Part 6 (1/2)
117) says: ”The Boulder clay is bedded against the slope of the chalk, shewing that this escarpment had retired to its present position in pre-glacial times.” By what precise process this was effected must be left to our savants to decide; but the remarkable fact remains, that a solid stratum, or rather series of allied strata, from 500ft. to 1,000ft.
in thickness, has, by one process or another, been wiped out of existence, over the large area now coated by the Kimeridge clay. Through ages of enormous length the chalk was forming as the bed of a sea; a deposit consisting of inconceivable myriads of beautiful minute sh.e.l.ls, mainly of the foraminifera, which can be detected by the microscope; and its destruction probably occupied as long a period as its formation.
Mr. Jukes Brown, whom I have just quoted, says: ”The Wold hills must have been, in some way, exposed to a severe and long-continued detrition, when erosive agencies were very active.” Active, indeed, they must have been, to efface from an area so extensive a solid formation from 500ft. to 1,000ft. in thickness. And this boulder clay, as Mr. Jukes Brown further observes, has forced its way up the sides of the chalk, in places, to a height varying from 300ft. to 400ft.
The Oxford clay, which lies next below the Kimeridge, is a deep sea deposit, dark blue, with brown nodular stones; some of the fossils found in it are Nucula Ornata, Ammonites Plicatilis, A. Rotundus, Cucullaea, Gryphaea Dilatata, Leda Phillipsii, Annelida Tetragona, and A.
Tricarinata, Avicula inequivalvis. {94b}
Kellaway's rock, which lies just below, so called from a village in Wilts.h.i.+re, near Chippenham, is a mixture of yellowish and buff sands, with brown and buff sandstone. The chief fossils are Gryphaea Dilatata, and G. bilobata, Belemnites in abundance, and Avicula Braam-buriensis.
{95a}
The Cornbrash, which succeeds (so called also from a district in Wilts.h.i.+re, favourable to corn), is a light grey, fine-grained limestone, often so hard as to need blasting. It abounds in fossils. Among them are Avicula Echinata, Ostraea Sowerbyi, Clypeus Ptotii, Ammonites Macrocephalus, A. Herveyi, Nucula Variabilis, Astarte Minima, Trigonia (of four kinds), Modiola (of four kinds), Myacites (five kinds), Cypricardia, Corbicella Bathonica, Pholadomya (two kinds), Cardium (three kinds), Pecten (six kinds), and several more. {95b}
The great Oolite (so named from the Greek Oon, an egg, referring to the number of small stones, like fish-ova, found in it) is divided into Oolite clays and O. limestone. The clays are mottled green and bluish, with bands of ironstone, and concretions of lime. They indicate a shallow sea, as contrasted with the Oxford clay. Fossils are not numerous, but Rhinconella Concinna, Gervillia Cra.s.sicosta, Modiola Ungulata, Ostraea Gregaria, O. Sowerbvi, O. Subrugulosa, Perna Quardrata, Trigonia Flecta, and Palate of Fish are found. {95c} These beds correspond to the so-called Forest Marble of the South of England.
The Oolite limestone beds consist of white soft limestones, having at intervals bands of marly clay. This formation burns well, and makes good lime. Its chief fossils are Serpula, Rhynconella, Terebratula, and T.
Intermedia, Avicula Echinata, Corbicella, Lima Rigida, Lucina, Modiola Imbricata, Myacites Calceiformis, Mytilus Furcatus, Ostraea Sowerbyi, Pecten Vagans, Pteroperna plana, Trigonia, T. costata, T. flecta, T.
striata, T. undulata. {95d}
The Estuarine deposit, underlying the great Oolite limestone, is composed of light blue, green, and purple clays, intersected by soft bands of sandstone, and having at its base a band of nodular ironstone. It is not very fossiliferous, but the following are found:-Rhynconella Concinna, Modiola Imbricata, Ostraea Sowerbyi, Monodonta. {95e} The sandstone bands contain plant-markings in considerable numbers. As its name implies, this formation was produced as the bed of an estuary or tidal river.
The next lower formation is the Lincolns.h.i.+re limestone. This enters largely into the making of what is called ”the Cliff,” which is the high land running south from Lincoln (visible from Woodhall) to the west of the Witham Valley and the Fens. It is a hard building stone, though once the muddy bed of a sea. It is sub-divided into the Hibaldstow and Kirton beds, so called because these strata are exposed in those parishes.
Dipping to the east, it underlies the Fens and other upper strata to be found in the Woodhall well. It abounds in fossils, there being as many as 340 species cla.s.sified, {96a} and consists, indeed, very largely of the hard parts of sh.e.l.ls and corals compressed into a solid ma.s.s. To a Lincolns.h.i.+re person, it is sufficient to say of this stone that our grand Cathedral is mainly built of it. We can only give here a few of the more frequent species of fossils:-Three kinds of Echinus, Coral (Thecosmilia gregarea), Serpula socialis, Lima (five kinds), Ostraea flabelloides, Pecten (two kinds), Hinnites abjectus, Astarte elegans, Cardium Buckmani, Ceromya Bajociana, Cyprina Loweana, h.o.m.omya Cra.s.siuscula, Isocardia, Cordata, Rhynconella (four kinds); among the bivalves are Avicula Inequivalvis, and A Munsteri, Lima (three kinds), Lucina Bellona, Modiola Gibbosa, Mytilus Imbricatus, Pholadomya (two kinds), Trigonia costata; of univalves, Natica (two kinds), Nerinea Cingenda; of fishes, Strophodus (two kinds). {96b} This is a most useful stone for building purposes.
The so-called ”Lincoln stone” is largely used in our churches; whilst the ”Ancaster quarries,” which also belong to this formation, are famous.
The commissioners appointed in 1839 to report on the building stones of England, for the new houses of Parliament, stated that ”many buildings constructed of material similar to the Oolite of Ancaster, such as Newark and Grantham churches, have scarcely yielded to the effects of atmospheric influences.” (”Old Lincolns.h.i.+re,” vol. i., p. 23.) The well-known Colly-Weston slates are the lowest stratum of this rock. The fine old Roman ”Newport Arch,” which for some 700 years has ”braved the battle and the breeze,” a pretty good test of its durability, is built of this stone.
The base on which this lowest Oolite lies is the Northampton Sands, an irony stratum of red ferruginous sand and sandstone, the upper portion of it also being called the Lower Estuarine deposit. It is from this stratum so many springs arise in various parts of the county, as already mentioned, and among them the Woodhall well water. Its fresh water conditions show it to have been the bed of a great river, but a tidal river, as among the fossils which it contains some are marine sh.e.l.ls. In this formation is found the iron-stone, which is worked at Lincoln. Its commoner fossils are Lima duplicata, L. Dustonensis, Hinnites abjectus, Astarte elegans, Cardium Buckmani, Modiola Gibbosa, Ammonites Murchisoniae, Belemnites Acutus. Its ferruginous layers are (as given by Capt. Macdakin), {97a} Peroxide bed, clay ironstone, hard carbonate of iron, hard blue carbonate peroxidised band, blue ferruginous sand, ironstone nodules, bed of coprolites with iron pyrites.
And this brings us to the Lias formation, in which lies the lower part, amounting to rather more than a third, of the Woodhall wells. It is divided into the upper Lias of clay and shale; the middle Lias of Marlstone rock bed, clay, and ironstone; and the lower Lias of clays, ironstone clays, limestones. {97b} This formation, with a thickness of from 900 to 1,000 feet, runs across England from Yorks.h.i.+re and Lincolns.h.i.+re down to the coast of Dorset. The upper Lias of the Woodhall wells also helps to form the slope from 100 feet to 150 feet in thickness of the escarpment called ”the Cliff,” to the west of the Witham Fens, and to the north of Lincoln, by Fillingham, and so on. Lincoln itself stands on Lias beds, with a capping of the lower Oolite limestone. {97c} It contains many Belemnites, Lucina, Ammonites Bifrons, A. Serpentinus, A.
Communis, A. Heterophillus, Nucula Hammeri, Pleuromyae, {97d} and especially the Leda Ovum, which distinguishes it from other strata. The middle Lias, which underlies the upper, contains Ammonites Spinatus, A.
Margaritatus (in great abundance), Rhinconella, Icthyosauri, Plesiosauri, and fossil wood, etc. {98a} The lower Lias contains Ammonites Capricornus, with many pyrites, A. Ibex, A. Jamesoni, A. Armatus, A.
Oxynotus, A. Obtusus, A. Semicostatus, A. Bucklandi, A. Angulatus, A.
Planorbis, Grypha incurva very abundant, and fossils of many other kinds. {98b} This brings us to the base of the Woodhall Spa wells. For a full list of the fossils so far found at Woodhall, the reader is referred to Appendix II. at the and of this volume.
These strata are shewn in the diagram given at the head of this chapter.
In giving the history of the well in Chapter I., the writer did not state the properties of the Woodhall water; but as these depend upon the geological elements, from which it originates, this seems to be the proper place to state them. The official a.n.a.lysis made by Professor Frankland, F.R.S., 1875, is as follows:-{98c}
Parts Grains per gallon
Total solids in solution 2361.200 1652.8400
Organic carbon .362 .2604
Organic Nitrogen .532 .3724
Ammonia .810 .5070