Graduation Year

2006

Document Type

Thesis

Degree

M.A.

Degree Granting Department

Environmental Science and Policy

Major Professor

Rick Oches, Ph.D.

Keywords

Ostracodes, Oxygen isotopes, Wadi Hadramawt, RASA, ITCZ, Gemorphology, Paleoclimate

Abstract

Tufa and lacustrine deposits are useful paleoclimate archives in reconstructing the early to middle Holocene climate and paleohydrology of southern Yemen's Wadi Idim and Wadi Sana, which are north-flowing tributaries to Wadi Hadramawt. Numerical age estimates and oxygen-isotopes are used to assess the onset and cessation of tufa formation and reconstruct the environment of lacustrine sediment deposition in the region in order to understand the broader early to middle Holocene hydrologic system.Numerical age estimates from the studied wadis show a correspondence between early to mid-Holocene humid-phase sediment deposition and the northward shift of the ITCZ, as documented in paleoclimate records from other East Africa -- Arabia --

India continental and marine sediments. The interval between ca. 10-5 ka B.P. corresponds to a period of greater availability of moisture from the Arabian Sea region. Increases in precipitation allowed for a lake and wetland systems to develop, and increased spring discharge contributed to the formation of the tufa. Within the lacustrine sediments are ostracodes, mollusks, and flora casts that are found in a much wetter climate compared to today's hyper-arid environment. This early to mid-Holocene humid phase corresponds with a more northerly positioned ITCZ, which shifted south to its present day position around 5,000 yr B.P.Oxygen isotope measurements from ostracods show a range of isotope values from ~ -4.0%â?? at approximately 10 ka B.P. to ~ -6.0%â?? at approximately 5 ka B.P. Theses values represent the early to middle Holocene pluvial phase. Changes in the oxygen isotopic signature represent a change in evaporation or a possible change in source.The early to middle Hol

ocene humid phase also corresponds with periods of agricultural activity, which are being investigated by the archaeological team of the Roots of Agriculture in Southern Arabia Project (RASA). Research into the effects of climate change on human activities, specifically agricultural processes, is the focus of RASA. Southern Arabia offers not only a convergence of three major agricultural regions, but also preserves a sedimentary record of the climate shift that affected the region during the period of study.

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