XXXIII. a Sketch of the Geology of West Norfolk

Philosophical Magazine Series 3 ISSN: 1941-5966 (Print) 1941-5974 (Online) Journal homepage: http://www.tandfonline.com/loi/tphm14 XXXIII. A sketch of the geology of West Norfolk C.B. Rose To cite this article: C.B. Rose (1835) XXXIII. A sketch of the geology of West Norfolk , Philosophical Magazine Series 3, 7:40, 274-279, DOI: 10.1080/14786443508648715 To link to this article: http://dx.doi.org/10.1080/14786443508648715 Published online: 01 Jun 2009. Submit your article to this journal Article views: 2 View related articles Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=3phm20 Download by: [University of Arizona] Date: 13 June 2016, At: 13:42 ~7# Mr., Rose's Sketch of the Geology of West NoTfolk. satisfactory. For the purpose, however, of dispelling any doubts of its accuracy which may exist in the minds of others, I undertook another series of test experiments~ to the descri p- tion of which I shall now proceed. [To be eontinued.] XXXllI. d Stretch of the Geology of West No~sfollc. Bff C. B. RosE, Fellow of the Rogal Medical and Chh'urgical Society of London. ['Continued from p. 18~.] The Challc Rangq. HE chalk hills of West Norfolk constitute a portion of T the .great range of that formation extending across En- gland in a south-westerly direction from Flamborough Head in Yorkshire to near Sidmouth in Devonshire. The greatest elevation they attain in this county is insignificant in com- parison with the hills at either extremity of the range: at Sedgeford, and between Heacham and Hunstanton, the face of the country possesses some boldness of feature, and again near Holt the hill and vale are strongly contrasted : with these exceptions, the course of the chalk outcrop through the county is marked by the gently undulating surface peculiar to such districts. • I have been favoured with a communication from Captain Robe, R.E., in reply to my inquiry respecting the height of the hills in this portion of the county. After stating that tile ~' triangulation of Norfolk was performed with instruments too small to be depended up6n for the vertical angle obser- vations," he continues, " I cannot now lay my hands on the sketch on which my judged altitudes were written ; but if I re- collect right, I considered the ground round Docking to be the highest, which was somewhere about 600 or 650 feet; Swaff- Downloaded by [University of Arizona] at 13:42 13 June 2016 ham is probably ~50 or 500, Gr~t'Massingham 600. But these are very rude guesses ; indeed without using accurate instruments, it would be impossible to class the several ranges according to their relative altitudes, as they vary so very little from each other, and few of them exceeding 600 feet." The width of the rant~ taken at Swaffham is about seven miles; its course through the eotmty is nearly due north and south, and its esealgment is to the west, forming generally a somewhat abrupt declivity, bounded along the greater parl~ of its extent by a narrow valley occupied by the lowest strata of Chalk, and the gault. Tile strata dip to the south-east, pro- The Chalk Ra~e. 275 bably about five yards in the mile, and are covered by dilu- vium of varying thickness. The thickness of the chalk in this county has been but recently ascertained, as appears fi'om a communication to the Geological Society by John Taylor, Esq. It states that a well has been sunk at Diss by Mr. Thomas Lombe Taylor, and the following is the order and thickness of ttle beds pene- trated : 1. Clay ........................... 50 ft. 9. Sand ........................... 50 $. Chalk without flints, soft and of a marly nature 100 4. Chalk with flints in layers of single stones distant about a yard from each other ... ~ 330 5. Gray chalk, with an occasional layer of white ~. chalk, and fi'ee from flints . ........ J 60 6. Light bright blue chalk approaching to clay,q,. 20 with white chalk-stones ......... --- J 7. Sand ........................... 5 615" No. 6. must be gault ; and 7. the lower green-sand, Tile general surface of the chalk must have suffered prodi- gious abrasions from the violence of the elements, as evidenced by the immense quantity of gravel tbrmed and collected in various situations, as well as by the different altitudes at which the chalk is found: it appearing immediately beneath the ve- getable soil, even on the highest ground; and at a level not less than fifty feet lower, it may be found covered by more than 150 feet of sand and clay containing boulders. I shall describe the chalk strata under the natural divisions, Chalk without Flints' and ~ Chalk with Flints'. Chalk without Flints.-- Under this denomination I include allthe lower cretaceous beds. At Hunstanton Cliff, where they are exposed, reposing immediately upon the red chalk Downloaded by [University of Arizona] at 13:42 13 June 2016 (as it has hitherto been called), three natural divisions of them may be observed; the lowest is made up almost entirely of a ramose zoophite, which strongly characterizes it; the middle above has a gra.y colour and arenaeeous texture, abounds in organic remams ; the gray shale forcibly distin- guishes this; and the uppermost bed, usually denominated the lower chalk, which here forms the upper portion of the cliff, is readily distinguished by its pure whiteness. It has been attempted to separate and arrange these beds by theh" zoological characters; the zoophutic bed has been considered. * Proceedings of Geol. Society, vol. ii. p. 93. 2N2- ~76 Mr. Rose's Sketch of the Geology of West No~olk. the equivalent of the upper green-sand or d~restone ; and the ra3/bed that of the chalk-marl; but I find the characteristic ssils of the upper green-sand, and chalk-marl so intermingled in the gray bed, that it is impossible to draw a line of de- marcation between those two strata; and from this circum- stance we a're led to infer that at the epoch when the upper gree~t-sand and chalk-marl of Wiltshire and Devonshire were depositing, and the then existing marine Testace~e were en- tombed," similar ph~enomena were in progress in this portion of the great chalk basin ; but the material supplied being more cretaceous, the strata consequently exhibited a dissimilar mi- neralogicaleharacter. The lowest of these .beds. (No. 4, of the section of Flunstanton Cliff) reposes upon the thin seam of dark red argillaceous matter (described page l81), which separates it from the red limestone or gault equivalent. The texture of this bed varies, some portions of it being very loose, others exceedingly hard and compact; its substance is throughout intersected by a ramose zoophyte**, the original texture of which is so completely obliterated, that it appears impossible to determine precisely the nature of what it is the relic: the formation of the stratum is best explained by sup- posing it originally a coral reef, and its interstices filled with cretaceous mud ; it is about eighteen inches in thickness, and contains very few organic remains. Chalk resembling it in hartlness and fracture oeeurs at. Heytesburyin Wiltshire. • The next bed in the ascending series to be described~ is No. $ of the same section. Its colour is gray, and its texture less compact than the harder parts of the last-mentioned ; on being fractured it exhibits an arenaeeous surface, from its having a larger proportion of silex incorporated than the white chalk above. It is probable that thisstratum at the cliff receives its hardness fi'0m the action of sea-water upon it; for the chalk of the same bed met with inland can be cut with a common knife, being much softer. This bed abounds Downloaded by [University of Arizona] at 13:42 13 June 2016 with organic remains, and contains the characteristic Testaeea of the Upper green-sand, and also of the chalk-marl, viz. Ostrea carinata and Turrilites tuberculatus. In this bed at Hunstanton are found the Saurian remains ; and I believe their charnel-house is at present confined to one block. The thickness of this bed varies from two feet and a half to three feet. Large flattened Ammonites occur in it, also a Nautilus; and innumerable fragments oflnoceramus Criflsii are scattered through it. A stratum containing similar fossil remains is seen at Sand- * A nearly corresponding bed, composed of ramose zoophytes,occurs in Sussex : vide Geology of S.-E. of England, p. 384 note d. The Chalk Range. 27T Marham, Shouldham, West Doreham Orange, toKe ~erry, and Hoekwold-eum-Wilton. The gray chalk- marl at Sandringham is of nearly as dark a shade as that of Hunstanton; and in it are found the same Ammonites, and Peeten Beave~'i and orbicularis. The same bed at Shouldham has a lighter shade, and has many ochraeeous stains : at this locality blocks of an exceedingly hard nature are irregularly distributed through the softer marl; their solidity defies the blows of the quarrymen, and they are not convertible into lime by the heat of the kiln. Here I found.4mmonites Mantelli, Plicatula iz~ata, and other shells common to the lowest beds of chalk. At rff'est Dereham Grange, the Inoeeramus Cripsil (?) in fi'agments is very abundant, in a matrix of the same character as at the last-mentioned locality. In the lower beds of chalk at Marham have been found two claws of Astacus Sussexiensis, and part of a striated tooth with fragments of bone of some Saurian animal, all of which I possess.

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