BGS karst report series: J2. Karst in the Jurassic limestones of Central England

Mathewson, E.; Maurice, L.; Farrant, A.R.; Atkinson, T.C.. 2022 BGS karst report series: J2. Karst in the Jurassic limestones of Central England. Nottingham, UK, British Geological Survey, 52pp. (OR/21/060) (Unpublished)

Before downloading, please read NORA policies.

Preview

Text OR21060.pdf Download (12MB) | Preview

Abstract/Summary

This report documents the evidence for karst and rapid groundwater flow in the Jurassic limestones of central England. It is part of the BGS karst report series on karst aquifers in England in which cave development is limited – the Chalk and the Jurassic and Permian limestones. The series is the main output of the NERC funded Knowledge Exchange fellowship “Karst knowledge exchange to improve protection of groundwater resources”. The term “karst” applies to rocks that are soluble. In classic karst there are extensive caves and large scale surface karst landforms such as dolines, shafts, river sinks, and springs. In the past the Chalk and the Jurassic and Permian limestones of England were not considered karstic because they have limited cave development, and because karst features are usually small and have not been well documented. However, permeability in these aquifers is determined by their soluble nature and groundwater flow is predominantly through small-scale karstic solutional features. These reports provide data and information on karst in each area. Karst data are compiled from the British Geological Survey databases on karst, springs, and transmissivity; reports and peer reviewed papers; from geological mapping; and through knowledge exchange with the Environment Agency, universities, water companies and consultants. This report shows that in the Jurassic limestones of central England there is extensive evidence for karst, with surface geomorphology, tracer tests and hydrogeological studies all highlighting the role of karstic solutional development in the aquifers. Karst is best documented in the Grantham to Stamford area, associated with the East Glen, West Glen and Witham rivers; but there is evidence for karst throughout the area. Karst is particularly developed in the Lincolnshire Limestone Formation, but there is also evidence of karst in the limestones of the Great Oolite Group. Stream sinks, dolines, dissolution pipes, and springs are all present. There are many stream sinks, and several major rivers in the area have large losses to the aquifer as they cross the limestone. Some stream sinks are very substantial with inflows of 200-300 l/s. There are also many springs, and some have large reported discharges of up to 355 l/s. Several tracer tests indicate rapid groundwater flow velocities ranging from 21 to 10000 m/day over distances of up to 11.9 km. Tracer tests demonstrate connections to multiple outlets over a wide area, suggesting that the karst comprises complex networks with divergent and convergent flow. Some tracer breakthrough curves had very long tails, with tracer discharged for more than 100 days following injection indicating high attenuation via dispersion and/or diffusion. Hydrogeological studies in the area also indicate the importance of karstic solutional development including evidence from rapid water level responses in monitoring boreholes, and powerful artesian boreholes with large discharges. Further work is needed in the area to improve understanding of karst: Data on spring discharges are very sparse, and for most springs there discharge is unknown. There is almost no information on long term variations in spring discharges or how they respond to rainfall. Further studies of dolines and stream sinks, and further tracer testing would also be useful. Indicators of karst at abstraction boreholes (e.g. conduits observed in borehole images; water quality indicators of rapid groundwater flow) have not been considered for this report, and would enable understanding of the impacts of karst on groundwater abstractions. Although karstic caves have not been identified in this area, conduits are observed in quarries and unexplored small karstic caves may be present. The Jurassic limestones of central England are karstic in nature with extensive solutional networks of conduits and fissures. Karst is an important factor that should be considered in hydrogeological studies, and which affects groundwater protection and management in this area.

Item Type:	Publication - Report
Funders/Sponsors:	British Geological Survey
Additional Information. Not used in RCUK Gateway to Research.:	This item has been internally reviewed, but not externally peer-reviewed.
Additional Keywords:	GroundwaterBGS, Groundwater
Date made live:	24 May 2022 10:58 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/532661

Actions (login required)

View Item

Document Downloads

More statistics for this item...