Download reconstructing sedimentary processes in the Irish Sea Basin after

NERC quota PhD studentships 2012-2013
Title: From glacial deposits to giant sediment waves: reconstructing sedimentary
processes in the Irish Sea Basin after the retreat of the last British-Irish Ice
Sheet.
Supervisors: Dr Katrien Van Landeghem, Dr. Richard Chiverrell and Professor
James Scourse
Collaboration/case partners:
Background/Context of Project:
The Irish Sea was occupied by ice during the Last Glacial Maximum (LGM, 24 ka BP), leaving
behind glacial sediments that have since been reworked by currents in the marine
environment. The resulting complexity of the seabed is well preserved, with glacially carved
trenches, ice-moulded drumlin fields, sand banks and unusually large sediment waves
(reaching world-record-breaking heights of 36 m).
These immense sediment waves are a key to understanding the evolution of the shelf sea.
Given their extraordinary size and coarse nature, it is likely that the initiation of these
bedforms is linked with the environmental setting of the Irish Sea immediately following ice
sheet decay, and subject to the distribution of sediments and bedforms left on the seafloor
during the last deglaciation. The Natural Environment Research Council (NERC) has funded
a consortium of scientists via the project BRITICE-CHRONO to reconstruct the timing, rate
and pattern of the demise of the former British-Irish Ice Sheet (BIIS). Van Landeghem,
Scourse and Chiverrell, all members of this Consortium, share expertise and datasets in
order to focus on the reconstruction of BIIS retreat from the Irish Sea.
Many of the same controls that influence fast moving ice streams to the margins (e.g. tides,
relative sea-level changes, slope of the seabed) will continue to influence the volume,
character and geomorphological evolution of glacial deposits on the newly exposed shelf
sea.
This project, linked with various BRITICE-CHRONO work packages, provides a unique
opportunity for a PhD candidate to study the legacy of glacial events on subsequent postglacial hydrodynamic and sedimentological processes and patterns, and the resulting
seafloor geology that influences our offshore environment today. This will additionally help
us understand the nature of the sub-seabed (with potential natural resources) and the
dynamics of present-day seabed morphology (crucial for a whole variety of engineering
projects).
Aims and Objectives:
The overall aim is to reconstruct the morphological and sedimentological history of the Irish
Sea. The Irish Sea’s glacial legacy has various sedimentological and hydrodynamical
components, and the aim is to understand the role of these various components in the
subsequent evolution of the post-glacial seafloor. A holistic approach to marine geological
research is applied, with several specific objectives:
1) to map subsurface and surface structures in the Irish Sea to identify glacial erosive and
depositional processes. This inventory will be presented as a map and Geographic
Information System (GIS) data that will complement the existing inventory onshore.
2) to map the surface sediments and the bedforms that developed on them. There will be a
focus on giant sediment waves, including the development of a. conceptual model of
their geomorphological evolution.
3) to compare granulometric and geochemical variations between preserved glacial
sediments and surficial mobile sediments
4) to measure the granulometric variations of post-glacial sediments in deeper cores in the
southern Irish Sea and compare the inferred variation in hydrodynamics with existing
palaeotidal model simulations.
5) to integrate these elements together in a model of the Irish Sea's post-glacial evolution.
Materials / Methods / Training element:
The PhD candidate will integrate marine geophysical (seismics and multibeam echosounder)
and sediment granulometry with palaeo-hydrodynamic model outputs (generated by
external third parties). The PhD candidate will join at least one of the high-profile BRITICECHRONO offshore sampling campaigns, during which marine cores will be collected from key
localities targeted by geophysical data surveying. PI Van Landeghem already has collated a
large amount of geophysical and geological data from various sites in the Irish Sea. The
AmSedIS project, funded by the European Committee, resulted in granulometric data of the
extremely large sediment waves collected in April 2012. SP Transmission, who are
developing the high voltage direct current link (i.e. seafloor cable), have granted access to
their geophysical data and their 245 vibrocorer samples from the proposed route in the
northern Irish Sea, and these are stored at the University of Liverpool. The project's
momentum will thus not depend on BRITICE-CHRONO's planned survey timing (likely 2013
and 2014) and survey outcomes. The PhD candidate will acquire multiple marine geological
skills and the outcomes of the data analyses will feed into various other projects allowing for
extensive networking across the wider scientific community of marine geological,
sedimentological and Quaternary sciences.
Costs:
The offshore sampling campaign would normally constitute the highest costs in a project like
this but these costs are covered by BRITICE-CHRONO. BRITICE-CHRONO in turn benefits
from having an extra PhD candidate working on the substantial dataset that will be collected
as a result of the project.
The cost of using the non-invasive elemental GeoTek core scanner system in the University
of Liverpool is estimated at £75 per 1.5m.
The costs for all other analyses (geophysical and sedimentological) are small, as Bangor
University has the appropriate software licenses and laboratory equipment in place.