HOLOCENE TERRESTRIAL CLIMATE CHANGE IN SOMALIA REVEALED THROUGH BULK AND INTRA-TOOTH OXYGEN ISOTOPE ANALYSIS OF WARTHOG AND DIK-DIK TOOTH ENAMEL

The climate of North and East Africa has changed over the last several thousand years from warm and humid to hot and dry. The timing and pacing of this climate transition is disputed, especially for the Horn of Africa. Two rockshelter sites in southern Somalia, Gogoshiis Qabe and Guli Waabayo, occupied from about 12,000 to 2,000 years before present, provide an opportunity to investigate past changes in aridity in this understudied region. To track changes in aridity at these sites, we are using the oxygen isotope aridity index, which exploits the difference in tooth enamel oxygen isotope (δ¹⁸O) values between evaporation insensitive (EI) obligate drinkers and evaporation sensitive (ES) non-obligate drinkers to calculate a water deficit value. Preliminary δ¹⁸O values measured in paired, same depth dik-dik (ES) and warthog (EI) tooth enamel samples recovered from these sites suggest a significant increase in aridity toward the present; water deficit values shift from ~800 mm at lower depths to ~1500 mm closer to the surface at both sites. Serial-sampled warthog teeth from a range of levels also demonstrate an increase in the seasonality of rainfall toward the present.