Overview

Project Highlights:

  • Key aim: Resolving the detailed progression of basaltic volcanism in the Antrim plateau
  • Developing a methodological framework, including petrological and magnetic method for lava unit correlation
  • Exploring magma productivity during N. Atlantic rifting

The Antrim lavas were erupted during continental rifting that led to the opening of the North Atlantic ca. 56 Ma and now form a basalt plateau in NE Ireland including the iconic UNESCO World Heritage site the Giant’s Causeway. Much work to date has focused on the petrology and geochemistry of the basalt, resulting in a sophisticated understanding of the genesis and evolution of the basalt magma. However, relatively little is known about the internal stratigraphy of the lava sequence. This project aims to determine the stratigraphy of the Antrim Lavas from 20 cores drilled across the plateau that penetrate the basalt sequence, plus 14 more logged boreholes (5 with geophysical logs), complemented by field sampling, logging, mapping and a suite of laboratory analyses and modelling. In addition to stratigraphic analysis based on textural, petrological and geochemical characteristics, the project will use magnetic analyses to aid stratigraphic interpretation, including anisotropy of magnetic susceptibility (AMS) and palaeomagnetism. This will enable us to develop the most detailed model for the stratigraphy and emplacement of the Antrim lavas to date, developing our understanding of the volcanism that accompanied the rifting of the N. Atlantic, and one of the most detailed datasets worldwide that can be used to explore how magma productivity and effusive eruption frequency vary during rifting on kiloyear timescales. 

 

The principal aim of the project is to develop a detailed stratigraphic model for the Antrim Lava sucession. The project objectives involve a combination of field work, core logging and laboratory analyses (including petrology, geochemistry and rock magnetism). The main objectives are therefore:

  1. Establish basalt and interbasalt facies: Examination of core and detaled logging of texture, composition, colour, structures, sediments, zeolites, veins, etc. This will be supported by magnetic analyses (establish magnetostratigraphy using magnetic properties)
  2. Correlation of facies between cores: quantitative analysis of basalt texture and composition. This can be supported by field work and logging sections in quarries and coastal cliffs.
  3. Generation of stratigraphc model: facies correlations used to establish a sequence and develop 3D framework using Move modelling software.
  4. Eruption sequence for Antrim lavas: this will include the newely established stratigraphic framework and examination of eruption vents and lava emplacemnt directions. Emplacement directions will use facies and stratigraphy as well as textures that record lava flow (vesicles, AMS fabrics).

Methodology

  • Stratigraphic analysis of cores including establishing correlations between basalt facies, magnetostratography and petrological analyses.
  • Texture and fabric analyses achieved through AMS measurements of split cores and oriented outcrop samples.
  • Petrological analyses using quantitative petrological techniques and scanning electron microscopy.
  • 3D modelling of the internal stratigraphy using correlated facies to establish facies architecture and structure using geological modelling software MoveTM

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes.

Project specific training will include volcanic stratigraphy and facies analysis involves identifying and interpreting different types of lava flow and volcanic deposit. From cores this will be done through detailed description of the texture and petrology. Additional data may be collected from outcrop. Rock magnetic analyses can contribute to facies analyses through varying magnetic parameters such as magnetisation, polarisation, susceptibility and fabrics. Student will attend rock magnetism course DTP training course and carryout AMS analyses host lab in Birmingham. Key rock magnetic analysis will be susceptibility and AMS used for fabric analysis. As well as laboratory rock magnetic analysis, the project will involve field sampling of oriented samples using block sampling and field drilling

The principal supervisor will be Dr Carl Stevenson who is a specialist in rock magnetic analysis. Dr Sebastian Watt will co-supervise the project providing expertise from a volcanological perspective.

Timeline

Year 1:

  • Literature review and compilation of published data
  • Planning and development of field programme
  • Comprehensive logging of cores
  • Fieldwork on lava sequence exposures
  • Development of correlation for core and field samples

Year 2:

  • Substantive rock magnetic analyses
  • Petrological and geochemical analyses
  • Second field season
  • Production of first manuscript

Year 3:

  • Completion of all major analyses
  • Integration of dataset
  • Analysis of event frequency, rates of magmatism and relationship to rifting processes.
  • Writing up main outputs and thesis
  • Presentation of major findings at international conference

Partners and collaboration (including CASE)

Dr Rob Raine, based in Belfast, is the external supervisor providing a link with the BGS and access to core material at the BGS core store at Keyworth, Nottingham, and contributes stratigraphic analyses expertise. Professor Dougal Jerram specialises in volcanic stratigraphy and is a member of the Centre for Earth Evolution and Dynamics at the University of Oslo. Move software is provided by Midland Valley Exploratin Ltd, a Glasgow based SME that provides consultancy and develops modelling software in structural geology for the mineral and hydrocarbon exploration industry.

Further Details

Please contact the project supervisors for further details.

Carl Stevenson: c.t.stevenson@bham.ac.uk

Sebastian Watt: s.watt@bham.ac.uk