干旱区生态环境知识资源中心

Linear dunes in the southwestern Kalahari provide evidence of the nature of paleoclimates. They have special significance because their alignments indicate a previous circulation pattern with prevailing northwesterly winds. At present, the bases of the dunes are fixed by vegetation and only the dune crests are active. In contrast to previous suggestions final dune stabilization took place before about 9-8 ka. This corresponds to reduced wind velocities accompanied by more humid conditions. This seems to be the last important environmental change recorded by significant landforms in the southwestern Kalahari. Since about 8 ka the region remained more or less semi-arid: The long distance to seasonal south-shifting humid tropic air masses (Innertropical Convergence Zone, ITCZ) and the climatic barrier of the Namib and the Karas Mountains against Atlantic influences allowed only minor fluctuations. The Holocene is a period of reduced pan development. The palls are partly buried by the early Holocene linear dunes as well as by young sand fields. At Pan 1073, southeast of Grootpan, intra-pan dunes have formed during the last 1000 years. (C) 1998 Elsevier Science B.V.