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Editorial:
Geomorphology, palaeoenvironments and geoarchaeology of tropical environments

Laurent Lespez et Aline Garnier
p. 221-223
Cet article est une traduction de :
Éditorial :
Géomorphologie, paléoenvironnements et géoarchéologie des mondes tropicaux

Texte intégral

1Geomorphological research on tropical environments has a long tradition in French geomorphology. This research was long centred on the explanation of large morphostructures, in the first half of the 20th century; the renewal of geomorphology occurred through the study of processes of alteration, erosion and accumulation around the world, favouring the emergence of a climatic geomorphology for which the study of tropical environments plays a major role. Following in the steps of De Martonne (1946), much work was carried out that gave rise to this branch of the discipline, illustrated by the different manuals of Tricart and Cailleux (1969, 1974). At the same time, many geomorphologists devoted their scientific lives to the study of models of dry and humid tropical regions and produced a series of synthesizing works based on their personal research (e.g., Demangeot, 1976; Dresch, 1982; Rognon, 1989; Beaudet and Coque, 1994). From this basis many studies developed in relation to contemporary processes, in particular within the framework of the anthropisation and management of risks specific to these environments, for example synthesizing works recently produced in English by Gupta (2011), and its recension made by Thouret (2012). Thus a profound renewal has been taking place over the last twenty years, in particular because of the expansion of geomorphological research seen as palaeoenvironmental research in relation to climatic changes and geoarchaeology, which has stimulated the development of studies on the impact of anthropisation and its different modalities. It is within this movement that our proposition of a special issue devoted to geomorphology, palaeoenvironments and geoarchaeology of tropical milieux is situated.

2This issue is intended to include contributions related to different types of sedimentary archives (lake, fluvial system, continental and coastal humid zones, dune systems, etc.), with special attention to the relation between geomorphological dynamics and the transformation of environments affected by climatic changes and anthropisation. The assembled articles lie fully within this perspective but also portray a geomorphology that lies in the continuity of its predecessors, as four contributions concern sub-Saharan Africa and one concerns areas located farther afield. Yann Callot and Maël Crépy propose first of all a reflection on the genesis and dynamics of continental dunal edifices. After a review of new advances in laboratory modelling and experimentation on the mobility of sands that reveal the role of their availability, a factor as important as wind for understanding dunal morphologies and their dynamics, they return to data gathered in the Sahara of Niger to propose a new interpretation. Their work emphasizes the fruitfulness of combining theoretical and physical approaches, modelling, experimentation and field work. It opens new perspectives for the interpretation of dunal environments.

3Next, the work of Sarah Davidoux and her colleagues, like that of Aline Garnier, Barbara Eichhorn and Caroline Robion‑Brunner, concentrates on the late Holocene, in which the effects of human occupation of catchment basins and climatic oscillations are linked. The article by Sarah Davidoux and her colleagues presents a system of terraces fitted together in the ravine of a tributary of the Falémé in eastern Senegal in the Soudanian zone. It demonstrates a morphological instability over the last two millennia. Based on dating by radiocarbon and luminescence, chronostratigraphic and morphological analysis reveals a succession of dryer periods favourable to incision and humid periods that engender an aggradation of the alluvial plain. The discussion suggests the domination of the climatic impact over the effects of anthropisation, although the latter exacerbates the phases of sedimentation. To this theme, the article by Aline Garnier and her colleagues adds a discussion on the role of the impact of ancient metallurgical activities. It addresses the alluvial dynamics of a small watercourse, the Tatré, in the Bassar country in northern Togo, situated in one of the major iron manufacturing centres of the pre-colonial period in West Africa. Based on a geomorphological and phytolithic study of the sedimentary fill of the upper and middle valley of this watercourse, near the vestiges of iron manufacturing, it presents a succession of four hydro-sedimentary phases. These provide evidence for the responses of the fluvial system to an external climatic forcing, although the third phase identified (15th–20th centuries) shows an aggradation mainly controlled by direct (exploitation of wood) and indirect (extension of agriculture) environmental effects of metallurgical activity.

4Finally, the work of Ninon Blond and her colleagues and that of Jeanne Brancier and her colleagues are even more closely concerned with the impact of human activities on tropical environments. In the former case, the work concerns investigation of the origin of terraces for cultivation constructed across thalwegs in the mountainous areas of northern Tigray in the north of Ethiopia. However, the discovery by archaeological excavation of human settlements of the last four millennia gives rise to questions concerning the age of these. The geomorphological study, the dating of deposits as well as the exploitation of archival documents and evidence from witness accounts suggest that these terraces are later and had developed on earlier sedimentary accumulations related to the history of human occupation in the region. Finally, the work of Jeanne Brancier and her colleagues had the objective of defining and understanding the development of anthropogenic soils observed in pre-Columbian archaeological contexts in Martinique and French Guiana. Rather than a classic chronostratigraphic approach, it is the micromorphological study of soils that was favoured. The comparative analysis of two anthropogenic soils from Martinique and Guiana shows that they developed in relation to pre-Columbian activities but that they are evidence of activities that differed locally. The results obtained enable the authors to question the definition of anthropogenic soils in the current pedological references, and to propose a revision.

5The articles received thus demonstrate the renewal of the discipline, based on multi-indicator approaches that combine geomorphological investigations in the field, bio-indicators and archaeological and historical data. Mainly produced by young researchers, they also demonstrate the vitality of this renewal.

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Bibliographie

Beaudet G., Coque R. (1994) – Reliefs et modelés des régions tropicales humides : mythes, faits et hypothèses. Annales de Géographie, 103, 577, 227‑254.
DOI : 10.3406/geo.1994.13780

de Martonne E. (1946) – Géographie zonale. La zone tropicale. Annales de Géographie, 55, 297, 1‑18.
DOI : 10.3406/geo.1946.12700

Demangeot J. (1976) – Les espaces naturels tropicaux. Paris, Masson, 190 p.

Dresch J. (1982) – Géographie des régions arides, PUF, Paris, 277 p.

Gupta A. (2011) – Tropical geomorphology. Cambridge University Press, 386 p.

Rognon P. (1989) – Biographie d'un désert. Paris, Plon, Coll. Synthèse, 347 p.

Thouret J.-C. (2012) – Avijit Gupta, Tropical geomorphology. Géomorphologie : Relief, Processus, Environnement, 18 (4), 477-478.

Tricart J., Cailleux A. (1969) – Le modelé des régions sèches. Traité de géomorphologie, tome V, SEDES, Paris, 472 p.

Tricart J., Cailleux A. (1974) – Le modelé des régions chaudes. Forêts et savanes. Traité de géomorphologie, tome V, deuxième édition, SEDES, Paris, 1974, 345 p.

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Référence papier

Laurent Lespez et Aline Garnier, « Editorial:
Geomorphology, palaeoenvironments and geoarchaeology of tropical environments
 », Géomorphologie : relief, processus, environnement, vol. 24 - n°3 | 2018, 221-223.

Référence électronique

Laurent Lespez et Aline Garnier, « Editorial:
Geomorphology, palaeoenvironments and geoarchaeology of tropical environments
 », Géomorphologie : relief, processus, environnement [En ligne], vol. 24 - n°3 | 2018, mis en ligne le 23 novembre 2018, consulté le 23 janvier 2019. URL : http://journals.openedition.org/geomorphologie/12428

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Auteurs

Laurent Lespez

Laboratoire de Géographie Physique (LGP), CNRS-UMR 8591 – 1 place Aristide Briand, 92195 Meudon CEDEX | Département de Géographie, UFR LLSH, Université Paris-Est Créteil – 61 avenue du Général de Gaulle, 94010 Créteil, France (laurent.lespez@lgp.cnrs.fr).

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Aline Garnier

Laboratoire de Géographie Physique (LGP), CNRS-UMR 8591 – 1 place Aristide Briand, 92195 Meudon CEDEX | Département de Géographie, UFR LLSH, Université Paris-Est Créteil – 61 avenue du Général de Gaulle, 94010 Créteil, France (aline.garnier@lgp.cnrs.fr).

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