Reconstructing Holocene Soil Formation and Palaeoclimate Signals in the Jos Plateau, North Central Nigeria: An Original Pedological and Isotopic Investigation

This dissertation reconstructs the Holocene history of soil formation on the Jos Plateau, Plateau State, North Central Nigeria, using pedological stratigraphy and multiple isotopic proxies to recover palaeoclimatic signals preserved in the soil profile and to provide a deep-time framework for understanding current soil properties and their trajectory under future climate change. The Jos Plateau, with its relatively stable geomorphic position and diverse parent materials, offers an exceptional natural archive of Holocene environmental change in Central West Africa, yet systematic pedological and isotopic investigation of its soil profiles for palaeoclimate reconstruction has not been undertaken, representing a fundamental gap in the region's palaeoenvironmental record. This study excavates 20 deep pedons (greater than 2 metres) across representative geomorphic positions on the Plateau. Holocene soil formation is reconstructed from micromorphology (thin sections), optically stimulated luminescence dating of aeolian and colluvial sedimentary horizons, stable carbon isotope ratios (delta 13C) of organic matter fractions reflecting C3/C4 vegetation shifts, oxygen isotope ratios (delta 18O) of secondary pedogenic carbonates, and phytolith assemblages. The dissertation proposes an original Jos Plateau Holocene Pedogenic Chronology (JPHPC) identifying four distinct pedogenic phases correlating with West African palaeoclimate events including the African Humid Period. The carbon isotope record reveals a vegetation shift from C3 forest-dominated (10,000 to 4,000 BP) to C4 savanna-dominated assemblages (4,000 BP to present), consistent with regional palaeoclimate reconstruction. Original contributions include the 20-profile deep pedological dataset, the JPHPC, and the first OSL chronology for Jos Plateau colluvial soils. Keywords: Holocene pedogenesis, palaeoclimate, Jos Plateau, stable isotopes, optically stimulated luminescence.