Exploring palaeoaridity using stable oxygen and carbon isotopes in small mammal teeth: a case study from two Late Pleistocene archaeological cave sites in Morocco, North Africa

Thesis

Revised chronologies from Moroccan cave sites have raised questions concerning the timing of changes in human cultural behaviour in relation to past climate shifts. However, many of the inferences about past moisture regimes are based on external records. Therefore, this thesis aimed to develop a palaeoclimate record using oxygen and carbon isotope values (δ¹⁸O and δ¹³C) in Gerbillinae (gerbil) teeth from two Late Pleistocene cave sites, El Harhoura 2 and Taforalt, in Morocco. Since small mammals are not commonly used to construct proxy climate records, a modern isotope study was undertaken in northwestern Africa to understand the influences on the stable isotope composition of small mammal tissues in semi-arid and arid settings.

The results from the modern study show that δ¹⁸O composition of gerbil teeth is strongly correlated with mean annual precipitation (MAP), and therefore in arid settings reflects moisture availability. Predictably, the δ¹³C values of the gerbil teeth reflected C3 and C4 dietary inputs, but arid and mesic sites could not be distinguished because of the high variability displayed in δ¹³C. The δ¹⁸O isotope-based MAP reconstructions suggest that the Mediterranean coastal region of North Africa did not experience hyper-arid conditions during the Late Pleistocene. The δ¹³C values of the gerbil teeth show that C₃ vegetation dominated in the Late Pleistocene, but there was a small amount C₄ vegetation present at Taforalt. This indicates that small mammals are extremely sensitive to discreet shifts in past vegetation cover. Both the modern and archaeological studies demonstrated that the isotope values of molars and incisors differed. The results indicate that tooth choice is an important consideration for applications as proxy Quaternary records, but also highlights a new potential means to distinguish seasonal contexts. Comparisons of proxy climate records and cultural sequences at Taforalt and El Harhoura 2 show that Middle Stone Age occupations of both sites occurred during relatively humid and arid climate phases. The transition to the Later Stone Age appears to have taken place during a period of increased aridity, hinting that this cultural transition may be related to changing environmental conditions.

Authors: Jeffrey, A

• DOI: 10.5287/ora-pmo7j9rm9
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Keywords: oxygen; carbon; isotope
• Subjects: Palaeoenvironment; Archaeology