Analysing human-climate interactions in the Holocene using a high-resolution pollen and tephra record from Diss Mere, England

Research output: ThesisDoctoral Thesis

Abstract

Understanding Holocene climatic complexity is compounded by the evolving relationships between humans and the environment. To capture landscape responses to climate forcing and human activity on a sub-decadal scale, robust chronologies and precise dating methods are essential. Due to the resolution attainable, annually-laminated (varved) lake records are highly valued in geochronological and palaeoenvironmental studies because their varve timescales enable precise dating and the acquisition of high-resolution palaeoecological data. Diss Mere (Norfolk, UK) is one of only three known lakes in the British Isles with a partial Holocene varve sequence. The record provides a unique opportunity to enhance our understanding of processes related to the deposition of key chronological and stratigraphic tephra markers as well as changes in Holocene climates and environments in Southern England. This is due to the excellent preservation of the record, the lake's high sensitivity to North Atlantic climate variability and the fine chronological resolution of its sediments. Specifically, the deposition of varves from 2.1 to 10.2 ka BP, with very high sedimentation rates (0.5 cm/yr) in the last 2000 years, where the laminations are less regular.
Given this context, this PhD research focuses on two main approaches using the Diss Mere sediments to better understand the interplay between human activity and climate change during several key Holocene periods. Firstly, cryptotephra analyses returned geochemistry on 25 tephra layers, providing precise chrono-stratigraphic markers that enhance the varve-based timescale and our understanding of tephra deposition in this understudied area of the British Isles. These tephra findings demonstrate how well-resolved records can provide detailed insights into volcanic histories and ash dispersal, serving as a tool to correlate archives and assess the spatio-temporal variability of climatic transitions.

Secondly, high-resolution palynological analyses were performed in conjunction with existing proxies from the same stratigraphic sequence (e.g., diatoms, varve thickness, isotopes) to examine variations in climate and human activity. This research advances our understanding of environmental responses to two abrupt climate events: the 8.2 ka event, where the lack of vegetation change at Diss Mere contrasts with other records, raising questions about landscape resilience; and the 2.8 ka event, which is marked by a transition from the Bronze to Iron Age and a decrease in human activity, synchronised with climatic changes. The study also explores the Roman Period, during which human activity significantly overshadowed climate influences in driving landscape changes. Palynological analyses show a transition from predominantly pastoral to arable agriculture toward the end of this period, which may be related to economic shifts.
Original languageEnglish
QualificationPh.D.
Awarding Institution
  • Royal Holloway, University of London
Supervisors/Advisors
  • Blockley, Simon, Supervisor
  • Martin Puertas, Celia, Supervisor
  • Milner, Alice, Supervisor
Thesis sponsors
Publication statusUnpublished - 2024

Keywords

  • Pollen
  • Tephra
  • Varves
  • Palaeoecology

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