Abstract/Summary

The vast Arabian deserts sit at a crucial interface between Europe and sub-Saharan Africa and acts as a geographical barrier between Afrotropical and Eurasian fauna. However, punctuated increases of rainfall throughout the Pleistocene created “green” deserts that are increasingly related to mammalian dispersals. These “windows of opportunity” were crucial for occupation and dispersal of hominin species and acted as important steppingstones on the way to the global colonisation of Homo sapiens. Despite a growing body of palaeoclimate information from marine sediment cores and relict palaeolake deposits, there remain significant gaps in important palaeoclimatological questions. For example, what was the precise timing, duration and frequency of wet events? What precipitation regime delivered precipitation across Arabia? How did precipitation vary within and between pluvial periods? What sorts of environments flourished with increased precipitation? Not only are these pertinent questions for accurately characterising past climates and environments but answering these can identify favourable hominin dispersal windows throughout the Pleistocene. To elucidate these issues, this thesis aimed to generate new speleothem-based palaeoclimate records from Mukalla (Yemen), Hoti (Oman), Broken-Leg, Star and Surprise (Saudi Arabia) Caves. South Arabian Humid Periods (SAHPs) were identified by U-Pb and 230Th age determinations of stalagmite growth from Mukalla and Hoti Cave. These SAHPs were a result of African and Indian Summer Monsoon incursions during insolation maxima within peak interglacial periods and warm substages up to 1.1 million years ago, as identified by fluid inclusion water δD and δ18O and calcite δ18O measurements. This increased annual precipitation to >300 mm yr-1 and allowed C4 vegetation to flourish, as determined by calcite δ13C measurements. Identification of sub-annual cycles of δ13C and δ18O indicates environments were highly seasonal, characterised by a “wetter” summer and “drier” winter. Additional U-Pb and 230Th dating of stalagmites from Broken-Leg, Star and Surprise Cave reflect these findings, indicating that wet periods occurred during warm periods of the Pliocene and Early-Pleistocene, Together, this information shows that Saharo-Arabian palaeoenvironmental fluctuation – governed by monsoon variability – provided frequent opportunities for hominin occupation of Arabia and dispersal throughout the Plio-Pleistocene.