PALEOHYDROLOGY AND PALEOCLIMATES FROM LACUSTRINE ENVIRONMENTS OF THE DHAMAR HIGHLANDS, YEMEN

The Dhamar highlands of Yemen is a tectonically active region characterized by high intermontane valleys surrounded by the highest mountains (3000 masl) on the Arabian Peninsula. These highlands are bounded by the Rub al-Khali desert to the north, and the Indian Ocean to the south and east, which subjects them to the influence of the Indian Ocean monsoon. Lacustrine deposits from these highlands record significant changes in Quaternary paleohydrology. This poster presents sedimentary, geochemical, and chronological data analyses of the lacustrine sediments and their implications for paleohydrology and paleoclimate change in southwestern Arabia.

The intermontane basins record very long histories of paleohydrologic change. Currently the region is semi-arid without major reservoirs of surface water. However, thick lacustrine sequences suggest periods of significantly moister past environments. Additionally, a peat deposit with a radiocarbon age of 9,820 + 60 yrs B.P. also documents moister conditions during the early Holocene. The occurrence of multiple paleosols indicate periods of land surface stability, while carbonate-rich horizons are evidence of increasing aridity and again signal significant changes in the paleohydrology.

The relationships of paleohydrolgic change associated with active tectonics and paleoclimate changes such as influences of the Indian Ocean monsoon are examined through sedimentary and geochemical analysis. Fluctuations in sedimentation and chemical regimes extend into the Pleistocene and provide signatures in the sediment profile that identify episodes of lacustrine deposition, soil development, and periods of greater aridity. Fluctuations in the lacustrine record of the Dhamar highlands reflect both local changes in paleohydrology and a regional record of paleoclimatic conditions in southwest Arabia.