Reconstructing ‘Green Sahara Periods’ over the last 3 million years

Date & time

5.30–6.30pm 15 May 2018


Jaeger Seminar Room, RSES (building 61), ANU


Dr Katharine Grant

Event series

Numerous continental and marine archives document an expansion of vegetation and water bodies across the now arid Sahara desert during the early Holocene. This Green Sahara Period (GSP), also known as the African Humid Period (AHP), played a major role in human migration and settlement, and was linked to an intensification and northward displacement of the African monsoon rainbelt in response to orbitally driven insolation changes. Detailed records of earlier GSPs are sparser, however, due to the fragmentary nature of continental archives and/or dating issues, and relatively few marine core records of the African monsoon prior to the last glacial cycle. Given the significance of GSPs for hominin evolution and development, as well as the insights they provide into long-term African monsoon dynamics, robust evidence of the timing and nature of GSPs through the Plio-Pleistocene is much needed. In this talk I will describe how we established a new orbitally-tuned index of North African aridity/humidity, based on bulk geochemical and environmental magnetic records from Ocean Drilling Program (ODP) Site 967 (Eastern Mediterranean). Our index reveals the timing of GSPs throughout the Plio-Pleistocene, and allows us to highlight intervals where both North/West and East Africa likely experienced elevated humidity. Documenting such pan-African humid episodes may be of considerable importance for efforts to understand human evolution/migrations.

Speaker bio:
Katharine completed a Bachelor of Science with Honours, majoring in Marine Science and French at the Southampton University (UK) in 1997. She then moved to Townsville to undertake a Masters of Earth Science at James Cook University, working with Dr Bob Carter and Prof Jerry Dickens. Her thesis, completed in 2002, was titled Late Neogene biogenic sedimentation and carbon isotope shifts in the southwest Pacific. She then moved back to Southampton University to undertake her PhD with Prof. Eelco Rohling on Sea-level change, monsoon variability, and eastern Mediterranean climate over the Late Pleistocene. She is currently a post-doc at the ANU working with Prof. Rohling on reconstructing sea-level and African monsoon variability over the last 3 My.

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