Leeds – Humber catchment project: rock properties of the Sherwood Sandstone Group

Leeds Geological Association fieldtrip at Brimham Rocks run by BGS. Discussion on the generation of deformed crossbedding sets detailing the migration of in-channel bedforms.

Highly fossiliferous sandy limestone; note shelly debris highlights gently inclined surfaces.

Small cliff of undifferentiated Sherwood Sandstone Group. Note lower part of cliff is dominated by pebbly crossbeds and the upper by regular horizontal laminations.

Complex crossbeds representing the in-channel filling of an ancient river. Park Tunnel, Nottingham.

Vertically stacked crossbed sets that detail the migration of numerous sub-aqueous dunes.

The diverse geology of the Humber river catchment helps us to characterise structural frameworks and facies across the east Midlands shelf. Our research focuses on the stratigraphy and sedimentology of the Permo-Triassic Sherwood Sandstone Group and how this may affect the sandstone's ability to yield water or provide adequate foundation conditions for buildings. We are also investigating how historic human exploitation of the Pennine coalfield in Leeds is impacting on people in the 21st Century.

The geology of the Humber river catchment includes several Upper Carboniferous coalfields, economically valuable Permian evaporite (salt) deposits, major Triassic sandstone aquifers, and a variable but sometimes thick succession of comparatively young Quaternary sediments laid down by glaciers, rivers and wind.

The Leeds – Humber catchment project is primarily interested in the study of the Sherwood Sandstone Group, which is a 300 – 400 m thick succession of sand and in lesser amounts gravel, silt and clay. The Sherwood Sandstone Group is a sedimentary succession that was originally deposited in the Triassic (approx. 250 million years ago) in a dry and hot climate. The sediment that formed the Sherwood Sandstone Group was deposited by huge, wind blown sand dunes and by a series of ephemeral rivers that flowed and migrated over much of England's ancient landscape. This compacted sediment is responsible for some well known features like the brilliantly exposed cliff at Nottingham Castle.

As part of the Leeds – Humber project we are interested in the rock properties of the Sherwood Sandstone Group and how they vary within the succession. Central to the research aim of the project is to better understand the stratigraphical relationship of the formations that comprise the Sherwood Sandstone Group and also to better define and understand the sedimentology of the entire group.

This research will produce work that will help characterise the internal variation in rock type and properties within the Sherwood Sandstone Group, which has huge implications to numerous areas such as:

Water extraction: the Sherwood Sandstone Group is a huge and important source of water for the Leeds-Humber region. This research will help identify how the heterogeneity (differences) within the Sherwood Sandstone Group might affect the flow, extraction and recharge of the aquifer.
Hydrocarbon industries: the equivalent formations of the Sherwood Sandstone Group under the North Sea are oil and gas producing. As these oil and gas producing rocks are hard to observe, understanding the Sherwood Sandstone Group onshore can help provide useful information to the economically important equivalent successions offshore. Indeed, numerous producing reservoirs around the world share similarities to the Sherwood Sandstone Group.
Engineering and building: the arrangement, properties and relationships of the rocks that make up the Sherwood Sandstone Group vary throughout the succession and potentially provide some challenges to building and engineering projects undertaken where the Sherwood Sandstone Group is present.
Sand and gravel extraction: the Sherwood Sandstone Group throughout the Leeds – Humber region is extensively mined at the surface for the sand and gravel reserves it contains. Research within this project will better determine the presence and type of such reserves.

As well as the applied aspects of this research, the ability to study the ancient environments that deposited the Sherwood Sandstone Group and how they changed through time allows us an important insight into how the landscape we see today was influenced by past events and environments.