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While the geoarchaeological approach of a settlement usually focuses on sedimentary storage areas such as dry valleys or anthropogenic structures to understand the soil archives, roadways or natural thermokarst-type depressions can also be a source of information for pedologists and geomorphologists. Thus, the Faux-Fresnay site “Le Haut des Taupinières,” excavated by the French National Institute for Preventive Archaeological Researches (INRAP) in 2019 over an area of 10 hectares, offers new perspectives for documenting the major phases of pedogenesis and soil truncations, particularly through the presence of a medieval road axis that has preserved the Holocene rendosol horizons. This rendosol, also preserved within a dry valley and thermokarst depressions inherited from the Pleistocene, has been occupied by human societies since the Bronze Age and, like the rest of the site, has undergone multiphase and diachronic erosion. The colluvium stored in the thermokarst depressions regularly undergo renewed pedogenesis, suggesting a rhythmicity of erosion/sedimentation processes and a succession of periods of soil stability and instability. To characterize Holocene pedogenesis and to evaluate the different phases of erosion at the site, the geoarchaeological study is based on pedostratigraphic transects, geochemical analyses (measurement of organic matter and carbonates), and relative dating provided by anthropogenic structures, whether excavated or not, preserving these soil horizons as soil archives. Those anthropogenic structures and the relative dating they provide highlight, in particular, an initial phase of erosion following the Late Bronze Age occupation at Faux-Fresnay, followed by an acceleration of erosion processes during the second half of the Subatlantic period, linked to mechanized agriculture. The use of an ancient roadway as evidence of periods of erosion/sedimentation on a regional scale can also be extended to other archaeological, geomorphological, and pedological contexts. Thus, it is possible recontextualize these events at regional scale through other examples of more recent, sometimes modern to contemporary, roadways that have preserved ancient soils and bear witness to accelerated colluvial morphogenesis over more than half a century.
The characteristics of certain anthrosols are attracting growing interest due to their high carbon (C) stocks. With this in mind, we focused on anthrosols from South America and Central Africa. The South American samples come from three archaeological sites in the Llanos de Moxos region of Bolivia (Isla Manechi, San Pablo, and Isla del Tesoro). In Cameroon, a French-Cameroonian team from the French National Research Institute for Sustainable Development collected samples from two types of anthrosols (dark soils, which we have called Dark soils, and archaeological pit fillings, referred to as Refuse pits), as well as from forest soils (Forest soils). The objective of this study was to assess the impact of past human activities on these soils by conducting specific measurements of their organic status (soil organic carbon content and quality – Corg). The originality of this work lies in its empirical approach and the use of a method rarely applied in archaeology: Rock-Eval® thermal analysis, which allows for the quantification and characterization of soil organic carbon. Thermal analyses of soil samples from archaeological sites were compared with one another and against a reference model. The results indicate that in the Cameroonian sites, the measured carbon is of organic origin. In Bolivia, we focused solely on organic carbon forms, although inorganic carbon forms were also present at San Pablo and Isla del Tesoro, which are shell middens. Findings on the thermal stability of soil organic matter (SOM) highlight that soils from natural environments (Forest soils) or abandoned sites (Dark soils) have a signature comparable to a general model based on a set of undisturbed natural soils. In contrast, soils from human occupation sites deviate from this model. Our hypothesis is that this deviation serves as an indicator of ancient human occupation. The magnitude of this deviation could reflect the intensity or type of anthropogenic activities that took place on these intertropical archaeological soils. We propose an integrative parameter to measure the degree of SOM disturbance in relation to human impact on soils. This preliminary study suggests that the method could, in principle, detect the imprint of human activities on archaeological site soils.
From Herodotus and his vision of Egypt as a gift from the Nile to the present day, Egyptian civilization has been examined in many aspects. By observing the Egyptological Bibliography, the perception of the agrarian landscape and its exploitation seem to remain generalist, with imprecise knowledge, although certain geophysical and geological analyzes have been conducted in the plain for ten years. In addition to these geoarcheological approaches, the reading of notarial acts of the Ptolemaic era (4th centuries before J.-C.) makes it possible to discern and reposition precisely in the landscape of the study area (Louxor) of the Topographic elements and types of cultivated fields. The lexicographic analysis of four demotic terms used to qualify the types of land shows not only that the Egyptians distinguished soil by its characteristics (real or potential yield, composition, color) and its location but also shows how an environmental reading of these contracts allows us to advance our knowledge and better understand the nuances of the agrarian landscape.
Particles translocation exists in both subarctic/alpine and sub-arid climate contexts. The geochemical surface properties of the particles (loess, alluvium, fossil beaches or slope deposits) induce a translocation of fine or silty clays under control of the pH. The process of illuviation corresponds to an early and precise period of soil evolution, depending on decarbonization or desaturation. It requires the percolation of a water flash: a meltwater, or a harsh rain in arid context. Any excess cations (Ca++ or Mg++ in alkaline or Al2 O3 in acid context), allows rapid flocculation and locks the leaching process. Several processes can hinder fine illuviation as in acid, calcareous or volcanic palaeoenvironments. The “Zero Point Charge” (ZPC) of the mineral surface or of clay-humic complex regulates the optimum conditions for particle dispersion or flocculation. This implies that illuvial process is an early stage in the soil evolution within a narrow pH window, but it can be reactivated by the chemical rejuvenation of the soil after erosion or by loess deposition as natural or anthropogenic superficial inputs, by burial, by changes in hydrologic functioning or in vegetation cover. The soils of our regions are the result of a complex and cumulative history since at least 50 ka or even 120 ka, modulated by the evolution of the climate and the biosphere. Clay coatings do not necessarily represent Holocene or older interglacials but can attest as well to Weichselian interstadials, even very brief. A rejuvenation or fertilization by a sedimentary contribution or a truncation will allow a very brief return of the illuvial functioning followed by a rapid return to an oligotrophic status of the surface soil. This phenomenon also makes it possible to understand the succession of illuvial phases observed in thin sections. Most Bt horizons are cumulative and often polyphased. This succession of events, in addition to the evolution of the climate and the precipitation regime, makes it possible to understand, the genesis of the current pedocomplex in function of the loessic quaternary inputs. In regions with limited sedimentary input, the soil very early acidifies, degraded and the illuvial horizon no longer evolves since at least the MIS 3, or the Last Interglacial, as in the south-west of France and the margins of the Massif central or the Vosges. An acido-complexolysis of the clays is superimposed on the leaching, especially in the glosses of the inherited fragipan.
In order to gain a more detailed understanding of the interrelations between archaeology and pedology, it is possible to describe in detail the targeted objects and the protocols used by each, by comparing concrete experiments and attempting to make the comparison more general. We have decided to include here a few considerations on the metaphysics of time, because we feel that they are rarely used in the ordinary scientific exercise, and yet are likely to shed new light on the subject. Thus, the fundamental ontological distinction between events and processes seems to us to be particularly fruitful in this debate and allows us to temper somewhat any attempt at fusion (or intersection) between these disciplines.
Excavations carried out on a 5-hectare hillslope, in the commune of Woippy (near Metz, France), uncov-ered estate active between the 7th and 12th centuries. Finds include areas of dwellings and associated plots of land and paths. The steep hillside was developed on a low-permeability silty-clay to sandy-clay substrate. The soil horizons un-covered are linked to the small strip-shaped affected by erosion to various extents relating to topography. In addition, the excavations uncovered a complex system of drains and water-collecting ditches, which constituted a preliminary stage to the siting of the buildings and gradually organized the final shape of the plot. The water drainage management thus appears to be a key factor in the archaeological structuring of the landscape, just as to recreating drains and retention basins became necessary during the 2018 excavation to limit the impact of colluvium in the present-day village.
