Developing luminescence dating methods to refine and extend the age range for the Chew Bahir Lake core from eastern Africa

Abstract

Paleoclimate research, particularly in areas that are closely linked with human evolution and dispersal such as eastern Africa, is of great interest not only for Quaternary researchers but also for the general public. The Hominin Sites and Paleolakes Drilling Project was carried out in eastern Africa to provide long, continuous, and unweathered sediment cores from lake deposits in the proximity of archeological sites with important fossils. One of these cores is the Chew Bahir Lake core. Chronological information is required to assess sediment accumulation rates and interpret other paleoclimate proxy records obtained from these lakes. The potential of different luminescence chronometers to refine and extend the luminescence age range for this core is investigated in this research. The violet stimulated luminescence signal from quartz demonstrates signal instability over geological times, and hence is not capable of extending the age range for the core. The high temperature post-IR infrared stimulated luminescence (pIRIR225) signal from polymineral fine grains shows good agreement with independent age control for the upper ~90 mcd of the core. The pIRIR225 signal is successful in extending the available quartz OSL chronology up to ~200 ka. The recently introduced post-Isothermal infrared stimulated luminescence (pIt-IR) method is examined, and the ability of the method to obtain paleodoses that do not need any
fading correction is confirmed; however, the pIt-IR De is bound to the earlier saturation limit of the IR50 signal (~100 ka). Increasing the first IR temperature in the pIRIR225 protocol from 50 to 150 ºC can extend the upper age limit in the pIt-IR protocol. Two different sediment accumulation rates, in addition to a hiatus or a significant reduction in the accumulation rate, is observed based on the age-depth profile generated using the fading corrected pIRIR225 ages for the upper ~80 mcd of the core.

Date of Award	2023
Original language	English
Awarding Institution	Aberystwyth University
Supervisor	Helen Roberts (Supervisor) & Geoff Duller (Supervisor)