ARCA unpublished report series

A gradiometer and resistivity survey were carried out, and each discovered a series of anomalies thought to represent negative archaeological features. Further work was suggested to examine the nature of these anomalies. [Au(adp)]

A geoarchaeological borehole survey was carried out in August 2012 of an extension to the ASDA supermarket at Dock Road, Gosport, Hampshire. The work was undertaken for Bristol and Region Archaeological Services and on behalf of their client, ISG PLC. The objectives of the geoarchaeological project were to determine the Quaternary stratigraphic sequence present on the site, provide a chronology for deposition and to assess the archaeological and palaeoenvironmental potential of the strata encountered. Two geoarchaeological boreholes were drilled using a Pioneer dual percussive/rotary rig, Strata from the boreholes were logged to standard geological criteria and the descriptions entered into the RockWorks 15 database. That software was then used to plot a composite cross sections through the site. Two 14C dates were obtained, while eight palynological, eight diatom and eight Foraminifera/ostracod samples from silt/clay strata were also assessed. Three stratigraphic units are present on the site. Compact laminated clays, silts and sands of the Early Tertiary Wittering Formation (53-35my BP) are found at depths >6.3m below ground level (BGL). Holocene intertidal deposits unconformably overlie the Wittering Formation between 6.5 and 5.2m BGL.

This document reports the results of a geoarchaeological borehole survey of 53 Parchment Street, Winchester, carried out by ARCA. Fieldwork was carried out on 13 May 2014. Two boreholes were drilled from the ground surface to the base of the Holocene sedimentary sequence.

Between 12th and 14th February 2014 ARCA drilled eight geoarchaeological boreholes at 2-4 St Cross Road, Winchester in order to investigate a ditch thought to run across the site immediately south of the medieval walls of the city of Winchester. A transect of six boreholes (BH1-BH6) running from north to south across the western part of the site was drilled to provide a composite cross-section of the ditch, whilst two further boreholes (BH7 and BH8) were drilled in the eastern part of the site to ascertain whether or not the ditch came to a terminus short (i.e. west) of St Cross Road.

In November 2013 and January 2014, four geoarchaeological boreholes were drilled by Geotechnical Engineering Ltd on the site of the former Magistrates' Court, Nelson Street, Bristol, in order to establish the nature of the Holocene stratigraphy at the site. Strata in the borehole cores were described by ARCA geoarchaeologists and the resultant data incorporated within a lithological/stratigraphical database held by that organisation for the central Bristol area. This document reports on the stratigraphy of the boreholes and assesses the archaeological and palaeoenvironmental potential of the sediments encountered. Bedrock of the Quartzitic Sandstone Formation (QSF) was encountered at the base of the Quaternary sedimentary sequence in BH1, BH2 and BH3 outcropping at between -0.59m and +0.83m OD. In BH4 and BH4A bedrock of the Mercia Mudstone Group was encountered at the base of the sequence, outcropping at +6.99m OD and +6.84m OD, respectively. The bedrock was unconformably overlain by up to c.5m of Holocene silt/clay strata of the Wentlooge Formation in BH1, BH2 and BH3. Made Ground deposits of up to 3.80m capped the alluvial/intertidal sedimentary sequence in all boreholes, unconformably overlying Wentlooge Formation strata in BH1, BH2 and BH3, and unconformably overlying MMG bedrock in BH4 and BH4A.

An assessment ('Phase 1') of three geoarchaeological boreholes and 57 geotechnical boreholes drilled at Long Reach, Dartford, in 2010 demonstrated that strata of moderate to high palaeoenvironmental potential existed throughout the site within the Holocene sedimentary sequence. As a result a programme of bio- and geoarchaeological assessment ('Phase 2') was carried out by ARCA and Quaternary Scientific (Quest) between January and June 2012. The work focussed on cores recovered from two of the geoarchaeological boreholes drilled during the Phase 1 assessment and comprised mass specific magnetic susceptibility, palynological and diatom assessment and AMS 14C dating. Following the Phase 2 works, and an additional geoarchaeological watching brief on further geotechnical boreholes, recommendations for a final analytical phase of works ('Phase 3') were made. The Phase 3 works reported here comprised the drilling of three additional geoarchaeological boreholes, the production of updated deposit models for the site, AMS 14C dating of organic strata from to boreholes, and a programme of bioarchaeological assessment (ARCA BH6) and analysis (ARCA BH8) of pollen, diatom and waterlogged wood remains.

This report is a geoarchaeological assessment of strata sampled in ten boreholes drilled at Plot A, Uxbridge Business Park. Gravels of the Late Devensian Colney Street Gravel Member were encountered at the base of the sedimentary sequence. In several boreholes the Colney Street Gravel Member was overlain by minerogenic alluvial strata of possible Lateglacial to Early Holocene date comprising both channel (lithoclast tufa) and point bar (fining-upwards sandy silt/clay) facies. The minerogenic strata were overlain by peats which formed across the site, most likely during the Mesolithic period. Later, rising base levels led to the formation of a reedswamp across the site resulting in the deposition of organic mud strata. Following the formation of the reedswamp, channels filled with oncoidal tufa deposits formed at the site, overlain in places by thin silt/clay deposits, related to later overbank deposition in a floodplain environment. The sedimentary sequence at the site is capped by modern Made Ground, probably related to the construction of the Sanderson factory, which truncates the Late Quaternary sedimentary sequence.

This report is a geoarchaeological assessment of borehole logs obtained during Ground Investigation works carried out on the site of the proposed Cannington Flood Defence Scheme (FDS), Cannington, Somerset. The assessment was carried out by ARCA on behalf of Cotswold Archaeology. The boreholes drilled at the site encountered bedrock of the Otter Sandstone Formation (FDS BH1 only) and of the Mercia Mudstone Group (MMG). The bedrock geology was overlain by Quaternary superficial strata comprising river terrace deposits of the Parrett Formation and by Holocene alluvial/intertidal strata of the Somerset Levels Formation. With the exception of some partially-decayed organic matter between 1.40m and 2.20m below ground level in FDS BH8, no other specific archaeological or palaeoenvironmental indicators were noted in the Quaternary strata encountered at the site. Holocene alluvial strata at the site were assessed as being of low to moderate palaeoenvironmental potential, whilst all other strata were assessed as being of no or low palaeoenvironmental and archaeological potentials.

Borehole survey This report is a geoarchaeological assessment of strata sampled in six boreholes drilled at Highlands Farm, Henley-on-Thames, Oxfordshire. Bedrock of the White Chalk Subgroup was encountered at between 74.99m OD and 73.47m OD. Gravels of the Anglian Black Park Gravel Member overlay the bedrock and outcrop between 78.09m OD and 76.42m OD. Outside the old Quarry area the Black Park Gravel Member was recorded in five boreholes. Within the Quarry made ground overlay the Chalk in the sixth borehole. The thickness of the Gravel Member was between 2.3m and 3.7m. An area of maximum thickness is believed to lie south of the old Quarry. The Black Park Gravel Member is assessed as being of high archaeological potential and low palaeoenvironmental potential. No artefacts were recovered from the borehole cores.

Geotechnical groundworks (four observation trenches, sixteen pits and eleven boreholes) at the Silver Hill development site, Winchester, were monitored and recorded by PCA and ARCA. Investigation of the trenches and pits generally encountered limited archaeological evidence. However, Medieval structural remains found at the base of OP12. The pits indicate that in some parts of the site modern impacts are shallow and may indicate that archaeological stratigraphy exists at greater depth. Boreholes at the site encountered Chalk overlain by Pleistocene Gravels at the base of the sequence. The gravels, which formed on the braid plain of the Pleistocene River Itchen, were overlain by a succession of Late Glacial/Holocene deposits. Fine-grained mineral sediments, possibly Late Glacial to Early Holocene alluvium, were encountered over the gravels in some boreholes and were in turn overlain by Peat. 14C dating indicates that peat formation started at different times in the Early Holocene in various parts of the site. Tufa deposits were found over the peat in the western part of the site. Archaeological deposits, representing the accumulation of archaeological material in a marshy floodplain environment were encountered in all boreholes and were dated to the Roman to Medieval periods. Pollen assessments carried out on samples from two boreholes demonstrate high potential of the peat strata for reconstructing the prehistoric environmental history of the area. Archaeological deposits at the site are assessed as being of moderate to high archaeological potential as these may preserve evidence for the early development of Winchester.