26: lNl57li 187, ■ %'^:^^mp n S) AAr^A0r' ■■f^Rn irmmi 'jTf^Sr^^i §&^mmm^^^ Irilr^Wf^^ ^^^Af^i^^i ^ aU':;^^ A'/^'aa:'^'a Sh!^-^ -^i' j^ A A I r*^' E7? U)511 1^1^ BOUGHT WITH THE INCOME FROM THE SAGE ENDOWMENT FUND THE GIFT OF 1891 A,am '^^'^^'^'^^wi^ Cornell University Library QE 262.E78W571 1878 The geology o< thfi^fiffillllS^^ M Cornell University B Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924004550673 47. MEMOIRS OF THE GEOLOGICAL SIIRYEY. ENGLAND AND WALES. THE GEOLOGI OF THE N.W. PAET OF ESSEX AND THE N.E. PART OF HERTS. WITH PAETS OF CAMBEIDGESHIRE AND SUFFOLK. (EXPLANATION OF SHEET 47 OF THE MAP (ONE-INCH) OF THE GEOLOGICAL SURVEY OF ENGLAND AND WALES.) W, WHITAKER, B.A., r.(5^.S., W. H. PENNING, F.G.S,, W. H. DALTON, F.G.S. ; and F. J. BENNETT, F.G.S. PUBLISESD BT OSDEB OP THE XOSDS COHMISSIONEBS 01 BEE MAJESIX'B IBEASUBT. LONDON : PEINTBD FOR HEB MAJESTX'S STATIONEET OFFICE, AND SOLD BY Longman & Co., Paternoster Row ; Tbubneb & Co., Ludgate Hill ; Letts & Son, 33, King William Street ; Edwaed Stanfoed, 55, Charing Cross ; and J. Wtld, 12, Charing Cross ; ALSO BY Messrs. Johnston, 4, St. Andrew Square, Edinburgh ; HoDGBS, FosTBE, & Co., 104, Grafton Street, and A. Thoic, Abbey Street, Dublin. 1878. Price Three Shillings and Sixpence. LIST OF GEOLOGICAL MAPS, SECTIONS, AND PUBLICATIONS OF THE GEOLOGICAL SURVEY OF THE UNITED KINGDOM. The Maps are those of the Ordnance Survey, geoloj^callv coloured by the Geological Survey of Great Britain and Ireland nnder the Superintendence of Prof. A. G. BuisAT, LL.D,, F.B.S., &c., Director-General. The various Formations an traced and coloured in all their Subdivisions, ENGLAND AND WALES.-(Scale one-inch to a mile.) Maps, Nos. S to 41, 44, 64, priee 8s. 6d. eaoh/with the exceptions of 2, 10, 23, 24, 27, 28, 29, S2, 38, 39, 68, is. each. Sheets divided into four quarters, 42, 48, 46, 46, (48 SE), 52, 63, 64, 65, 66, S7A59 NE, SB), 60, 61, 62, 68, 64, 71, 72, 73, 74. 75, {76NS), (77N),V8, 79, 80, 81, 82, 87, 88,89, 105 (90 SB, NE,) (91 SW, NW, 98 SW,NW), (98 NE.SB.SW), (101 SB), (109 SE). Price 3s. Except (57 NW), 76 (N), (77 NB). Fricels.ed. SCOTLAND,— Maps2, 8, 7,14,16,22, 24, 31,32, 33,34, 40,41, 6s. each. Maps 1,13, 4s. IRELAND.— Haps 31, 28, 29, 36, 37, 47, 48, 49, 60, 69, 60, 61, 70, 71, 72, 74, 76, 78 to 92, and from 95 to 205, price 3s. each, with the exception of 38, 50, 72, 82, 122, 131, 140, 160, 169, 160, 170, 180, 181, 182, 189, 190, 196, 197, 202, 203, 204, 205, price Is. 6d. each. BORIZOIfTAK SECTION'S, Illustrative of the Geological Maps. 0120, England, price 5s. each. 1 to 6, Scotland, price 5s. each. 1 to 24, Ireland, price 6s. each. VERTXCA]^ SECTION'S, Illustrative of Horizontal Sections and Maps. 1 to 63, England, price 3s. M. each. 1, Ireland, price 3s. &d. 1 to 6, Scotland, price 3s. 6d. COBIPKETED COVNTIES OF ENGIiAND AND 'WAXiES, on a Scale of one-inch to a Mile. The sheets marked * have Descriptive Memoirs. Those marked t are illustrated by General Memoirs. ANGLESEY,- sheets 77 (N), 78. Horizontal Sections, sheet 40. BEDPOEDSHIEE,— sheets 46 (NW, NB, SWt, & SEt), 62 (N'W, NB, SW, & SE). BEaKSHIBE,— sheets 7*, ,8t, 12*, 13*, 34*. 45 (SW*). Horizontal Sections, sheets 59, 71, 72, 80). BfiBOKNOCKSHIEB,— sheets 36, 41, 42, 66 (NW & SW), 67 (NB & SB). Horizontal Sections, sheets 4, 5, 6, 11; and Vertical Sections, sheets 4 and 10. BUCKINGHAMSHIUB,— 7* 13* 45* (NB, SB), 46 (NW, SWt), 62 (SW). Horizontal Sections, 74, 79. OABRMABTHBNSHIEB, 37, 38, 40, 41. 42 (NW & SW), 66 (SW), 67 (SW & SE). Horizontal Sections 2, S, 4, 7, 8, 9 ; and Vertical Sections 3, 4, 6, 6, 13, 14. CABRNAEVONSHIEE,— 74 (NW), 75, 76, 77 (N), 78, 79 (NW & SW). Horizontal Section 28, 31, 40. CARDIGANSHIRE,— 40, 41, 56 (NW), 57, 68, 59 (SB), 60 (SW). Horizontal Sections 4, 6, 6. CHESHIRE,- 78 (NB & NW), 79 (NE & SB), SO, 81 (NW* & SW»), 88 (SW). Horizontal Sections 18, 43, 44, 60, 64, 65 67, 70. CORNWALL,— 24t, 26t, 26t, 29t, 30t, Sit, 32t, & 33t. DENBIGH,— 78 (NW), 74, 75 (NE), 78 (NE & SE), 79 (NW, SW, & SE), 80 (SW). Horizontal Sections 81, 35, 38, 89, 48, 44, and Vertical Sections, sheet 24. DERBYSHIRE,- 63 (NE), 63 (NW), 71 (NW, SW, & SE), 72 (NB, SB), 81, 82, 88 (SW, SE)). Horizontal Sections 18, 46, 60, 61, 69, 70. DEVONSHIRB,-20t, 21t, 22t, 23t, 24t. 251-, 26t, & 27t. Horizontal Sections, sheet 19. ' + The Geology of the Counties of Cornwall and Devon is fully illustrated by Sir H. De la Beche's " Report." 8vo. 14s. DORSETSHIRE— is; 16, 17, 18, 21, 22. Horizontal Sections, sheets 19, 20, 21, 22 56. Vertical sections, sheet 22. FLINTSHIRE —74 (NE), 79. Horizontal Sections, sheet 48. GLAMORGANSHIRE,— 20, 36, 37, 41, & 42 (SE & SW) . Horizontal Sections, sheets 7, 8, 9, 10. 11 ; and Vertical Sections sheets 3, 4, 6, 6, 7, 9, 10, 47. GLOUCESTERSHIRE,- 19, 34*, 85, 43 (NB SW & SB), 44*. Horizontal Sections 12, 13, 14, 15, 59; and Vertical Sections, 7, 11, 15, 48, 47, 48, 49, 60, 51. HAMPSHIRE,- 8t, 9, 10*, 11, 13*, 14, -16, 16. Horizontal Section, sheet 80. HERBPORDSHIRE,— 42 (NE & SE), 43, 65, 56 (NB & SB). Horizontal Sections 5, IS, 27, 30, 34 ; and Vertical Sections sheet 15. KENT,— It (SW & SE), 2t 3t 4*, 5, 6t. Horizontal Sections, sheets 77 and 78. MERIONETHSHIRE,— 59 (NE & SE), 60 (NW), 74, 75 (NE & SB). Horizontal Sections, sheets 26, 28, 29, SI, 82, 35, 87, 38, 39. MIDDLESEX,- It (NW & SW), 7*, 8t. Horizontal Sections, sheet 79. MONMOtTTHSHIRB,- 85, 86, 42 (SB & NE), 43 (SW). Horizontal Sections, sheets 5 and 12 ; and Vertical Sections sheets 8, 9, 10, 12. MONTGOMERYSHIRE,- 66 (NW), 59 (NE & SE), 60, 74 (SW & SB). Horizontal Sections, sheets 26, 27 29 80, 82, 8^ 36, 36, 88. NORTHAMPTONSHIRB,-64, 46 (NW&NB), 46 (NW), 52 (NW, NB, & SW) 53 (NE, SW, & SB), 63 (SE). 64. OXFORDSHIRE,— 7*, 13*, 34*, 44*. 45*, 58 (SB*, SW). Horizontal Sections, sheets 71, 72, 81, 82. PEMBROKESHIRE,- 88, 39, 40, 41, 58. Horizontal Sections, sheets 1 and 2 ; and Vertical Sections, sheets 12 and 13. KADNORSHIEB,— 42 (NW St. NB), 56, 60 (SW & SB), Horizontal Sections, sheets 6, 6, 27. RUTLANDSHIRE,- this county is included in sheet 64. SHROPSHIRE,— 56 (NW, NB), 66 (NB), 60 (NE, SB), 61, 62 (NW), 73 74 (NE, SE). Horizontal Sections, sheets 24, 25, 30, 83, 34, 36, 41, 44, 46, 68, 54, 58 ; and Vertical Sections, sheets 28, 24. SOMERSETSHIRE,— 18, 19, 20, 21, 27, 85. Horizontal Sections, sheets 16," 16, 17, 20, 21, & 22 ; and Vertical Sections, sheets 13, 46, 47, 48, 49, 50, and 51. STAFFORDSHIRB,-(54 NW), 55 (NE), 61 (NE, SE), 62, 63 (NW), 71 (SW), 72, 73 (NB, SB), 81 (SE, SW). Hori- zontal Sections 18, 28, 24, 25, 41, 42, 46, 49, 64, 57, 61, 60; and Vertical Sections, sheets 16, 17, 18, 19, 20, 21, 33, 26. SURREY,— 1 (SWt), 6t, 7*, 8t, 9. Horizontal Sections, sheets 74, 76, 76, and 79. SUSSEX,— 4*, 6, 6, 8, 9, 11. Horizontal Sections, sheets 78, 76, 76, 77, 78. WARWICKSHIRE,— 44*, 45 (NW), 58*, 64, 62 (NB, SW, & SE), 68 (NW, SW, & SB), Horizontal Sections, sheets 2J 48, 49, 60, 51, 82, 83 ; and Vertical Sections, sheet 21. WILTSHIRE,— 12*, 13*, 14, 15, 18, 19, 34*, and 36. Horizontal Sections, sheets 16 and 69. WORCESTERSHIRE,— 43 (NB), 44*, 54, 65,"62 (SW & SB), 61 (SB) Horizontal Sections IS, 23, 25, 60. and 59; and Vertical Section 16. 47. MEMOIRS OF THE GEOLOGICAL SLEYEI ENGLAND AND WALES. THE GEOLOGY OE THE N.W. PAET OE ESSEX AND THE N.E. PAET OE HEETS. WITH PARTS OF CAMBRIDGESHIRE AND SUEEOLK. (EXPLANATION OF SHEET 47 OF THE MAP (ONE-INCH) OF THE GEOLOGICAL SURVEY OF ENGLAND AND WALES.) BY W. -^IITAKEE, B.A., F.G.S., W. H. PENNING, F.G.S., wTh. DALTON, F.G.S. ; AND F. J. BENNETT, F.G.S. PUBLISHED BT OEDEE OE THE LOEES COMMISSlOlfEES OE HEE MAJESIT'S MEASCSY. LONDON : PRINTED FOR HER MAJESTY'S STATIONERY OFFICE, AND SOLD BT LoNGJiAN & Co., Paternoster Row ; Tkubnbk & Co., Ludgate Hil! ; Letts & Son, 33, King 'William Street ; BdwAed Stanfoed, .^5, Charing Cross ; and 3. "Wtld, 12, Charing Cross ; also by Messrs. Johnston, 4, St. Andrew Square, Edinburgh ; Hodges, Fostee, & Co., 104, Grafton Street, and A. Thom, Abbey Street, Dublin. 1878. Price Three Shillings and Sixpence. O 1 r : A. w^G-j. Ill NOTICE. In the following Memoir the Authors have described all the formations mapped in Sheet 47 including the Cretaceous strata from the Gault to the Upper Chalk, the Eocene beds from the Thanet Sand to the London Clay, the Red Crag, and the Glacial deposits of Boulder Clay and gravels and sands. The area described in- cludes parts of Essex, Herts, Cambridgeshire, and Suffolk, and the illustrative wood-cuts, and detailed Sections will be useful for reference long after some of the actual sections have become obscured or have alto- gether disappeared. The Appendix of Well-sections to all persons interested in water supply forms an impor- tant feature of the Memoir. Andw. Ramsay, November 22, 1878. Director-General. a 38S. Wt. B 1029. NOTICE. The district described in this Memoir was surveyed, under the superintendence of Mk. Whitakee, by himself and the following colleagues : — Mb. W. H. Penning (more than half the map, from the neighbourhood of Eoyston on the N.W. to that of Clare on the N.E., and of Harlow on the S.) ; Me. W. H. Dalton (the neighbourhoods of Witham and Coggeshall, forming the S.E. part of the map) ; and Mr. F. J. Bennett (separate areas in the neighbourhoods of Buntingford, Dunmow, and Halstead). Me. "Whitakee is himself answerable for the S.W. and N.E. corners, in the neighbourhoods of Hertford and of Siidbury, the latter of which, though small, involved much detail. Me. 0. E. Hawkins mapped a few square miles near Cavendish, Whilst each observer has described his own ground, the arrangement and editing of the whole Memoir, with the addi- tion of some general remarks and occasional details, has been entrusted to Mr. Whitakee. The lists of fossils have been revised by Me. Etheeidge. The description of the Eocene beds of the Western part, from Hertford to Stortford, is reproduced, with additions and corrections, from Vol. iv. of the Geological Survey Memoirs (1872). H. W. Bristow, Geological Survey Office, Senior Director. 28, Jermyn Street, S.W., November, 1878. CONTENTS. Page Notices -.....-. iii Chapter 1. Introduction. — Area. Rivers. Geological Divisions. Shape of the Ground. By W. Whitaker - - - 1 Chapter 2. Cretaceous Beds. — Gault. Chalk (Chalk Marl; Lower Chalk, with List of Fossils ; Chalk Rock, with List of Fossils ; Upper Chalk, with List of Fossils ; Line of Flexure). By W. H. Penning -...----4 Chapter 3. Lower London Tertiaries. Thanet Beds. By W. Whitaker - - - - - - - 12 Chapter 4. Lower London Tertiaries (continued). — Reading Beds (Main Mass ; Outliers). By W. Whitaker and W. H. Penning 18 Chapter 5. London Clay. Red Crag- By W. Whitaker, W. H. Penning, and W. H. Dalton - - - - - 27 Chapter 6. Glacial Drift. — General Remarks. Gravel and Sand (Valleys of the Lea, Rib, Ash, Cam, Stort, and Bourn). By W. Whitaker and W. H. Penning - - - - 32 Chapter 7. Glacial Drift (continued). — Gravel and Sand (Valleys of the Roding, Chelmer, Ter, Guith, Pant or Blackwater, and Colne). By W. Whitaker, W. H. Penning, W. H. Dalton, and F. J. Bennett - - - - - - - 42 Chapter 8. Glacial Drift (continued). — Gravel and Sand, Valley of the Stour, By W. Whitaker and W. H. Penning - - 49 Chapter 9. Glacial Drift (continued). — Boulder Clay, By W. H. Penning and W. H. Dalton - - - - - 59 Chapter 10. Post Glacial Deposits. — Various Loams and Gravels. Old River (or Valley) Drifts. Alluvium. By W. Whitaker, W. H. Penning, and W. H. Dalton - - - - 64 Appendix 1. Well-Sections. — Cambridgeshire. Essex. Hertfordshire. Suffolk. By W, Whitaker, W. H. Penning, and W. H. Dalton - - - - - - - -74 Appendix 2, Borings and Shallow Wells. Essex. Hertfordshire, Suffolk. By W. Whitaker - . - . 85 Index op Pi,aces, Authors, and Observers, By W. H. Dalton 90 LIST OF WOODCUTS. Page Fig. 1. Section in a Chalk-pit N. of Reed - - - - - 8 „ 2. „ „ N. of Barkway - - ■ - 8 „ 3.* General Section of the Great Pit S. of Ballingdon (Sudbury) - 14 „ 4. Section in a Chalk-pit E. of Sudbury - - - - 16 „ o.t General Section at Mr. Lines' Brickyard, E.S.E. of Hertford 20 „ 6. Section in Mr. Cornwell's Brickyard, Rye Street, Bishop's Stortford - - - - - - - 22 „ 7.t Section in a Pit at " Old Castle," Stansted Montfiohet - 24 „ 8. Section at the W. Part of the Brick-yard between Ware and Ware Park 35 „ 9. Section along a Roadway in the Brickyard, northward of fig. 8 35 „ 10. Road-cutting H miles N.E. of Thundridge (near " Barrack ") 37 „ 11. Railway-cutting just N. of the Bridge, Wenden - - 38 „ 12. Cutting on the SafFron Walden Railway, a mile N.E. of Audley End Station - - - - ■ - -39 „ 13. Railway-cutting E. of Harlow Station - - - 40 „ 14. Part of Cutting on the Colne Valley Railway, a mile N.W. of Yeldham - , - - - - - , - 46 „ 15. Section of Two Pits at the N.E. edge of Sudbury - - 54 „ 16. „ on the E. side of a Chalk-pit, about half a mile E. of St. Peter's Church, Sudbury - - - - 65 „ 17. Section in a Pit about three-quarters of a mile E. of St. Gregory's Church, Sudbury - - - 56 „ 18.* Section at Appleford Bridge, N.E. of Witham - - 67 „ 19. „ at Witham - - ... 69 • These are from the Quarterly Journal of the Geological Society. t These are from Vol. iv. of the Memoirs of the Geological Survey (1372). THE GEOLOGY OP THE N.W. PART OF ESSEX AND THE N.E. PART OF HERTS, ETC. CHAPTER I.— INTRODUCTION. Area. Sheet 47 of the Geological Survey Map represents an- area of about 840 square miles, chiefly in Essex (with the towns of Brainfcree, Coggeshall, Dunmow, Halstead, Saffron Walden, Thaxted, and Witham), but partly in Hertfordshire (Bishop's Stortford, Btintingford, Hertford, and Ware), partly in Gam- bridgeshire (Linton and Royston), and partly in Suffolk (Clare, Haverhill, Long Melford, and Sudbury). This tract forms part of the London Basin. Rivers. The rivers of the district are the Lea (between Hertford and Hoddesdon), with the following tributaries : — the Bib and Quin which, rising in the neighbourhood of Buckland and Barkway, join each other at Braughing, the united stream flowing south- wards into the Lea at Bengeo (Hertford) ; the Ash, rising in the neighbourhood of the Pelhams, flowing S.S.W., and joining the main stream below Ware; the Start, rising near Langley, Farnham, and Elsenham, flowing S.S.W. and joining the Lea near Hoddesdon, with the tributary Pincey Brook, which rises north of Hatfield Forest, and joins the Stort near Harlow. The upper part of the Boding, which river rises westward of Dunmow, and flows southwards beyond our district. The above drain into the Thames. The Blackwater, 28 miles long, rising, under the name of Pant, near Radwinter and Finchingfield, and flow- ing south-eastward to Feering, thence south-westward to below Witham, and finally eastward to the sea, with the following tributaries : — the Gann, 11^ miles long, rising east of High Roding; the Ghehner, 29 miles long, rising north of Thaxted and flowing S.S.E. with a tributary stream from Lindsell ; the Ter, 12 miles long, rising westward of Braintree, and also flowing S.S.E. ; and the Brain, Ouith, With or Pods Brook, 15 miles long, rising near Bardfield. G383. A 2 GEOLOGY OF THE N.W. PAET OF ESSEX, ETC. The upper part of the Golne, which rises near Birdbrook, with a tributary from near Gosfield. Some small streams that rise on Tiptree Heath flow eastwards and form the Layer Brook, a tri- butary to the Colne. The Stour (from Haverhill and Kedington, E.S.E., to below Sudbury). All the above streams flow southwards or eastwards, but the- head-waters of the Cam or Granta rising near Quendon, with the streams N. and E. of Royston, which run into its tributary the Ehee, and the upper part of its other tributary the Bourn, which rises eastward of Linton, flow northwards. Geological Divisions. The beds shown on the Geological Survey Map are as in the following table, in which the right-hand column gives the divisions coloured on the map : — r Kecent - - - . Alluvium. Pleistocene - rValley, or Post- J Kiver, Drift. Glacial ^ [_ Plateau Drift Glacial Drift Old r Briokearth, or loam. Gravel. Loam. Gravel. Boulder Ctey. Briokearth; Gravel and sand, with occa- sional Boulder Clay. . Preglacial ? - ' Pebhle-gravel. Pliocene . - Eed Crag. r . - London Clay. Eocene Lovper London Tertiaries -{ Reading Beds. Thanet Beds. Cretaceous - r Chalk. Gault. Of these the Chalk, either bare or covered with Drift, takes up the north-western half, and the London Clay, still more Drift-covered, the south-eastern, the Lower London Tertiaries having but a narrow outcrop between. The various divisions of the Drift cover by far the greater part of the district, the Boulder Clay alone occurring over more than two thirds of it. The gravels and sands beneath the Boulder Clay crop out mostly along the bottoms and flanks of valleys ; whilst the smaller tracts of Post-Glacial gravel, &c. in great part border the streams or their alluvial flats ; but there are also patches of " plateau- gravel " that seem to be of this age, and others of loam that clearly overlies the Boulder Clay. W. W. INTRODUCTON. Shape of the Ground. The highest ground within the limits of the map occurs near its northern boundary, where the range of Chalk hills slopes sharply to the north, overlooking the Cambridge Valley. Some points along this range reach a height of over 500 feet (TharfieM being 550). There is some high ground towards the centre of the district also, Thaxted being 324 feet above the sea. Although a part of the northern slope of the range comes within the area, by far the larger part of the Cambridge Valley is beyond our limits, and will be described in a Memoir to illustrate Sheet 51, S.W. The southern slope of the ground from the range of hills is much more gradual, and continues across the district with but little variation, except where carved out by the valleys. The range itself is in one part cut through by the valley of the Cam. At the S.W. corner of the district, between Hertford and Hoddesdon, the London Clay, mostly covered with Boulder Clay and gravel, rises to a fair height, and at the S.E. corner the range of Tiptree Heath (London Clay, with cappings of gravel) rises above the surrounding tracts, and makes a marked feature in the landscape. W. W. and W. H. P. A 2 GEOLOGY OF THE N.W. PAET OF ESSEX, ETC. CHAPTER 2.— CRETACEOUS BEDS. Gault. " The Gault occupies an area of only a fraction of a square mile in the western corner of sheet 47. It consists of a stiff blue clay, about 60 feet thick, and having at its base a bed of sand 3 feet thick, which rests on a water-bearing " rock " that forms the top of the Lower Greensand. A bed of phosphatic nodules occurs a few feet up from the base of the Gault, (see Appendix, p. 74), and the upper surface of the clay is very uneven, having been much eroded before the deposition of the overlying Chalk. W. H. P. Chalk. Although shown as one mass on the map, the Chalk'may here be described under the following heads : Chalk Marl, Lower Chalk, Chalk Rock, and Upper Chalk. No attempt has been made to trace the " zones " of Professor Hubert in this district, but I have been shown by Mr. Jukes-Browne, that they can be made out to the north, in Sheet 51, and a notice of them wiU therefore be given in the description of that map. W. W. Chalk Marl. Resting upon the eroded surface of the Gault is the bed known as the "Cambridge Greensand." It is, in reality, the glauconitic base of the Chalk Marl, into which it gradually passes ; it is seldom more than a foot thick, and in this area is always found at the junction of the two formations. About one- tenth of its bulk consists of fossils and phosphatic nodules, some 75 per cent, of which have been derived from the Gault, as re- corded by Mr. Jukes-Browne, who has carefully worked out the history of this bed, its fauna, and relations.* The deposit is, as its name implies,' a Mar], it is white, or rather very light grey in colour, and its thickness is about 60 feet. It is exposed in many sections near its basg, where the fossiliferous bed is dug out for the phosphatic nodules, or so--called " copi'olites," which it contains in such abundance. W. H. P. In the tract to the west the Chalk Marl is ended at top by a firm and somewhat sandy bed, known as the Totternhoe Stone ; but this has not been noticed incur district, though it must occur having been traced through the sheet to the north (51, S.W.) W. W. * Quart. Joum. Geol. Soc, vol. xxii., pp. 256-316 (1875). CHALK. Lower Chalk. This division forms the gently-slopiBg ground from the escarpment to the plain of the Chalk Marl. It is shown in many sections, chiefly quarries, in the harder beds, which are sufficiently compact to be used for building purposes. There is a great similarity in the texture and position of some of these beds, indicating the possibility of identifying them over larger areas, or even of correlating them with distant deposits. And this is borne out as regards some of the beds by the fossils they contain, and by which they are recognised as the equivalents of deposits that occur in Bedfordshire, Buckinghamshire, Wiltshire, the Isle of Wight, and other places in the south of England and on the Continent. The Lower Chalk occupies the area N. and W. of the dotted line on the map, which gives approximately the line of division between it and the Upper Chalk. Its thickness is about 300 feet, as ascertained from its outcrop and average dip, a result agreeing fairly with the recorded thickness of strata passed through in making a deep well at Saffron Walden. It has been erroneously asserted, and many calculations have been based upon the state- ment, that the boring for this well was entirely in Chalk. No doubt chalky matter from the upper part of the bore-hole got mixed with that brought up by the tool, and gave it a white chalky appearance, but Dr. James Mitchell has recorded that •' samples at 800 feet, blue when taken out, got whitish, and by muriatic acid were found to be clay with some calcareous matter."* This would probably be time of other portions also, and the boring almost certainly went through the Gault and down into the Oxford Clay. (See Appendix, p. 79.) In the chalk-pit IJ miles N. of Royston the following beds occur, all without flints, and dipping 4° E. : — Feet. Rubbly chalk - - - - 8 or 10 Hard white chalk, in blocks - - 2 Yellow marly chalk, much broken - 2 to 3 Hard white chalk, in blocks - - 2 White chalk, broken up - - - 6 At the lime-kiln about a third of a mile S.W. of Royston there is chalk with few flints, dipping 5° S., with Terebratula semiglohosa and Inoceramus ; and at the chalk-pit, i mile S.E. of that town, there is white chalk, 30 feet shown, rubbly at the top, the lower part tabular, with irregular lines of bedding and one thin layer of flint nodules, thrown down 1 or 2 feet in places by small faults. Dips slightly to E. or S.E. A pit J mile W. of Meldreth Station shows 3 feet of rubbly chalk over 5 feet of hard grey chalk (? Totternhoe Stone). At the chalk-pits S. of Melbourne the W. end of the W. pit gave the section below : — _, Feet. White rubbly chalk - - - - 5 Yellow „ dipping 4° W. by S. - 1 White „ • ■ - - I Tabular chalk . - - - 8 "• MSS., vol. ii. p. 102. For an examination of this valuable collection I have to thankiProf, Prestwich.— W. W. GEOLOGY OF THE N.W. PAKT OF KSSEX, ETC. In the pit a quarter of a mile S.W. of Duxford there is white chalk with much " slickenside," and in places with a thin marly layer. The pit half a mile E. of Great Chesterford shows 40 feet of white chalk, dipping E. 5° (?). About 18 feet from the top is a band of marl, 3 or 4 inches thick, not so light in colour as the chalk, and immediately above it some hard splintery chalk containing fossils (Peciere, TerebratuUna,B,ni Cidaris : the other species of the list are from below the marly band). A layer of flints occurs 5 or 6 feet below the marl. The peculiar striated or fibrous chalk is well shown in this pit, occurring especially around many of the flints, but only where these are in a vertical or nearly vertical position. [In this case the fibrous appearance is clearly not due to slickensides, but to structure, as it is not limited to the faces of joints, &c., but extends some little way into the mass of the chalk. — W. W.] W. H. "P. Other sections of the Lower Chalk will be noticed under the next heading, and a description of the lithological divisions that can often be made out in the Lower Chalk westward of this district may be seen in Vol. IV. of the Geological Survey Memoirs, pp. 42-46. The following list of fossils from the Lower Chalk has been compiled from separate lists furnished by Mr. Penning, the species in this and the other Chalk lists (pp. 9, 10) having been named by Mr. Etheridge. W.W. Fossils prom the Lower Chalk. 1ft Pit on B. side ol high road about a mile N. of Pit about a third of araile S.B. of Boyston Pit on B. side of high road nearly a mile N. of Pit 4 mile. N.of Barley. Pitli miles W. by S. of Ickle- Pit just B.of Great Chester- ford. Boyston. Church. Reed. ton. Otodus appendiculatus, Aff. - X Ptychodus, tooth — — — — — X BelemniteUa plena, Blainv. X Scaphites sequalis, Sby. - — — — X X Dianchora striata, Sby. - — X Gryphaea vesiculosa ?,Si2'- X Inoceramus, sp. X — — X X X Lima spinosa, Sby. . - — X Ostrea canaliculata, Sby. — — — — — X „ vesicularis, Lam. X „ sp. ■ — • — — — X Ehynchonella Cuvieri, D'Orb. — — — X Rhynchonella plioatilis, Sby. X — X X Terebratula semiglobosa. Sby. - X — X X X Terebratula, sp. — — — — — X ScalpeUum, sp. - — — — — — V Discoidea Dixoni, Fnrbes X Goniaster, ossicle of — — — — X Holaster planus Mant, • — — X Micraster cor-anguinum, Leske — X Micraster cot-ho\is,Forbes — — X Ventriculites unpressus, Smith — — -^ X Ventriculites mammilla- ris, Smith ~~' " ^^l X CHALK. Clialk-rocJc. The Lower Chalk ends upwards in a hard crystalline bed, frequently yellow and broken up into lumps 2 or 3 inches across, with a marly substance between them ; but the latter is probably a wash into the joints from the chalk above. This bed, or rather deposit divided into two crystalline beds with soft chalk between, has been described under the name of Ghalk- rock,* and is tolerably persistent from Wiltshire up to and probably far beyond this district, though, from the scarcity of sections, the outcrop cannot be accurately traced. It contains many fossils, Holaster planus being somewhat characteristic, and its upper limit is sharply defined ; it indicates a change in the conditions of deposit which, brief as it may or may not have been, was certainly considerable. The Chalk-rock divides the Upper from the Lower Chalk, but not the Chalk-with-flints from that without, as sparse bands of flint nodules occur in the chalk some way below the rock. Other bands are found nearly down to the Chalk Marl, indeed it is rare to see a chalk-pit in which flints cannot be discovered. There are to the S. of Royston a few sections of the Chalk- rock, which is not again-seen eastward until we get to the chalk- pit by Great Chesterford Park. W. H. P. These pits are interesting as showing a dip northwards, that is, down the escarpment, or .in the direction reverse to the regular dip, and gradually increasing from to a high angle. They are indeed along a line of flexure (see p. 11). The most westerly of them is close to the top of the escarpment, a mile north of Reed, and its section is shown in Fig. ] . The next is also just below the top of the escarpment, on the western side of the road, more than half a mile northward of Barkway Church, and in it the dip increases to about 60°, being well shown by four distinct layers (hard beds, marl, and flints) : this section is shown in Fig. 2. The third, only about 1.3 feet deep, is at the southern part of Smyth's End, just south of Barley, and gave the following section : — Boulder Clay, in a hollow on the north. Chalk, with fiints in layers 5 feet apart, dipping N. by W. 40° to 45°. Stained chalk just seen at the bottom at the corner, probably Chalk-rock (with Lima spinosa and Terehratula semiglobosa). ^ W. W. and W. H. P. The chalk-pit a quarter of a mile S.S.E. of Great Chesterford Park shows the rock, the section being — Chalk with flints, dipping slightly S.E. ; Yellowish crystalline chalk in lumps, m a marly matrix, a few inches to a foot. Rubbly chalk. , , ^ , , Hard crystalline chalk, passing down mto the bed below. Soft tabular chalk, with few flints. The top of the Chalk-rock is here very definite, though somewhat irregular and the bed contains many fossils and phosphatic nodules, as well as decom- posed iron-pyrites. " • "• ^' » See Geological Survei/ Memoirs, vol, iv. p. 46. GEOLOGY OF THE N.W.. PART OF ESSEX, ETC. Fig. \,— Section in a Chalk-pit N. of Reed, (Scale 25 feet to an inch.) a. Boulder Clay (at one part only), with hard crystalline "band beneath. b. Upper Chalk, with layers of flints, dipping N. 21°, and a marked layer of tabular flints(*). A Ventriculite was the only fossil found. rCream-coloured crystalline chalk, very fossiliferous (see c. unaiK-rocK. < g^^j compact chalk, 8 or 10 feet. l_Cream-coloured crystalline chalk, about 2 feet. d. Lower Chalk; with a layer of sparse flint-nodules at top, bent over from a nearly horizontal position to an angle of 5° N. Fig. 2. — Section in a Chalk-pit N. of Barkway. N. a. Whitish Boulder Clay ; occurs in a hollow at S.W. corner. b. Upper Chalk, with scattered flints. c. Chalk-rook. Hard cream-coloured crystalline chalk, irregular beds, 2 to 24 feet.thick. The chalk between with a thin layer of marl (^) and a broken-up layer of flint-nodules. d. Lower Chalk. (Inoceramus, Scalpellum, etc.) [When at these pits I was inclined to limit the name chalk-rock to the upper bed c. in Fig. 1, and to the lower in Fig. 2.— W. W.] CHALK. Fossils from the Chale-rock. Pit on B. side ot high road nearly a mile N. oi Reed. Pit i mile northwards of Barkaway Church. Pit IJ miles N.E. of Great Ctesterford. Fish teeth — — X Ammomtes prosperianus, D'Orb. — X Cypricardia Inoceramus - . . - Lima spinosa, Sby. „ sp. X — X X X Rhynchonella Cuvieri, D'Orb. - „ limbata, Schlot. „ Mantelliana, Sby. „ plicatilis, Sby. ? Terebratula oarnea, Sbif. „ semiglobosa, Sby, - X X ■ X X X X X X X X Ananchytes ovata, Leske Cidaris, spine Holaster planus, Mant. - - - Micraster cor-anguinum, Leslie X X X? X? X X Ventriculites mammillaris, Smith „ radiatus, Mant. - — X X Upper Chalk. A very large part of our area is occupied by the Upper Chalk, although it is to a great extent hidden by the Drift deposits. Beneath these it occurs over the tract of country between the outcrop of the Chalk-rock and the boundary of the Lower London Tertiaries, and it may be seen in many sections where the overlying strata have been denuded. It is more homogeneous than the Lower Chalk, and, even if sections were sufficiently plentiful, it is doubtful whether in a limited area it could be as easily divided into palseontological zones ; certainly they would be neither as numerous nor as definite as those of the lower division. The Upper Chalk is about 450 feet thick, judging from its out- crop and inclination, but only 268J /eet (the depth below the top of the division of a hard bed, 9^ feet thick) if it be the Chalk- rock met with in boring a well at Epping. It contains many layers of flint-nodules, and occasionally bands of tabular flint, which latter often fill the vertical and diagonal joints also, and sometimes cut across the bedding and through layers of nodules in a most irregular manner. The flint-nodules are black, with a white coating, the tabular flint is of the same colour, with its upper and under surfaces white also ; occasionally, as at Sudbury, it presents alternations of black flint and white partings, each 10 GEOLOGY OF THE N.W. PART OF ESSEX, ETC. in thin layers less than a quarter of an inch thick, the white suhstance being almost as hard as the black. The first three of the following sections are at about the horizon of the Chalk-rock ; but there is no stratigraphical evidence to show whether that bed is above or below them. In the chalk-pit N. of Tharfield there are few flints, but several small pipes of gravel run down into the Chalk. The i)it half a mile N.E. of the same village is also in Chalk with few flints, and in some of the gravel-pipes the flints are green-coated (derived from the base of the Eocene beds). In the pit N. of Great Chishall Church the lines of bedding dip apparently 25° N. by W., this being on the line of flexure already noticed. The pit N. of Little Chishall Church shows the thin edge of the Boulder- clay, with a hardened crystalline band of limestone at the bottom, over chalk, with layers of flint, tabular and in nodules, every 4 feet. About horizontal, and It) feet shown. Fossils from the Upper Chalk. Pit Pit just N. of Tharfield, Pit at Smyth's Pit itnile S.S.E. of li miles S.E. of Lirae-kiln imile-N. Pit E. of Newport Station. End, Barley. Wenden Lolts. Great Chester- of Saffron ■Walden.- ford. - Saurocephalus lancifor- mis, Harlan — X Dianchora striata, Sby. - X Inoceramus Cuvieri, Shy. — — — — X „ sp. - X X — — — X Lima Hoperi, Shy. — — — X „ spinosa, Sby. — — — X Ostrea — — — — — X RhjTichouella Cuvieri ?, D'Orb. X Rhynchonella plicatilis ?, Sby. - X Terebratula semiglobosa, Sby. - ■ X Scalpellum X Ananchytes ovata, Leske X — — — X Cidaris sceptrifera, Mant. — — X „ serrifera, Forbes — — X — X Goniaster, marginal plate - - - — X Mieraster cor-anguimim, Leske — — X X X Mieraster cor-anguinum, var. gibbus — — * — ■ — X Sponge, new, allied to Etheridgea X Ventriculites impressus, Smith — — — — — X Ventriculites quincunci- alis, Smith — — -"- — X Ventriculites, sp. ~ " X CHALK. 11 At the pit half a mile S.S.E. of Wenijen Lofts there is at the S. end a thin edge of the Boulder Clay, in a slight hollow, beneath this a thin bed of brown loam, and beneath this again the hardened crystalline band, 3 inches thick, which sometimes occurs at the base of the Boulder Clay. The white chalk has horiz'ontal bands of flint-nodules ; and a thin band of tabular flint runs diagonally across the bedding and through a nodular layer, at one point inclined thereto at an angle of 11°. At one part the tabular layer is wanting, but there are, just above the gap, several pieces of similar fiint (in all about equal to the missing portion), arranged in a nearly vertical direction, the effect probably of some disturbance.* The pit li miles W. of Littlebury shows 24 feet of chalk with flints, with, in some places, a thin band of yellowish chalky clay. -About 15 feet from the top, there is a horizontal bed of fine yellow sand, chalky and very finely laminated', 2 feet thick, and about 10 yards in length. This is probably a branch from a large pipe. The pit E. of Newport Station is in chalk with flints. A very persistent horizontal layer of tabular flint is in one part thrown down 18 inches by a fault, and two large pipes of gravel stop at this layer. At Sudbury the uppermost beds of the Chalk are largely worked, under- neath the Tertiary beds (s6e pp. 13-17) : they contain few flints and compara- tively few fossils. Line of Flexure. As a rule the Chalk lies very evenly, being either horizontal or dipping slightly to the S.E. But S. of Koyston there is a very definite line of flexure which may be traced, by various pits above described, for a distance of 5 miles along the line of escarpment, when tlie Chalk again assumes its level condition. This line of disturbance is a curve ; it begins near the high road 2 miles S. of Royston, passing through the chalk-pits shown in Figs. 1 and 2, sweeps round Smyth's End, where the beds are again seen in the highly-inclined position (p. 7), and then runs N.E., by the pit just N. of Great Chishall (p. 10), which, however, is probably not quite on the line of greatest disturbance. The flexure appears to have been very local, and of no great vertical extent. It occurs so near the top of the escarpment that all evidence of the lower part of the curve seems to have been obliterated by the denudation of the range. Still as there ' are no signs of Upper Chalk, but Chalk without flints occurs in all exposures at a lower level, it is probable that just below the level of the pits the beds begin i;o resume their horizontality. W. H. P. * Like the broken and displaced flint-layer near Berkhampstead, described in Geological Survey Memoirs, vol. iv. p. 53. 12 GEOLOGY OF TEE N.W. PART OF ESSEX, ETC. CHAPTER 3.— LOWER LONDON TERTIARIES. Thanet Beds. During the progress of Geological Survey in ] 873 the presence of Thanet Sand along part of the northern edge of the London Tertiary district, on the borders of Essex and Suffolk, was established. Before that the possibility of its occurrence in North Essex had been alluded to, but with doxibt, by Prof Prestwich.* It consists of a fine compact sand, with a very slight admix- ture of clay ; and at the bottom a more clayey bed, coloured green by glauconitic grains, and with green-coated flints derived apparently from the Chalk, by a process of slow dissolution of that rock ;t and therefore its character here is the same as in Surrey, "West Kent, and South Essex, and it is not like the more local fossiliferous beds of East Kent. This division seems here to occur at the expense of the over- lying Reading Beds, which are very thin, and there is most likely a continuous mass undergi'ound from this outcrop to that in South Essex, &c., many deep wells in the tract between seeming to pass through Thanet Sand (see Appendix 1). Both the Thanet Sand and the Reading Beds are here so thin and so hidden by Drift that they could hardly be everywhere separated on the " one-inch " map, and consequently the former has been included with the latter. It is first seen a little east- ward of Gestingthorpe, whence the boundary-line, winding along the right flank of the- valley towards Sudbury, is for the most part hidden by the Glacial Drift that covers nearly the whole district. From Balingdon it can, however, be clearly traced along the right. bank of the Stour to below Middleton, when it is lost under the gravel and marshland. On the other side of the Stour the boundary is somewhat vague, being hidden by the gravel-flat, south of Great Cornard, when it is fairly traceable along the flank of the valley past Sudbury, though partly hidden under Drift, until beyond St. Bartholomew's it is wholly masked by the Boulder Clay. Beyond this it is not to be seen for some miles (in Sheet 48, N.W.). It is possible that the green claj'ey bed at the base of the Eocene Series northwards of Bishop's Stortford may belong to this division of the Lower London Tertiaries rather than to the Reading Beds ; but as this is uncertain it will be more con- venient to describe it under the last head. Eastwards however of our district, near Ipswich, the similar bed does belong to the Thanet Sand, with little doubt. * Quart. Journ. Geol. Soc, vol. viii. p. 241 (1852). Ibid., vol. x. p. 92 (18.54). f For a fuller account of this peculiar bed see Geological Survey Memoirs, vol. iv. pp. 55-60. THANET BEDS. 13 The first sign of this division that I saw, beginning at the west, was about half a mile north-eastward of Gestingthorpe Church near the bottom of the lane to Hill Farm, where a little of the pink sand universally found at the bottom of the grey and buffi sand in the neighbourhood of Sudbury was shown over the clayey green sand of the base-bed, at one spot only, there being Drift elsewhere along the lane. At the cottage on the road to Bulmer a little north of this the sand was found (see p. 23). At the old chalk-pit, marked on the Ordnance Map, three quarters of a mile west of Bulmer Church, the general order of the beds is as follows : — TBoulder Clay, mostly pale, but in parts darker, some feet. P, „i n "W-J Chalk-rubble, with a layer of the dark-green sand from the uiaciai unn< „ ^^^^ ^^^ „ ^^^^ ^^^ bottom, from to 2 feet. l^Brown loam with stones (replacing the above). "Fine pinkish loam (sometimes resorted and with stones), from to 3 feet (at the western end only). Thanet Beds-^ Base-bed. Dark-green sand, with brownish lumps ; a few green-coated flints at the bottom in parts, from to 14 feet, resting fairly evenly on the Chalk. Chalk with a few flints ; a tabular layer of flint, mostly thin, within 2 inches of the foot. At the northern part of the pit there is only a little Boulder Clay over the Chalk ; the southern and highest part is mostly hidden by talus. At no part perhaps are all the beds to be seen together. On the lane from Balingdon to Bulmer Ohurch, and just out of the former village, there is a cutting on the southern side which, though overgrown, shows the sand, capped in parts by a little of the Reading Beds and with Chalk below, the junction being irregular. The windmill just west of Balingdon is on a small outlier, barely separated from the main mass, and forming a slight mound. The fine compact Thanet Sand may be seen on the road close to the mill, with Chalk lower down on the east, whilst at the top there seems to be a little sharp Drift sand (on the road west of the mill). At the hedge immediately beneath the mill (between it and the road), I saw the reddish bottom part of the sand, underlain by the upper dark green part of the base-bed ^about a foot thick), and then the lower part, partly pale green or yellowish, but mostly ferruginous, especially at the bottom, and this I dug to a depth of over 3 feet before touching Chalk, the junction with which must be wavy. The old chalk-pit southwards of the mill seems to continue eastward to the brickyard, but it is overgrown. At the mill the upper part of the pit is in Thanet Sand and the lower in Chalk, but the junction could not be seen. Towards the road above mentioned there is, over the fine Thanet Sand, a little coarse gravelly sand, ferruginous, and with a good many flint-pebbles at the bottom part, which is suggestive of Crag. The old chalk-pit marked on the Ordnance Map on the eastern side of the high road just S.W. of Balingdon was mostly overgrown when I saw it, but the following beds were to be seen:— a little very coarse gravelly sand, ferruginous and pebbly at the bottom (? Crag) over some 6 feet of Reading Beds, over Thanet Sand, over Chalk, all being even and flat. My notes of this section are incorporated in the account of the next, which is close by, at the very large pit south of Balingdon, on the road to Middleton, where the perfect succession from the London Clay to the Chalk is shown, the general section being as in Fig. 3, p. 14, but the highest beds occur only at the eastern and disused part. Close to the above, divided from it indeed only by the road to Middleton, and connected with it by a canal-tunnel, is another large old chalk-pit. It is overgrown, and for the most part turned into a shrubbery and wilderness, but Thanet Sand is to be seen at the top, and at the highest part, close to the road, a small pit was open in this, with indications of the Reading Beds. This old pit joins on to that supplying the large brickyard on the east (" The Grove "), where a little of the pink sand and of the green base-bed are cut into in parts, over Chalk, though nearly the whole section is in various beds of Drift (see pp. 57, 70). 14 GEOLOGY OF THE N.W. PART OF ESSEX, ETC. Fig. 3. — General Section of the Great Pit S. of Balingdon (Sudbary). 1873.* Scale 8 feet to an inch. Brown and dark grey stifp London Clay, with race, slipping much ; a few feet. I could see no sign of basement-bed. Feet. Reading Beds. ■ -" ." - '. ■' -' Thanet ' Beds. 'b. Blackish sandy clay and clayey sand - - - c. Pale greenish-gTsy red-mottled bedded sandy clay, the red mottling chiefly in the upper part ; the bottom part (with green grains) fills wee tubular holes in the underlying bed d. Buff and pale grey, fine, soft, and slightly clayey sand, firm and bedded. The bottom 3 feet or so (d') of a pinkish tinge, the lowest 6 inches {d") of a deeper colour, and harder ; a slight inteiinixture of this with the top of the next bed for 3 or 4 inches - about /. Chalk, with a thin layer of tabular flint, x , of alternate black and white layers, at 12 e. Clayey greensand,t very bright- coloured at top, with green-coated flints at the bottom (some large), and a few higher up - about 2 top it other flints rare - to water. The beds are even and flat, or with a S.S.W. dip (up to 3°). * From Quart. Journ. Geol. Sac, vol. xxx. p. 402. Kindly lent by the Council of the Geological Society. t This bed was noticed by W. Smith in his " Geological Map of Essex," (1820) as " Greensand, called Devil's Dung," which name is still used in the neighbourhood. t This layer was also noticed by W. Smith in his " Geological Map of Suffolk " (1819) as follows :— " Chalk, covered with a Floor of Stratified Flint." THANET BEDS. 1-5 . On the southern side of the lane a quarter of a mile N.N.E. of Middleton Church an old-overgrown pit shows a little gravel and loam, over a little of the reddish sand, over the green clayey sand, over Chalk; the pit has reached further westward (or there has been another close by), and in the ditch at the junction of the roads, the junction of the Chalk and the Thanet Beds is shown. In another overgrown pit about the same distance eastward of Middleton there is Thanet Sand at top. On the left side of the Stour the Thanet Sand extends, chiefly under Drift however, a little way into the next sheet (48 N.W.), but as the few sections are near the margin it will be convenient to describe them here. The railway-cutting a mile south-westward of Little Cornard must have given a fine section of Drift and older Tertiary beds ; but it is now turfed over, and therefore hard to make out, especially as the beds seem to be very irregular. Just south of the bridge the order seems to be. gravel over clay, over sand (with loam and clay), and the clay seems to thin out southwards, but it is hopeless to make out anything clearly. On the otkev side of the bridge Boulder Clay, with brown clay beneath go down to the bottom. On the eastern side at the highest part of the cutting the succession seems to be — C Gravel. Glacial Drift < A little Boulder Clay. I Brown clay, with a little coarse sand at the bottom. Fine light-coloured clayey (Thanet) Sand. On the opposite side there is red-mottled clayey sand (Reading Beds) above this last, and these reach nearly to the top of the cutting. At the northern part I saw only the fine Thanet Sand, sometimes capped with red-mottled sandy clay. Northwards to Great Cornard the beds are hidden under valley gravel. East of Sudbury is a line of chalk-pit, beginning more than a quarter of a mile north of Great Cornard Church, and running thence north-eastward for nearly half a mile. It is now mostly abandoned, part being orchard, but at the southern part the beds could be seen, and towards the other end the chalk was worked in (1873). The perfect succession of beds is given below, but the whole of them are not present at one spot ; the Boulder Clay often resting on the Thanet Sand, having cut through the beds above, and at the southern end lying on the Chalk ; sometimes, too, there is none of it. There are signs of a slight easterly dip. riapial f-P*^^ Boulder Clay, lying irregularly on the beds below. 1-) -fj. "1 Coarse brown ferruginous bedded sand, with layers of ironstone ■ L and a few gravelly layers. Reading Beds. — Light-grey sand with layers of Clay; the bottom part greenish and clayey up to 6 feet. 'Buff and pale grey, fine, soft and partly clayey sand, the bottom 3 or 4 feet with a pale pinkish tinge, darker at the lowest 6 inches ; bedded, compact, and weathering like a soft stone ; with a few small nodules of decomposed iron-pyrites; nearly 15 feet. Clayey greensand, brightest at top; a few green-coated flints, mostly small at the base (? some pebbles) and a few higher up ; from li to 2 feet. Chalk with a very few flints. A thin layer of tabular flint at the top. At parts this layer was seen to follow exactly the slight waving of the junction for some yards. On the other (northern) side of the road, just before getting to the northern end of this section, a small pit showed Thanet Beds and Chalk; there being but little of the former, the junction was pipey. On the southern side of the road passing by the cemetery, east of Sudbury, where the lane turns off to the old pit above noticed, there was a small pit showing Thanet Sand and its base-bed, below which Chalk had been got. At the chalk-pit forming the northern part of the pits belonging to the old brickyard, a little westward, there is at top a little of the pinkish loam over the green base-bed, which is about 3 feet thick, with large green-coated flints, and rests evenly on the Chalk. At the entrance to this chalk-pit, however, the Thanet Beds sink suddenly and sharply, appearing to have been dragged down Thanet Beds. ■ 16 f-H lo y: ro u^ ^ THAKET BEDS. 17 with a mass of Glacial Drift that comes on southwards, and to the descrip- tion of which the reader is referred for details (see pp. 63, 65, and fig. 16.) The sand is also shown in the southern part of this series of pits, at the edge, by the footpath which divides it from the clearer section next to be described. The chief face of the chalk-pit just out of Sudbury, on the northern side of the road to Great Cornard, shows an even and flat junction with the Chalk, and also a mass of Boulder Clay and sand, which latter may belong to the Red Crag, above the Thanet Sand. My colleague, Mr. Penning, has favoured me with the drawing of this section represented in Fig. 4. There were slight variations in the uppen part of the section when I saw it on later occasions. The sides of the pit slope towards the river, and along them there is a good deal of wash at the top which thickens lower down, and, towards the road, attains the dignity of a Valley Drift, consisting of stony loam with a httle gravel at bottom in parts. At one part, on the western side of the pit, there is a hollow of the green sand divided by about half a foot of chalk from the tabular layer of flint. On the road east of Sudbury, before getting to the cemetery, the Thanet Sand may be seen with Boulder Clay above. The junction with the Chalk was clearly shown iil the pit at the Victoria lime-kiln and in another pit close by, on the S.E. side of the road to Chilton Hall, just outside the town, and on the other side of the valley in the Alexandra Chalk-pit, and in some smaller pits a little nearer the town. Details of these will be given in the description of the Crag and the Drift ■ (see pp. 31, 52-66). The base-bed was again seen over the Chalk in a pit just southward of the waterworks, on the north of the town, but here also the Drift is the most notable thing in the section (see p. 52). The chalk-pit just above the windmill and about a quarter of a mile W.N.W. of St. Bartholomews shows a few feet of loam and marl (not accessible) over the green base-bed, 2 feet thick, over the chalk. On the other side of the hedge (north) is a smaller pit than the last two. W. W. G383. 18 GEOLOGY OF THE N.W. PAET OF ESSEX, ETC. CHAPTER 4.— LOWER LONDON TERTIARIES— (continued). Reading Beds. This division of the Lower London Tertiaries consists, in our district, of mottled clay, sand, and loam, in varying proportions, and rarely reaching a total thickness of 40 feet. The component beds often pass into one another, and they are all linfossiliferous, except for the occasional occurrence of Ostrea Bellovacina in the green sand overlying the Chalk, vfhich bed, however, may per- haps rather belong to the Thanet Sand (see p. 12). The boundary runs irregularly from near the S.W. corner of the map, near Hertford, to near the N.E. corner, near Sudbury; but it is mostly hidden by Drift, and therefore uncertain. Where, however, there is an outcrop, a fairly marked feature is usually made. A description of the Reading; Beds in the Hertfordshire part of sheet 47 (from Hertford to Bishop's Stortford) has already appeared in the Geological Survey Memoirs,* and this description will be reproduced, with some revision, in the following pages. Main Mass, South of Hertford there is no outcrop to be seen, on account of the Boulder Clay that spreads up the gentle slopes of the hills. Thence to Amwell the Reading Beds are hidden by Glacial Gravel, those two deposits having almost the same boundary- line, near the top of the sharp slope that forms the right bank of the Lea. Southward to Hoddesdon the outcrop is somewhat vague, and then this series is hidden by the Valley Gravel. The Reading ■ Beds reappear on the other side of the Lea, above the Stort valley, and then the outcrop runs at first north- wards along the flank of .the valley of the Lea for about two miles, when it turns eastward, and runs with a generally N.N.E. course along the left side of the Ash for about 10 miles, the narrow outcrop being however much hidden by Drift. The boundary-line then turns, and crossing the county- boundary (between Herts and Essex) for a short way, runs nearly south to Bishop's Stortford, the outcrop extending through, and a little soutli of, that town, and returning northwards along the other side of the Stort, and its tributary from Elsen- ham, the beds being however much hidden by Glacial Gravel. From Elsenham eastwards the Reading Beds are hidden under the mass of Boulder Clay for many miles, and their boundary- * Vol. iv, " The Geology of the London Basin," Part I,, pp. 227-232, 238 (1872). READING BEDS. If) line is therefore doubtful until they reappear on the east of Gestingthorpe, whence this line, partially hidden by Drift, closely follows that of the Thanet Beds along the flank of the hills and the valley of the Stour, again to be lost under Boulder Clay for many miles beyond Sudbury. At the kiln half a mile south-west of Rush Green, near Hertford, there is London Clay in an old overgrown pit close to and east of the house. The present pits are north-west of the house, and give the only good section in the neighbourhood, the beds being ag in Fig. 5, p. 20. An old chalk-pit in the small wood just north-west completes the section, and shows the following beds : — Glacial Gravel, a few feet. rSand, with flint pebbles scattered at the bottom, where I there are also oyster-shells here and there. Reading Beds. ■{ Flint-bed, about a foot thick, many of tlie flints large : in I parts with a thin blackened clayey layer at bottom : [ resting irregularly (with a waved junction) on Chalk with flints. In the road-cutting about a quarter of a mile south-eastward from the Hertford Union a little sand and the flint-bed are shown between the gravel and the chalk, and in .the chalk-pit just north the flint-bed is again to be seen in the same position. In a small pit in a hollow a little southward of the New River Head, the sand and the flints were found below gravel, and along the sharp slope just east of the house at Amwell Bury I saw here and there fine sand) most likely belonging to the Reading Beds, just over chalk, whilst above, the gravel comes on at once. Whether the sand at Amwell is an outlier or not is hard to say, but if not quite must be almost so. The only section of it that I siw was in an old pit (marked on the Ordnance Map) on the western side of the high road and south-west of the church, in great part filled up, but showing the following beds : — Gravel, 8 feet or more. r Light-coloured fine sand, mostly white or nearly so ; with Reading Beds, J a few thin clayey lines, showing the bedding, and in the about 20 feet. 1 lower part two lines of scattered flint-pebbles. L Layer of flints, many large. Chalk. In the hollow about half a mile north-east of Little Amwell Church the remains of a " chalk well " showed sand and clay of the Reading Beds, as also did a ditch a little to the east. " In an old pit at the road-fork S.E. of Stanstead Abbots there is London Clay (2 or 3 feet) on grey sand."* The following succession of beds was made out from a deep overgrown ditch down the hill about half a mile north-eastward from St. Margaret's Railway Station : — Irregular wash of gravel. ("Mottled clays, mostly sandy; some thickness. u A- n A J ^ ^***^^ sand, and lower down — • Keading Jieas.-^ g^^^^^ ^^^.j^ ^ broken line of pebbles close to the bottom. L Green-coated flints, 6 inches. Chalk, The clayey Reading Beds throw out water from the gravel that caps the hill. A little N.N. W., at a small gravel-pit, the variously coloured and partly sandy clays again occur beneath the gravel ; and at an old pit just north (marked on * From Mr. Penning's notes. B 2 20 GEOLOGY OF THE N.W. PART OF ESSEX, ETC. Fig. h.— General Section at Mr. Line's Brickyard, E.S.E. of Hertford (1869). Scale 8 feet to an inch. [0^^iy!^Mi^ fe?4gsssga^^^5a?!\ ii^Hit^l a. Small pipes of gravel in parts. 6. Thin wash of London Clay, with flints and pebbles, chiefly at the N.W. end. "c. Dark brown clay ; very little, and at the S.E. end only. d. Basement-bed. Brown bedded sandy clay and (in lower part) clayey sand, with thin layers of clay. Green grains here and there, and small ferru- ginous concretions, in one of which I found an im- pression of a bivalve. At the bottom a layer of black flint- pebbles (e) - - about [The above was a long section ; its con- tinuation downwards was from smaller pits just below.] y- " Feet. 12* m be a - 2to3 OtoU 2 to 3 Pale grey land brownish sand and clay, irregularly 'resting on, or passing down into, very pale greenish ochreous clay if') . g. Pale lilac firm fine sand thinning out at the N.W. ft. Purple grey red and brown mottled clay, in part sandy j passing into the bed below - i. Pale grey sandy clay with some small flint-pebbles ; passing into the bed below - nearly k. Light-grey sand streaked with brown, false-bedded ; with an interrupted layer of sma.ll flint-pebbles close to the top (or more) I. Flints (some large) and flint- . pebbles in sand, touched at bottom. Chalk. 16 _m, This section differs so much from that published by Mr. Prestwich in 1854, as from the same place, or close by, that I have been led to suspect some accidental error in his account (? from misplacement of the section). The diff^erence seems too great to be accounted for by variations in the beds, although there were differences in the various pits at the time of my visit. The older account is as follows* : — Feet. Basement-bed of the London Clay, with casts of Panoptea ("Light-greenish sand I White or ash-coloured sand Beds -i J'jght-ysllow' sands 31 feet. Chalk. Light-coloured mottled red and grey clays Yellow sand with Ostrea Bellovacina in places at its base Green-coated flints - . . . . 6i 4 6 4 10? 6? 1 Quart. Journ. Geol. Sac, vol. x. p. 92. READING BEDS. 21 the Ordnance Map) then only clear in parts, the section was as follows (in 1869), the Reading Beds being however inaccessible : — Feet. Gravel, in parts with a wash of loam, &c. - - about 6 TGrey and red clay, seemingly sandy, 1 and passing down into the bed below - 1 to 3 Reading Beds.«^ Grey sand, stained brown at top - - 4 to 6 or more. I Green-coated flints, resting unevenly on L the Chalk. Chalk with .flints. W. W. _ In the road-putting south of Widford Railway Station the following succes- sion was seen, but no measurements could be taken : — r Grey Boulder Clay. Glacial Drift, j f ^Boulder Clay. L L Gravel. Reading Beds. Fine light-green sand, from a foot to 3 feet thick, the lower part clayey, with green-coated flints. Chalk. In a section along the western side of the road east of Hadham Mill, Boulder Clay, Gravel, and Reading Beds are cut through to the Chalk. A pit a quarter of a mile east of Hadham Mill gave the following section, the Reading Beds being cut off towards the valley (westward), so that the gravel then rests on the Chalk : — Gravel and Sand (Glacial Drift) chalky at the bottom,? 20 to 30 feet. r Light-brown clay, with race, a foot. Reading Beds, j Light-green fine sand, the bottom part somewhat clayey, L and with green-coated flints, 3 feet. Chalk. Just east of Hadham Ford another pit showed a like section. [This was cut further back at the time of a visit, with Mr. Penning, in 1873, from a note of which I have made some addition to the former account, in Vol. IV., p. 229.— W. W.] Glacial Drift, gravel, and sand, 8 feet. 'Fine white sharp sand, a few inches. Mauve-grey sand, 12 to 18 inches. Reading Beds.'^ Layer of flint-pebbles. Pale greenish fine soft sand ; here and there a pebble, and t_ at the bottom green-coated flints and pebbles, 8 or 9 feet- Chalk, with horizontal layers of flint about 8 feet apart. At the neighbouring brickyard white sand occurs beneath the basement-bed. of the London Clay (see p. 28). In an old pit by the road leading to a farm half a mile • north-east of Little Hadham, sand and pebbles occur on Chalk, but the section is overgrown. Mr. Prestwich has noted the following section (now bidden) at Patmore Heath.* :— Feet. Brown clay and gravel ... . i Mottled red-brown and grey sandy clay - . -2 Ash-coloured sand, with seams of brown clay and a seam of flint.pebbles - - - . - - 2^ Flint-pebbles in light greenish-grey clay - - 1^ The Chalk crops out about 6 feet lower. In a pit at the south-western corner of the wood, a quarter of a mile east of Patmore Heath, loam and pebbles cap the chalk. * Quart, Journ, Geol. Soc, vol. x, p. 92. 22 GEOLOGY OF THE N.W. PART OF ESSEX, ETC. In another chalk-pit on the eastern side of the road, half a mile north of the same place, there are traces of the Reading Beds at top, and they were seen in a ditch on the higher ground a few yards further back. At Bishop's Stortford there are three brickyards near together in Rye Street. The following notes were taken in 1877, when the pits had been cut further back into the hill than was the case when the earlier notes of two of those pits were made.* The most northerly brickyard is Mr. Cornwell's, and this gave a good section for a length of more than 50 yards, a part of which is shown in Fig. 6, the beds o and A occurring only on the souths and the lowest bed being -touched on the north. In the description of this and the other two sections the same letters have been used for the same beds. Fig. 6. — Section inMr. Cornwell's Brickyard, Rye Street, Bishop's Stortford, 1877. Scale 25 feet to an inch. Reading Beds. 'a. Very fine light-coloured evenly-bedded sand b. Grey sandy loam, with a few flint-pebbles and many nodules of bright red ironstone in all stages of decomposition - - - - . c. Fine light-coloured false-bedded sand; d. Pebble- bed, like b. ; e. Fine sand ; /. Pebble-beds. ■^ All these are false-bedded, at an angle of about 12*^, and rest irregularly on the bed below : up to about g. Grey sandy loam, with a thin bed of clay g', about the middle, above which it is mottled with deep red patches : clayey at bottom - . . - h. Brown clay, with green-coated flints and pebbles i. Chalk with flints, the top few inches stained yellow {Belemnitella mucronata.) 10 17 1 The pit in Mr. H. Glasscock's brickyard, just south, gave the following section : — Brown Londoil Clay, 5 feet. J a. to /. represented by mauve sand (the same as in Mr. . Dickenson's brickyard), in one place only, up to 2 feet. Beds . I g. Grey sandy loam as before, the upper part mottled j not L bottomed. * Geological Survey Memoirs, vol. iv. pp. 230, 231 (1872). READING BEDS. 23 The pit in Mr. Dickenson's brickyardj just south of the last, sho-yved — Feet. Brown London Clay ------ 10 'a. to/, are represented by a bed of very fine light- mauve sand, (lenticular patch) - - - to 3 g. Grey sandy loam, with a thin bed of clay about Reading J the middle, above which it is mottled with deep Beds. ' red patches. (Impressions of shells, are said to occur in this) - - - - - 15 '. Brown clay ----- 4 „ „ with green-coated flints and pebbles 1 to IJ Chalk with flints. In these three sections the surface of the grey mottled loam is very irregular, having been probably denuded by the currents to which the falsfe-bedding of the overlying sands and pebble-beds is due. In the southern pit the London Clay rests directly on the mottled loam (except where the lenticular patch of mauve sand intervenes), and the sands and pebble-beds above the loam in the northern pit are most likely the remaining portion of a narrow ridge which does not extend far in any direction. They probably thin out beneath the London Clay, which comes on just above the pit. The mass of loam is sandy throughout, except towards the bottom, where it is more clayey, and in all the sections it has a thin band of clay, with small patches of sand about the middle. Below this there is no mottled staining, it having checked the water charged with salts of iron (derived from the decom- position of the ironstone nodules) in its downward percolation. The brickyard just south-east of the Nonconformist School, at the same town, gave the following section : Feet. Soil and wash - - - - - - -2 London Clay, brown and tenacious, passing into the bed below - 2 ("Whitish rather clayey sand, passing down into the [? Basement- next bed - - - - - 3 bed of London <, Whitish clayey sand. At one part near the base Clay. — W.W.] I 2 inches of very dark sand, with race and an I occasional flint-pebble - - - - 9 j Green finely bedded sand - - - 2 I Whitish clayey sand - - - - 7 Reading Beds ^ Brown clayey sand - - - - 2 Dark green clayey sand - - ■ - •■4 LHidden by slips, &c. - - - - 3 ? Chalk. The sands are generally laminated, some very finely, and all the beds pass into one another without any definite line of separation. In a pit at the corner of the wood at the north-eastern end of Stansted Park, about half a mile east of the castle, the following beds are shown : — T. J- r> J r Mottled greenish and yellowish clayey sand, 8 feet. Readmg Bedsj p^^^^^ -^ brownish clay, 9 inches. Chalk with flints. A pit at the " Castle," Stansted Montfitchet, gave a good section, with a small fault, as in Fig. 7, p. 24. . W. H. P. From Elsenham we have seen nothing of the Reading Beds for a distance of nearly 18 miles, when they again appear at Gestingthorpe. Here I found a little green sand [? bottom-bed] underneath the Drift in the small valley N.W. of the church, and at the brickyard the top of the series is touched in one of the pits (see p. 28). In the garden and old pit at the cottage on the road to Bulmer, about two thirds of a mile N.E. of Gestingthorpe Church, the following section was got, chiefly by digging, as the shallow pit is overgrown : — C Light-coloured sand, at the highest part. Reading J Pale green clayey sand, shghtly mottled red. Beds. I Light-coloured and pale green sand with a layer of clay, L greenish at the bottom. Fine buff and grey Thanet Sand. ;24 GEOLOGY OF THE N.W. PART OF ESSEX, ETC. N. Fig. 7.— Section in a Pit at " Old Castle," Stansted Montfitchet. (Scale 16 feet to an inch.) X Fault, downthrow 5 feet. a. Soil. h. Gravel and sand (Glacial Drift) - . - - "c. Green sand mottled red d. Green loamy sand e. Dark sandy loam with occasional pehbles and a thin white clay-layer /. Green sand, slightly mottled yellow J. Thin layer of green-coated flints. Chalk with layers of flints at regular intervals. Reading Beds < Feet. up to 20 ito 4 2 to 3 to 3 The London Clay is touched in a ditch on the south, and a little higher. Beyond this nothing is to be seen for some way, except for some indistinct signs in the valley S.W. of Bulmer. There are signs of the Reading Beds' along the lane nearly a mile eastward of Bulmer, and they are shown, above the Thanet Sand, in the sections at Balingdon, (pp. 13, 14), where their thickness is very small. In the fields on the slope of the valley about a quarter of a mile south- eastwards of Middleton greenish red-mottled sandy clay (Uke that in the Balingdon section) is ploughed up in places, whilst higher up there is a brown loamy soil with flint-pebbles (the basement-bed of the London Clay). At the north-eastern corner of the small wood half a mile south-east of Mid- dleton there is again a little of this clay, whilst in the field just west the ground shows unmistakable signs of the outcrop of a sandy pebble-bed, which seems to have been dug for gravel, as there is a trace of a pit just below where the London Clay comes on. Close by, at the western edge of the wood, there is some sand, which must come between the pebbles and the mottled clay. I know of no other sign in this neighbourhood of such a bed as this mass of flint-pebbles, which must be a very local patch, rising up.in a hillock, and may represent the Oldhaven Beds, the comparatively local series between the London Clay and the Reading Beds, in which case this is theflrst record of their occurrence along the northern edge of the London Basin, the local outcrop at Ipswich not halving been described. Southwards the Reading Beds are hidden uiidei: the Valley Gravel; but they reappear a little way up the short tributary valley from' Great Henny, on the northern side of which green and red mottled sandy clay (the same as that of the BaUngdon section) was seen in two field-ditches on either side of the lane that crosses the valley westward of the high road, whilst on the high road itself the same occurs immediately bordering the stream, with the higher bed of black clay above. READING BEDS. 25 On the other side of the Stour the Reading Beds are' touched in the railway- cutting south-westward of Little Cornard and at one part of the large pit north of Great Cornard Church {see p. 15). The only sign of the Reading Beds from Sudbury northwards is in the lane about a quarter of a mile north of St. Bartholomew's, where a little greenish red-mottled clay and sandy clay may be seen : a small spot bare of Drift, which hides everything on the east for a long way. Outliers. In the western part of the district there are a few outlying- masses of the Reading Beds, wholly cut off from the main mass, that show the former extension of the beds over the Chalk, from oif which they have been removed by denudation to a very great extent. It may be noticed that four of these outliers are roughly in line, from W.S.W. to E.N.E., the spur of the main mass N.N.W. of Bishop's Stortford being also in the same alignment.* Sacomb. — This outlier is much hidden by Boulder Clay, which makes the boundary doubtful. " The road nearly half a mile east of Sacomb Pound gives a section of about six feet of mottled clay and sand, with two lines of pebbles; higher up, where the rise is sharp, London Clay may come on, but if so it is concealed by the Boulder Clay over the high ground. "f At the bottom of the Reading Beds there are green-coated flints. Colliers End. — The larger outlier here, also mapped by Mr. Bennett, is in like manner covered by Boulder Clay ; but there is one good section, which I saw in good order ; it is given by the pit at the kiln, on the northern slope of the side-valley just south of the village . and east of th« high road, which showed the following beds in 1869 : — Feet. "Brown clay with race, especially in one layer . .... 8 Black clay ----- about 3 Light-coloured clay and red mottled clayey sand, with flint-pebbles (3 inches) at bottom - - - - - „ 2 Light-grey bedded sandy clay, red-mottled, except in the lower part, which is more sandy . . - - - over 7 Yerj small flint-pebbles and green-coated flints in greenish clayey sand (bottom- L bed) resting evenly on the Chalk - about J Chalk with flints. This section is most likely clearer than when seen by Mr. Prestwich, who speaks of the mottled clay resting directly on the Chalk,J perhaps from a slip ? W. W. BraugUng. — Between this village and Hadham Ford there is a large outlier, in great part with a doubtful boundary, being much covered by Glacial Drift. Three sections showing the junction with the Chalk were noted, the layer of green-coated flints being present in each next above that rock : in one, three quarters of a mile N.E. of Stondon, 3 feet of flint-pebbles were seen ; in another, a quarter of a mile S.W. of Warren's Farm (S. E. of Braughing), 4 feet of mottled loam ; and in the other, just south, a foot of pebble-gravel over 5 feet of mottled loam. * See Geological Survey Memoirs, vol. iv. pp. 351, 252, for a notice of such lines of outliers, &c. f ri-om Mr. F. J. Bennett's Notes. X Quart. Joxirn. Oeol. Soc, vol. x. p. 92 (1854). Reading Beds, _, about 21 feet 26 GEOLOGY OF THE N.W. PART OF ESSEX, ETC. South-west of Manewden (in Essex) is another outlier, also partly hidden by Drift, but the junction with the Chalk is shown in a pit a quarter of a mile south-east of Mallows Green, the section being : — Bottom-bed. Dark green clayey sand, with small patches (4 or 5 inches thick) of pebbles on the top, and a thin layer of green-coated flints in brownish clay at the bottom ; 2. to 3 feet. Chalk, surface irregular. On the hill "W.S.W. of Stansted Station is a smaller patch almost wholly hidden by Drift, but in the large pit, marked on the Ordnance Map, south-east of Bendfleld Mill, the following section may be seen : — Feet, Glacial Drift ( Patch "f gravel. . ' I Grey boulder clay - - - - up to 8 Trace of pale grey sapd with pebbles. ("Greenish sandy clay,' brown in the middle, and 1} Au A J light-coloured at bottom [This is much Ijke Keamng iieds< ^j^^ y^^se-hei of the Thanet series.— W. W.] - 7 LGreen-coated flints and pebbles - - - J Chalk with flints ; one very regular flint-layer, 4 inches thick, 2 feet from the top -..-.- 40 At the northern edge of the district, and miles from any mass of the Reading Beds, there is a remnant in a chalk-pit by the road about two-thirds of a mile S.S.E. of Kedington Church, on the border of Suffolk, where the following section occurred : — Boulder Clay, with a thin layer of reconstructed chalk at the bottom. Reading Beds. Fine greenish sand with flint-pebbles and flints. A thin layer on an irregular surface of the Chalk. Chalk with few flints. W. H. P. LONDON CLAY. 27 CHAPTER 5.— LONDON CLAY AND RED CRAG. London Clay. This deposit is for the most part of a uniform character, con- sisting of clay, bluish-grey where not exposed, but changing to brown at the surface, and sometimes with nodular masses of cement-stone (septaria). There- are more sandy beds occa- sionally, especially at the top (which does not occur in our district) and at the bottom. The base indeed is marked by the occurrence of the peculiar and generally easily recognized " base- ment-bed," a loam or clayey sand; mostly with green grains and layers of flint-pebbles, often with fossils, and sometimes with hardened calcareous masses. Speaking of the S.E. corner of our district, Mr. Dalton re- marks that " in some parts friable nodules of carbonate of lime occur near the surface of the clay, whilst in other parts chalk or lime is required to neutralize the sulphuric acid, whether free or combined with iron, which is formed in the clay by the oxidation, of pyrites. In the presence of pyrites and carbonate of lime crystals of selenite, and carbonate of iron soluble in water containing carbonic acid, are formed, the last speedily changing to peroxide, with the evolution of carbonic acid." Although it occurs over the S.E. half of the tract represented in Sheet 47, yet the London Clay crops out over no large area, -owing to the very general covering of Drift. Its boundary-line, which is for the most part doubtful, from this Drift-covering, follows that of the Reading Beds at varying distances, from a tenth of a mile to three miles. After passing under- the Drift near Bishop's Stortford the boundary is hidden until it reappears W.S.W. of Sudbury ; but the formation has been exposed by the cutting-out of the deeper valleys, the sections along which will be noted in order, from west to east, and from the head downwards, after describing the northern outcrop. There is a good section of the junction with the Reading Beds near Hert- ford (see p. 20). At the brickyard on the left bank of the Stort, about half a mile below Roydon Station, I saw the section below, in company with Mr.. Penning, in 1873 :— Feet. "Brown and grey bedded clay, with some sharp casts of radiating crystals of selenite ; fairly divided from the bed below - - 15 or more London Clay. <| gasement-bed. Brown loam with a few sheUs and some lumps of stone (with a few shells and pieces of plants) ; 6 feet shown, but said to be 7 feet deeper - - - about 13 Reading Beds. Greenish mottled clay and puce clay - „ 2 W. W. GEOLOGY OF THE N.W. PART OF ESSEX, ETC. [? Reading Beds]. 14 1 1 At the brickyard east of Hadham Ford there is a good section of the base- ment-bed, the following account of which was taken in 1869 [with an additional note in 1873, when the pit was deeper. — W. W.] Feet. 'Brown clay, rather sandy, especially towards the bottom ; with patches of small darker lumps of tenacious clay, some pieces of septaria and lumps of race, impressions of shells and an occasional small pebble or piece of ironstone. rr J - rci 1 J Near the bottom two or three thin layers of [London Clay]. ^ da^u day " - - - - - Yellowish finely-bedded sand - „ „ „ full of shells, too friable for preservation, with some pebbles : in places a thin layer of clay between the two beds of sand - - - - - 'Very fine white sand, finely bedded, with some dark grains, and here and there small lumps of dark clay - - - - about 8 [Pebbles. To the " basement-bed " probably belongs the greater part of the top bed as well as the next two beds. South-east of Hadham Park there is a brickyard in brown sandy London Clay. About a mile and a quarter N.E. of Bishop's Stortford, at the edge of Birchanger Wood, the London Clay is worked in a brickyard. W. H. P. At the higher kiln, Gestingthorpe, about a third of a mile S.S.E. of the church, a fine section of the bottom part of the London Clay is laid open, and shows a thick development of the sandy basement-bed, which at Sudbury, a few miles eastward, seems to be absent. The details were as follows, the bed below the pebbles being shown only in a small pit at a lower l^vel than the chief one, and those beneath that not being open at the time of my visit, (1873) :— A little pale Boulder Clay at the easte'rn part. 'Brown and grey mottled clay, passing down into the next about Brown sandy clay, with an even bottom - - up to "Very pale buff fine sand (like that of the Oldhaven Beds) ; a long lenticular mass at one part cutting down suddenly into the bed beneath to a depth of over 2^ feet ; at one part a layer of brown clay at top and another at bottom, which join together where the sand thins out - to about 3 Brown loam, with a few layers of clay throughout ; the lower part more clayey and passing down into the next - - - - over 12 Darker brown and grey clay, passing down into * the next ..... about 2 Brown loam, like that above . . - I or more Sandy pebble-bed ; the pebbles mostly small, but some large. The lower half sand with pebbles. Teeth of Lamna were found in this bed by Prof. ^ Prestwich .... about 2 'Buff sand, the upper part fine soft and with a little clay, the rest sharper said to be 6 Clay (not seen, information from workmen) . 6 or 8 [White sand „ The cut surface of the loamy basement-bed stands almost vertically ; the thicknesses given are maxima. The pebble-bed and the loam above were also seen on the opposite side of the valley, eastward, close to the bottom, where there may be a small inlier of the Reading Beds, as the loam occurs further down northwards, pointing to a slight uprise southwards. Feet. 6 34 o S I « ID a Reading Beds. London Clay (basement- ■ bed.) LONDON CLAY. 29 At Wisboro Hill, a mile and a quarter S.W. of Bulmer, is a pit to supply the brickyard, by the high road on the south, which showed (1873) : — Drift sand at the highest part, over brown grey-mottled bedded and more or less sandy London Clay ; and at the north of the kiln there is a sandy wash, gravelly at the bottom, over like London Clay. The London Clay is again shown at one part of the large pit at Balingdon (p. 14.) W. W. Chelrner Valley. The London Clay is shown at the brickyard a' quarter of a mile N.-W. of Thaxted (see p. 42). In a deep water-course half a mile S.S.E. of Thaxted Church the following section occurs : — Feet. Glacial Drift. — Coarse yellow sand^ and fine gravel, bedded and with iron-shot streaks. The lower part Red Crag, or rearranged Red Crag, containing phosphatic. nodules - - 8 'Light-coloured loamy sand - - - 1 Hard brown sand, concretionary - - 5 Light-brown sandy clay, streaky and slightly con- torted, with calcareous concretions and patches of tenacious clay, passing down into the bed below - - - - - 2 to 3 Dark fine loamy sand, somewhat muddy, with very fragile shells - - - 5 In a similar guUy 2 miles S. of Thaxted may be seen similar dark fine muddy-looking sand, and a brick-pit half a mile N.N.E. of Little Easton Church is in sandy loam over London Clay, 3 feet. W. H. P. Ter Valley. The London Clay was shown (1872) in recently-dug ponds at Maddox Farm, about a mile below Terling, and it may be seen further south, on the left bank, along the high road. Guith Valley. In the railway-cutting south of Bulford Station the Clay seems to be im- pregnated with sulphate of iron or free sulphuric acid, as dm:ing the construc- tion of the line the hair was taken ofp the legs of the horses employed. London Clay has been dug, to a small extent, in the bottom of the valley at the brickyard a quarter of a mile S.S.E. of Faulkbourn Hall. BlaeJcwater Valley. A brickyard was worked (1872) in the London Clay near Bay Tree Farm, on the high road south of Stisted. . It has been worked at the kiln northward of Coggeshall, and it was shown in the brickyard north-west of that town (see p. 62). The clay may be seen on the northern bank of the artificial lake in Braxted Park, and, on higher ground, at an old brickyard a quarter of a mile north of Bung Row. It forms the floor of the railway-cutting at.Wickham Bishop, from the station to halfway between the bridges, the gravel being cut through. Septaria occur close to the surface in the wood a mile S.W. by S. of Wickham Station. Tiptree Heath. The great brickyard half a mile west of Primrose Hill shows, at one part, several feet of the clay, which there contains soft friable calcareous nodules, apparently segregated by the action of the weather, At Chiseldine Gtrange I was told that masses of apparently the same nature, and of the size of a man's head, occur at intervals in the clay to the depth of 30 feet, which is about the depth to which the discoloration of weathering generally extends. W. H. D. 30 GEOLOGY OF THE N.W. PART OF ESSEX, ETC. Colne Valley. At the brickyard nearly a mile westward of Castle Hedingham the following section was noted : — Coarse ferruginous sand with nodules and thin beds of ironstone here and there, and some flints and pebbles [? Crag or Drift], 7 feet. Basement-bed of the London Clay. Brown sandy loam, ^vith layers of clay, and a layer of fine white sand, 6 feet. A better section was shown at the kiln on the other side of the railway, about three quarters of a. mile south of the same village, and close to the railway, the beds being : — Feet. Glacial Drift. {f^,t^%, ". I I I ijlto^ Basement-bed f^™'*^" ^^""^y '^^^J - " ' - 4 to 6 c -I , J Fine buff sand, with a layer of clay at top and Clav 1 ^* ''°^*°" - - - - - 3 to 4 ■'' L Brown sandy clay, not bottomed. The basement-bed is also shown in the railway-cutting, close by to the west, but the section is not clear and is difficult to make out, from the way in which the Drift (Boulder Clay and sand to a thickness of 20 feet) cuts into the other beds. At the Wash, in the side-valley eastward of Halstcad, stiff chocolate- coloured clay is dug for the supply of the kiln. F. J. B. Outliers. The only outliers of the London Clay known in our district are on those of the Reading Beds. At Sacomb (p. 25) there is no good section ; but at Colliers End (p. 25), though great part of the outlier is hidden by Drift, a. fair section was seen in a pit on the western side of the highroad, opposite the kiln, which showed the following beds : — Brown finely-bedded sandy clay and loam, nearly 10 feet. Brown clayey sand (basement-bed), 4 feet (to water). At the S.W. of Benfield End the brown loain of the basement-bed was seen, in cutting a drain, but it cannot extend far. Eed Crag. There is no trace of the Bagshot Beds in our district, and until the Geological Survey of it was almost finished the London Clay was thought to be here succeeded by the Drift ; but in 1873 un- mistakable remains of the Red Crag, with the phosphate-bed at the base, were found at Sudbury, round which town there has been of late 5'ears a great development of pits, for chalk, brick- earth, &c. A notice of this discovery, but without details of the sections, was communicated" to the Geological Society.* , The most westerly traces of the Crag noticed were on the south of Tbaxted, where Mr. Penning and myself found in the water- course, noted at p. 29, some small phosphatic nodules and a piece of phosphatized bojie in a thin layer of gravel at the bottom of sand; and lying on London Clay ; besides some larger phosphatic nodules on the surface further south, at the junction of the sand and clay. I also found a like piece of phosphatized bone in the flint-bed at the base of the sand, and resting on the Chalk, near Stoke * See Quart. Journ. Geol. Soc, vol. xxx. p. 401 (1874). EED CEAG. 31 (see p. 49). A mass of shells was said to have been found at one spot just above this flint-bed, and some of these that were shown to us were the common shell at Sudbury, Purpura lapillus. It" is only at the north-eastern corner of our disti-ict that there is anything more than a mere trace of a former existence of the Crag, unless, as is not impossible, some of the sand that has been dassed with the Drift should turn out to belong to the Crag. In the outskirts of Sudbury are the only patches that can be shown on the map, and these, moreover, are small, the Crag being mostly covered by Drift, underneath which its extension is doubtful. Some of the sections where Crag occurs have been already described (pp. 13, 16, 17), and others will be noticed further on (pp. 5"2-56). At the N.E. edge of. Sudbury, by the side of a footpath running N.E. from near the top of Suffolk Road, two small chalk-pits (Webb's) gave the best sections of the Crag (1873-6). The further of these is close to the pit described on p. 62, where also Crag was touched, and sho\\-ed the following beds : — Boulder Clay, at one spot, cutting down to the greensand of the Thanet Beds. 'Ferruginous sand, slightly false-bedded; in parts" a light- coloured grit, with broken shells, and with unbroken specimens of Purpura lapillus (var. crispata). With layers of ironstone, and at the bottom a firm bed of it. A line of pebbles &c. about 2 feet from the bottom. Up to 6 feet thick. Layer of iiint-pebbles, phosphatic nodules, and flints, 3 to 12 _ inches. Clayey greensand, with green-coated flints (base of Thanet Beds), Ig to 2 feet. Chalk. The other pit, close by to the S.W., gave a like section, with a shallow trough of Boulder Clay on one side, and the Crag having less ironstone and less of the pebble-bed (sometinies hardly any). Down the slope of the side-valley, just south-eastward of the above, and facing the road in that valley, another pit (Harding's) gave a like section of the same beds, without the Boulder Clay, in a slight hollow in the Chalk, the Crag consisting of ferruginous sand, up to 10 feet thick, with pebbles and nodules (one layer at the bottom and others above), and with sandy ironstone, one bed of which contained many casts and impressions of fossils. The following is a list of the fossils from the Crag in these pits. As however the specimens were in the state of casts or impressions, except in the cases marked with an asterisk, Mr. Etheridge had some difficulty in naming the species : — Nassa elongata. Mya arenaria. Natica occlusa. Mytilus edulis. ♦Purpura lapillus, var. crispata. Panopsea? Trophon antiquum (lotver whorls). Pecten opercularis. Tellina. ""Anomia ephippium (1 small valve). — — — — Cardium Parkinsoni. Balanophyllia (fragment). Mactra. Pollicipes. Modiola modiolus. W. W. Red Crag. < 32 GEOLOGY OF THE N.W. PART OF ESSEX, ETC. CHAPTER 6.— GLACIAL DRIFT. General Remarks. The various beds massed under the heading "Drift" are perhaps the most important in our district, forming as they do some four-fifths of the surface, though often of no great thick- ness. The great mass of this area consists of what is known as " Glacial Drift," which was deposited at a period when glacial conditions prevailed in this part of England. A very small part of the Drift, however, is of later age, and known as "Post Glacial." In many cases it is a difficult matter to determine the age of a mass of gravel, brickearth, &c., and in some cases our classifi- cation must be taken as doubtful ; but these will be duly noticed. A Memoir like this, descriptive of a limited area, is ha,rdly the place for an essay on the classification of these beds. The three- fold division proposed by Mr. S. V. Wood, junr., is well known, and indeed is the only systematic diArision of the Glacial Drift in East Anglia. Without entering into its merits, it is enough now to say that of the " Lower Glacial " of that geologist no sure sign has been observed here, though perhaps some of the beds included by us with the series which he has named "Middle Glacial" might be classed with the lower divisions by him. Until the work of the Geological Survey in Norfolk and Suffolk is in a more advanced state, it is better for us not to commit ourselves to a scheme of classification, and to be content with the detailed mapping of the beds and their lithological description. Speaking roughly we may here divide the Glacial Drift into two, the equivalents of the Upper and Middle Glacial of Mr. Wood, the lower consisting essentially of gravel and sand, and the upper being the great deposit of Boulder Clay. Before proceeding to the description of the older or Glacial Drift of the district it will be convenient to notice a small deposit of pebble-gravel that occurs on the London Clay hills between Hertford and Hoddesdon, and which may be of Pre- Glacial age. It is composed almost wholly of pebbles, the larger mostly of flint, and the smaller of quartz, and it has' been inferred to be the oldest Drift-bed in the district (and to the west), and to have been largely denuded before the deposition of the succeeding bed. All that is known of it with absolute certainty is that it is older than the Boulder Clay (which occurs over it in other parts), and Mr. S. V. Wood, junr., has classed it with his "Middle Glacial." Glacial Gravel and Sand. These beds are of varying composition, from very coarse gravel to fine sand ; sometimes with valuable deposits of loam, GLACIAL 6EAVEL, ETC. 33 and with layers of Eoulder Clay (or clay with glaciated stones) not to be distinguished from the thick mass of such clay that comes on above. .The stones composing the gravel are of many sorts, flints being the most common ; but pebbles of flint, quartz, and quartzite are plentiful. Pebbles of hard chalk abound locally, and sometimes there are pieces of pudding-stone oi' greywether- , sandstone (of Eocene age) and of septaria from the London Clay. In a list " of the Mineral Substances, and of the (derived) Organic Eemains, found in the Gravel at Stan way, Essex, and .... within a Radius of Fifteen Miles,'' published by the late Mr. John Brown, of Stanway,* a great variety of rocks are noticed, which must be chiefly from Glacial gravel. In some sections there are no signs of bedding; in others, the beds are roughly stratified, and in some the sand is finely bedded. False bedding (current-bedding) is common. The gravel and sand are sometimes cemented into hard masses by ferruginous or calcareous infiltrations, and this is especially the case just under the Boulder Clay, the junction of the two deposits being often marked by a hardened surface of sand or gravel. No fossils have been found in these beds but those derived from older formations, in our district, except at one spot, south of Thaxted, where Mr. Penning found two small shells, and some fragments, in gravel. These shells were submitted to Mr. S. V. Wood, who has determined them to be Venus fasciata 1 and Astarte compressa (young). Mr. S. V. Wood, jun., writes to me that " both species are the commonest of all the shells in the IVTiddle Glacial of Hoptoii (near Yarmouth), and both also occur at Billockby ; whilst Venus fasciata is extremely rare (almost unique) in the Red Crag." This puts aside the supposition that the shells may have been derived from the Crag, and supports the view that they belong to -the bed in which they were found. The discovery is the more interesting, as it is not until we go far eastward, beyond Ipswich, that shells have been found in these beds, and none are known further west. W. W. Many of the valleys running S. and E. from the Chalk escarp- ment are, almost to their source, cut through Boulder Clay, and expose beneath it the gravel and sand. This series appears to be persistent over a large area, within which it is a rare occurrence for the Boulder Clay to be seen resting on the Tertiary beds or the Chalk. For it is probable that the gravels extend beneath the clay over nearly all the intervening area, in greater. force, perhaps, along the lines of the larger valleys, and in a more attenuated or even patchy condition under the * Mag. N'at. Hist, voj. viii. pp. !i49-353 (1835"). See also ibid., n. ser., vol. i. p. 145. G 383. ■ • c 34 GEOLOGY OF THE N.W. PART OF ESSEX, ETC. higher grounds. But in no instance do they run up to the top of the Chalk range, neither do they occur on the N.W. face of that escarpment. ^ W. H. P. These deposits are found in nearly all the valleys of any im- portance S. and E. of the Chalk escarpment, running up to the places named below, beyond which the Boulder Clay rests upon the Chalk, without any gravel or sand between. The Rib Valley, to Buckland. „ Ash „ „ S. of Brent Pelham. „ Stort „ • „ Bearden and Elsenham. Chelmer „ „ N. of Thaxted. „ Ter „ „ Peak HaU, B. of Felatead. „ Guith „ „ above its source, near Great Bardfleld. „ Pant „ „ Radwinter. „ Colne „ „ Ridgewell. „ Stour „ „ Haverhill. It will be convenient, therefore, to describe the sections accord- ing to the valleys in which they occur, beginning at the head of each and working doAvnward. W. W. and W. H. P. Valley of the Lea. Along the high road, a little south of Hertford Gaol, there is some Boulder Clay in the gravel. The following notes of the section in the great brickyard between "Ware and Ware Park were taken in 1869. The whole of the bed& were not shown at any one place, but their order seemed tolerably definite (though the divisions were not always clear) and as below : — a. Boulder Clay ; a little, at the most north-easterly pit only (abandoned). h. Brown and bufF sand, in parts (western side), sometimes gravel. Brick-earth beds, ("c. Brown loam, with dark grey layers ; 10 to 12 feet seen, sometimes not! d. Grey sandy clay ; 8 to 10 feet, less in parts, divisible j 25 ] e. Brown laminated . clayey sand, with thin blocks of feet or more. L concretionary sandstone at or near the bottom. ("/. Sand, also with concretionary sandstone, sometimes Gravel and sand. < with gravel ; 8 feet seen. Ig. Gravel, with sand. Chalk seen low down on the western side. In parts the gravel and sand at the bottom rise up in a ridge nearly to the surface of the ground, and the accompanying figures (8, 9, p. 35) serve to show the irregular position of the beds. In a pit just E. of Ware Union the gravel was seen to be hardened at the bottom. At Widbury Hill, E. of Ware, there is a layer of Boulder Clay in the gravel, just up the lane running eastward. On the hill more than half a mile nearly north of St. Margaret's station, is a small gravel-pit, just south of an old one that is marked on the Ordnance Map. The ditch above shows Boulder Clay over gravel, and the pit itself 12 feet of the latter over clay of the Reading Beds. A little more than a mile N.E. of the Station there is some buff laminated loam with chalk pebbles (? rising from under the Boulder Clay). * Valley of the Rib. The gravel-pit on the south-eastern side of the side-valley, a little east of the high road, a mile S.S.E. of Buntingford church "showed (1873) a little GLACIAL GEAVEL, ETC. 35 Fig. 8. -Section at the W. Part of the Brickyard between Ware and Ware Park (1869). Fia. 9. — Section along a Roadway in the Brickyard northward of Fig. 8. (1869). About 150 feet long and 14 feet deep at the most. The beds above have been worked off. X Wash of loam, &c. The other references the same as in the general section (p. 34). c. Brown loam. d. Grey sandy clay. e. Brown laminated clayey sand. /. Sand. g. Gravel. 36 GEOLOGY OF THE N.W. PART OF ESSEX, ETC. whitish Boulder Clay, slightly scooping into gravel, rather fine at top, but coarse lower down. There is a large block of conglomerate close by, and other smaller blocks lie about. . In the railway-cutting just N. of Westmill Station, there is chalky Boulder Clay and chalky gravel over Chalk-with-flints. On the right bank of the stream, eastward of Knight's Hall, a pit showed 20 feet of gravel. About a third of a mile westward of Stondon Church there is gravel with Boulder Clay and loam. W. W. At the brickyard, half a mile N.E. of Stondon, there is sandy loam, on yellow sand, with some pebbles in jjatches, 10 feet thick. A pit a quarter of a mile N.E. of Stondon Lodge is in gravel of small quartz, flint, and other pebbles, with an intercalated bed of hard yellow sand, 7 feet thick. The cutting for a new road from "Barrack" to "Moat Farm," Much Hadham, and just east of the former place, gave the section shown by Fig. 10, p. 37 :— A pit just N., of Timber Hall, Thundridge, gave the following section : — /-■I • 1 Ti -li r Gravel, 3 feet. Glacial Drift - | j^oam (in places), a foot. Chalk, its surface very uneven and with small patches thereon \ of green-coated flints and pebbles in greenish sand - J " At Hare Street, in the valley of the branch called the Quin, a brickyard showed 10 feet of brickearth under gravel, close to the hatnlet. " The brickearth was also dug at another kiln about a quarter of a mile N.W., by the lane to Alswick Hall, and between the two kilns."* Valley of the Ash. The gravel in the pit S. of Hadham Ford consists chiefly of pebbles, with some subangular flints and patches of yellow sand, to a depth of 1 6 feet ; and in that half a mile N.W. of Little Hadham Church it is of the same descrip- tion ; 10 feet exposed. A junction of the Boulder Clay and underlying gravel is shown in a small pit on an occupation-road, S. of Berry Green. In a Pit N. of the road from Hadham to Perry Green, and half a mile E. of Hadham Cross, there was gravel, iron-stained in places, and with small patches of sand' to a depth of 12 feet. Boulder Clay was seen in the road towards higher ground on the E. ; the Reading Beds with pebbles towards the valley on the W. ; and Chalk in a pit below. A road-cutting half a mile N. of Widford, exposed 10 feet of yellow sand and 8 feet of pebbly gravel. A gravel-pit, half a mile W. of Widford' Station, shows subangular stones and pebbles in a coarse sandy matrix, to a depth of 12 feet. W. H. P. Valley of the Gam. The outcrop of the Glacial gravel in this valley is continuous with that of the Stort valley, from Quendon and Henham in ■ the former to Stansted and Elsenham in the latter • but whilst the Stort cuts into this gravel along its whole length, the Cam shows it as a continuous mass only so fax* as Audley End. W. W. * From Mr. F. J. Bennett's Notes. 37 w Bq eq O 4 s g Co ^ TS la's •^3 03 --^^ -^