The full programme book (PDF) - Royal Geographical Society

T5
Geophysical prospecting for BRITICE-CHRONO geochronological targets
M.J. Burke* 1 , R.C. Chiverrell 1 and the BRITICE-CHRONO consortium
1 School of Environmental Sciences, University of Liverpool, Liverpool, L69 7ZT
The terrestrial sampling campaign of the NERC-funded BRITICE-CHRONO consortium is
now well underway (see associated posters). During this first phase of fieldwork, sampling
has been focussed on ice-scoured and meltwater eroded bedrock (TCN dating), as well as
quarries/sediment exposures within glaciofluvial and glaciolacustrine deposits (OSL
dating). However, some transects lack sufficient sediment and/or bedrock exposure, and
existing sites are not evenly distributed through transects or always aligned in the direction
of ice retreat. The second phase of the terrestrial campaign aims to fill gaps within ice
retreat zones by dating material from boreholes. The consortium includes funding for a 35
day borehole campaign using a Dando Terrier Rig, which has the ability to collect dark
cores (using opaque PVC tubes) from which OSL samples will be collected. Given the
relatively short amount of time allocated to this sampling programme (35 days at a drilling
rate of ≤15 m per day) and the need to cover a large area, it is most cost-effective to run
the drilling as a single campaign across all sites. To facilitate an efficient drilling
programme a list of target sites will be compiled prior to the second phase of sampling.
Broad target areas will be identified using the geomorphology and existing borehole data
(BGS), but specific drill locations will be directed from Ground-penetrating radar (GPR)
data. GPR is a non-invasive technique that detects changes in the electrical properties of
the shallow subsurface by propagating electromagnetic energy into the ground and
detecting energy reflected from subsurface features. Correctly processed GPR data can
be used to reconstruct past depositional environments because reflections usually
correspond to primary depositional structure. Where the resolution of a survey allows
(depending upon the antenna frequency) the radar facies (lithofacies) most suited to OSL
sampling will be targeted (e.g., delta topsets, sheet-stratified or planar cross-set sand).
Because GPR performs best in dry sand and gravel and worst in wet clay-rich materials, a
number of considerations need to be made during the site selection process. This poster,
using examples from transect 3 (Irish Sea Ice Stream East), presents a framework for site
selection and details the methodology for GPR data collection, processing and
interpretation using test data collected at Four Ashes SSSI, a type site for the late
Devensian. The GPR campaign will take place in early 2014 to allow sufficient time for
data processing and analysis prior to the drilling campaign in the summer.
Keywords: BRITICE-CHRONO; TCN dating; OSL dating; ground-penetrating radar.