Contextualising archaeological models with geological, airborne and terrestrial LiDAR data: the Ice Age landscape in Farndon Fields, Nottinghamshire, UK

摘要

Archaeological models of past human occupation of the landscape build upon the understanding of the natural palaeo-environment. This cognitive process relies on the study of the sediment units at a level of spatial resolution that might not be achieved with available maps. This paper presents a new approach to combine traditional ground investigation methods and new technologies to detect, extract and analyse stratigraphic records, with particular application to vanishing landscapes with limited exposure of the sediments. The demonstration site is Farndon Fields, an extremely rare Late Upper Palaeolithic open-air site at the southern outskirts of Newark-on-Trent in Nottinghamshire, UK. Since the early 1990s when the upgrading of the new A46 road was planned, ground and archaeological investigations have been carried out. The test-pitting undertaken by Farndon Archaeological Research Investigations (FARI) in the field 373A in September 2015 offered an ideal occasion for the British Geological Survey (BGS) to test the methodology. A palaeo-geographic understanding from regional to local scales is here proposed based on 5-m airborne Light Detection and Ranging (LiDAR) data and multispectral aerial photographs of the site prior to the alteration due to the A46 works. Features of the palaeo-landscape are vanishing and intrusive investigations are required to unveil the presence of the archaeological context. Samples were taken for particle size analysis of the sediment units to characterise the aeolian sand deposits (‘coversands’) and the underlying clayey silty sandy sediments interbedded with paler laminae. For the first time state-of-the-art terrestrial LiDAR technology was used for stratigraphic profiling, strata delineation and geological feature extraction based on the intensity return and surface roughness. The combined use of point clouds, 3D models and cloud intensity from terrestrial LiDAR provides an added level of confidence to the ability to subdivide the sediment units and discriminate them from ploughsoil. Internal bedding of the coversands is enhanced in the LiDAR elaborations. This is new evidence not otherwise observed by the naked eye. On the other side, the classification of point clouds by roughness index seems promising for recording the grading of the sediments. The experiment in Farndon Fields therefore demonstrates the benefit of phased technology-based investigation combining archaeology and geology towards a more cost-effective assessment through strategic sampling and digital recording of landscape domains.