To what extent do Milankovitch cycles dominate over more regional forcings from the context of palaeo Lake Tana and east Africa over the Holocene and late Pleistocene.

: To what extent do Milankovitch cycles dominate over more regional forcings from the context of palaeo Lake Tana and east Africa over the Holocene and late Pleistocene.

Abstract

Lake Tana is a crater lake located in northern Ethiopia, throughout millenia, the site has been a recipient of varying environmental conditions, primarily between arid and humid conditions. This has been associated with Milankovitch forces driving such changes as the tropical latitude’s expression of glacial and interglacial periods respectively. Despite previous studies from Lake Tana and the wider area of east Africa observing fluctuating conditions in their data, understanding the individual modulating forces behind this has always presented challenges for researchers. This study aims to elucidate upon what the main controlling factors were on climatic changes and how dominant they were in north-eastern Africa approximately over the last 227 thousand years. This study will therefore need to establish what environmental conditions were present at different time periods and correlate them with the appropriate Milankovitch frequencies. A two-discipline approach was taken utilising over 200km of seismic survey lines and over 90m of a single core, previously collected from the lake. Using seismic facies analysis and elemental proxy ratios The results showed that between 109 and 56 ka BP. was a strong period of overall aridity. This partially to fully desiccated lake conditions. The periodicity this occurred at provided strong evidence this was driven by orbital precession dominance. Further research showed this was due to further modulation by high orbital eccentricity.

Date of Award	19 Jun 2026
Original language	English
Awarding Institution	Bangor University
Supervisor	Dei Huws (Supervisor)