High resolution sonar for the archaeological investigation of marine aggregate deposits
Justin Dix, 2008. https://doi.org/10.5284/1000040. How to cite using this DOI
Data copyright © Dr Justin Dix unless otherwise stated
This work is licensed under the ADS Terms of Use and Access.
Primary contact
Dr
Justin
Dix
Lecturer
Ocean and Earth Science
University of Southampton
Avenue Campus
Highfield
Southampton
SO17 1BJ
England
Tel: 023 8059 3057
Resource identifiers
- ADS Collection: 867
- ALSF Project Number: 3364
- DOI:https://doi.org/10.5284/1000040
- How to cite using this DOI
Overview
Project Background and Methodology
Penetrative and non-penetrative sonar systems have been periodically used for the investigation of marine archaeological sites for at least the last four decades. Such sonar systems have been used to investigate both wreck sites (e.g. Rule, 1982) and latterly submerged landscapes, where the data has been used to provide a back-drop to a series of pre-historic archaeological studies (e.g. Ballard et al., 2000; Dix, 2001; Quinn et al., 2002). Unfortunately, the success of these systems for such investigations has been highly variable and as such, the archaeological community has understandably viewed such methodologies with a high degree of scepticism. However, more often than not the poor results obtained from sonar surveys have actually been the result of incorrect choice and use of equipment as well as more fundamental misconceptions of the acoustics of archaeological materials.
The last decade has seen an increase in research that specifically addresses the use of high-resolution sonar to identify marine archaeological materials (e.g. Quinn et al., 1998a; Momber & Geen, 2000; Lawrence & Bates, 2001; Arnott et al., 2002). The majority of the published work has focused on the use of Chirp sub-bottom profiling systems (e.g. Quinn et al. 1997; 1998a and b; Quinn et al., 2000). These are swept frequency sources capable of producing high-resolution imagery to a sub-seabed depth of c. 20m particularly in fine grained materials. These systems have been demonstrably shown to detect archaeological material (shipwrecks) buried beneath the seabed (e.g. Quinn et al. 1998a; Quinn 2001) and to reconstruct Holocene (Mesolithic - Neolithic) landscapes (e.g. Dix et al., 1998, 2001; Cooper et al., 2002a).
However, there are two fundamental problems with the Chirp sonar systems as the current technology stands: firstly, their ability to penetrate coarse grained stratigraphies (medium to coarse sands and gravels) is inconsistent, and secondly, as with all sonar profiling systems they only acquire two-dimensional data ("slices through the seabed") and consequently object or structure detection frequently depends on the spacing of the survey lines which may achieve a minimum separation of only 5 m and more typically 10 - 100m. The first of these issues is particularly pertinent to the aggregates industry, as their target deposits are these coarser grained materials. The aggregate industry has therefore understandably failed to embrace Chirp technology and continues to deploy lower frequency, higher energy, sources (Boomers) which more reliably penetrate coarse seabeds. These systems provide the aggregate companies with the majority of the data they require for prospection purposes. The company's principal aim being to identify the deposit and calculate aggregate volume from the identification of it's upper and lower reflectors. However, due to an inherent trade-off between penetration and resolution of sonar systems the vertical and horizontal resolution capabilities of the Boomer systems means that they are frequently incapable of detecting small buried objects (under c. 0.5 m) or identifying internal stratification, particularly of fine grained layers, within the aggregate volume.
This lack of detailed structural information is a major problem from both the archaeologist's and the aggregate industry perspective. The former are obviously interested in the identification of buried artefacts (e.g. wrecks) but are equally interested in the aggregate deposits as potential secondary (and even tertiary) contexts of Palaeolithic material. As is being shown by the work of Hosfield (1999, 2001, ALSF 3361) and others if we are to fully realise the potential of secondary contexts, such as fluvial terrace gravels, we have to be able to understand the complexity of the aggregate deposit geometry. Further, one of the major dilemmas with secondary context archaeological material is finding suitable methods of dating these coarse grained deposits. From the extensive archaeological studies of terrestrial aggregate deposits, it is evident that, intercalated, fine grained and frequently highly organic horizons can provide essential datable material for reconstructing depositional events and thus constraining the archaeological material they contain. Consequently, the identification of such horizons can be a major criteria determining the usefulness of anyone site. From the aggregate industry perspective, in addition to the intrinsic archaeological importance of the material, the presence of large quantities of wood/metal and/or fine grained organic sediments significantly degrade the quality, and therefore profitability of the aggregate deposit itself.
This project aimed therefore to tackle these two fundamental problems to the detailed archaeological investigation of coarse grained aggregate deposits. This aim was achieved through the optimisation of new Chirp sources, developed by the School of Ocean and Earth Science, University of Southampton, in conjunction with GeoAcoustics Ltd, Great Yarmouth, specifically for the penetration of coarse grained materials. These sources have been deployed in both 2D and 3D modes. The latter has utilised a brand new design for the acquisition of high-resolution data volumes (a SOES-GeoAcoustics Ltd design) capable of imaging objects and layers beneath the seabed that are greater than 0.5 m in lateral extent, thicker than 0.2 m and down to a depth of 15 m beneath the seabed. This work has encompassed extant data collected in 2002, during the initial trial period of the SOES 3D-Chirp system, as well as extant core and seismic data made available by Hanson Marine Ltd. The sites targeted for data acquisition as well as those already surveyed have all been of intrinsic archaeological importance and in many cases compliment other ALSF projects already funded (e.g. Imperial College: ALSF 3277/3543 Submerged Palaeo-Arun Rivers, Hampshire & Wight Trust for Maritime Archaeology: ALSF 4740 Assessment of Archaeology within Marine Aggregate and Hosfield: ALSF 3361 The Archaeology of Secondary Contexts).
References
Arnott S, Dix JK, Best AI, Gregory D. 2002. Acoustic propagation in waterlogged wood. Acta Acustica United with Acustica 88 (5): 699-702
Ballard RD, Coleman DF & Rosenberg GD. 2000. Further evidence of abrupt Holocene drowning of the Black Sea shelf. Marine Geology 170 (3-4): 253-261
Cooper, A., McErlean, T, Lenham, J. and Forsythe, F., 2002a. The Evolution of the Lough. In: Strangford Lough: An Archaeological Survey of the Maritime Cultural Landscape. McErlean, T., McConkey, R. and Forsythe, W. (Eds): Blackstaff Press, Belfast, ISBN 0-85640-723-2, 21-31.
Cooper JAG, Kelley JT, Belknap DF, Quinn R, McKenna J. 2002b. Inner shelf seismic stratigraphy off the north coast of Northern Ireland: new data on the depth of the Holocene lowstand. Marine Geology 186 (3-4): 369-387.
Dix JK. 2001. The Geology of the Solent River System. In Wenban-Smith F. & Hosfield R. (eds). Palaeolithic Archaeology of the Solent River. Lithic Studies Society Occasional Paper No.7. pp. 6-14.
Dix JK, Arnott S, Best AI & Gregory D. 2001. The geoacoustic characteristics of archaeological wood. Institute of Acoustics, Underwater Acoustics Group Conference on Acoustical Oceanography. pp. 299-305
Dix, J.K., Long, A.J. and Cooke, R., 1998. The Evolution of Rye Bay and Dungeness Foreland: New Evidence From the Offshore Seismic Record. In: Romney Marsh: Environmental Change and Human Occupation in a Coastal Lowland (Ed. Eddison, J., Gardiner, M. and Long, A.); Oxford University Committee for Archaeology Monograph, 46: 1-12.
Hosfield RT. 1999. The Palaeolithic of the Hampshire Basin: a regional model of hominid behaviour during the Middle Pleistocene. BAR British Series 286. Archaeopress, Oxford.
Hosfield RT. 2001. The Lower Palaeolithic of the Solent: 'Site' formation and interpretive frameworks. In Wenban-Smith F & Hosfield R (eds). Palaeolithic Archaeology of the Solent River. Lithic Studies Society Occasional Paper No.7. pp. 85-97.
Lawrence, M. L. and Bates, C. R. 2002. Acoustic Ground Discrimination Techniques for Submerged Archaeological Site Investigations. Marine Technology Society Journal, v. 35, No. 4, pp. 65-73.
Momber G & Geen M. 2000. The application of the Submetrix ISIS-100 Swath Bathymetry system to the management of underwater sites. International Journal of Nautical Archaeology 29 (1): 154-162.
Quinn R, Bull JM & Dix JK. 1997. Buried scour marks as indicators of palaeo-current direction at the Mary Rose wreck site. Marine Geology 140 (3-4): 405-413.
Quinn R, Adams JR, Dix JK & Bull JM. 1998a. The Invincible (1758) site - an integrated geophysical assessment. International Journal of Nautical Archaeology 27 (2): 126-138.
Quinn R, Dix JK & Bull JM. 1998b. Optimal processing of marine high-resolution seismic reflection (Chirp) data. Marine Geophysical Researches 20(1):13-20.
Quinn R, Cooper AJA & Williams B. 2000. Marine geophysical investigation of the inshore coastal waters of Northern Ireland. International Journal of Nautical Archaeology 29 (2): 294-298.
Quinn R, Rooney S, Barton K, O' Hara D & Sheehan K. 2001 An integrated marine geophysical investigation of the La Surveillante wreck-site. In Breen C. (ed.) Integrated Marine Investigations on the Historic Shipwreck La Surveillante. University of Ulster.
Quinn R, Forsythe W, Breen C, Dean M, Lawrence M & Liscoe S. 2002. Comparison of the Maritime Sites and Monuments Record with side-scan sonar and diver surveys: A case study from Rathlin Island, Ireland. Geoarchaeology 17 (5): 441-451.
Rule M. 1982. The Mary Rose. The Excavation and Raising of Henry VIII's Flagship. Greenwich: Conway Maritime Press.
The digital archive
The digital archive currently consists of the following resources:
-
Dix,J.K., Bastos,A., Plets,R., Bull,J. and Henstock,T. 2007: High resolution sonar for the archaeological investigation of marine aggregate deposits. English Heritage ALSF project no. 3365. School of Ocean and Earth Science, University of Southampton.
Non-digital Archive and Publications
In addition to the reports contained within the digital archive the project also produced the following outputs:
| Literary Outputs |
|---|
| Plets, R., Dix, J., Bastos, A. and Best, A. 2007: Characterization of buried inundated peat on seismic (Chirp) data, inferred from core information. Archaeological Prospection, 14, (4), 1-12. (doi:10.1002/arp.318) |
