Dr Noel Worley (formerly chief geologist, British Gypsum):
The Genesis and Evolution of Sulphate Evaporites
Evaporites not only provide information about past climates, but also because they are chemically very mobile, present a record of the changes they have undergone through geological time. These changes very often hinder sedimentological interpretation but provide valuable evidence about the effects of diagenetic, metamorphic and hydrogeological processes.
Evaporites are economically important industrial minerals and are essential sources of raw materials for not only manufacturing a wide range of goods but also to sustain life. The United Kingdom is fortunate to have World Class evaporite resources the most important of which formed during the Permo- Triassic. Triassic rocks underlie most of the Midlands and contain evaporite deposits gypsum and anhydrite as well as halite. Important deposits also occur in the Permian of northern England and in the Upper Jurassic in southeast England.
It is rare to be able to see evaporites exposed at the surface and this has limited the geological study of these interesting rocks. However because of the widespread underground mining and associated activity a significant amount of geological evidence is available. A synthesis shows that the sulphate evaporites often experienced a common deposition history and were deposited as gypsum and anhydrite in a sabkha environment. They have subsequently undergone conversion to anhydrite during burial followed by reconversion to gypsum during Tertiary uplift.
Noel Worley is a geologist and has worked for British Gypsum for 35 years as Minerals & Estates Manager responsible for geological services and resources. He graduated from the University of Sheffield and was awarded a PhD from the University of Leicester. He was President of the Yorkshire Geological Society 2011-2013.