BGS karst report series : C9. Karst in the Chalk of the Isle of Wight

Maurice, L.; Mathewson, E.; Farrant, A.R.. 2022 BGS karst report series : C9. Karst in the Chalk of the Isle of Wight. Nottingham, UK, British Geological Survey, 44pp. (OR/21/073) (Unpublished)

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Abstract/Summary

This report documents the evidence for karst and rapid groundwater flow in the Chalk of the Isle of Wight in Southern England. It is part of the BGS karst report series on those karst aquifers in England in which cave development is limited – principally the Upper Cretaceous 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, stream/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 generally 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 there is some evidence for karst in the Chalk of the Isle of Wight, but that karst may be less well developed than in some areas of the mainland. Overall there is more evidence for karst in the Central Chalk Downs than in the Southern Downs. Dolines and dissolution pipes appear to be less common on the Isle of Wight than in some other areas of the Chalk, but dissolution pipes can be observed in Chalk coastal cliffs, and in excavated pits inland. Two stream sinks are recorded on the Isle of Wight. Springs occur in the Chalk at the boundaries with the overlying Palaeogene deposits, and underlying Upper Greensand Formation; and springs in the Upper Greensand Formation also discharge water from the Chalk where there is connectivity between the two aquifers. There are little data on spring discharge, and discharges are likely to have been substantially reduced by groundwater abstraction, but large springs appear to be rare. Caves are exposed in the Chalk coastal cliffs, and appear to have a predominantly marine origin, but there is evidence of some karstic development in some of these caves. Smaller conduits have been observed in inland quarries. Transmissivity data for the Chalk of the Isle of Wight are limited, with two sites where higher transmissivity indicates well connected solutional networks, but other sites indicating lower transmissivity than on the mainland. Coliforms have been occasionally detected in groundwater suggesting a rapid flow component. Further work is needed to assess the extent of karstic conduit development in the Chalk of the Isle of Wight, which could include coastal surveys of conduits, consideration of karstic indicators at abstraction boreholes, investigations of spring discharges, and tracer tests.

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:	25 Mar 2022 16:09 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/532325

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