The Geologist/Volume 5/On the Microscopical Examination of some Bracklesham Beds

by Thomas Rupert Jones

ON THE MICROSCOPICAL EXAMINATION OF SOME BRACKLESHAM BEDS.

By T. Rupert Jones, F.G.S.

In Vol. I of the 'Geologist,' at page 249, was published a paper on the preparation of sands, clays, and chalk, for microscopical purposes, under the heading of "Geological Manipulations;" and, as both pleasure and geological profit are to be obtained from the exact examination of various fossil-bearing deposits, both as to their constituents and their contents, I beg to offer you an example of the results of such an examination of some tertiary beds from Bracklesham. These notes I have had by me several years, and their shortcomings are so great in some respects that I should not send them, were it not that they may serve as a plan to some young careful observers who might feel inclined to enter upon the strict examination of some definite series of fossiliferous strata. What the series under notice is deficient of, is a statement of the exact relationship of these several deposits, examined nearly twenty years ago. I received the materials at that time from a friend who was collecting "Bracklesham fossils,"—a term which will be more definite, now that the Rev. O. Fisher, F.G.S., has indicated the exact limits of the Bracklesham formation.^[1]

The specimens were chiefly, I believe, from Bracklesham and Selsea; but some may have been brought from the Isle of Wight. By the presence of certain fossils, however, in some of the deposits, their exact place may probably be determined. However deficient in these stratigraphical requirements the following account of the deposits may be, they will serve the purpose here intended, namely, to show young beginners what to look for in sands and clays. Instructions have been already given as to how such materials are to be examined, in the first volume, p. 249.

The careful microscopical examination of a good series of successive deposits, in the way that Ave propose, cannot but be useful both to the geologist and the palæontologist. The conditions of deposit will be elucidated by the proportions of fine and coarse materials in the beds; especially if these be traced along a considerable tract by the examination of many samples of the deposit, through its variations from clay to sand (or vice versâ), or in its changes from an argillaceous or arenaceous to a calcareous condition. Such variations are not always recognized with sufficient exactness by the eye or by the pocket-glass, and require mechanical, if not chemical, analysis; recourse being had to the aid of acids in determining the relative proportions of lime and other constituents. Except by careful separation in water, and patient sorting and picking, the minute shells and other fossils cannot be obtained in anything like a fair average; and year by year the Foraminifera, Entomostraca, Bryozoa, and the small fry of the Mollusca, are becoming more and more valuable as leading characteristics of strata, as our knowledge of these microzoa in the fossil and recent states advances.

Such researches as these, made on any series of deposits, whether British or foreign, must be of use, either for the improvement and correction of observations already made and published, or for the groundwork of future descriptions of strata and their fossils.

Schafhäutl, Sorby, Ehrenberg, Reade, Bryson, and others, have worked at this subject in their own several ways, and it is to be hoped that not only will these older labourers continue to work in "Microgeology" or "Clinology," as the study is termed, but that others, with equal patience and acumen, will come forward to labour in this wide and promising, but as yet little cultivated field of research.

The Results of the Examination of Five Specimens of Sands and Clays from the "Bracklesham Beds" of the Isle of Wight Basin.

No. 1. Light-blue sandy clay;^[2] very friable; full of crushed shells.

Quantity examined, 480 grains.

			Grs.	Grs.	Proportions.
Calcareous	Shells, fragments of shells, ⁠and other fossils[3] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	92	736	19
Arenaceous	Sand[4] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		138	1104	29
Argillaceous	Clay[5] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		250	2000	52
			——	——	——
			480	3840	100

No. 2. Very light-blue, friable, sandy clay.

Quantity examined, 480 grains.

		Grs.	Grs.	Proportions.
Calcareous	Shells, etc., and fragments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	23	184	5⋅
Arenaceous	Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	185	1480	38⋅5
Argillaceous	Clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	272	2176	56⋅5
		——	——	——
		480	3840	100⋅0

No. 3. Dark-green clayey sand; very friable.

Quantity examined, 3840 grains.

			Grs.		Proportions.
Calcareous		Shells etc., and fragments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	497		13
Arenaceous	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Flint pebbles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	20	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	66⋅5
		Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	2530
Argillaceous		Clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	793		23⋅5
			——		——
			3840		100⋅0

No. 4. Reddish-yellow sand, very friable, abounding with large Nummulites.

Quantity examined, 3840 grains.

			Grs.		Proportions.
Calcareous		Shells[6] etc., and fragments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	878		23
Arenaceous	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Pebbles of flint, greenstone, ironstone, and brown pellucid quartz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
			23	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	58
		Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	2205
		Ferruginous concretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	12	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	19
Argillaceous		Clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	722
			——		——
			3840		100

No. 5. Light-blue sandy clay; hard, but easily separated in hot water.

Quantity examined, 3,840 grains.

		Grs.	Proportions.
Calcareous	Shells etc., and fragments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	16	1⋅2
Arenaceous	Sand (very fine) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1296	33⋅8
	Pyritous concretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	70	1⋅8
Argillaceous	Clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	2428	63⋅2
		——	——
		3840	100

TABLE OF THE FOSSILS FROM THE FIVE SPECIMENS OF "BRACKLESHAM BEDS."

No. 1.	No. 2.	No. 3.	No. 4.	No. 5.
Fish Bones.	Fish Tooth and Otolite.	Fish Bones, Teeth, and Otolite.	Fish Bone and Otolite.	Fish Bones and Otolites.
MOLLUSCA: GASTEROPODA.
				Murex.
			Fusus?
Ringicula.			Ringicula.	Ringicula.
Pleurotoma.				Pleurotoma, 2 s.
			Voluta.
Natica.		Natica.	Natica.	Natica.
		Cerithium.	Cerithium.
Potamis.			Potamis, 2 sp.
Turritella.	Turritella.	Turritella.	Turritella, 3 sp.	Turritella, 2 sp.
Solarium.		Solarium?	Solarium.	Solarium.
			Infundibulum.
Dentalium.	Dentalium.	Dentalium.	Dentalium.	Dentalium.
			Planorbis.
		Bulla (minute).		Bulla.
LAMELLIBRANCHIATA.
Ostrea.		Ostrea.	Ostrea.	Ostrea.
Pecten.
				Pinna?
		Arca.
		Cucullæa.	Cucullæa.	Cucullæa.
			Chama.
			Cyprina, 2 sp.
				Astarte?
Crassatella.		Crassatella.
Venericardia.	Venericardia.	Venericardia.	Venericardia.	Venericardia.
		Venus?
Cytherea.		Cytherea.	Cytherea.
Corbula.	Corbula.	Corbula, 2 sp.	Corbula, 2 sp.	Corbula.
			Panopæa?
			Pholas.
BRYOZOA.
Cellepora petiolus.		Flustra.		Cellepora petiolus.
			Lunulites.
ENTOMOSTRACA.
				Cythere scabropapulosa.
				C. costellata.
				C. horrescens.
				C. cornuta.
				Cytherella compressa.
				C. Mueusteri.
ECHINODERMATA.
		Echinoderm.	Echinoderm.	Echinoderm.
ANNELIDA.
			Serpula?
CORAL.
			Turbinolia sulcata.	Turbinolia sulcata.
FORAMINIFERA.
		Nummulina lævigata.	N. lævigata.
Nummulina scabra.		N. scabra.	N. scabra.
	Nummulina variolaria.	N. variolaria.		N. variolaria.
	Miliola (Triloculina).			Miliola (Quinqueloculina).
		Guttulina.		Guttulina.
				Rotalia obscura (and others).
Lignite.				Lignite.
Pyrites.	Pyrites.			Pyrites.

Should one wish to take in hand the examination of a series of the tertiary strata of any part of the Isle of Wight basin, in the manner above suggested, well assorted samples, collected and labelled with care, can be readily obtained of Henry Keeping, of Freshwater, who is an intelligent and trustworthy collector, and whose charges are moderate.

1. See Report of the Geological Society's Proceedings, Dec. 4th, 1861.
2. The clays and sands in this paper are described as they appear when dry.
3. The specimens No. 3, 4, and 5 being given in lots of 3840 grains, Nos. 1 and 2 (which were examined in lots of 480 grains) are given also as 3840 grains for the sake of comparison. With regard also to Nos. 1 and 2, their lists of fossils must be regarded as less perfect in relation to the other specimens, on account of the small quantity of the deposit examined.
4. For the list of fossils, see the table further on.
5. The sands of all the lots are chiefly composed of green grains (silicate of iron?) and quartz sand. Further details respecting the relative size, angularity, etc., of the sand-grains in the several specimens ought to have been given.
6. The shells in this specimen are larger than in the other lots. In the latter the shells, etc. found in this examination were chiefly of small size, although larger shells, of course, are sometimes abundantly distributed in the mass of the beds.