park on behalf of Gazeley UK Ltd,
through the agency of CgMs/John Samuels Archaeological Consultants in relation to
a planning application for warehouse development, associated offices and car
parking facilities.
The development area is located within the Avonmouth Levels, a former salt marsh
reclaimed from the sea, which contains a deep sequence of post-glacial alluvial
deposits known as the Wentlooge Formation. The excavation of the site consisted of
a twenty trench evaluation, targeted excavation of the densest concentration of
archaeological features, and an investigation of the underlying alluvial sequence.
The investigation of the Wentlooge Sequence identified a northeast to southwest
aligned ridge in the Mudstone bedrock underlying Plot 5000, the surface of which
drops sharply to the southeast. The deposits in the depression formed by the
Mudstone evidence outer estuarine influence and episodes of peat formation, and
may have formed in a backwater channel or lagoon that was occasionally cut off
from the tide. While the upper part of the sequence in Plot 5000 appears to similar to
that which has already been investigated in Plot 4000, the lower part provides a new
sequence through the Lower Wentlooge Formation which has not been recorded to a
comparable depth within the Distribution Park. These lower deposits record a
sequence of earlier Holocene hydrological and sedimentary change which extends
beyond the depths reached in Plot 4000.
Plot 5000 lies close to Plot 4000 where Romano-British settlement has been identified
by Wessex Archaeology. The excavations in Plot 5000 uncovered a series of
interconnecting coaxial enclosures and droveways dating to the mid-late Roman
period (2nd to 4th century AD), probably forming part of a permanent settlement.
Several phases of enclosure suggest that this was part of a managed landscape that
saw frequent periods of reorganisation, perhaps in response to environmental and
sedimentary change. No clear structural evidence was identified in Plot 5000, and it
seems likely that the remains in this area were related to the settlement identified in
Plot 4000.
Environmental and sedimentary evidence from the Roman ditches indicates brackish
conditions within an open landscape. The environmental indicators suggest a
gradual transition from a high salt marsh to a slightly drier and more open
environment on an alluvial island within the Levels. The Roman drainage of the site
would appear to have been successful, but the area may still have been prone to
flooding. The presence of domestic refuse, including crop processing waste and
pottery, indicate that the site was predominantly dry, and more than just a seasonal
pastoral settlement.
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The archaeology recorded at the site adds to the growing body of evidence for
Romano-British rural settlement on the Avonmouth Levels. Although the evidence
from Plot 5000 provides no conclusive evidence for systematic reclamation in this
part of the Levels, the appearance of permanent settlements on the Levels
demonstrates that drainage and settlement did occur in the later Roman period. Such
settlement could, however, have been opportunistic, and was probably dependent
upon local hydrological conditions. It may also have been assisted by a slow down in
the rate of sea-level rise during this period. The changes evidenced in Plot 5000
formed part of a process of modification and transformation of the Levels that was
played out in many regions of the Severn Estuary.