Developing a refined tephrostratigraphy for Scotland, and constraining abrupt climatic oscillations of the Last Glacial-Interglacial Transition (ca 16-8 ka BP) using high resolution tephrochronologies. / Timms, Rhys.

2016. 494 p.

Research output: ThesisDoctoral Thesis

Unpublished

Documents

Abstract

Understanding the abrupt climatic oscillations that characterised the Last Glacial to Interglacial Transition (LGIT, ca. 16-8 ka) requires an ability to precisely correlate the archives within which such transitions are recorded. One way in which to scrutinise the timing of abrupt events in the LGIT is tephrochronology, a technique which exploits the isochronous potential of tephra horizons derived from the geologically ‘instantaneous’ settlement of volcanic ash. In NW Europe, macro- and crypto-tephra layers of varying age and provenance have become increasing utilised as a means to correlate palaeoclimate records, and to test the spatial and temporal synchronicity of key climatic transitions.

At present, however, tephrostratigraphies in NW Europe are limited by: 1) the number of horizons that have robust chronological constraint, and 2) our abilities to trace these tephras across multiple sites. As a result, the potential of generating continental-scale tephra lattices is greatly restricted, and a spatial disparity in the number and type of tephras has emerged. It is hypothesised that part of this disparity may relate to the resolution at which sequences are studied and the inconsistent manner in which methodologies are applied. In order to test this hypothesis, five terrestrial basins from western Scotland were examined in detail for tephra content. Four of the sites were examined contiguously at high resolutions, whilst the fifth was examined using traditional ‘scan and resample’ strategies. Three new tephras for the LGIT are identified, and several existing tephras previously unknown in the British Isles were also detected. The results from this tephrostratigraphic study suggest that the series of eruptive episodes impacting Northern Britain through the LGIT is richer than appreciated hitherto. Results also indicate that tephras may have been missed in previous tephrostratigraphic investigations due to: 1) incomplete stratigraphic refinement, 2) a propensity to focus on tephras of greatest concentration, and 3) a conflation of horizons.

Using the high-resolution site-tephrostratigraphies, a composite tephrochronological age model was developed. The purpose of this exercise was to establish whether age models constructed exclusively from tephra horizons could provide a viable means to constrain abrupt climatic oscillations in sites which traditionally are difficult to date e.g. carbonate basins. The resulting age model achieves centennial-decadal scale precision through the early Holocene, and is used to accurately constrain the first record incidence of the 10.3 ka event in the British Isles. This study emphasises the importance of contiguous high resolution refinement, and demonstrates that this approach is essential if the true tephrostratigraphic complexity of NW Europe is to be fully understood, and if tephras are to be used successfully in constraining abrupt climatic events.
Original languageEnglish
QualificationPh.D.
Awarding Institution
Supervisors/Advisors
Publication statusUnpublished - 2016
This open access research output is licenced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

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