Jörg Grunert

Aeolian sedimentation in arid and semi-arid environments of Western Mongolia

Research on aeolian sediments in Mongolia shows two main cycles of aeolian sedimentation: first the accumulation of major sand fields neighbouring the eastern bank of rivers and lakes, and second the distribution of loess-like sediments on the mountain slopes. The first is resulting from strong westerly winds, being more strength especially during the glacial periods. The latter is resulting in the erosion and accumulation of silt in this region in more humid periods in Interstadial stages and at the end of glacial periods. Both cycles are described on the case study area of the Uvs Nuur Basin in Western Mongolia.

The formation of alluvial fans and young floodplain deposits in the Lieser catchment, Eifel Mountains, western German Uplands: A study of soil erosion budgeting

This study deals with the exploration and spatiotemporal quantification of the young Holocene, nearly skeleton-free floodplain sediments of the Lieser River, a tributary of the Mosel River in the Eifel Mts. The deposits are primarily a consequence of anthropogenic-triggered soil erosion in the catchment. To observe the phenomenon of corresponding soil erosion on multiple levels two small alluvial fans of tributary catchments were investigated. For comparison, one location in the neighboring Salm valley was described. The results were compared with those of other streams. With extensive fieldwork more than 100 drillings and pits were made at 12 locations. For dating the sediments OSL dating, 14C dating of organic contents and archaeological artifacts were used. In the floodplains of the Lieser and its tributaries, 35.1 × 106 t of overbank fines are stored. To achieve this, an average soil erosion of 61.4 mm in the whole catchment would have been necessary. About 28% of young floodplain sediments in upper and lower course were deposited before ad 1000. However, prehistoric deposits could not be positively proven. Only 18% of floodplain sediments were deposited between ad 1000 and 1320 (early and high Middle Ages) and 54% during late Middle Ages and early Modern Time (ad 1320–1850), respectively. The thickness of floodplain sediments is mostly independent of the valley gradient. The largest sediment thickness (> 5 m) was found by drilling in the upper reaches. However, a part of this could be dated to the early Holocene. In the narrow middle reaches, the maximum thickness of the skeleton-free deposits was only 1.2–2 m. The average thickness of the floodplain sediments rose again in the depression of Wittlich up to 2.4 m. The formation of the investigated small fans was quite different. Sedimentation occurred within limited periods as a result of single events.

Reconstructing fluvial, lacustrine and aeolian process dynamics in Western Mongolia

At the eastern rim of the Mongol Els, the largest dune field of Mongolia, the rivers Shurgyn Gol and Zavkhan Gol converge and form a flood plain at the dune front. Interfingering fluvio-lacustrine and aeolian sediments are found in different spatial contexts in the area. By investigating the chronostratigraphy of these sediments, valuable information can be derived for the reconstruction of geomorphological processes and forcing-response relations in the past. The flood plain is locally covered by lacustrine sediments representing an Early to Mid-Holocene lake only a few meters deep. This can be deduced from several 14C and OSL dates and tachymetric measurements, and is in accordance with high stands of other lakes in Western Mongolia. Relics of a lake sediment on top of an old dune 17 m above the floodplain have been OSL-dated to 114 10, 119 10, and 127 10 ka, indicative of an Eemian age. At that time a large and deep lake must have covered the plain. There is evidence of two causes of lake formation: increased discharge of the rivers due to increased precipitation in the mountainous catchment areas and, at the same time, ponding of the rivers by strong dune advance due to persistingly arid conditions in the foreland. The transition phase to more humid con ditions, together with a relatively high humidity gradient, appears to have been morphodynamically very efficient. No evidence could be found of the assumed modern climate change. Recent reduction of the sparse grass cover of the region reflects overgrazing, and the reduction of river discharge is due to water-consuming irrigation.

Naturschutz in Westafrika. Das Beispiel des Pendjari-Nationalparks (Benin)

Die ursprungliche, uberwiegend waldbedeckte Naturlandschaft Westafrikas ist durch den Menschen stark verandert worden. Sudlich der Sahara herrschen heute Savannen mit unterschiedlichen Geholzanteilen vor. Insbesondere in den bevolkerungsarmen und wildreichen Trockensavannen wurden infolge internationaler Konventionen zahlreiche grosflachige Schutzgebiete ausgewiesen. Hierzu zahlt auch der Pendjari-Nationalpark in Benin, an dessen Beispiel die Situation des Naturschutzes in einem westafrikanischen Schutzgebiet dargestellt wird. Abschliesend werden Perspektiven fur eine an den Nationalparkzielen orientierten Entwicklung des Gebietes aufgezeigt.