Department of geography
Najat Bhiry (Regular member)
Dominique Todisco (External collaborator)
IntroductionOne of the main indicators of climate change in northern regions is the accelerated degradation of permafrost. Few is known of the impact of this process on archaeological heritage. However, pre-Inuit and Inuit archaeological sites are mostly located on coasts, in arctic or subarctic environments. Permafrost thaw may lead to erosion of these sites by coastal processes, and organic artefacts once preserved in permafrost could be affected by bacterial processes leading to their alteration. Archaeological excavations and geoarchaeology allow the study of these phenomena but they are costly in time and financial resources, hence the interest of using geophysical techniques; they are fast and non-destructive. Thus, the research question is: how does the characterization of Subarctic soil and subsoil through a multi-method geophysical approach add to the understanding of the spatial variability of permafrost supporting archaeological sites?ObjectivesThe main objective of this research is to characterize the substrate supporting archaeological sites in the Nain Archipelago (Labrador, Canada) using data collected by three complementary geophysical methods and photogrammetry. Three specific objectives are targeted: 1. To determine the spatial variability of permafrost, bedrock, and Quaternary sediment stratigraphy. 2. To define the visible and invisible archaeological structures in relation to the surrounding cryogenic context. 3. To develop a geovisualization of the topographic expression of the soil in relation to the cryogenic conditions of the subsoil. Study sitesTwo sites will be studied: the Oakes Bay 1 site, situated on a bank of a bay in the north of Dog Island, and the South Aulatsivik 6 site located on a tombolo in the southern part of South Aulatsivik Island; these two islands are among the largest islands of the Nain Archipelago (Labrador, Canada). Both sites are in a subarctic environment. There is therefore discontinuous permafrost. Seven semi-subterranean houses, dating from 17th century Inuit occupation, form the main component of the Oakes Bay 1 (HeCg-08) site on Dog Island. On South Aulatsivik Island, excavations at the South Aulatsivik 6 (HdCi-20) site have so far helped identify eight semi-subterranean houses, dating from the 18th to 19th centuries. On the islands, the houses are located near the coasts and near thermokarst formations such as ravines and ponds.Material and methodsThe sites were studied using an innovative interdisciplinary approach combining geophysics, photogrammetry and geoarchaeology, and various surveys were carried out. Indeed, three complementary geophysical methods have been chosen: electrical resistivity tomography (ERT), ground penetrating radar (GPR), and electromagnetic induction (EMI). Using these methods, 26 areas and profiles of interest were studied in the field, including seven in or crossing semi-subterranean houses. Numerous results illustrating the electrical and magnetic properties of the substrate have thus been obtained, which will be supplemented by geoarchaeological data in order to produce a multiproxy analysis of the study sites. Drone photogrammetric surveys were also carried out in the field by members of the research team.Expected resultsAll the required geophysical surveys were carried out in summer 2022. The upcoming months will be devoted to data processing and interpretation of electrical and magnetic signatures, as well as modeling of geophysical data using microtopography (photogrammetry). The combination of geophysical data with archaeological and geoarchaeological information already acquired and published will make it possible to characterize (in three dimensions) the physical and archaeological attributes of the study sites and their interrelations.
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