Quaternary ice margins

Investigating ancient glacial lake deposits (about 25 000 years old) within a landfill site in East Yorkshire
A BGS geologist taking a sample of glacial till

The sedimentary and structural record of ancient ice margins can provide important clues as to how an ice sheet interacted with its bed (the substrate), the processes that operated at the ice margin and the dynamics of the ice sheet itself and how these evolved temporally and spatially. The sedimentary and structural architectures of ice marginal sequences often exert a significant bearing on the material and sequence properties, influencing fluid storage and mobility (e.g. groundwater, contaminants, hydrocarbons and gas hydrates), geotechnical properties and ground conditions (e.g. landslides, foundation conditions).

Ancient glaciations can therefore provide valuable insights into the behaviour and processes associated with modern ice sheets such as those in Greenland and Antarctica, whereas understanding the character and processes by which these sequences form is extremely important for understanding groundwater resources, coastline management and civil engineering projects.

Geological evidence reveals that glaciers have been an active geomorphological agent within Britain on and off for the past 2.5 million years. At times, these glaciers have been restricted to highland, mountainous areas of Britain, but during others they have grown into larger bodies of ice called ice sheets and have extended into adjacent lowland and offshore parts of Britain. Two large scale expansions of the British – Irish ice sheet have been recognised in our Quaternary geological record and these coincide with much larger glaciations that occurred across Eurasia and North America. The largest of these British glaciations — the Anglian glaciation — occurred about 450 000 years ago when almost two thirds of our land area was covered by ice, which extended to the outskirts of what is now London. The second and smaller glaciation — the late Devensian glaciation — occurred more recently between about 35 000 and 15 000 years ago with glaciers only having been absent from Britain for the past 10 000 years.


BGS geologists studying coastal cliff sections in East Yorkshire
>Large slabs of chalk bedrock that have been ripped up from the glacier bed and pushed infront of the glacier before being dumped

Much of the form and shape of the landscape that we see today in northern, central and parts of southern Britain is a relic of the geomorphological work done by these glaciers and ice sheets. This is because glaciers act like giant pieces of geological sandpaper that abrade, erode and crush surface materials, then transport them away towards their margins where they are deposited.


Folding in sediments produced by a glacier. Skelding Hill near Sheringham, Norfolk

Spectacular products of glacial erosion include the U-shaped valleys of Snowdonia, the Lake District and the Scottish Highlands, plus the coastal lochs (fjords) of western Scotland. In more lowland parts of Britain, such as the Mersey Basin, English Midlands, East Anglia, East Yorkshire and County Durham, thick sequences of glacigenic sediment were deposited directly by the ice (till) or by meltwaters that emanated from or beneath the ice. The marginal areas of these ice sheets — representing the maximum ice extent and successive phases of ice marginal recession — exhibit a remarkable geological and geomorphological complexity reflecting the range of sedimentary and tectonic processes that operate in glacial environments. It is this geomorphological and geological complexity that we are examining within this project.

Why look at former ice marginal areas?

The highly complex sedimentary and structural architecture of ice marginal sequences often exert a significant bearing on the material and sequence properties, influencing fluid storage and mobility (e.g. groundwater, contaminants, hydrocarbons and gas hydrates), geotechnical properties and ground conditions (e.g. landslides, foundation conditions).

Understanding the character and processes by which these sequences form is therefore very important for understanding groundwater resources, coastline management and civil engineering projects.

Where are we working?

Many areas of enhanced coastal erosion in Britain such as Holderness shown in the photo possess geology dominated by soft glacial sediments

We are currently working in two classic ice marginal areas relating to the late Devensian ice limit — Holderness in East Yorkshire, and the West Midlands and Staffordshire. Our work in these areas involves the examination of available exposures, targeted geological mapping, analysis of high resolution digital surface models and the 3D modelling of sub-surface data to develop new process based geological models for each region.

Contact

Team leader: Jonathan Lee.