Overview

Project Highlights:

  • The key aim of this work is to develop a superior understanding of the stratigraphic and spatial heterogeneity of the lava group, with a view to their sustainable use for commercial extractions of aggregates, minerals and groundwater.
  • The major output will be a detailed model of the stratigraphy and emplacement of the Antrim lavas within the wider setting of the North Atlantic Igneous Province.
  • Develop a methodological framework, including chemostratigraphic, petrological and magnetic methods for correlation of lava units.
  • Contribute to volcanological understanding of effusive eruption rates and magma productivity during continental rifting, including correlation with distal volcanosedimentary units and the progression of basaltic volcanism during N. Atlantic rifting on kiloyear timescales.

Overview:

Basaltic traps and related intrusions, globally, host a variety of resources including aggregates (Mitchel, 2015), minerals (Lusty, 2017), geothermal (Campbell et al., 2016), and groundwater (Seneger et al., 2015; Babar and Muley, 2018). A detailed understanding of lava emplacement and stratigraphy can provide robust models to aid related resource management and sustainability. This project will focus on the stratigraphy and emplacement of the Antrim Lava Group, with implications and impacts that relate to the management and sustainability of related resources regionally and in similar geological settings worldwide.

During continental rifting that led to the opening of the North Atlantic ca. 56 Ma, the Antrim lavas erupted to form the basalt plateau in NE Ireland that includes the iconic Giant’s Causeway UNESCO World Heritage site. Much work to date has focused on the petrology and geochemistry of the Antrim Lavas, resulting in a sophisticated understanding of the genesis and evolution of the basalt magma (Gamble et al., 1999). However, relatively little is known about the internal stratigraphy and spatial heterogeneity of the lava sequence. This gap in knowledge inhibits exploration for potential resources such as aggregates, subsurface geothermal sources, platinum group elements, rare metals and groundwater (Robins et al., 2011). The excellent exposure of the lavas, alongside an extensive set of cores and geophysical data, provide an as yet untapped opportunity to generate a high resolution reconstruction of lava emplacement.

This project’s major work will involve analysis of 20 cores drilled across the plateau that penetrate the basalt sequence, plus 14 more logged boreholes (5 with geophysical logs), complemented by field sampling, collection and analysis of groundwater data, geological logging and mapping, augmented by a suite of laboratory analyses and subsequent modelling. In addition to stratigraphic analysis based on textural, petrological and geochemical characteristics (chemostratigraphy), the project will use magnetic analyses to aid stratigraphic interpretation (critically anisotropy of magnetic susceptibility (AMS) and palaeomagnetism). This will enable development of the most detailed model for the stratigraphy and emplacement of the Antrim lavas to date, improving our understanding of the volcanism that accompanied the rifting of the N. Atlantic, and generating 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 main objectives are:

  1. Establish basalt and interbasalt facies: Examination of core and detailed logging of texture, composition, colour, structures, sediments, zeolites, veins/joints, fractures, alteration, etc. This will be supported by magnetic analyses to establish magnetostratigraphy
  2. Correlation of facies between cores: quantitative analysis of basalt texture and composition. This can be supported by fieldwork and by logging sections in quarries and coastal cliffs, utilising modern remote sensing and drone technology where applicable.
  3. Generation of stratigraphic model: facies correlations will be used to establish a sequence and develop a 3D framework using MoveTM modelling software.
Figure 1: Lower basalt (tabular compound flows) overlying Ulster White limestone (chalk lower left at water level) and overlain by interbasalt laterite (red). Interbasalt is in turn overlain by upper basalt (columnar jointed). N. Antrim coast near Giant’s Causeway (paulbraterman.files.wordpress.com)

Methodology

  • Stratigraphic analysis of cores including establishing correlations between basalt facies, weathering, zeolite distribution, fracture/joint style and fill, magnetostratography, palaeomagnetic and petrological analyses.
  • Texture and fabrics from AMS measurements of split cores and oriented outcrop samples.
  • Use of available groundwater data and mapping of surface features to determine distribution of groundwater bodies and fluid pathways within the Antrim Lava Group.
  • 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

Project-specific training will include volcanic stratigraphy, facies analysis for identification and interpretation of the different types of lava flow and volcanic deposits. Rock magnetic analyses will contribute to facies analyses using magnetisation, magnetic polarisation, susceptibility and fabrics. The student will attend a rock magnetism course, a DTP training course, and carry out AMS analyses in the host lab in Birmingham. In addition to this, the project will involve field sampling of oriented samples using block sampling.

The principal supervisor will be Dr Carl Stevenson who is a specialist in rock magnetic analysis and the emplacement and structure of igneous rocks. Dr Sebastian Watt will co-supervise the project providing the necessary volcanological expertise.

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
  • Professional placement 1

Year 2:

  • Substantive rock magnetic analyses
  • Petrological and geochemical analyses
  • Second field season
  • Production of first manuscript
  • Professional placement 2

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
  • Professional placement 3

 

Partners and collaboration (including CASE)

Dr Rob Raine, GSNI, provides access to core material at the GSNI Core Store in Belfast, 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. MoveTM software is provided by Midland Valley Exploration, part of the Edinburgh-based consultancy Petex that develops modelling software in structural geology for the mineral and hydrocarbon exploration industries.

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