For one reason or another (including some business over a U-boat, but that’s another story…), updates to this blog have been non-existent over the past 18 months. However, this doesn’t mean that research on Irish submerged landscapes has completely stopped. In fact, we’ve had a couple of projects ticking over during that time, generally trying to continue ground-truthing the JIBS work with field surveys.
1) NFSD ground-truthing phase 2
The NERC NFSD team returned in summer 2011 to finish up their allotted dive support. Fortunately, the weather was with us and, in addition to the Ballycastle submerged cliffline mentioned in a previous post, two additional sites were dived. The first site was just off Portstewart harbour, where a local diver had reported seeing what he thought was a submerged peat. This had happened some years ago, so his directions were unfortunately quite vague but seemed to roughly coincide with a patch of seabed off Portstewart Head where the JIBS data showed that the seabed sand had been stripped away. A number of dive transects were run over this site, but no peat was located. The original report could have been a case of mistaken identity, as patches of dark sand/gravel were noticed amongst the normal light-coloured sand. Alternatively, the strong waves and currents which pass over the site could easily have moved enough sand to cover over any palaeo-landscape remains.
Results were better from the second site – the West Bay at Portrush. The beach on this bay has a series of Holocene (7400-6600 cal BP) peats which are occasionally exposed each year during the winter storms. Hand augering on the beach had previously traced these peats under the sand and into the intertidal zone. Interestingly, the JIBS data from almost in front of the peat layer show a patch of seabed with a different backscatter signature to the surrounding sand. Intriguingly, this patch appears within a bathymetric hollow – in other words, where the seabed sand has been stripped away. Finally, Boomer data from the bay, taken during pre-installation work for the Hibernia fibre-optic cable, show a distinct reflector running just beneath the seabed. All in all, this strongly suggested that the peat extended under the seabed as well. The NFSD team were tasked with finding the peat by hammering small hand cores into the seabed. Eight cores were taken – of which one reached the peat layer. This was also the longest core, recovering almost a metre of sediment, but only just nipping into the top of the peat. The other cores unfortunately, were probably just too short to reach it. Not enough peat was recovered to allow analysis beyond a sample for radiocarbon dating (which is still at the Chrono centre undergoing dating), but at least it has demonstrated that the peat runs offshore, and could therefore be the target of future underwater work.
2) Eleven Ballyboes
The site of Eleven Ballyboes, near Greencastle (Co. Donegal) has been the main focus of our fieldwork over the last two summers. The site presently consists of two small bays on the western shore of Lough Foyle. In the first phase of the JIBS project, we identified the general area of Lough Foyle as high potential on the basis that it was the sort of riverine/estuarine landscape favoured by Mesolithic hunter-gatherers when sea-levels were lower.
The specific site of Eleven Ballyboes was targeted, because during further research on the Foyle area, we found that local collector Brian McNaught had found and accumulated a collection of over 900 worked flints from the intertidal zone of the two bays. None of the material was in situ, but there was enough of a sample that Peter Woodman and colleagues were able to typologically assign it to the early Mesolithic. Within the last year, the collection has been temporarily exported under licence to the CMA from the National Museum of Ireland for cataloguing along with other finds from the Inishowen peninsular. Right now, not including more finds made this year, the Eleven Ballyboes intertidal collection is up to over 1500 worked flints.
In 2011, a small campaign of intertidal test pitting and scuba survey was carried out in one of the bays (the one where the vast majority of intertidal finds had come from) to test the hypothesis that the flints were washing in from offshore rather than eroding out of the beach itself or rolling down from further inland. Only a handful of finds were made offshore, including one relatively fresh small blade. However, the intertidal work confirmed that the source of the flints was not the beach (because it is covered by a thick layer of reworked sediments with flints mixed in with modern litter), and neither were they washing down from further inland (because half the scarp behind the beach is protected by a seawall, and the other half is vegetated and stable).
In 2012, thanks to a grant from the Heritage Council, we were able to undertake longer and more intensive fieldwork. The aim was to dive both bays more systematically, but also to extend the surveys onto the deeper shelf outside the bays using divers and sidescan sonar. The more intensive survey inside the first bay paid off almost immediately, with successive dives locating over 30 worked flints on the seabed. These were scattered across the width of the bay, but in a band from the intertidal zone to c. 2m water depth (relative to low tide). The flints themselves were similar to those from the intertidal zone and included various blades, flakes and cores. Unfortunately, all of them were lying loose on the seabed in secondary context, but a few were less water-rolled than the intertidal finds promising that at least part of an intact site could still be out there.
The offshore work was less successful. Although the sidescan worked brilliantly, we weren’t able to identify any palaeo-landscape features or areas of definite erosion. On the diving side, several days were lost to bad weather while the strong tidal currents made life tricky for the divers. In any case, no finds were made out here. Consequently, work then switched back to the shallow waters of the two bays.
Despite being smaller and having far fewer intertidal flints, the second bay proved as interesting as the first, mainly because of a peat layer found underwater about 20-30m off the beach in 1.5-2m water depth. The peat was mostly buried under a veneer of modern sand, and seemed to span the entire bay and stretch at least 10m along its long axis. Preserved wood fragments and larger chunks were clearly visible within the peat, in much the same way as the intertidal peat at Portrush. A sample taken from the peat has returned a radiocarbon date of 8693–8985 cal BP, while another sample from the base of the peat is still at QUB’s Chrono centre undergoing radiocarbon dating. At the time of writing, the peat has not been surveyed intensively, so there isn’t any confirmation that the intertidal flints are actually associated with it. However, the date does seem fit with the independent typological attribution of the flints to the early Mesolithic. More work needs to be done to confirm this, and to also recover samples for palaeo-environmental reconstruction.
Back in the first bay, a transect of small hand cores was used to provide a sample of seabed sediments and the underlying layers. Although none of the cores penetrated very deeply into the seabed, they gave enough information to show that at least three different layers are present under the seabed sand. In the intertidal and adjacent subtidal zone, the seabed sand and gravel overlies distinct red-brown gravel. Moving further offshore, a thin sludgy black layer intervenes between the seabed sediment and the red-brown gravel. We still haven’t worked out exactly what this is, beyond that it seems to be some sort of anoxic deposit of the type seen in restricted water bodies. A little further out to sea, the red-brown gravel disappears and is replaced by a grey sandy gravel under the sludge. Beyond this, the cores recovered only clean marine sand. Since no in situ finds were made from the red-brown gravel in the intertidal zone, it was felt that the grey gravel gave the best chance of finding archaeological material. Also, it was located within the depth range where most of the loose finds had been made.
The final stage of the 2012 season was to excavate five small test pits centred on the core transect and adjacent areas. Unfortunately, conditions weren’t great when the work was done, with visibility being especially poor. Consequently, large bucket samples were removed from each pit and sieved back at the lab. Although none of these turned up spectacular finds, at least three of the pits (all within 5m of one another) have flints which were much finer and fresher than any previously found. One pit in particular had at least six small relatively fresh flakes and a handful of tiny flakes suggestive of knapping debris. This would seem to hint at the presence of some in situ, or at least less reworked material still in the bay. As with the second bay though, more work would be needed to confirm this.
All in all, over the last couple of years, we’ve been able to back up some of our original conclusions from the JIBS work by demonstrating that fragments of the former landscape can be found, even on the wave-swept north coast of Ireland. So far we’ve only scratched the surface in terms of what could be out there, and lots more work needs to be done to obtain useful scientific information from these sites and landscapes. But hopefully, we’ve made enough of a start to show that submerged landscape research can work in Irish waters and is an avenue worth pursuing.