Denys Smith Memorial Trip: The Geology of Knaresborough Gorge - YGS 1st June 2008 Geology Programme Open Report OR/08/044 BRITISH GEOLOGICAL SURVEY GEOLOGY PROGRAMME OPEN REPORT OR/08/044 The National Grid and other Denys Smith Memorial Trip: The Ordnance Survey data are used with the permission of the Controller of Her Majesty’s Geology of Knaresborough Gorge Stationery Office. Licence No: 100017897/ 2008. - YGS 1st June 2008 Keywords Knaresborough, Permian, Cadeby Formation, dolomite, Carboniferous, unconformity. A H Cooper National Grid Reference SW corner 434313,455375 NE corner 436412,457629 Map Sheet 62, 1:50 000 scale, Harrogate Front cover Knaresborough. (SE 351 564) Chapel of Our Lady of the Crag hewn from the Cadeby Formation, Sprotbrough Member dolomite of large-scale (5-18 m. sets) of cross-bedded oolite. Bibliographical reference COOPER, A.H.. 2008. Denys Smith Memorial Trip: The Geology of Knaresborough Gorge – YGS 1st June 2008. 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It is based on the Yorkshire Geological Society field guide by Cooper (1994 & 2006) with additions from the Harrogate Memoir (Cooper & Burgess, 1993). Contents Foreword.............................................................................................. i Contents................................................................................................ i Summary............................................................................................ iii 1 Denys B. Smith, 1929-2007– Permian Geologist .......................1 2 Geological Setting.........................................................................2 2.1 Topography and glacial morphology....................................2 2.2 Bedrock Geology of the Knaresborough area ......................4 3 Excursion Details..........................................................................5 References ..........................................................................................11 i OR/08/044; Version 1 Last modified: 2008/05/30 10:56 FIGURES Figure 1 Denys Smith leading a field trip and demonstrating collapse breccia formation due to evaporite dissolution at Marsden Bay, Co Durham in 1984 to mark his retirement from the British Geological Survey. .................................................................................................... 1 Figure 2. Digital terrain model of the Vale of York (Ordnance Survey and CEH DTM) with the inferred position of the ice at the Devensian maximum. Knaresborough Gorge at the side of the ice–sheet is arrowed. Escrick Moraine in black, eskers in red, glacial diversions in dark blue, ice in pale blue.............................................................................................................. 2 Figure 3. The glacial geology of Knaresborough Gorge at the Devensian glacial maximum, from Cooper and Burgess 1993, Figure 26. ................................................................................... 3 Figure 4. Extract from British Geological Survey 1:50,000 scale geological map 62 (Harrogate – Solid & Drift) showing the geology of the Knaresborough Gorge area................................ 5 Figure 5. Geological map of Knaresborough Gorge and cross-section through the Carboniferous and Permian sequence. Showing the Cadeby Formation oolite bank thinning to the west (it also thins to the north and south). The Cadeby Formation is overlapped by the Edlington Formation and the Brotherton Formation which rest unconformably on the upstanding Carboniferous strata of the Harrogate Anticline. The localities visited are numbered; those numbered 14, 15 and 16 will only be visited if there is time. ............................................... 6 Figure 6. Abbey Crags, Knaresborough. The Carboniferous Permian unconformity at Abbey Crags, Knaresborough. Large-scale cross-bedded oolitic limestones of the Cadeby Formation – Sprotbrough Member (Lower Magnesian Limestone - Upper Subdivision) rest unconformably upon a buried hill of slightly reddened Upper Plompton Grit (Namurian).. 8 Figure 7. SW of Grimbald Bridge, Knaresborough. Saint Robert's Cave, Knaresborough. The cave believed to be the ancient dwelling place of St. Robert has been cut into the cross- bedded and shelly, oolitic dolomites of the Cadeby Formation. The steps and foundations belong to another dwelling built in front of the cave. ........................................................... 9 Figure 8. Generalised isopachyte map for the Cadeby Formation in the Harrogate district (Figure 13 from Cooper and Burgess, 1993)...................................................................................... 10 TABLES Table 1. The Permian sequence in the Knaresborough area ........................................................ 4 Table 2. Chemistry of mineral water from the Dropping Well, Knaresborough; composition in mg/l. Date 1896 (recalculated from Fox-Strangways, 1908; partly after Edmunds et al., 1969)...................................................................................................................................... 7 ii OR/08/044; Version 1 Last modified: 2008/05/30 10:56 Summary This guide is dedicated to Dr Denys Smith, expert on the Permian rocks of Britain and Europe. The field excursion illustrates the Permian and Quaternary geology of Knaresborough Gorge. The Gorge is a marginal glacial feature cut at the edge of the Devensian Ice sheet during the last Ice-Age. The River Nidd has cut down through the Permian and Carboniferous sequence. The Permo-Carboniferous unconformity is exposed revealing a buried relief of low hills. The Permian Cadeby Formation dolomites above the unconformity show massive subaqueous dune bedding and traces of ooids indicative of formation in a Bahamas Banks environment. Tufa-rich spring activity on the west side of the gorge has resulted in the formation of a large tufa screen with a small cave behind where it has partly collapsed; this is Mother Shipton’s Cave. iii OR/08/044; Version 1 Last modified: 2008/05/30 10:56 1 Denys B. Smith, 1929-2007– Permian Geologist For more than four decades Dr Denys Smith and Permian geology were synonymous. His name graces more than 60 eminent publications about Permian geology and he chaired important working groups on the Permian rocks. His enthusiasm for geology and the Permian in particular were illustrated by his roles as both president of the Leeds Geological Association and later as president of the Yorkshire Geological Society. His presidency of the YGS culminated with his presidential address on “The Late Permian