BOUGHT WITH THE INCOME FROM THE SAGE ENDOWMENT FUND THE GIFT OF iletirs W, Sage 1S91 A3.mm 9mik 3777 Cornell University Library QE 262.L49F79 1903 The geology of the country near Leiceste 3 1924 004 550 327 156. MEMOIRS OF THE GEOLOGICAL SURVEY. ENGLAND AND WALES. THE GEOLOGY OF THE COUNTEY NEAE LEICESTER. (EXFI,ANATI0N OF ShEEI 156.) BY C. FOX-STRANGWAYS, F.G.S. FinUSBID BX ORQEB OF THE L0BD9 COUUIBSIUNEKS Ot HIB MAJESl'X'B IBEAaVSlit LONDON : FEINTED FOE HIS MAJESTY'S STATIONEEY OFFICE. BY WYMAN AND SONS, LIMITED, FETTER LANE, E.G. And to be purchased from E. STANFORD, 12, 13, AND 14, Long Acte, London j JOHN MENZIES and CO., Rose Street, Edinburgh; HODGES, FIGGIS, and CO., 104, Grafton Street, Dublin; From any Agent for the sale of Ordnanee Survey Maps ; or through anyr Bookseller from the Ordnance Survey Office, Southampton. 1903. Price Sa, {Price of Sheet 156, colour-printed. Is. 6d.) LIST OF MAPS, SECTIONS, AND OTHER PUBLICATIONS OF THE GEOLOGICAL SURVEY OF ENGLAND AND WALES. TFhb Maps are those of the Ordnance Survey, geologically coloured by the geological Survey ol the United Kingdom, xmiet The Superintendence oJ J. J. H. Tball, F.K.S., Director. For Maps, details of Sections, and Memoirs issued by the Geological Survey, see " Catalogue." ENGLAND AND VrALBS.-(Scale 1 inch to a mile.) Maps marked * are also published as Drift Maps. Those marlsed t are published only as Drift Maps. Sheets 3», 6, 6», 7», 8«, 9, 11, to 22, 25, 26, 80, 31, S3 to 37, 40, 41, 44, 4V*, 64*, 66t, 60t, 70* 83», 86*, pnce 8«. ed. each. Sheets 4, 6«. Sheets 2*, 2.3, 24, 27 to 29, 32, 38, 89, 58, 84t, 86t, 48. each. Sheets divided into quarters : all at 3s. each quarter-sheet, excepting those in brackets, whi(jh are 1«. 6d. each. I* 42, 43, 45, 46, NW, SW, ISTE*, SE», 48, NWt, SW*, NEt, (SE*), (49t), 50t, 51*, 52 to 57, (67 NW). 69 to 63, 66 SWf, NEt, •SW*, SEf, 67 Nt, (St), 68 Bt, (NWf), SWf, 71 to 75, 76 (N), S, (77 N), 78, 79, SW*, SW, NE* SE* 80 NW*, SW*, NB*. SB*, 81 NW*, SW, NB, SE, 82, 83*, 87, 88, NW. SW* N B, SE, 89 NW* SW*. NB, SE*, 90 (NE*), (SE*), 91, (NW*), (SW*), , NE*, SB*, 92 NW*, SW*, WE, SE, 93 WW, SW, NB*, SB* 94 NWt, SWt, (NEt), SBt, 95 NW*, NB*, (SB*), 96 NW*, SW* are*, se* 97 nw*, sw*, nb*, se, 98 nw, sw, ne*, sb, 99 (nb*), (se*), 100*, loi, sb, nb*, nw«, sw*, 102 nw» nb*, aw*, SB*, 103*, 104*, 105 NW*, SW*, (NE*), SB* 106 NW*, SW* NB*, SB*, 107 SWf, NE*, SB*, 108 SW*, NB*, SB*, 109 NW*, SW*,SB*,110(NW*),(NE*),SE*,SW*. ^ New Series.— I. of Man* 36, 46, 46, 56, 67, 8s. ed. I. of Wight, with Mainland* 380, 331, 344, 345, 8g. 6d. (123*), 166* 187t, ■203t, 231*, (232*), (248*), 249*, 261 and 262*, 268*, 267t, 268*, 282t, 283t, 284t, (298t), 299t, SOOt, (314t), S15t, 316t, 326t, 328t S29*, 330*, 331*. (332*), (333*), 334*, 339t, (340tA (341 1), 342t, 343t, 349t, 350t, 865t, (3S6t). Price 3s. each, excepting those in ibrackets which are la. 6i2. each. , OEITBItAli BXAP :— (Scale 4 mUes to 1 inch.) England and wales.— sheet l (Title) ; 2 (Northumberland, &e.) ; 3 (Index of Colours) ; 4'(I. of Man) ; 5 (Lake District) : 8 (K. Yorkshire) j 7 (N. Wales) j 8 (Central England) ; 9 (Eastern Couniiss) ; 10 (S. Wales and N. Devon) ; 11 (W. of England and 8.E. Wales); 12 (London Basin and Weald); 13 (Cornwall, &c.); 14 (S. Coast, Q^rquay to I. of Wight), 16 (S. Coast, Havant to listings). New Series, printed in colours, sheet 1, 2s. ; sheets 2 to 16, 28. ed. each. HORIZONTAL SECTIONS. 1 to 140, 146 to 148, England, price 68. each. VBBTICAL SECTIONS. 1 to 83, England, price 38. 6if. each. COMPLETED COUNTIES OF ENGLAND AND WALES, on a Scale of 1 inch to a mUe. Old Series. Sheets marked * have descriptive Memoirs. Sheets or Coimties marked t are illustrated by General Memoirs. ANGLESEY t,— 77 N, 78. BBDFOUDSHmB,— 46 NW, NE, SWt, SBt, 62 NW, NB, SW, SB. BERKSHIEE,— 7*, 8t, 12*, 13* 34*, 46 SW*. BBECKNOCKSHIKBt,— 36, 41, 42, 66, NW, SW, 67 NE, SE. BUCKINGHAMSHIRB,— 7*, 13*, 46* NB, SB, 46 NW, SWt, 52 SW. CABKMARTHBNSHIllEt,— 37, 38, 40, 41, 42 NW, SW, 66 SW, 57 SW, SB. CABENABVONSHIEBt— 74 NW, 76, 78, 77 N, 78, 79 NW, SW. CAMBRIDGESHIBEt,— 46 NE, 47*, 51*, 62 SB, 64*. CARDIGANSHIRE t,— 40, 41, 66 NW, 67, 68, 69 SE, 60 SW. CHESHIRE,— 73 NB, SW, 79 NB, SE, 80, 81 NW*, SW*, 88 SW. CORNWALL t,— 24t, 26t, 26t, 29t, 30t, 31t, 32t, & 33t. ^ CUMBERLAND,— 98 NW, SW*, 99, 101, 102, NE, NW, SW*, 106 SE, SW, NW, 107. DBNBIGHt,— 78 N W, 74, 76 NB, 78 NB, SE. 79 N W, SW, SB, 80 SW. ©BRBYSHIRBt,— 62 NB, 63 NW, 71 NW, SW, SB, 72 NE, 72SB, 81, 82, 88,SW, SB. BEVONSHIREt,— ZOt, W, 22t, 23t, 24t, 25t, 26t, & 27t. BORSBTSHIRB,— 16, 16, 17, 18, 21, 22. DURHAM,— 102 NE, SB, 108, 106 NB, SE, SW, 106 SB. aiSSEX,— 1", 2* 47*, 48*. I'LINTSHIREt,— 74 NB, 79. «LAM0RGAN8HIRBt,— 20, 36, 87, 41, & 42 SE, SW. GLOUCBSTEKSHIREt,- 19, 34*, 35, 43, NE, SW, SE, 44*. iHAMPSHIE;B,— 8t, 9t, 10*, lit, 12», 14, 16, 18. HBBBFORDSHIRB,— 42 NE, SB, 43, 65, 66 NB, SB.. aBRTFORDSHIEE,— It NW, 7*, 46, 47*. HUNTINGDON,— 61 NW, 62 NW, NE, SW, 64*, 65. KENTt,-lt SW & SE, 2t, 3t, 4*, 6*. SJANCASHIRE,— 79 NE, 80 NW*, NE, 81 NW, 88 NW, SWt, S9, 90, 91, 92 SW. . , See also New IBICESTERSHIKE,— 63 NE, iB2 NE, 63* 64*, 70* 71 SB, SW. LINCOLNSHIREt,— 64* 66*, 69, 70*, 88* 84*, 86*, 86*. MERIONBTHSHIREt,— 59 NE, SE, 60 NW, 74, 76 NE, SB. MIDDLKSEXt,— It NW, SW, 7*, 8t. MONMOUTHSHIRE,- 36, 36, 42 SE, NE, 43 SW. MONTGOMERYSHIREt,-56 NW, 59 NE, SE, 60. 74 SW SB. NOEFOLEt,— 50 NW* NE* 64* 66*, 66* 67*, 68», 69. NOETHAMPTONSHIRB,— 64*, 46 NW, NE, 46 NW, 62 NW NE, SW, 63 NB, SW, & SE, 63 SB, 64. NORTHUMBERLAND,— 102 NW, NE, 105, 106, 107,108* 109, 110. NW*, SW», NE*, SB. NOTTINGHAM,— 70», 71* NB, SE, NW, 82 NB*, SB*. SW 86, 87* SW. OXFORDSHIRE,- 7*, 18*, 34*. 44*, 46*, 53 SB*, SW. PEMBROKESHIREt,— 88, 39, 40, 41, 58. RADNORSHIRE,- 42 NW, NB, 56, 60 SW, SB. RUTLANDSHIRE,— this county is wholly included within , Sheet 64*. SHROPSHIRE,— 65 NW, NE, 66 NE, 80 NB, SB, 61, 62 NW 73, 74NB, SE. . '' SOMERSETSHIRE t,— 18, 19, 20, 21, 27, 35. STAFPOEDSHIRE*,— 54 NW, 65 NE, 81 NB, SB, 62, 63 NW 71 SW, 72, 73 NE, SE, 81 SE, SW. aUFFQLE,— 47*, 48*, 49*, 50* 61*, 66* SB*, 67*. SURREY,- 1 SWt, 6t, 7*, 8t, 12t. SUSSEX,-4«,6t, 6t, 8t, 9t, Uf. WARWICKSHIRE,— 44*, 45 NW, 63*, 64, 62 NB, SW SE 68 NW, SW, SB. WESTMORLAND,— 97 NW*, SW*, 98 NW, NE*, SB* 101 SE*, 102. ' ' WILTSHIRE -12*, 13*, 14, 15, 18, 19t, 34*, and 36t. WORCESXERSHIRE,-43 NE, 44*. 64, 55, 62 SW, SB 61 SB. YORKSHIREt,-86-88, 91 NB, SE 92-97* 98 NE* SE*, 102 SB, ' SB, 103 SW, SB 104. Series Maps. The original of tiiis book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924004550327 Geology of Leicester. Plate I. HAWCLIFF HILL, M.0UI|TS0RREL. Crags of Granite, shewing horizontal grooving. Ji'rom a Photograph by W. T. Tucker, 156. MEMOIRS OF THE GEOLOGICAL SURVEY. ENGLAND AND WALES. THE GEOLOGY OF THE COUNTEY NEAE LEICESTER. (Explanation op Sheet 156.) BY C. :^X-STRANGWAYS, F.G.S. PUBLISBEI) BY OEDEK OF THE LOKDS OOMMISSIONEKS OF HIS HAJESTST'S TEEASUEX. LONDON : PRINTED FOE HIS MAJESTY'S STATIONERY OFFICE. BY WYMAN AND SONS, LIMITED, FETTER LANE, E.G. And to be- purchased from E. STANFORD, 12, 13, and 14, Long Acre, London ; JOHN MENZIES AND CO., Rose Street, Edinburgh ; HODGES, FIGGIS, and CO., 104, Grafton Street, Dublin; From flny Agent for the sale of Ordnance Survey Maps ; or through any Bookseller from the Ordnance Survey Office, Southampton. 1903. Price 3s. (^Price of Sheet 156, colour-printed, h. 6d.) Ut,J PREFACE. The area described in the present Memoir is contained in Sheet 156 of the New Series one-inch Map of England, and embraces parts of central and eastern Leicestershire, and of the adjoining county of Eutland. It includes most of the area represented in the quarter-sheet 63 N.E. of the Old Series Geological Survey Map, which was surveyed by Mr. H. H. Howell and published in 1855 ; also the northern part of quarter-sheet 63 S.E. surveyed by Mr. W. T. Aveline and Mr. H. H. Howell and pubHshed in 1859, to- gether with a small descriptive Memoir published in 1860 ; and the north-western part of Sheet 64, surveyed by Prof. J. W. Judd and Mr. W. H. Holloway and published in 1872, together with a Memoir issued in 1875 on " The Geology of Rutland." The area is also referred to in the Memoir on " The Triassic and Permian Rocks of the Midland Counties of England " by Prof. Hull published in 1869. A comparison of Sheet 156 of the New Series with the former Sheets of the Old Series, which it replaces, will show that considerable changes have been made in the delineation of the geology of this part of the Midlands. The outcrop of the granite and other old rocks in the neighbourhood of Mountsorrel has been shown with more exactness than was possible with the smaller scale map. The outcrop of the Rhsetic Beds in this part of the Midlands has now been traced, and slight modifications have been made in the mapping of the Keuper Marl. The use of larger scale maps has also enabled the suD-divisions of the Middle Lias to be traced with more precision. The Drifts have been surveyed in detail, for the first time over much of the area, and the most striking feature of the map is the evidence which it affords of their plateau-like character. The present map differs again from the old map so far as the alluvium is concerned ; the lines have been traced with greater accuracy in the main valleys and extended into the smaller valleys, thus bringing out more clearly the drainage system of the country. The river terraces are also shown. A new feature is the insertion of a longitudinal section to show the general structure of the ground. IV The whole of the area has been surveyed by Mr. C. Fox-Strang- ■ways, who has prepared the present Memoir. The catalogue of fossils has been revised by Mr. E. T. Newton. Manuscript copies of the six-inch maps have been deposited in the Office for reference, and copies may be obtained on pajraient of the cost of copying. The Drift edition only of the map is colour-printed, but hand- coloured copies without Drift may be obtained at a cost of 3s. A bibliography of Leicestershire was published in the Memoir on the geology of the country between Atherstone and Charnwood Forest and is not, therefore, included in the present Memoir. Geological Swrvey Office, B8, Jermyn Street, London, nth February, 1903. J. J. H. TEALL. Director. CONTENTS. Page Peeface by the Director - . • iii Chapter I. Introduction. General Description of the District. Table of Strata. Soil and Economic Products - 1 Chapter II. Pre-Cambrian. Bocks of Charnwood. Mountsorrel Granite and Associated Rocks - - 7 Chapter III. Trias. Keuper. Rhaetic Beds . - - n Chapter IV. Lias. Lower Lias. Middle Lias. Upper Lias 21 Chapter V. Inferior Oolite. Northampton Sand - 41 Chapter VI. Pleistocene and Eecent Glacial. River Gravels avd Alluvium - 43 Chapter VII. Faults. Barrow and Sileby Fault. Billesdon Fault. Loddington Fault • - 58 Appendix I. Boeings and Well Sections - - - . gO Appendix II. CATALOGUE OF FOSSILS recorded from the Trais, Rhcetic and Lias Formations 0/ Leicester- shire and Rutland, or just beyond the Borders of those Counties - - 95 Appendix III. On the MICROSCOPICAL CHARACTERS of some of the Boulders, and of Rock Specimens from Borings. By Dr. J. S. Flett, M.A. - - - il6 Index .... . . - - 118 6470. 600— Wt. 16024. 4/03. Wy. & S. 514r. VI LIST OF ILLUSTEATIONS Plate I. Gkanite Cliffs at Hawclifp, Mountsoeebl, Showing WiNDEEOSiON IN Teiassic Times- Frontispiece Plate II. Kailway Cutting at Tilton. Showing Uppbe Lias Shales Eesting on the'Eock-bed of the Middle Lias -• lo face page %Q Page Fig. 1. Section showing the general position of the strata across the area from north-west to south-east 5 „ 2. Junction of Keuper Marl and Granite at Mountsorrel 10 ,„ 3. Section about 50 yards east of the junction of Hinckley fioad and Fosse Boad, Leicester 13 „ 4. Village of Somerby, Eutland, situated at the head of one of the deep sinuous valleys of the great escarpment formed by the Marlstone Eock-bed - 29 ,, 5. Section exhibited in a pit between Keythorpe and Hal- laton - ... 35 „ 6. Section in pit above Hallaton Ferns, showing a small out- lying patch of Northampton Sand capped by Boulder Clay - %• - - 41 ,, 7. Section on the west side of Spinney Hills, Leicester 47 „ 8. Section on the Midland BaUway, just south of the tunnel. Freeman's Common, Leicester - 47 „ 9. Cutting on the Great Central Eailway, south-east of Stock- ing Farm, Leicester 48 „ 10. Section in cutting west of Enderby Hill 49 „ 11. Pit in Glacial Gravels between Whatborough and Ouston 50 „ 12. Sand Pit near Union Inn, Blaby - 61 „ 13. Balls of sand in Boulder-clay, corner of EatoliflFe Boad and Elms Boad, Leicester ... 52 „ 14. Section in upper part of Limestone Quarry ("Darby's Pit "), north-east of Barrow - - ■ - "sk „ 15. Plan of., North Evington, Leicester, showing position of bore-holes of the Evington Coal Boring Company h. GEOLOGY OF THE COUNTRY NEAR . LEICESTER. CHAPTER I. Inteoduction, The sheet described in this Memoir contains an area of 216 square miles, the greater part of which lies in the County of Leicester, but it includes also a small portion of the County of Rutland. It covers the larger part of the area shown in 63 N.E. of the old one- inch survey, but extends nearly three miles further to the south ; it also contains a considerable portion (72 square miles) of the ground covered by Sheet 64. Owing to the Drift, which overlies the solid strata, being shown, this map has far more detail than the former of these sheets ; and, owing to six-inch maps being now used, the lines can be drawn in with greater accuracy than was possible in 1872, when the eastern part was surveyed. Since the old surveys were made much additional information has been obtained. For instance, in 1855, when the district surrounding Leicester was surveyed, the Rhaetic beds were not recognised, and were consequently included with the Lower Lias, a part of the outcrop at Leicester being entirely overlooked. The. only large town in the district is the county town of Leicester, but there are several important manufacturing villages, such as Mountsorrel, Sileby, Systoh, Thurmaston, Wigston, Blaby, Narborough, and others along the valley of the Soar. In the eastern part of the map, the gi-ound being entirely agricultural, the villages are not so large, but all are fairly prosperous, from the district being near the centre of the most famous hunting country. On this side the largest place is Billesdon, but there are quite thirty other villages that are of considerable importance. Although the greater part of the drainage of the district is within the Trent basin, a large part of the water on the east side passes away to the Welland, and thence into the Wash. The watershed dividing, these two runs from B^f ^^orough Hill, by CoM Overtol K~C'cS'Trts r kn'^Siofof tS ?otLr bS^eeniSd^on 5 T^n, but declines to about 500 S Tt oSn and at the southern edge of the map. Near SbwtrtS to the si of this, it is below the 400 contour Une. ^^ 5470. INTRODUCTION. The physical aspect of the country is greatly influenced by the Drift. This, in former times, appears to have completely covered the district, and to have obliterated its older features, so that the surface of the land gradually declined in one broad sheet from the Une of watershed. Along the outcrop of the Middle Lias between Burrow and Billesdon there must have been a pre-Glacial feat\u-e as fine as the present escarpment, where the fall in the ground was somewhat rapid ; but beyond this there was a nearly uniform slope, which was so slight that the ground may be considered to have been nearly level. This plateau, which was lowest along the line of the present Soar valley, has been cut into by the tributaries of this stream; so that the present aspect of the country is that of a great plain intersected by numerous furrows, that have been carved out by the tiibutary streams. The same thing has taken place on the eastern side of the watershed, the present streams apparently flowing nearly along the same lines as they did before the deposition of the Drift, which they have cut through, leaving only patches on their flanks. The effect of this denudation is that the escarpment of the Middle Lias, forming the highest ground in the map, rises in a more or less abrupt bank, overlooking a general plain, of lower ground to the west, which has been furrowed into a series of ridge-like hills by the numerous streams that flow down to the main Soar valley. To the east of the Middle Lias escarpment the ground falls away gradually towards the Vale of Catmos, in the centre of Rutland ; but this is principally along the valleys, as the ridges between maintain a fair altitude to beyond the limit of this map. The following table gives a list, in descending order, of the subdivisions of the strata :— Recent and /Alluvium. Post-Glacial (.Eivei- gravels. Valley Prift. Chalky Boulder-play with intercalated beds of sand and gravel. ( Older Boulder-clay (upper part). Quartzose Sand. Older Boulder-olay (lower part). Older Sand and Gravel (?) Northampton Sinds. Shales. j Marlstone Rock-hed (zone of Ammonites M'A n T ■ J spinatus). lumaieiiias i g^^^^y ^,,^1^^ ^^^ ^^^^^ ^^j^ ironstone, &c. \ (zone of Am. margaritatns). Lower Lias Lower Lias Shales with limestones in the lower part. RhoDtic Rhaetio Beds. Keuper Keuper Marl with lenticular sandstone beds and bands of gypsum, f Graniteof Mountsorrel, and associated rocks. Charnian -j Slates, homstones, and agglomerates of { Oharnwood Forest. The older formations that come to the surface within the limits of the map occupy a very small space, but they have been proved Recent AND Pleisto CENE JUKASSIC Glacial Inferior Oolite iper Liars Lias Trias -} Pre-Cambeian\ OR AECIivEAN I INIBODtTCTION. 3 to extend further beneath the newer rooks at Leicester and else- where. They include a small outcrop of the Pre-Cambrian slates of Bradgate Park, and the intrusive granite and other rocks of Mountsorrel, which form the fringe of the Charnwood Forest district. The principal formations, however, are the Trias and the Lias, which practically cover the whole of the district. The Keuper Marl crops out along the Soar valley, covering a considerable area, but the most extensive formation is the Lower Lias, which crosses the centre of the district ; between these is a narrow band of Rhaetic shales which has now been mapped for the first time. This is followed by the Middle and Upper Lias, which cover the eastern part of the district, and form the higher ground that is found in that direction. A few isolated hills of Inferior Oolite rise here and there above the general mass of the Upper Lias Clay. Finally, the whole of these strata are more or less covered by Boulder-clay and sands, which have somewhat altered the general character of the country. The soil of the country, being in the main derived from the under- lying formations, is mostly clay of a very retentive character. It is diversified here and there by beds of sand and gravel, which render it much Ughter. This is particularly the case with the alluvial gravel that occurs along the margin of the Soar valley, especially about Syston. In the eastern part of the area the Rock-bed of the Middle Lias, where not covered by Drift, also forms a light rubbly soil, that is the best arable land in the district. In consequence of the large proportion of heavy clay land the greater part of the country is devoted to grazing purposes, and is noted for its extensive pastures and its renown as a hunting district. Although there is no coal mining in the country now under consideration, the proximity of the coalfields to Leicester, and their early connection by one of the first railways made in the kingdom, has enabled that town to become an important manufacturing centre. A large industry, and one which has greatly increased of late years, is the quarrying of roadstone. This is actively carried on at Mountsorrel, where the granite forms an excellent material both for mending roads and for pavements ; it is also used in the preparation of artificial flagstones. These quarries are very extensive, and,' being connected by branch hues with both the Midland and Great Central Railways, a large amount of road-metal is sent away to other districts. The Keuper Marl is extensively used along the Soar valley for the manufacture of bricks, and has entirely superaeded the Glacial and Liassic clays, which were formerly worked to a small extent locally for this purpose. There are no minerals of any importance. The Rock-bed of the Middle Lias contains a certain amount of ironstone, which has been tried at Tilton : but, from the abandonment of the works, 5470. B ^ 4 INTRODUCTION. it does not appear to have been of much value. The Inferior Oolite is also very ferruginous, but the area covered by the rock is too small to be of any importance. A thick bed of gypsum oooiu-s in the Keuper Marl at Thurmaston, and other bands of this rook have been met -with in borings ; but it does not appear to have been used commercially in this district, although extensive works exist further north, between Eegworth and Gotham. There is no building stone of any value. The soft white sandstone of the Keuper to the west of Leicester, the limestone bands in the Lower Lias, the Eock-bed of the Middle Lias, and the Liferior OoUte have been used, but they are generally too soft and friable for the pm-pose. Some of the new bridges on the Melton and Market Harborough Eailway are built of the hard fossiUferous blocks (" jacks ") of the Middle IJas, and appear to stand fairly well. The limestone bands in the lower part of the Lias, from which the well-known cement at Barrow is made, are worked for lime at Kilby Bridge, but the beds are more shaly and impure than at Barrow. These beds have also been worked on the Crown Hills near Leicester, Imt the quarries are now abandoned. Beds of sand and gravel occur at numerous places thi'oughout the area, especially along the Soar valley, about EJnossington and Tilton, and further south. The gravel was formerly, in the country districts, the usual material for road-mending, but now it is entirely superseded by " granite," except foi- purely local pm'poses. The sand is, of course, still used for mortar, large quantities being " excavated near Leicester, where the building trade is very active. The water Supply of a district like this, which has been derived chiefly from superficial deposits resting on imper- vious clays, is neither aljundant nor good. Por this reason the rapidly growing town of Leicester, which has been supplied by catchment reservoirs in the neighbourhood, is now seeking to obtain water from the far better but distant Carboniferous rocks of the Peak district of Derbyshire. When this scheftie has been carried out the western portion of the" area under con- sideration will have an admirable supply. By considering the subject of the water-bearing properties of the rocks'of this district we shall see why it has been necessary for Leicester to seek its supply from another soiu-ce. The Keuper Marl with its subordinate bands of sandstone, when bored into, is usually .found to yield a considerable amoimt of water ; but, owing to the quantity of gypsum contained in these rocks, it is so impregnated with sulphate of lime as to be too hard for domestic purposes. In the limestones and shales of the Lower Lias the supply of water is usually very scanty, and the shaly beds are so full of decomposing pyrites that the water is generally, strongly impreg- nated with sulphuretted hydrogen, ' ■ ' INTRODUCTTOX. s •^ §= =? I— ( w & a B ^ 8 ^ 5 »3 >>: ^ O o ^ ^ s ^ _ "a ai > •' n-h /'\ ill! I) =)' ■III I 6 INTRODUCTION, The Eock-bed of the Middle Lias, being very porous, furnishes a copious supply, which is probably the best water in the district, but from the ferruginous nature of the rock it is liable to be strongly impregnated with iron ; so that it is usually a strong chalybeate rather than a good water for domestic purposes. The Upper Lias, from its generally impervious character, gives the poorest supply of any formation, as the water is only held in thin limestone bands ; and from the pyrites in the shales it is not often fit to use. The gathering ground covered by the Inferior Oolite is too limited to give, a supply of any quantity, but good springs generally issue from this rock, although the water is liable to be rather f errugino\is. The sandy bands in the Drift frequently give good water, and no doubt may fiu-nish a valuable source of supply ; but the springs being only shallow, and the water being often conveyed for some distance between enclosing sheets of Boulder-clay, it is very liable to be contaminated by surface pollution, and great care should be used in the selection of sites for wells. (6) The MaplewBll Series. PKE-CAMBRIAN BOCKS OF CHARNWOOD. 7 CHAPTER II. PRE-CAMBRIAN. On the western margin a small portion of these old rocks just comes within the limit of the map. These rocks were described by Professor W. W. Watts in the explanation of the neighbouring sheet (155) ; so that we need not devote much attention to them here. They constitute the main mass of the Char n wood Hills, but only the extreme eastern outcrop, just as it becomes buried beneath the Trias, is seen here. Professor Watts has divided these rocks into the following series, but only the Swithland Slates and a part of the Bradgate beds are. exposed in this map : — Pre-Cambrian Rocks of Chamwood. {(c) Swithland and Groby Slates. (6) Conglomerate, Grit, and Quartzite. (a) Purple and Green Beds. „. (e) Olive Hornstones of Bradgate. (d) Woodhouse Beds : Hornstones and Volcanic Grits, (c) Slate-Agglomerate of Eoecliffe. (b) Hornstones of Beacon HUl. ,(a) Felsitic Agglomerate. (a) The !^lackbrook Series : Hornstones and Volcanic Grits. These rooks protrude through the Keuper Marl in isolated knolls in Swithland Wood and Bradgate Park ; and extend across the reservoir at Cropston, where they are last seen in this direction. The Olive Hornstones of Bradgate are well represented in the Park, just beyond the edge of the map. "They are fine olive- green hornstones, deveid of coarser seams, but ashy in composition, and more or less fissile or slaty." The Swithland Slates were formerly quarried at Swithland Wood and in the neighbourhood of Woodhouse Eaves. They are much heavier and rougher than the ordinary Welsh slate ; consequently they are not now used except in a few instances where a more picturesque aspect is desired. These slates, which have a coarse cleavage, are purple or green in colour, and the best of them have a satiny or glossy texture. Mountsorrd Granite and Associated Rocks. Intimately associated with these slaty rocka is the granite of Mountsorrel and the neighbouring hills. It was shown in the description of Chamwood Forest, by Professor Watts, that the rocks of that district were traversed by numerous masses of syenite, which had been injected through the older strata. Probably a still later intrusion is the Mountsorrel granite, which, although about two miles from the main mass of the Charnwood area, is 8 PRE-CAMBKIAN. nevertheless connected with rocks of this age, a junction with altered slates being shown at the extreme south-west and north-west corners of the Mountsorrel group, although everywhere else the relation to the older rocks is hidden by the overlap of the Keuper Marl. The granite crops out in several isolated knolls, the largest of which is the fine wooded eminence of Buddon Hill. Around this are grouped several smaller hills to the number of about twenty-two, varying in size from conspicuous hills like that at Mountsorrel to small patches, just rising through the Boulder-clay, not more than a yard or two in diameter. The rock is a pink biotite-granite ; a full description of its mineral constituents has been given by Prof. Bonney* and by Mr. J. J. H. Teall.f It varies somewhat in composition, the easternmost exposure, at Mount- sorrel being the most acid, while the westernmost, at Brazil Wood, is the most basic. Besides the pink felsitic veins by which tliis rock is frequently traversed there are several dykes of a more basic character. The principal of these is that seen in the old Mountsorrel quarry. This dyke runs in an east and west direction (W. 15° N.) across the quarry, and is 22 feet thick at the west end. It is seen again in the small quarry near the Cottage Hospital, where it is only 4 inches thick and dips at an angle of 45°. In the opposite direction, at Cocklow Wood, which is on the same line, we could find no trace of this rock, so that it probably dies out in both direc- tions from its maximum width in the large quarry. Other dykes occur at Buddon Wood and Brazil Wood. About 80 yards west of the latter there is a curious mound of diorite, now concealed by the water of the reservoir. This is no doubt a portion of another dyke, but there is not enough seen of the rock to indicate its direc- tion. This remarkable rock, which is unique in the district, is a plagioclase-hornblende rock with some pyroxene. It is coarsely crystalline, with large plates of hornblende that are very con- spicuous. Where the granite is in contact with the older rock, as at the two spots mentioned on the west side, the latter is greatly altered, and full of minute garnets. At Brazil Wood the rock, which might be called a micaiornfels, is split up by numerous dykes for a distance of about 20 yards or more from the granite, which was evidently intruded at a very high temperature. A good section of these rocks was exposed here in the trench connecting the two hills at the tinie the reservoir was made, of which Professor Watts has supplied the following notes :— J " The intrusive rocks are entirely separate from the metamor- phosed slate, but along the trench the beds are too much cut up by dykes to throw much light on progressive contact meta- morphism. No unaltered rock occurs in Brazil Wood. * Quart. Journ. Geol. Soc. (1878), vol. xxxiv., p. 218. t British Petrography (1888), p. 321. J A fuller account will be given by Prof. Watts in his forthcoming Memoir on the Charnwood rocks. MOUNTSORREL GRANITE AND ASSOCIATED ROCKS. 9 " The granitite of Kinchley is more basic than that of Mount- sorrel, and contains plenty of hornblende in addition to brown mica. The rock of Brazil Wood is still more basic, and hornblende is always m excess of mica ; it also contains much plagioclase (oligo- clase or albite) in addition to orthoclase. The hornblende is in part brown and in part green — mostly compact, that is, not fibrous. The hornblende, mica, and felspar have consolidated before the quartz. Apatite and sphene are usually present. The dark rock is fine-grained, with porphyritic felspar set in a fine felspathic matrix. Hornblende and mica are present. The pink veins which seam this are chiefly micropegmatite, consisting of more acid ' mother liquor.' Some of the dark rocks contain so much horn- blende and plagioclase that, if occurring alone, they would be called diorite. The contact rocks, which look Hke hard bands in the ' slate,' are fine-grained dykes from the granite. They contain felspar like the granite, but the matrix consists of rounded grains of quartz set in a very fine-grained felsitic matrix instead of irregular masses of interstitial quartz. The rock is almost devoid of hornblende or mica, and may be micropegmatite veins quickly cooled. The ' felsite ' of the east end is of the same type. One of the hard veins in the slate is different, and contains abun- dance of crystals, probably of brown mica set in plagioclase with a little quartz, resembling the mica traps sometimes found in dykes from granite. The diorite differs in the deep brown colour of the compact hornblende and the presence of much fibrous actinolite, the small amount of orthoclase, and the absence of quartz. " The altered rocks show no trace of the original clastic structure, and have been much altered. A few patches of aggregates of white mica occur, but not many recognisable crystals. The bulk of the rock is spotted and contains abundance of iron-ore dust. The lighter spots apparently consist of a felt of minute micaceous minerals separated by patches of brown matter also fibrous, which may be dark mica. " The slate at the end of the trench is much more altered, and consists almost entirely of two kinds of mica with quartz in clear patches. All the mmerals have been recrystallized. The spotted appearance is still preserved in places, but the light material consists of felted white mica passing into aggregates of larger crystals of the same, while the dark patches are now a pale olive brown pleochroic mica with inclusions of zircon, and passing in places into a dark brown mica. As the rock is not schistose it may he called (according to Mr. Teall) a mica-homfels. No felspar has been detected. It is not more altered at the actual junction, except that the micas are larger and better formed. It also contains a brown biaxial mineral. The Buddon Wood contact- rock is full of minute garnets." The junction of these isolated granite bosses with the surrounding Keuper Marl is found nearly everywhere to be very precipitous, and shows that they must have formed peaks and nearly vertical 10 PBE-CAMBRIAN. cliffs in the Triassic lake. At Mountsorrel, a well which is 50 yards from the edge of the granite, is sunk to a depth of 40 feet entirely in Keuper Marl.* At Hawcliff the edge of the granite goes sheer down to the bottom of the quarry, a depth of 20 feet or more. In the old brickyard at Nunckley there is a deep well within 30 yards of the granite. At the end of the reservoir embankment on the west side of Buddon Hill the edge of the granite was found to be very steep, and, in fact, wherever the junction of the two formations has been opened out it has been found to be of the same character. Fig. ^.—Junction of Keuper Marl and Granite at Mountsorrel. Jiad Marl v/UK baruCt of :z , — Ske-rry SauLoLsUiiit' dipputy ~ ' ~^ hu^^thero Lar^ablacJis of Grajutet 7^ larger hlock. of CnutUe/ oUpreiSta Uui /.fixrl uftan/ wfU£fu Ct rcsti as if bC hzui. falLeru vnta it ifl/ttMif tilt, Mori waj soft RtJ-MarltblacJu of Crarute- LrrcffuJarly irUxed atjunctiarif yVUJt. nuUJv