Contenu du sommaire

Abstract. — The Spanish economic development has considerably increased the electric production and staggered the structures of this industry. The hydroelectricity part is remaining relatively tall, but the preponderant productive is no more the Pyrenees but the Meseta and the N.W. The chief part of electricity is now produced by thermic power stations of the coast (fuel and natural gas imported). To free oneself from the petrol servitude, Spain in increasing electric power stations working with national coal, nuclear and solar energy. The modernization and the building of a few of strong power stations is the fact from the industrial concentration in a few of great companies.

Abstract. — Free zones form a special study of boundary effects upon landscape. Among five free zones located on Switzerland's border, Livigno (Valtellina) and Samnaun (Graubiinden) are the most important by spatial consequences they generate. Although two isolated mountain areas, they originate from a duty free specialized trade and their tourism activities involve a chief development stage. Historic and law reasons explain duty free exemptions. The economic future of these two areas is linked with EEC and EFTA' s political evolution and possible unification.

Abstract. — The valley of the oued Ighyghayene (High Atlas, Morocco) offers a wide range of wurmian glacial patterns of a semi- arid mountain. The traces of the wurmian maximum as well as two stages of retreat can be found there. All three are materialised by morainic deposits. Downstream the oued is bordered by two principal levels of terraces of a heavy heterogeneous material. Nevertheless the most original phenomenon is the late-wurmian rock glacier of Aremd. The importance of the accumulation is linked up with the particularly favourable supplying conditions. As a matter of fact, it is situated at the foot of the Northern wall of the Aksoual Mountain with a drop of 2000 m. In the later Pleistocene, the evolution of the slopes is also caracterised by large peri-glacial screes and landslips. At present in the Toubkal Mountain, there is a rock-glacier and many active screes. The action of frost-cracking is particularly vigourous.

Abstract. — Palynological research in the Aïr Massif (Niger) - Contribution to the knowledge of paleoclimates. The geomorphological and sedimentological study of the middle terrace of the Air, implies the existence of more humid climates and whose characteristics have fewer contrasts around the period between 12.000 and 10.000 years B.P. The comparison of fossile pollens extracted from this terrace, with the current pollenic rains, brings forth arguments which are convergent.

Abstract. — The badly known central plateaux of Bilanktaung offer two splendid examples of tropical karsts: karst-buttes and karst- plateaux with plenty of sink-holes. These numerous sink-holes are either caverns with plentiful concretions, or very working system of rivers rised from the leakage of exogen surface waters.