Part 2
We shall soon meet it no more. At Leziate, a little to the north-east of Lynn, it becomes extinct. Mr. C. B. Rose, who always thought the Red Chalk would prove to be the equivalent of the gault, and who argued from the evidence of fossils and from the direction of the outcrops that the true gault and the Red Chalk must ultimately meet,--Mr. Rose, I say, has informed me that he has observed the Red Chalk and the gault incorporated together at Leziate. Henceforward to the south the Red Chalk is no more seen.
Thus, then, we have come to the termination of our journey. We have noted the beginning and the ending of the Red Chalk, we have also taken some account of its neighbours. We have noticed, too, that in Yorkshire it for the most part reposes on the Speeton clay, though in certain localities it is next the lias and Kimmeridge clay, and that in Lincolnshire and Norfolk it rests on a dark brown pebbly mass supposed to belong to the lower greensand formation of the south of England.
The Red Chalk has also been discovered in a very unexpected place, although not _in sitû_. I allude to the drift of Muswell Hill. In that collection of different materials, comprising examples from every formation from the London clay to the mountain limestone in a stratum of eighteen feet, the Red Chalk has been seen in a bouldered condition.
By the kindness of Mr. Wetherell of Highgate, I am enabled to exhibit specimens from the drift of Muswell Hill. Any person who compares them with others from Hunstanton, would declare they came from the same bed, so alike are they in appearance.
There was a time no doubt when this Red Chalk had a more extended range: its presence in the drift of Muswell Hill, as well as in the drift of other places, implies as much. Perhaps it may still exist elsewhere, deep down in the earth.
In a well sunk at Stowmarket a red substance was found under the White Chalk, at a depth of 900 feet; and in another well sunk at Kentish Town, the workmen met, at a depth of 1,113 feet below the surface, beneath the gault, a bed of red matter 188 feet thick--some of this red matter appeared to contain belemnites.
Geologists are divided in opinion with respect to this deep-sunk red bed, which certainly is not always continuous (for instance, it was not found at a boring at Harwich), and some incline to the opinion that it belongs to the New Red, others that it is the equivalent of what is styled the Red Chalk. But it is difficult to give a solution at present. It is certain that in the gault formation, or near it, beds of a red colour are occasionally found. Near Dorking the lower greensand is capped by a local bed of bright red clay, eight feet thick. And examples of red clays from the gault of Ringmer in Sussex and Charing in Kent can be seen in the Museum of the Geological Society of London. Whether they have any relation with the Red Chalk proper of England depends upon the position which is given to that formation.
Geologists generally consider the Red Chalk as really equal to the Gault. Many of the fossils certainly are gault species; others no doubt belong to the Lower Chalk; and, therefore, probably it is better to regard it as an intermediate formation between the Lower Chalk and the Lower Greensand, which comes into being when the Gault and Upper Greensand have almost thinned out.
One of the members of our Committee, Mr. Rickard, has been good enough to make me an analysis of the Red Chalk of Speeton and Hunstanton. The Speeton is as follows:--
Carbonate of lime, with a little alumina 81.2 Peroxide of iron 4.3 Silica 14.5 ----- 100. -----
From Hunstanton--
Carbonate of lime, with a little alumina 82.3 Peroxide of iron 6.4 Silica 11.3 ----- 100. -----
The latter of which agrees remarkably well with the colour of the specimen, for the Red Chalk of Hunstanton is brighter than that of Speeton.
Two specimens of the borings of Kentish Town, one a red argillaceous and the other a siliceous mass, gave the following results:--
Argillaceous--
Peroxide of iron 6.5 Carbonate of lime 13.5 Silica and alumina (chiefly the latter) 80.0 ----- 100. -----
Siliceous--
Peroxide of iron 2.5 Carbonate of lime 23.5 Silica, with a little alumina 74.0 ----- 100. -----
Whether any connexion can be traced between these last two and the two former, I leave for others to decide.
The following list of books may perhaps be useful to those who wish to further investigate the subject:--In
Professor Phillips' Geology of Yorkshire,
Young and Bird's Survey of the Yorkshire Coast,
Dr. Fitton's Memoir of the Strata below the Chalk,
Taylor's Hunstanton Cliff (Phil. Mag. vol. lxi.),
Woodward's Geology of Norfolk,
Rose on the Geology of West Norfolk (Phil. Mag. for the years 1835 and 1836),
will be found some account of the English Red Chalk. And in
Sedgwick and Murchison on the Structure of the Eastern Alps (Geol. Soc. Trans. vol. iii. Second Series),
Sir. R. I. Murchison on the Geological Structure of the Alps (Quart. Geol. Journal, vol. v.),
Prof. T. A. Catullo on the Epiolitic Rocks of the Venetian Alps (Quart. Geol. Journal, vol. vii),
Count A. de Zigno on the Stratified Formations of the Venetian Alps (Quart. Journal Geol. Soc. vol. vi.),
will be seen an outline of the Scaglia or Red Chalk of Italy.
By the kindness of Dr. Bowerbank, Messrs. Wetherell, Bean, Leckenby, and Rose, in permitting me to see the specimens in their respective cabinets, and to whom, as well as to Mr. Rupert Jones, I must express great obligations for much valuable information, the accompanying list of the Red Chalk fossils of Speeton, Hunstanton, and Muswell Hill has been compiled. To the Council of the Geological Society, I am also indebted for permission to figure from the Society's Museum the Inoceramus Crispii, on pl. i. fig. 4.
LIST OF FOSSILS FROM THE RED CHALK.
Key to Table Columns:
S: Speeton H: Hunstanton MH: Muswell Hill
S H MH Cristellaria rotulata, D'Orb. Pl. II. fig. 8 × Sowerby's Min. Conchology, tab. 121, page 45. (In the collection of Mr. Jones.)
Siphonia pyriformis. Pl. II. fig. 2 × Goldfuss Petrifacta, tab. 6, fig. 7, page 16. (In the collection of Mr. Rose.) This is probably the head of the next.
Spongia paradoxica. Pl. II. fig. 1 × Geol. Trans. 2, tab. 27, fig. 1, page 377. (In the collections of Mr. Rose and Author.)
Bourgueticrinus rugosus. Pl. III. fig. 5 × D'Orbigny's Hist. des Crinoides, tab. 17, fig. 16-19. (In the collections of Mr. Rose and Author.)
Pentacrinites Fittonii × × Austin's Crinoids, page 125. (In the collections of Mr. Rose, Author, and Mr. Wetherell.)
Cardiaster suborbicularis, Forbes. Pl. II. fig. 3 × Gold. tab. 45, fig. 5, page 148. (In the collections of Mr. Rose and Author.) Mr. Rose's specimen is far better than the one figured.
Cidaris Gaultina (?), Forbes, Dec. v. Pl. III. fig. 7 × (In the collection of Mr. Rose.)
Spines with 8 ridges, 10 ridges, and 20 ridges × × (In the collections of Mr. Rose and Mr. Wetherell.)
Diadema tumidum, Forbes, Dec. v. Pl. III. fig. 6 × (In the collection of Mr. Rose.)
Serpula antiquata. Pl. III. fig. 4 × Sow. Min. Con. tab. 598, fig. 4, page 202. (In the collection of Mr. Rose.)
Serpula irregularis. Pl. III. fig. 3 × (In the collection of Author.)
Serpula triserrata. See notice, page 18 × (In the collection of Mr. Rose.)
Vermicularia umbonata. Pl. III. fig. 2 × Mantell's Geol. of Sussex, tab. 18, fig. 24, page 111. (In the collections of Mr. Rose and Author.)
Vermicularia elongata, Bean MS. Pl. III. fig. 1, 1^a × (In the collections of Mr. Bean, Dr. Bowerbank, and Author.)
Cytherella ovata, Roemer. Pl. II. fig. 7 × Jones, Cretaceous Entomostraca. Pal. Soc. page 29. (In the collection of Mr. Jones.)
Idmonea dilatata × D'Orbigny's Terrains Crétacés, tab. 632. (In the collection of Mr. Bean.)
Diastopora ramosa, Dixon × Geol. Suss. page 295. (In the collection of Mr. Bean.)
Ceriopora spongites × Goldfuss, page 25, tab. 10, fig. 14. (In the collection of Author.)
Terebratula capillata. Pl. IV. fig. 4, 4^a, mag. surface × Davidson's Cretaceous Brachiopoda, plate 5, fig. 12, page 46. (In the collections of Mr. Rose and Author.)
Terebratula biplicata. Pl. IV. fig. 1, 1^a, mag. surface × David. plate 6, fig. 34. (In the collections of Dr. Bowerbank, Mr. Rose, and Author.)
Terebratula Dutempleana × David. 6, fig. 1. (In the collection of Mr. Rose.)
Terebratula semiglobosa. Pl. IV. fig. 2, 2^a, mag. surface × × David. plate 8, fig. 17. (In the collections of Dr. Bowerbank, Mr. Bean, and Author.)
Kingena lima. Pl. IV. fig. 3, 3^a, mag. surface × David. plate 5, fig. 3, page 42. (In the collections of Mr. Rose and Author.)
Avicula, cast of. (In the collection of Mr. Bean.) ×
Exogyra haliotoidea. Pl. II. fig. 10 × Sow. M. C. tab. 25, page 67. (In the collections of Mr. Rose and Author.)
Inoceramus Coquandianus. Pl. I. fig. 1 × D'Orb. Ter. Crét. tab. 403, fig. 6-8. (In the collection of Author.)
I. Crispii. Pl. I. fig. 4 × Mant. G. S. tab. 27, fig. 11, page 133. (In the collections of Mr. Rose and Geol. Soc.)
I. tenuis. Pl. I. fig. 5 × ? Mant. G. S. page 132. (In the collections of Mr. Rose and Mr. Wetherell.)
I. gryphæoides × Sow. M. C. tab. 584, fig. 1, page 161. (In the collection of Mr. Rose.)
I. læviusculus, Bean × (In the collection of Mr. Bean.)
I. sulcatus × Sow. M. C. tab. 306, page 184. (In the collection of Mr. Rose.)
Ostrea frons. Park. Pl. II. fig. 4 × Sow. M. C. tab. 365, page 89. (In the collection of Mr. Wetherell.)
O. vesicularis, Lam. Pl. II. fig. 5 × Sow. M. C. tab. 392, page 127. (In the collection of the Author.)
O. Normaniana × D'Orb. tab. 488, fig. 1-3, page 746. (In the collection of Mr. Rose.)
Pecten Beaveri × Sow. M. C. tab. 158, page 131. (In the collection of Mr. Rose.)
Spondylus latus × × Sow. M. C. tab. 80, fig. 2, page 184. (In the collection of Mr. Rose and Author.)
Ammonites alternatus ? × Woodward, Geol. Norfolk, tab. 6, fig. 23.
Ammonites complanatus × Sow. M. C. tab. 567, fig. 1. (In the collection of Mr. Rose.)
A. rostratus × Sow. M. C. tab. 173, page 163. (In the collection of Mr. Rose.)
A. serratus, Parkinson × Sow. M. C. tab. 308, page 3. (In the collection of Mr. Rose.)
Belemnites attenuatus. Pl. IV. fig. 5 × Sow. M. C. tab. 598, fig. 2, page 176. (In the collection of Author.)
B. minimus. Pl. IV. fig. 8 × × × Sow. M. C. tab. 598, fig. 1, page 175. (In the collections of Messrs. Bowerbank, Bean, Rose, Wetherell, and Author.)
Belemnites Listeri. Pl. IV. fig. 6 × Phil. Geol. York. tab. 1, fig. 18. (In the collection of Author.)
B. ultimus, D'Orb. Pl. IV. fig. 7 × Sharpe, Chalk Moll. tab. 1, fig. 17. (In the collections of Mr. Bean and Author.)
Nautilus simplex. Pl. I. fig. 3 × × Sow. M. C. tab. 122, page 122. (In the collections of Mr. Rose, Mr. Wetherell, and Author.)
Otodus appendiculatus × Ag. vol. iii., page 270, tab. 32. (In the collection of Mr. Wetherell.)
Tooth of Saurian × (In the collection of Mr. Bean.)
Vertebra of Polyptychodon (?) × (In the collection of Author.)
Siphonia pyriformis is probably the head of Spongia paradoxica. In the cabinet of Mr. Rose is a mass of the latter, to which a head similar to the one figured is attached.
Bourgueticrinus rugosus. The diameter of the specimen figured is 3/4 of an inch, the depth of each plate 3/16. The surface of attachment is covered with very fine mamillæ, in rays of seven in number; a smaller specimen in possession of the author measures 3/8 of an inch in diameter and 1/8 in depth.
The serpula represented in Plate III. fig. 3 varies in its irregular growth from the specimens figured on the same plate. This character perhaps can scarcely be regarded as a specific difference; both V. elongata and the serpula under consideration have the same thickness of the calcareous tube. The former occurs only at Speeton and the latter at Hunstanton; in order to distinguish the two, the title "irregularis" may be applied to the latter as a variety.
Serpula triserrata, a species found on a specimen of Ammonites complanatus, is distinguishable by its three serrate longitudinal ridges. A similar form occurs on ostreæ from the Kimmeridge clay of West Norfolk.
Terebratula semiglobosa is common at Speeton, but very rare at Hunstanton. T. biplicata is very common at Hunstanton, but is not known at Speeton.
Inoceramus læviusculus, Bean, a large smooth species something like I. Cuvieri.
The Ammonites alternatus of Woodward is now lost; it was probably a variety of A. serratus, Park.
Belemnites minimus is sometimes two inches long in the Hunstanton Cliff.
The vertebra of Polyptychodon would be, if perfect, about six inches in diameter and three in thickness.
The small specimen shown in Plate II. fig. 9 evidently belongs to the Turbinolian family of corals, and possibly to the genus Trochocyathus instituted by Messrs. Milne-Edwards and J. Haime, in 1848. The specimens as yet obtained are not sufficiently numerous nor perfect for a rigid comparison with other forms, or to admit of a sufficiently detailed description should the species prove to be new. The constricted form of growth is very common in the Parasmilia of the Upper Chalk, and has no specific value.
The characteristic fossils of the Red Chalk at Speeton are Terebratula semiglobosa, Belemnites minimus, and Vermicularia elongata; and at Hunstanton, Terebratula biplicata, Belemnites minimus, and Spongia paradoxica.
In conclusion, I have endeavoured all along to confine myself to facts, and to abstain from theories, because I think the Geologists' Association ought rather to follow in the steps of learned men than to wish to take the lead. I am sure by doing so we shall gain respect. If the strictly scientific workers see we wish to acquire information, rather than to purchase an empty name, they will hold out the right hand of fellowship and help us mightily; whilst, on the contrary, if they perceive we aspire too much, and attempt to grasp what we cannot hold, then well-merited ridicule will undoubtedly be ours. The Geologists' Association was only formed to bring amateurs together, to give them a place to meet in, and a room where they could speak on kindred subjects. I trust the members will always use the opportunity, and not be afraid to speak, ever remembering that each one has some little knowledge which his neighbour has not, and that when each helps his fellow, much must be the gain at last.
End of Project Gutenberg's On the Red Chalk of England, by Thomas Wiltshire