Rory Quinn
Identifying and characterising submerged archaeological deposits:Case Studies from Rathlin Island and Bantry Bay
Rathlin Island, off the north coast
of Ireland, has a history of settlement and seafaring from the Late Mesolithic
period to the present day. The maritime Sites and Monuments Record (SMR) for
Rathlin indicates high wrecking incidences. In 1999, a reconnaissance side-scan
sonar survey confirmed the presence of 46 targets of possible archaeological
potential around Rathlin Island. Thirteen of these anomalies were positively
identified as shipwrecks. Of the remaining 33 targets, nine were dived on in
order to ground-truth the geophysical data. A successful and rapid methodology
of ground-truthing side-scan sonar data for archaeological purposes was developed.
The results from the side-scan survey and diver-truthing exercise enhanced the
existing maritime SMR.
Between 1998 and 2000, a series of geophysical surveys were conducted over the
site of La Surveillante, a French Frigate wrecked in 1797 in Bantry Bay, Co.
Cork, Ireland. The objectives of the surveys were to accurately relocate the
wreck-site, delineate the extent of site, map the seafloor and subsurface lithologies
in the wreck-environs and provide basemaps for more detailed diver investigations.
The integrated surveys employed a suite of equipment consisting of a digital
echo-sounder, side-scan sonar, Chirp sub-bottom profiler and an Overhauser-effect
magnetometer. Integration and interpretation of the geophysical data indicate
La Surveillante was wrecked on a fine-grained substrate in a low energy environment,
with site distribution limited to an area measuring 50 x 25m centred on the
wreck. Integration of geophysical- and diver-survey data with tidal and sediment
records indicates the La Surveillante was wrecked in a low energy environment,
with site formation being dominated by biological and chemical processes.