WELCOME

Welcome to issue 8 of the Submerged Landscapes Archaeological Network (slan) newsletter at our new home on WordPress. In this issue:

  • 2008-2010: Archaeological applications of the JIBS data – conclusions.
  • NFSD support for ground-truthing of the JIBS data.
  • Ben Thebadeau reports on his PhD project – testing mathematical models of sea-level change.
  • New NERC-funded project on late glacial sea-level minima in the western British Isles.
  • Researchers on the move
  • Undergraduate student training
  • Recent publications

If you want your name added to the SLAN mailing list, please e-mail Rory Quinn (RJ.Quinn@ulster.ac.uk) with the term ‘SLAN newsletter’ in the subject field. Past issues of the SLAN newsletter are available at the base of this blog.

 

2008-2010: ARCHAEOLOGICAL APPLICATIONS OF THE JIBS DATA

Funding agency: Heritage Council (INSTAR)

Investigators: Rory Quinn (UU), Wes Forsythe (UU), Kieran Westley (UU), Ruth Plets (UU), Annika Clements (UU), Chris McGonigle (UU), Trevor Bell (MUN), Fergal McGrath (MI), Sara Benetti (UU) and Rhonda Robinson (NIEA)

Researchers from the Centre for Maritime Archaeology (CMA) at the University of Ulster (UU), the Marine Institute (MI), Memorial University Newfoundland (MUN) and the Northern Ireland Environment Agency (NIEA) have completed the 3-year project ‘Archaeological applications of the Joint Irish Bathymetric Survey (JIBS) data’ funded through the Irish National Strategic Archaeological Research (INSTAR) Programme (2008-2010).

To address the need for high-resolution bathymetric data off the north coast of Ireland, the Joint Irish Bathymetric Survey (JIBS) was instigated as a partnership between the Maritime and Coastguard Agency (MCA) and the Marine Institute (MI), under INTERREG IIIA (€2,133,508). The project provided 100% multi-beam bathymetry coverage within the 3nm coastal strip from the Fanad Peninsula (Co. Donegal) to Fair head (Co. Antrim). Under INSTAR 2008-2010, this project was funded to assess the JIBS data for archaeological applications. The potential for the discovery of submerged archaeological material related to the early colonization of Ireland has been confirmed through this research project. Through the spatial mapping and interpretation of sonar, archaeological, sea level and glacio-isostatic data, ten areas of high archaeological potential are identified on the basis of the following criteria: [i] whether a given area was attractive to past humans, providing shelter, access to inland and coastal resources, freshwater and raw material sources, and [ii] the likelihood of burial rather than erosion of palaeo-land surfaces as sea level rose. Likely areas should presently be characterized by sediment deposition and smooth seabed surfaces with few traces of the underlying bedrock. Palaeogeographic reconstructions derived for these sites indicate that: [i] when relative sea level (RSL) was lower, easy access was allowed to the exposed coastal lowland and resources therein; [ii] travel to the interior would have been facilitated by adjacent rivers; [iii] the surrounding highlands provided a measure of shelter compared to the open lowstand coast and a vantage point for resource monitoring, and [iv] environmental conditions promoted deposition instead of erosion, promoting material conservation.

Coverage of the JIBS survey from Fanad Peninsula in the west to Fair Head in the east (click for hi-res image).

Even at 1m-resolution, the JIBS data do not allow detection of individual prehistoric archaeological sites characteristic of the Mesolithic (ephemeral scatters of lithics and bone). Instead, their value lies in the ability to aid the reconstruction of the prehistoric landscape and delimit areas with archaeological potential. The lowstand reconstructions modelled in this project suggest an open linear coast extending out from the modern shoreline by several hundred metres to several kilometres, possibly characterized by rock-platforms and cliffs with small inlets and embayments. By the time of the earliest phase of Mesolithic colonization, RSL had risen from the lowstand though wide areas of exposed shelf were still open, such as off the Bann Estuary and Trawbreaga Bay. The palaeo-shoreline was probably still more open and linear than the present, though embayments were starting to develop. However, the large sea-loughs of Foyle, Swilly and Trawbreaga were still cut off from the sea, and instead held rivers which extended across the exposed shelf.

Areas identified as having archaeological potential alongside known terrestrial prehistoric records and overlaid onto JIBS data (click for hi-res image).

In more general terms, although the high resolution of multibeam bathymetric data provides a more accurate representation of the seabed than conventional hydrographic-chart data, when interpreting palaeogeographic reconstructions based on the multibeam data, it must always be remembered that the contemporary seafloor surface is not a direct analogue of the past landscape surface. Sedimentary processes accompanying and following marine transgression have buried the past landscape in some areas and eroded it in others. Where more accurate reconstructions are needed, for instance to prospect for submerged archaeological sites, then the multibeam data must be combined with other marine geophysical records (such as seismic profiles and cores) to model local patterns of erosion and deposition and re-create how the landscape has changed since its inundation. This approach was successfully employed for the Bann Estuary, where a refined high-resolution palaeo-geographic reconstruction was constructed by integrating the JIBS mutli-beam data with high-resolution seismics and a glacio-isostatic RSL model.

Palaeogeographic reconstruction of the Bann Estuary for 12 kaBP when sea level was approximately 14 m lower than today (click for hi-res image).

Although the three-year INSTAR funding ended in 2010, the project has now moved into the next phase – the ground-truthing and sampling of the areas of high archaeological potential (items below).

 

2010-2011: NATIONAL FACILITY FOR SCIENTIFIC DIVING [NFSD] SUPPORT FOR ‘ARCHAEOLOGICAL APPLICATIONS OF THE JIBS DATA

Funding agency: NERC [NFSD/2010/01] £32,127.00 (in-kind)

Investigators: Kieran Westley (UU), Rory Quinn (UU), Ruth Plets (UU) and Wes Forsythe (UU)



To initiate diver-based ground–truth surveys for the JIBS data, UU successfully applied for support from the NERC Facility for Scientific Diving (NFSD). This support consisted of a 4 person dive team, with boat and specialist equipment (e.g. high resolution cameras and video).  Four target areas were selected, on the basis of interpretations made from the JIBS data and supplemented by previously reported archaeological/palaeo-environmental finds.  The target areas were:  1) Greencastle, 2) Portrush, 3) Portstewart and 4) Ballycastle-Ballintoy. The rational for each was as follows. Early Mesolithic finds had previously been reported washing ashore at Greencastle, while palaeo-landscape reconstructions indicated that the study area probably was a bluff overlooking a river; a situation regarded as favourable for Mesolithic settlement. Late Mesolithic intertidal peats are known from Portrush, though their seaward submerged extent is uncertain. The JIBS bathymetry and seismic profiles were therefore used to identify shallow buried layers which could be diver sampled. Portstewart has a sport diver report of possible submerged peats. As the position given was highly approximate, the JIBS bathymetry and backscatter were used to identify a zone of erosion which could be inspected by the divers. Finally, the JIBS bathymetry between Ballycastle to Ballintoy shows  a clear submerged cliffline at c. 15 to -13m which could be a lowstand shoreline. Divers were therefore tasked with identifying its geological composition and looking for shoreline features such as wave-cut notches.

JIBS 1m data for the seabed in western Ballycastle Bay showing the potential shore platforms/submerged cliffs and dive survey transects. Aerial photo is from the Ordnance Survey of Northern Ireland (click for hi-res image).

NFSD divers about to drop onto potential submerged shoreline between Ballycastle and Kenbane (click for hi-res image).

Possible wave-eroded notches cut into chalk on the submerged shoreline off Ballycastle (click for hi-res image).

The initial period of work was scheduled for October 2010. Unfortunately, weather conditions wiped out half the time available and prevented dives at Portstewart and Portrush. Work at Greencastle was prevented by difficulties with archaeological licences from the Republic of Ireland. Several dive transects were run between Ballycastle and Ballintoy; these indicated that the cliffline was cut into chalk rather than basalt (important because the local basalt erodes along weaker inter-basaltic layers generating stepped profiles which bear no relation to sea-level) and identified possible wave-eroded notches (see photo). A further season of work is planned for June 2011 and which will ideally cover the unsampled areas.

Acknowledgements: Many thanks are due to the NFSD dive team (Martin Sayer, Hugh Brown, Simon Thurston and Elaine Azzopardi) for their support and efforts.

 

2009-2013: TESTING MODELS OF RELATIVE SEA-LEVEL CHANGE

Funding agency: Science Foundation Ireland (SFI)

Investigators: Benjamin Thebadeau (PhD student) and Robin Edwards (TCD), CMA (UU)

Models of the glacio-hydro-isostatic adjustment process play a central role in understanding past, present and future sea level change. Misfits between model simulations and field-based reconstructions are subjects of recent debate in the academic literature, with some authors contending the current generation of models are fundamentally flawed. This project uses a novel combination of geophysical modelling and ground-truthed marine acoustic data to identify and map palaeoshorelines along the northern coast of Ireland. These are used to test an explicit hypothesis regarding the competing and mutually exclusive geometries of RSL change inferred from model simulations and field-based reconstructions.

 

 

Ben writes…..The first type of features we looked at are shore-platforms, hard rock erosional features which are present in numbers on the study area seabed. Although these features are undatable, they provide an interesting constraint on the erosion rates of the various lithologies present on this coast, mainly Cretaceous chalk, Palaeocene basalt and Precambrian metamorphic rocks. The assumptions here are that the oceanographic conditions have not changed dramatically since the British-Irish Ice Sheet retreated from the coast and the North Atlantic as a whole (the last 18kyrs BP). So after recording the morphological parameters of all the shore-platforms identifiable on the sea bed (about 500 features for the study area) and plotting them on a database, a first analysis of the hypsometric curves displayed unexpected results as the main relict shorelines did not seem to respect the gradual uplift expected from the GRM simulations. This could be interpreted first due to the durability of the various lithologies but it is most probably due to the remanence of shore-platforms from previous interglacials.

Profile showing two submerged shore platforms in Church Bay, Rathlin Island.

The next step is the comparison of the coastal profiles with profiles created from an erosional model taking into account the RSL variations and the various environmental parameters present on the coast. This model has been developed over 20 years by Dr Alan Trenhaile of the University of Windsor (Ontario) and has already changed many aspects of our understanding on shore-platforms formation and rock coast evolution as a whole. Several localities where we have the clearest shore-platform signal are being targeted for comparison. This should help us recognise the potential for an erosional signal since the LGM and give us a better understanding of the evolution of the coastal landscape.

In the coming years, it is planned to look at sub-bottom profiles to assess the presence of more erosional features under sediment cover as well as identify any soft sediment accretional features still present. These could potentially give some datable logs and add to the RSL database. It is clear that more sea-level data points are needed, especially for the pre-Holocene lowstands,  to better constraints any further attempt at modelling the RSL curves for the area.

 

2011-2014: LATE GLACIAL SEA LEVEL MINIMA IN THE WESTERN BRITISH ISLES

Funding agency: NERC  [NE/H024301/1 and NE/H024069/1] £716,274.00 to Ulster and £213,104.00 to Durham

Investigators: Andrew Cooper (UU), Derek Jackson (UU), Rory Quinn (UU), Anthony Long (Durham), Dave Long (BGS), Robin Edwards (TCD), Glenn Milne (Ottowa), Xavi Monteys (GSI), Dan Belknap (Maine), Joe Kelley (Maine)

 

Abstract: Relative sea level (RSL) change reflects the interplay between a large number of variables operating at scales from global to local. Changes in RSL around the British Isles (BI) since the height of the last glaciation (ca. 24 000 years ago), are dominated by two key variables (i) the rise of ocean levels caused by climate warming and the melting of land-based ice; and (ii) the vertical adjustment of the Earth’s surface due to the redistribution of this mass (unloading of formerly glaciated regions and loading of the ocean basins and margins). As a consequence RSL histories vary considerably across the region once covered by the British-Irish Ice Sheet (BIIS). The variable RSL history means that the BI is a globally important location for studying the interactions between land, ice and the ocean during the profound and rapid changes that followed the last glacial maximum. The BI RSL record is an important yardstick for testing global models of land-ice-ocean interactions and this in turn is important for understanding future climate and sea level scenarios. At present, the observational record of RSL change in the British Isles is limited to shallow water areas because of accessibility and only the later part of the RSL curve is well studied. In Northern Britain, where the land has been rising most, RSL indicators are close to or above present sea level and the RSL record is most complete. In southern locations, where uplift has been less, sea level was below the present for long periods of time but there is very little data on RSL position. There are varying levels of agreement between models and existing field data and we cannot be certain of model projections of former low sea levels. Getting the models right is important for understanding the whole global pattern of land-ice-ocean interactions in the past and into the future. To gather the missing data and thus improve the utility of the British RSL curves for testing earth-ice-ocean models, we will employ a specialised, interdisciplinary approach that brings together a unique team of experts in a multidisciplinary team. We have carefully selected sites where there is evidence of former sea levels is definitely preserved and we will use existing seabed geological data in British and Irish archives to plan our investigations. The first step is marine geophysical profiling of submerged seabed sediments and mapping of surface geomorphological features on the seabed. These features include the (usually) erosional surface (unconformity) produced by the rise in sea level, and surface geomorphological features that indicate former shorelines (submerged beaches, barriers and deltas). These allow us to identify the position (but not the age) of lower than present sea levels.

MBES data from Belfast Lough acquired by the British Navy and AFBI in 2008 and 2009 (click for hi-res image).

The second step is to use this stratigraphic and geomorphological information to identify sites where we will take cores to acquire sediments and organic material from low sea-level deposits. We will analyse the sediments and fossil content of the cores to find material that can be closely related to former sea levels and radiocarbon dated. The third step in our approach is to extend the observed RSL curves using our new data and compare this to model predictions of RSL. We can then modify the parameters in the model to obtain better agreement with observations and thus better understand the earth-ice-ocean interactions. These data are also important for understanding the palaeogeography of the British Isles. Our data will allow a first order reconstruction of former coastlines, based upon the modern bathymetry, for different time periods during the deglaciation. This is of particular importance to the presence or absence of potential landbridges that might have enabled immigration to Ireland of humans and animals. They will also allow us to identify former land surfaces on the seabed. The palaeogeography is crucial to understanding the evolving oceanographic circulation of the Irish Sea.

 

RESEARCHERS ON THE MOVE

Dominic Lacroix (Memorial University Newfoundland) is spending five weeks in Ireland in April/May 2011 visiting and training at the Centre for Maritime Archaeology (University of Ulster) and the Landscapes, Seascapes and Wetland Archaeology Research Group (University College Dublin). Dominic’s research interests lie in the study of cultural landscapes generally and particularly how the first inhabitants of Newfoundland, the Maritime Archaic Indians (MAI), would have perceived, lived in, and utilized coastal and interior landscapes of the province.

After three years working on the INSTAR/JIBS project at MUN and UU, Ruth Plets was appointed as a PDRA to the NERC late glacial sea-level minima project at UU in January 2011.

Chris McGonigle has moved back to UU for a permanent position after spending 12 months as a PDRA in Imperial College London, examining the relationship between backscatter and grain size.

 

UNDERGRADUATE STUDENT TRAINING

In November 2010, the University of Ulster (UU) and the Marine Institute (MI) ran a week-long student training cruise off the north coast of Ireland onboard RV Celtic Explorer under the ‘Sea Change Strategy’ (Marine Institute). The training cruise, co-ordinated by Rory Quinn, Ruth Plets, Kieran Westley, Annika Clements and James Strong (AFBI), provides the next generation of marine scientists graduating from Ulster with the necessary offshore seabed survey and data processing skills to meet the demands of a range of employers within the marine sector in Ireland. In recent years Ireland has experienced rapid growth in this area with initiatives such as the Irish National Seabed Survey, INFOMAR and the Joint Irish Bathymetric Survey projects generating high-resolution large-volume data sets and a demand for skilled graduates to process and interpret these data.

University of Ulster undergraduate students join RV Celtic Explorer at Derry (click for hi-res image).

The training programme is divided into two main sets of objectives:

[1] Field-based skills training: The shipboard training focuses on geoacoustic surveys, providing experience and understanding in the acquisition and real-time processing of high-resolution sonar and seismic data, benthic grab samples, benthic core samples, fisheries samples (epifaunal and demersal) and underwater image (video and stills) data.

[2] Post-cruise skills training: The data generated from the cruise is used to meet scientific objectives in taught modules at UU and in undergraduate and postgraduate dissertation projects. Post-cruise training objectives include: acoustic data processing and interpretation from geological, archaeological and biological perspectives; sediment grain-size analysis; organic material dating; benthic grab sampling processing and community analyses.

Selection of sampling devices deployed from R.V. Celtic Explorer and R.V. Celtic Voyager during the 2009 and 2010 training cruises. a) Drop down video camera. b) Box corer. c) Day grab. d) Hamon grab. Of all the direct samplers used, the Day grab was found to give the best results and was therefore used to take the vast majority of sediment samples (click for hi-res image).

Spin-out dissertation projects from the cruises over the last few years have resulted in final year projects investigating a wide range of environmental systems from the post-glacial colonization of the island through the study of submerged archaeological landscapes to the classification of sonar data with a view to characterizing the morphology and composition of the seafloor to the investigation of linked biological and geological systems.

Commercial seabed developers are increasingly required to ensure that they cause minimal disturbance to the underwater environment. EU Council Directives require that environmental assessments are undertaken in the face of development applications, including an assessment of the archaeological and biological impact. For example, licenses are required to dredge and dispose of material and other substances at sea, and also for work that involves engineering below the average spring high-water level (wind farms, fish farms etc.). Skills developed by Ulster students on these training cruises will equip them to tackle these issues and ensure for more coherent and effective management of our fragile marine environment.

Acknowledgement: This training programme was carried out under the Sea Change strategy with the support of the Marine Institute and the Marine Research Sub-programme of the National Development Plan 2007–2013. Thanks also to Dr James Strong/AFBI for support.

 

SOFTWARE TRAINING

As part of the SLAN training initiative, software workshops are being run in April at UU – a CARIS HIPS and SIPS workshop by Fabio Sachetti (UU) concentrating on the processing of multibeam echosounder data and an SMT Kingdom Suite workshop led by Ruth Plets (UU) on the processing and interpretation of high-resolution seismics. Researchers from Memorial University Newfoundland, Trinity College Dublin and the University of Ulster are participating.

 

Left to right: Kieran Westley, Ruth Plets, Fabio Sacchetti and Chris McGonigle during the CARIS training session in the marine geophysics lab at UU.

 

NEW PUBLICATIONS

  • Dunlop, P., Shannon, R., McCabe, M., Quinn, R. and Doyle, E. (2010) Marine geophysical evidence for ice sheet extension and recession on the Malin Shelf: New evidence for the western limits of the British Irish Ice Sheet. Marine Geology, 276 (1-4): 86-99.
  • Quinn, R. (2011) Acoustic Remote Sensing in Maritime Archaeology. In: A. Catsambis, B. Ford and D.L. Hamilton (eds.) The Oxford Handbook of Maritime Archaeology. Oxford University Press, pp. 68-89.
  • Vardy, M.E., Bull, J.M., Dix, J.K., Henstock, T. J., Plets, R.M.K., Gutowski, M. and Hogarth, P. (2011) The geological Hubble: A reappraisal for shallow water. The Leading Edge, 30 (2): 154-159.
  • Westley, K., Quinn, R., Forsythe, W., Plets, R., Bell, T., Benetti, S., McGrath, F. and Robinson, R. (2011) Mapping Submerged Landscapes Using Multibeam Bathymetric Data: a case study from the north coast of Ireland. International Journal of Nautical Archaeology, 40 (1): 99-112.
  • Westley, K, Bell, T, Plets, R and Quinn, R (2011) Investigating Submerged Archaeological Landscapes: a research strategy illustrated with case studies from Ireland and Newfoundland, Canada. In: J. Benjamin, C. Bonsall, C. Pickard and A. Fischer (eds.) Submerged Prehistory. Oxbow Books, pp. 129-144.
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