SEDIMENTARY AND GEOCHEMICAL INVESTIGATION OF LACUSTRINE SEDIMENTS FROM THE YEMEN HIGHLANDS AND IMPLICATIONS FOR CLIMATE CHANGE

Lacustrine deposits from the semiarid Dhamar highlands of Yemen record significant changes in paleoclimate. This paper presents sedimentary and geochemical analyses of lacustrine sediments and their implications for climate change in southwestern Arabia. The study area, on the southeastern tip of the Arabian Peninsula, is located in a climatic transition zone. It is bounded by the Rub al-Khali desert to the north, and to the south and east, the Indian Ocean, which subjects the highlands to the influence of the Indian Ocean monsoon. The Dhamar highlands of Yemen consist of high intermontane valleys surrounded by the highest mountains (3000 m asl) on the Arabian Peninsula.

The intermontane basins contain very long sediment histories. Lacustrine deposits occur within the basins where, today, the area is semi-arid without major reservoirs of surface water. Lakes with restricted outlets are evidence of periods in the past, characterized by climates significantly moister than the present. A peat deposit with a radiocarbon age of 9,820 + 60 yrs B.P. is also evidence of moister conditions in the early Holocene.

Sedimentary and geochemical analysis of paleo-lake sediments record fluctuations in sedimentation and chemical regimes that extend into the Pleistocene. These fluctuations provide signatures in the sediment profile that identify episodes of soil development and episodes of lacustrine deposition. The occurrence of multiple paleosols indicates periods of stable land surface. Paleosols are separated by thick lacustrine deposits indicative of increased surface water and moister overall conditions. Fluctuations in the sediment record of the Dhamar highlands reflect a regional record of climatic conditions for southwest Arabia.