From Megachad to Microchad - environmental changes during the Holocene

The investigations carried out within the project in NE-Nigeria since 1989 have been focussing on the late Pleistocene and Holocene landscape development of the south eastern Chad basin. Areas of interest include palaeodune fields, clay plains and former beach ridge systems of Lake Chad. Transgressions and regressions of Lake Chad played an important role in the younger landscape history of NE-Nigeria and have also caused great environmental changes. The term „Megachad“ is well known and describes an enormous lake with an extension comparable with the Caspian Sea of today. The term „Microchad“ stands for the other recent extreme in terms of the lake dimensions varying during the times. Environmental changes in the surroundings of Lake Chad are closely connected with transgressions and regressions of the lake. These lake level changes can be climatically induced as well as non-climatically, due to human impact. Nearly all land units have more or less been influenced by the lake, spatially as well as temporally. It is important, though, to notice the scales of the changes. Some changes took place in a millennial scale, some in the scales of centuries or decades, and at least – as can be observed every year – in a seasonal scale

Systems of Land Use in the Firgi Plains of the Chad Basin

Studies on land use in Africa have usually been carried out by ethnologists or human geographers and were rarely concerned with data on the physical conditions of soil. There is hardly any issue, however, where interdependencies between natural and cultural factors are as evident as in the topic of land use. For this project the approach of three ethnologists, Braukämper, Kirscht and Platte, was therefore combined with the analysis of Thiemeyer as physical geographer. The area of research is the Local Government Area of Marte in the Nigerian State of Borno. As part of the Chad Basin this region is mainly characterised by clay sediments which are commonly labelled firgi by its inhabitants. Beside this general term, however, the local peasants clearly distinguish five types of soil (Kanuri: katti), to which different physical conditions and qualities with respect to their cultivation are attributed. The question arose how far can this popular knowledge, accumulated by agricultural experiences over generations, be correlated with scientific data. That is why samples of the mentioned types of soil were collected by the members of our team and analysed in the laboratory of the Frankfurt Institute of Physical Geography. The detailed presentation of this analysis has to be preceded by the classification of the respective soil types in the terminology of the indigenous farmers

Ethnologische und geomorphologische Aspekte zum Bau von Brunnen und Getreidespeichern in Musene (Nordost-Nigeria)

Bei den hier vorgestellten ethnologischen und geomorphologischen Aspekten von Brunnen und Getreidespeichern in der firgí-Region Musenes wird besonders die "angepaßte Technologie" der hier lebenden Menschen deutlich. Die kulturelle Entwicklung der Region hängt eng mit den besonderen naturräumlichen Bedingungen zusammen. Die Eigenbezeichnung als firgiwú (die Leute des Tons) verweist auf eine Beziehung der Bewohner zum Naturraum, in dem Ton eine besondere Rolle spielt und für den es spezielle Berufszweige gibt. Die Ressource Ton wird, gleichwohl im Bewußtsein, daß es sich hierbei um regionalspezifische Aspekte handelt, als integrierendes Moment über die ethnischen Grenzen hinweg als Teil ihrer firgiwú -Kultur verstanden. Offensichtlich hat diese eine lange Tradition. Interessant wäre, ob in anderen ähnlich ausgestatteten Naturräumen in Westafrika eine vergleichbare Anpassung bzw. Nutzung des Naturraumes zu finden ist, bzw. wie dort die Nutzungsstrategien aussehen

What kinds of museums for what kinds of societies?

The article reflects the broader political contexts of the current debate about ICOM’s museum definition. It focuses on the aim to commit museums to specific values that define their place within their respective societies. What kind of values are addressed? What is specific about them? And why did they trigger such a lively debate? To my mind the decisive question at the heart of the controversy is: Is the new text about an ambitious museum vision for the future? Or should ICOM rather pursue the cultural policy matters of formulating (minimum) standards with its definition which (should) already apply to all museums today and which policy respects?L'article reflète les contextes politiques plus larges du débat actuel sur la définition du musée de l'ICOM. Il se concentre sur l'objectif du nouveau texte qui est de définir la relation entre les musées et la société avec des valeurs spécifiques. Quels types de valeurs sont annoncées ? Quelles sont leurs spécificités ? Et pourquoi ont-elles déclenché une controverse aussi vive ? À mon avis, la question décisive au cœur de la controverse est la suivante : Le nouveau texte porte-t-il sur une vision ambitieuse des musées pour l'avenir ? Ou bien l'ICOM devrait-il plutôt s'occuper de formuler des normes (minimales) avec sa définition qui s'applique (devrait s'appliquer) déjà à tous les musées aujourd'hui

Mikromorphologische Untersuchungen geschichteter Böden im Hessischen Spessart

Mit Hilfe feldbodenkundlicher, schwermineralanalytischer und mikromorphologischer Methoden wird die Genese eines typischen Bodenprofils im hessischen Teil des Vorspessarts untersucht. Die Ergebnisse zeigen, dass der große Tongehaltsunterschied zwischen Haupt- und Mittellage keine Folge von Tonverlagerung ist, sondern dass der meiste Ton schon vor der Formung der Hauptlage in der Mittellage vorhanden war. Ohne die mikromorphologischen Analysen wäre die Genese des Profils als Phäno-Parabraunerde nur schwer zu belegen, da der schichtungsbedingte Tongehaltsunterschied durch rezente Tonverlagerung maskiert wird. Weitere aktuelle, bodenbildende Prozesse wie eine starke Bioturbation und die hydromorphe Prägung des Profils sind in den Dünnschliffen nachweisbar

Die spätmittelalterliche Agrarlandschaft in Nord-Brabant - Mikromorphologische Untersuchungen von Plaggeneschen

Im späten Mittelalter zeichnete sich im Raum Nord-Brabant (Niederlande) innerhalb kurzer Zeit ein Wandel der landwirtschaftlich genutzten Flächen ab. Ackerland wurde erweitert. Es erfolgte eine systematische Parzellierung und die Plaggenwirtschaft setzte ein. Mit Dung und Hausabfällen angereicherte Plaggen wurden zur Aufwertung der Podsole, die sich natürlicherweise auf den Decksanden dieser Landschaft entwickelt haben, auf die Felder ausgebracht. Durch diese Technik entstanden humose E-Horizonte, die den Bodentyp Plaggenesch charakterisieren. Diese anthropogenen Böden sind typisch für diesen Teil der Niederlande. Geoarchäologische und archäopedologische Untersuchungen in Veldhoven beschäftigen sich mit der Landnutzung, Ackersystemen und Ackerbau. Die mikromorphologischen Analysen sollen hierbei Fragen zu den Inhalten der E-Horizonte und der Herkunft der Plaggen klären

Dune ages in the sand deserts of the southern Sahara and Sahel

In this paper we aim to document the history of aeolian processes within the southern Sahara as part of the INQUA Dune Atlas. We review available luminescence ages for sand dunes across the southern Sahara to develop an improved understanding of the dune chronology on a regional basis and attempt to correlate periods of sand accumulation. This was achieved by analysing dune age by country, as well as by latitude and longitude. The results show a very patchy spatial distribution of dune ages with large gaps that encompass some of the largest sand seas. Despite these gaps, some related patterns in dune morphology and stratigraphy appear to be consistent between northern Nigeria and southern Mali where older linear dunes are distinct from younger Late Holocene transverse and barchanoid dunes. Elsewhere in Mauretania linear dunes with different orientations appear to have accumulated at different times, most likely in response to changes in atmospheric circulation. Regional climatic changes are identified where dunes are transgressed by lake deposits within endorehic basins. We identify four locations where dune accumulation is terminated by lacustrine transgressions, two of which, in Lake Chad and the Bodélé Depression, occur shortly after the last glacial maximum (LGM). The third example at Gobiero in Niger occurred later, in the early Holocene, around 8.4 ka and a fourth marks a later transgression of Palaeolake MegaChad after 4.7 ka. Larger-scale latitudinal and longitudinal distributions in dune ages across the southern Sahara do not show any consistent patterns, though this may be due to the small sample size relative to the study area. In addition, local variations in external controls such as wind regime, rainfall, vegetation and sand supply need to be considered, sometimes on a site by site basis. Limiting the analysis to dune ages determined using the single-aliquot regenerative-dose (SAR) protocol indicates a lack of dune preservation during the LGM and the Younger Dryas, times associated with increased dust input to the oceans which is assumed to indicate increased aeolian activity. The SAR dune dates suggest that preservation of dunes at the onset of succeeding humid intervals is an important component of the dune record. The most striking examples of this phenomenon occur where dunes are preserved within endorehic basins by lacustrine transgressions