Natural Environment Research Council INSTITUTE OF GEOLOGICAL SCIENCES Geological Survey of England and Wales Geological notes and local details for 1:lOOOO sheets NZl5NW, NE, SW and S-E Chopwell, Rowlands Gill, Consett and Stanley Part of 1:50000 Sheet 20 (Newcastle upon Tyne) D. A. C. Mills Bibliographic reftrence Mills, D. A. C. 1982.Geological notes and local details for 1: 10 000 sheets NZ15NW, NE, SW and SE (Chopwell, Rowlands Gill, Consett and Stanley) (Keyworth: Institute of Geological Sciences.) Author D. A. C. Mills, BSc, MIGeol Institute of Geologicd Sciences Windsor Court, Windsor Terrace, Newcastle upon TyneNE2 4HE Production of this report was supported by the Department of the Environment The views expressed in this reportare not necessarib those of the Department of the Environment @ NERC copynght 1982 KEYWORTHINSTITUTE OF GEOLOGICALSCIENCES 1982 PREFACE .. This account describes the geology of 1:25 000 Sheet NZ 15.The area falls within 1:50 000 Sheet 20 (Newcastle uponTyne); it was firstsurveyed by H.H. Howell, the maps being published onthe old Countymeridian six-inch scale between 1868and 1871. The area was resurveyed between1923 and 1948 by A. Fowler and W. Anderson, on the new County meridian, some of the maps being published in 1954. The present maps are based on a full scale revision begun in 1976 by D.A.C. Mills, with J .G.O. Smart and Denys B. Smith as District Geologists. G. M. Brown Direct or Institute of Geological Sciences Exhibition Road March 1982 London SW7 2DE .. 11 CONTENTS Page .. PREFACE 11 FIGURES iv SCOPE AND AIM OF REPORT V INTRODUCTION 1 GEOGRAPHY, LAND USE AND POPULATION 2 GENERAL GEOLOGY 2 (a) Exposure of solid rocks and drift deposits 3 (b) Classification and geological sequence 3 (c) Nomenclature 4 SOLID ROCKS 4 (a) General 4 (b) Details 5 (i) Viscan, Namurian and Westphalian A strata (lower part) 5 (ii) Westphalian A strata(upper part) 5 (iii) Westphalian B strata 7 (c) Structure 8 (d) Economic Geology 9 DRIFT DEPOSITS 10 (a) The rock surface and distribution of drift 10 (b) Details 11 (i) Boulder Clay 11 (ii)Sand and Gravel 11 (iii)Other drift deposits 11 (iv) Made Ground 12 (c) Economic Geology 12 GEOLOGY: RELATED CONSTRAINTS ON PLANNING AND ENGINEERING 12 (i) Subsidence 12 (ii)Settlement of madeground 13 (iii) Landslips 13 REFERENCES 13 ... 111 FIGURES Figure 1 Outline map of the area showing county boundaries and the main locations referred to in the text. Figure 2 Sketch map of the solid geology of the area showing the outcrop of a selection of coals and of the Harvey Marine Band. Figure 3 Generalized vertical section of strata in the area as proved by the West Stanley Shaft and the Chopwell Borehole. Figure 4 Sketch map showing structure contours on the Brockwell Seam. Figure 5 Generalized longitudinal sections illustrating the broad structureof the area. Figure 6 Distribution of drift-free ground, areas of thin drift, sand and gravel, and made ground. iv SCOPE AND AIM OF REPORT This report is a summary of the geology of 1: 25 000 Sheet NZ 15. Its aim in conjunction with the accompanying 1:lO 000 and 1:lO 560 maps, is to provide a framework and guide to the main aspects of the geology as theyaffect the long term planning and development of the area.The more fundamental . scientific aspects of the geology will be included in a study of a wider area. The information and details on which this study is based may be obtained initially by reference to files and documents held at the North of England Office of the Institute of Geological Sciences, Windsor Court, Windsor Terrace, Newcastle uponTyne NE2 4HE. Anyenquiries should be directed to the District Geologist at theabove address. V INTRODUCTION This account outlines the geology of 1:lO 000 Sheet NZ 15 NW and 1:lO 560 Sheets NZ 15 NE, NZ 15 SW and NZ 15 SE which are available as uncoloured dyeline maps. Details shown on the maps are supple- mented by notes on the margins which include information on the more important surface, borehole and shaft sections. The area (Fig. 1) forms part of Geological Survey of Great Britain (England & Wales) 1:50 000 Sheet 20 (Newcastle upon Tyne) which is currently under survey and approaching completion. It was first geologi- cally surveyed on the six-inch scale by H.H. Howell, the maps being printed between 1868 and 1871 as Six- InchNorthumberland County ‘Old Meridian’ andDurham County sheets. Subsequently, the area was resurveyed at various times between 1923 and 1948 by A. Fowler and Wlr W. Anderson. Some of these maps were published in 1954 as Six-Inch Durham County Quarter sheets, the remainder being issued as manuscript maps for consultation purposes. A partial revision of the area on Six-Inch National Grid sheets was undertaken in the late sixties by Messrs. P.M. Allen, D.W. Holliday, A. Reedrnan andG. Richardson and although these maps were not published they provided a valuable temporary coverage. The present Six-Inch and 1:10 000 maps are based on a full scale revision begun in 1976 by D.A.C. Mills. The generalized data will be included in 1:50 000 Geological Sheet 20 (Newcastle upon Tyne). Despite the mineral wealth that has been derived from the area largely over the last one and a half centuries no comprehensive account of the geology has ever been published. Only indirect reference has been made to the subject, and much of theinformation is available onlyin unpublished maps, plans, borehole records and internal reports, most of the latter relating to the coal mining industry and to a lesser extent to the steel industry. bhch of this information will remain unpublished although access to it will generally be available through the Institute of Geological Sciences (Newcastle Office). Overlays, isolating various aspects of the geology, can be produced if required but they would do little to augment i-he data already presented on the maps. 1 GEOGRAPHY, LAND USE AND POPULATION The area forms part of south-west Tyne & Wear and north-west Co. Durham; two small parts in the north- west notably HedIey Fell, andbetween the Milkwell Burn andthe River Derwent(Fig. 1) are in Northumberland. The main centres of population are Stanley, Consett, Annfield Plain, Chopwell, High Spen,Rowlands Gill andBurnopfield. Most of theground is of moderate rolling relief whose overall altitude falls from about 260 m A.O.D. in the west to c. 150 m A.O.D. in the east. The highest points are a at Pontop Pike (over 3 12 m A.O.D.), north of Chopwell and also in the north-west corner of the area near ... Hedley Fell. The steep-sided valley of the River Derwent forms a pronounced feature crossing the north- western part fromEbchester to belowRowlands Gill; the valley bottom ranges between 21 and 63 m A.O.D. and forms the lowest tract of ground in the area. Most of the drainage is into the Derwent system, the main exceptions being that in the Stanley and Annfield Plain vicinity where water drains into the Causey Burn (and thence into the River Team), and south of Leadgate where drainage is into the Iveston Burn (and thence the River Browney). Despite the extensive mining that has taken place most of the area retains a largely rural aspect; much of the ground is given over to mixed agriculture although pasture and livestock rearing predominates. A substantial area is woodland, more particularly along the Derwent Valley;Chopwell Wood east of Chopwell is by far the largest. The settlements and smaller townships that grew up largely owe their existance to the sites of former collieries and these include Chopwell, High Spen, Burnopfield, Dipton and Tantobie. The town of Stanley (together with Annfield Plain) chiefly owes its size to what was one of the largest collieries in the district. Consett falls into a slightly different category; its growth largely sprang from the develop- ment of the Iron Works sadly closed in 1979. With the run down of the coal industry over the last twenty years and more recently with the closure of BSC Consett the area has been dealt a crippling economic blow only partly cushioned by the incomingof less labour-intensive light industry. Despite the heavy industry that has played such an important role in its development the bulk of the area is rural; landscaping has removed almost all traces of the former coal mining industry. Much of the -. wooded Derwent valley here is regarded as a highly desirable residential area and there are many local . _. ._.. beauty spots. GENERAL GEOLOGY The area is composed of mainly gently dipping Carboniferous Westphalian (Cod Measures) rocks near the western margin of the Northumberland and Durham Coalfield; these are widely overlain by a mantle of drift deposits. A sketch map of the solid geology of the area and the outcrop of a selection of the coal seams is shown in Fig. 2. 2 Details of the distribution, nature, conditions of deposition and sedimentology of Carboniferous strata in north-east England are outlined invarious I.G.S. publications e.g. Taylor et al. 1971, while detailed consi- deration is given to Westphalian rocks in memoirs covering the Tynemouth District (Land, 1974) and the Durham and West Hartlepool District (Smith and Francis,1967). (a) Exposure of solid rocks and drift deposits Surface exposure of bedrock is largely confined to man-made excavations such as quarries and cuttings; scattered natural exposures may be seen on some steep hillsides and also in parts of some burns such as Pontop Burn near Hamsterley Hall, Causey Burn below Tanfield, and locally in the Derwentvalley.