# A Treatise on Geology/Chapter 6, part 2

MESOZOIC STRATA.
Triassic System.
(Part of Saliferous System in the former editions.)
Judging by mineral associations and great structural analogies, Mr. Conybeare united this group of variable strata with the subjacent magnesian limestone; nor is it without a species of divulsion that they can be separated. Yet their organic history is different, and it is by their palæontological relations that the strata are now most successfully gathered into large associations, which can be recognised over distant regions. The red marls and sandstones which compose the trias in Germany form three main groups,—viz.:
In France and England the muschelkalk is absent. Rock salt and brine springs occur in England and France only in the Keuper series: in Germany both in this and in the muschelkalk. Gypsum usually accompanies the marls which yield salt, but is also of more extensive occurrence.
In England the most complete section is probably that furnished by the beautiful and fertile vale of Severn, where every bed between the lias and the Palæozoic rocks of the Malvern and Abberley hills is easily traceable, in a thickness of 400 to 500 yards. The lowest of these beds, trappoid conglomerate, is probably of Palæozoic age,—a representation of some part of the Permian system. The series in general terms stands thus,—
Farther south, the lower sandstones nearly vanish (in Somersetshire), but the marls receive a peculiar (local) calcareous conglomerate (millstone), to which probably the reptiles of Durdham Down may be referred.
Farther north, the series is continued and very widely expanded the marly upper portions admitting rock salt in Worcestershire and Cheshire: the sandy ​lower part more distinctly splits into sandstone (above) and conglomerate (below) as we approach Nottinghamshire, Derbyshire, and Yorkshire. Here the series becomes triple.
The abundance of red oxide of iron in almost every part of this and the older Permian system deserves the more attention from the fact, that it is in general an investing substance—a sort of varnish covering the white clear rounded grains of quartz which compose the main part of the sandstones of these systems.
Rock salt occurs in the state of clear white cubically crystallized masses, or reddened by the argillaceous sediments among which it occurs: sometimes in Cheshire the red salt is fibrous. Brine springs, which issue from rock salt, contain combinations of iodine and bromine, though in the rock itself those substances can hardly be detected: a circumstance depending on the extreme solubility of the iodic and bromic salts.
Gypsum, a very frequent product of the red argillaceous members of this system, and very commonly found in the vicinity of rock salt, is granular at Chelwerton near Derby, but generally fibrous, as at Tees Mouth, Pocklington, Nottingham, Aust Passage. Sulphate of strontian forms nodules in these marls in Somersetshire.
Organic Remains.—In England we have scarcely an example of the true flora and fauna of this system; for the ramified leaves (Dictyophyllum) of the sandstone near Liverpool, and the almost traceless calamities in marl ​near Malvern, are poor representatives of the voltziæ, calamities, and ferns of the German trias: nor could we, from the little bivalve which occurs in the Keuper of Salop (Posidonomya minuta), conjecture the variety of testacea which is yielded by the coeval strata of Sulz les Bains. Our fish and reptile remains are more numerous. The latter in particular (Labyrinthodon), known by footprints in Cheshire and Dumfriesshire, and by bones and teeth from Warwickshire, are extremely interesting.
The German trias yields a sufficiently large series to remove all doubt as to the truly mesozoic character of the deposits.
Geographical Extent.—Slight traces of new red sandstone occur on the western coasts and islands of Scotland: some considerable area is occupied by it in the country between Coleraine and Dungannon, about Belfast, and on the coast of Antrim. The Solway Firth is in red marls and sandstones, and all the rivers which enter it from the Scottish frontier flow through the same; the plain of Carlisle; the western coasts, from Whitehaven to Furness; the peat mosses of South Lancashire, and the Vale of Clwydd are in the red formation. The river Tees enters the sea in gypseous red marls and sandstones; so does the river Exe in Devonshire; and between these two points is an almost uninterrupted line of the same strata, ranging by York, Nottingham, Warwick, Worcester, Aust Passage, Taunton, and Honiton. It expands westward from Nottingham to Derby, Manchester, Liverpool, and Shrewsbury,—thus occupying an enormous area in the centre of England, partially broken by the upheaved coal measures of Leicestershire, Warwickshire, and Staffordshire. Small detached portions appear in Monmouthshire, Glamorganshire, and Devonshire.
On the continent of Europe, still larger spaces are covered by the saliferous system than in England. A small continuation of the Devonshire red rocks appears ​in Normandy, about St. Lo: a much larger area lies between the Ardennes and the Vosges, running westward from Luxemburg to Florenville, northward to Witlich and Vlanden, southward to Thionville, Pont-à-Chaussy, Château Salins, and Vic (where rock salt occurs), Mirecour, Jussy, and Villersexel; eastward to Treves, Wadern, Kaiserslautern, Neustadt, Weisspenbourg, Weshoffen, St. Diey, &c. In this large and intricate tract, the hunter sandstein, muschelkalk, and keuper, are fully developed: there are some magnesian bands in the keuper, but no zechstein below the red sandstone. The Vosges are almost wholly surrounded by these rocks.
In like manner the Black Forest is principally surrounded by saliferous deposits, continuously so on the eastern side, from which spreads to the north and east an enormous area of the red rocks, which represent the bed of a sea ramifying in several directions, among islands and promontories of older, and slopes of newer, rocks. The principal part of the mass lies to the east of a long line drawn nearly north from Waldshut on the Rhine, to Minden on the Weser, including the Odenwald, Spessart, and Habichtwald. Portions run out eastward towards Osnaburgh. From Waldshut, by Stutgard, to Dietfurt, nearly parallel to the Danube, is the south-eastern boundary: it thence turns northwards to the Maine, and returns to the Danube at Ratisbon, and fills the narrow space between the Franconian oolites and the primary igneous rocks of the Bohemian border and Thuringerwald. Round the end of these latter mountains it bends to the east, fills all the space between the Harz and the grauwacke border of the Erzgebirge, arid passes the end of the Harz in a long tongue between Magdeburg and Brunswick. (In this enormous area, the zechstein, or magnesian limestone, is exhibited along the Thuringerwald, in Hesse Cassel, on the southern and eastern sides of the Harz, between the Elster and the Saale, and about Waldeck.) The muschelkalk occupies extensive areas, on a line from Waldshut ​to the Thuringerwald, and all around the Harz. Salt occurs in the keuper and muschelkalk especially. Considerable tracts of new red sandstone adjoin the Riesengebirge; and a line of these rocks, occasionally saliferous, borders the primary ranges of the Alps, from the vale of the Danube, by Rottenmann, Radstadt, to near Innspruck. On the south side of the Alps, the range is equally extensive, from Cilli, near the Save, by Villach to St. Lorenzen on the Eisach.
Physical Geography.—Spread over so immense a space in England, the triassic system offers the remarkable fact of never rising to elevations much above 800 feet (Barr Beacon, in Staffordshire, is a gravel hill on a base of red rocks); a circumstance probably not explicable by the mere wasting of these soft rocks by floods of water, but due to some law of physical geology yet unexplained. We only can conjecture that it is connected with the repose of subterranean forces, which prevailed after the violent commotions of the coal strata, over nearly all Europe till the tertiary epoch. The red sandstone system, folding its level surfaces round the broken coal strata, seems to be like the large uplifted bed of a shallow sea, full of rocky islands, and bounded by bold promontories. (The magnesian limestone range in the north of England constitutes a fine natural terrace of 100 to 500 or 600 feet in height above the sea; its escarpment being always to the west.)
Igneous Rocks.—Almost the only cases known in England, are dykes of greenstone. One of these, the great Cockfield dyke, extends from Middleton, in Teesdale, to near Robin Hood's Bay, and passes through mountain limestone, coal, magnesian limestone, red sandstone, red marl, the lias, and oolites. Another passes from the Breiddin hills across the plain of Shrewsbury, and dislocates and alters red sandstone at Acton Reynolds. In the Isle of Arran, dykes of pitchstone, claystone, trap porphyry, &c., divide red and white sandstones, supposed to be of this era. ​
Origin and Aggregation of the Materials of the Triassic and Permian Systems.
Peculiar in their mineral composition, rocky structure, and the nature and distribution of their imbedded organic remains, the constituent members of the red sandstone and magnesian limestone sometimes offer many points of inquiry to the inductive geologist, and much that seizes on the imagination of those who venture freely into the unsafe regions of speculation. What has caused in the sandstones, clays, and marls of these formations, such various tints of the oxides of iron? If the greenish and bluish tints of the clays and grit stones be due to protoxide of iron, what have been the circumstances which determined in these small portions that particular state, while all around, above, and below them, the masses are tinged, and the particles enveloped by the peroxide?
In particular cases blue centres to yellow rocks occur (oolite, calcareous sandstones), and may be thought to be the residuary primary tint, the outward parts having been decolonised. But this does not apply to the red marls and sandstones, among which (except at the weathered surfaces and in the soil), yellow tints are rare; the prevalent tint of red appears rather to be the original, and the rarer and detached tints of white, green, and blue, to be the decolonised portions of the mass. We may imagine chemical processes of change from protoxide to peroxide, but it is very difficult to find data for applying them to the cases before us.
The general extension of these tints appears to imply a very general cause. This can hardly be understood as a mere process of common oxidation; for this gives greater variety of tints, and cannot be supposed so uniform or extensive in its action. May we venture to offer as a question deserving attention, the possibility of explaining the red colour of these rocks by a general influence of volcanic eruptions on the sediments of the ocean?
The Permian limestones offer other curious topics of remark. Where they degenerate to a sandy state (near Nottingham), they assume a decided red tint; nor is this tinge any where entirely absent from large ​tracts of magnesian limestone. It is complicated with purple (Doncaster), yellow (Sunderland), or is totally replaced by a pure or creamy whiteness. The various modes and degrees of consolidation already noticed among these limestones imply, of course, different modes of aggregation: for the shelly rocks of Hawthorndean and Humbleton (Durham), we may, with some confidence, claim a coralligenous origin: the globular concretions of Sunderland remind us of the pisolite of Carlsbad, and, according to an unpublished suggestion of Dr. Forchhammer, may be really due to ancient submarine springs of great force, yielding mingled carbonates of lime and magnesia, which were afterwards consolidated together, or separately deposited. The dusty portions of rock seem to be really decomposed; and it is worthy of remark, that the tufaceous deposits from these rocks, as well as the crystallised spars in geodes, consist of carbonate of lime.
There appears no reason whatever to apply to these magnesian rocks either the speculation of Von Buch concerning Alpine dolomites, that they are common limestones impregnated with carbonate of magnesia by heat, or the notion of their mechanical origin from disintegrated magnesian beds of the carboniferous limestone.
Origin of Rock Salt and Gypsum.
In the present state of nature salt (chloride of sodium) appears in solution at the surface, under the following circumstances:—
1. In the sea, every where, but in variable quantities.
2. In springs arising from salt rocks, known or presumed to exist.
3. In springs arising in volcanic regions.
4. In small quantity in all springs whatever.
It is only by considering these existing sources of salt in combination with the phenomena accompanying ancient salt deposits, that we can expect to gain light toward the solution of the problem of the formation of rock salt.
This general investigation would here be out of place ​but we shall present a short view of some of the principal conditions ascertained to accompany these deposits.
First, as to the Rocks which inclose Salt.—The great abundance of this valuable substance in the red sandstone and red marl of England, as well as in the contemporaneous rocks of Germany, naturally produced a general impression that salt was peculiarly the product of that geological era; and it was sometimes assumed without evidence that all the well-known salt works of Switzerland, Poland, Spain, &c., drew their supplies from the new red sandstone formation. The inference was extended not only to the salt lakes and springs of European, but also of Asiatic, Russia, to the sands of Persia and salt-houses of Ormuz, and the salt works of India, between the Indus and the Chellum. Even the American salt deposits were thought to belong to the red sandstone formation of Europe.
The progress of information has corrected this over extension of a well-grounded inference: salt springs rise in Durham and Northumberland, and Leicestershire, from the coal system; some of the salt works of the Alps are supplied from the oolitic system: the famous mines of Cardona and Wieliczka have been referred, the former to green sand, the latter to tertiary rocks; and, to complete the series, salt springs abound in the volcanic regions of Sicily and Auvergne.
It appears then that salt is derived by the action of water from almost every stratum, formerly left by the sea, and from many volcanic and other products, and that large beds of salt occur at several stages of the series of marine formations, but that in Europe they are remarkable and frequent in the new red sandstone system. This may still, and without impropriety, be called the saliferous system.
Hence we may securely infer that although salt was more or less diffused through all the marine deposits, the enormous accumulation of this substance in certain places can only have happened in consequence of local peculiarities several times recurring, but at least, in ​Europe, more frequent in a particular period of the earth's lamellar incrustation.
It is very important to remark that the salt lies always in small narrow patches; therefore, most evidently it was not produced by a general extrication from the marine water, and most probably is to be referred to local heat, or some other cause at great depths, or else to evaporation from a limited area, filled at intervals by the sea.
In order to discover the nature of these local peculiarities, we must compare the different salt deposits, with reference to their situation, accompanying minerals, and other leading circumstances.
So little relation appears between the actual form of the ocean and the boundaries of the ancient seas in which the strata were formed, that it will probably be of little use to notice the geographical situation of the beds of rocksalt as compared to the present distribution of land and water. The salt mines of England are in very low ground: those of Wieliczka lie at the foot of the Carpathian mountains on the north, and those of Cardona beneath the Pyrenees on the south: many mines in Wurtemburg and central Germany are in the midst of rather elevated plains; and at Bex salt lies in an ancient valley, some distance above the Lake of Geneva, itself 1000 feet above the sea. With respect to the present ocean, the mines of England and Cardona are near to it, but the others far distant.
It does not seem possible to extract from such a discordant assemblage of facts any general character of situation depending on the present distribution of land and water, nor perhaps has it ever been attempted; but because in the instance of the Cheshire salt district, the local circumstances are such as to have given occasion for Dr. Holland's hypothesis, that the salt there was derived from the neighbouring sea, it will be worth while to discuss the formation of that salt basin separately.
The Cheshire deposits of salt lie along the line of the valley of the river Weaver, in small patches, about ​Northwich. There are two beds of rock salt, lying beneath 40 yards of coloured marls, in which no traces of animal or vegetable fossils occur. The upper bed of salt is 25 yards thick: it is separated from the lower one by 10½ yards of coloured marls, similar to the general cover; and the lower bed of salt is above 35 yards thick, but has nowhere been perforated. Whether any other beds lie below these two is at present unknown. They lie horizontal, or nearly so, and both beds of salt are below the level of the sea. They extend into an irregularly oval area, in length one mile and a half, in breadth about 1300 yards, ranging from N. E. to S. W. Gypsum, so abundant in many other salt mines, and generally plentiful in the tracts of red marl, is found in most of the clays associated with the Cheshire salt.
The physical features of the country about Northwich are not very peculiar, yet sufficiently favourable to Dr. Holland's hypothesis. The valley of the Weaver is separated from that of the Dee by the sandstone ranges of Delamere forest, and the Peckforton hills, and from the course of the Mersey by an extension of the elevated ridge, called Alderley Edge. Below Northwich these bordering hills come very close together, and naturally suggest the idea, that in ancient times there might at this place have been accidental bars formed, which while they lasted, would exclude the inroads of the sea. If by such an event the sea lake flowing up the valley of the Weaver was converted into an inland sea, and if the supply of fresh-water streams from the neighbouring country was very scanty, the natural progress of evaporation would certainly tend to dissipate the water, to concentrate the solution of salt, and finally to cause in it a partial precipitation. At first, gypsum or any other of the less soluble salts would be formed, and perhaps mixed with the earthy sediments mechanically deposited in the lake, and afterwards the salt be accumulated in the deepest parts of the water, in quantity proportioned to the evaporation of the liquid. If, at a subsequent time, the sea should again burst the barrier and inundate the valley, a new deposit of gypseous marls, and a bed of ​salt would naturally be occasioned, upon any renewed blocking up of the entrance.
The entire absence of marine exuviæ from these strata is no objection to the hypothesis; because this is the case with almost the whole extent of the red sandstone formation in England.
Upon the whole, it seems evident that this hypothesis is well adapted to the circumstances of the case for which it was framed, and is in itself very simple and plausible, but is liable to the serious objection that it employs data drawn from the present relations of land and sea to elucidate the phenomena of a period long gone by, and when, from unquestionable evidence, it is certain that their relations were generally very different. It is, however, not impossible that the district in question may have been undisturbed by any subsequent convulsion, and only altered in its physical features by the general elevation which our island appears to have undergone, by the rapid transition of diluvial currents, and the erosive action of rains and rivers. This is perfectly supposable, and may be true; for, as far as yet known, the circumstances of the case do not appear to contradict it; but before adopting this explanation, we must examine other salt deposits, and see whether a similar mode of origin can be reasonably ascribed to them.
Olitic System.
Composition.—The change of deposits from the saliferous to the oolitic system is in all respects great, and, from the contrast of colours in the rocks generally, very obvious. Instead of red, green, or white marls, we have blue clays: the red and white sandstones are exchanged for calcareous grits, tinted yellow, or ochraceous, by iron in a different state of oxidation: instead of powdery magnesian limestones, we have compact or oolitic rocks. Nothing can be a clearer truth than that this great difference of chemical and mechanical deposits requires the supposition of some great physical revolution in the relations of land and sea. If we suppose ​that, in consequence of a subterranean movement somewhere, the oceanic basins were filled by sediments from other lands, or other lines of wasting coasts, the change from coloured sandstones to oolitic deposits in the same basin would be intelligible, though we might never know the local position of such tracts of land or lines of coast.
Most frequently, the arenaceous deposits associated with the oolitic system are easily and obviously distinguishable from those of earlier date: they are not micaceous, and seldom felspathic, as many of the carboniferous grits are; they are never of the same red, and seldom so white as those of the saliferous period. A yellow tint prevails among them, which sometimes deepens into ferruginous stains; the grain is generally fine; quartz pebbles seldom occur; their substance is mixed with carbonate of lime. But from this description, which applies to the south of England, great variations occur in particular districts, as in Yorkshire, Sutherland, and Westphalia, in the wealden districts of Kent and Sussex. The first three tracts may be sufficiently illustrated by the Yorkshire type, which is eminently distinguished from the rest of England, by having, in the lower parts of the group, enormous masses of sandstone and shale, greatly analogous to the sedimentary rocks of the carboniferous system, interpolated among the reduced and deteriorated strata of oolitic limestone. What renders the resemblance of these to the older grits and shales the more striking, is the circumstance that thin beds of coal, with fossil plants, occur among them, and that some beds of ironstone, and abundance of diffused oxide of iron, augment the analogy. There can be no doubt that these great and numerous points of similitude between the oolitic and carboniferous systems, in the north of England, point to a similarity of causes, extensively acting in the earlier, but reduced to limited effects in the later periods.
In the wealden tracts of Sussex and Kent, an almost similar series of sandstones (quartzose, coarse or fine grained) and clays, with impure, but not oolitic ​limestones, occur, with ironstone beds and diffused oxide of iron, traces of coal and fossil plants. Were the beds of this local deposit placed by the side of others of the old carboniferous era, it would be difficult to distinguish them by any mineral characters capable of being expressed in language; we may therefore admit for this district, and some small tracts related to it, a renewal for a short period of the actions by which the carboniferous rocks were formed; and this is easily intelligible upon the principle of changes in the direction and depositions of oceanic currents, occasioned by subterranean movements.
The clays of the oolitic system are mostly of a decided blue colour (near the surface changing to yellow), often laminated, especially in the lias formation, but more frequently appearing like a nearly uniform mass of argillaceous sediment obscurely divided by a few laminæ of shelly limestone, or lines of septaria: pyrites and jet lie in many of them. The gradation from these clays to the limestones and sandstones is usually very gentle.
The limestones of this system are various: those associated with a great abundance of blue clays (as the lias limestones) are mostly of a compact texture, and of white, yellow, grey, blue, or blackish colour. Frequently, nodular masses collected by molecular attraction round organic bodies constitute the whole mass of the lias limestones. Those which appear in considerable thickness, as the Bath oolite, Portland oolite, Oxford oolite, are generally of the oolitic texture in the middle, though below and above this may be exchanged for compact or shelly beds. Thin detached limestones, like the forest marble, are sometimes very coarsely oolitic: calcareous layers in sand are usually charged with siliceous matter and often cleave able to slate or flags (Stonesfield). The grains of oolite vary much in size; the smallest are perfectly spherical, the largest irregular; they generally cohere; the interstices are sometimes filled by calcareous spar: the centres of the large grains of oolite are commonly occupied by small shells or portions of shells, corals, grains of sand, &c., which served as the points ​of attraction for the calcareous matter, while it was in a soft condition.
Structure.—In the whole series, not a mass occurs which can be viewed otherwise than as an original deposition, or a subsequent concretion of aqueous sediment. The sandstones are always stratified: sometimes the coarse-grained sorts (Whitby, Tilgate forest) exhibit oblique laminations, the finer sorts often split into flags or slate: shells and plates of oxide or carbonate of iron appear as the result of molecular arrangement round particular masses, as centres of attraction. The clays, as above stated, are either laminated, or appear as vast uniform masses of sediment; bedded they can hardly ever be said to be, unless where interposed between beds of sandstone, or limestone. The iron stones, septaria, and "cone-in-cone" masses occur in the clays, in surfaces always parallel to the planes of stratification, and thus appear to mark periodical changes in the nature of the sediments; but this accumulation is generally the result of molecular attraction round organic bodies. Jet, another frequent substance in the clays, (especially in lias,) lies in laminæ parallel to the stratification, being nothing less than chemically altered coniferous wood.
Thin limestones associated with thick clays, as the lias limestones, are usually laminated or thinly bedded, and interstratified with the clays: thicker rocks, as the Bath oolite, are formed in regular beds of two to four feet in thickness; thin layers of clay often occur between the beds. Oblique lamination belongs to many of the coarse shelly oolites: spongoid bodies, enveloped in siliceous matter, lie in the oolitic rocks of Portland and Oxford, but not so regularly as flints do in chalk: there is very little pyrites, and, except in the lower Bath oolite, little oxide or carbonate of iron in the calcareous rocks, above the lias.
Divisional planes.—All these rocks are traversed by divisional planes, but very unequally, for the massive clays show few of them; in the calcareous rocks they are both numerous and regular; in the coarse and irregular bedded grits of Yorkshire and Sussex, ​the joints are also irregular; but in the slaty beds of Collyweston, Stonesfield, &c., the contrary is true. The joints are most open in the thick oolites, where they are frequently lined by stalagmitic incrustations, and filled with clay from above, and sometimes terminate in caverns, which, in Yorkshire and Franconia, contain bones of quadrupeds introduced at much later dates.
In certain districts these joints contribute, by weakening the rocks in definite lines, to produce the phenomenon of sliding ground; this is especially the case in the Hambleton hills, Yorkshire, from which, at different historical times, even as late as 1790, great landslips have occurred by the sliding of the clays below the calcareous grit, and the separation of masses of that grit and the superincumbent oolite along the planes of great vertical joints. The main line of these joints is about N. by W., and parallel to the immense natural escarpment of the Hambleton hills.
Series of Strata.—On the continent of Europe, the oolitic system, as characteristically exhibited in the Jura mountains, shows less distinctly than in England the minor groups, which furnished to Dr. William Smith the first proofs that England was regularly divided into strata, following one another for great distances on the surface, and sinking in the same direction beneath it. The divisions of the oolitic system, recognised by that distinguished observer, near Bath, are found however to apply with sufficient general accuracy to all European countries; and, there is reason to think, the European type will be found applicable even to the flanks of the Himalaya.
Of the five formations which compose the oolitic system in England, the upper or wealden formation is the most local the lower or lias formation the most extensive: the three intermediate or properly oolitic formations are easily distinguishable in the south of England and the north of France; but in the south of France, and generally in the Jura mountains, from Geneva to Bayreuth, this discrimination is a work of difficulty. Even in England, the three oolitic ​are not coextensive, at least their calcareous portions: the upper or Portland limestone is the most limited and interrupted; the lower or Bath rocks are the most extensive and connected, but at the same time, perhaps, the most variable. These and other results will appear in the following comparative table, suited to the north and south of England.
| Peculiar to the North. | Common to both. | Peculiar to the South. |
| | | Wealden clay. Hastings sand. Purbeck beds. |
| | Kimmeridge clay. | Portland oolite. Sands. |
| | Upper calcareous grit. Coralline oolite. Lower calcareous grit. Oxford clay. Kelloways rock. | |
| Carbonaceous gritstones and shales. | Cornbrash and clays. | Hinton sandstones and sands. |
| Carbonaceous gritstone, shale, and coal. | Great oolite. Inferior oolite and sand. | Forest marble and clay. Fullers' earth rocks. |
| | Upper lias shale. Marlstone beds. Middle lias shale. Lias limestone. Lower lias shale. | |
If, comparing Britain with Europe, we view the oolitic system in gross, we shall find as the most general result, three considerable groups of rocks, viz.:—
and may consequently view the whole as a succession of argillaceous sediments widely disseminated in the sea, ​followed by calcareous accumulations from the oceanic waters, and closed by a local rush from some parts of the land. But analysis of these groups shows the effects of many alternations of oceanic rest and littoral movement, prevailing in the same parts of the sea, and producing at one time limestone with quietly imbedded shells and attached corals; at another, sandstones; at a third, clays. If we admit what is perhaps impossible to be denied that the production of each sort of rock spread from some centre, and that these centres were not coincident for different rocks, it becomes a very curious problem to determine what are the lines of contemporaneity in the oolitic system.
For let A be a point from whence a deposition of carbonate of lime spreads slowly through the ocean, but not reaching to B, a point from which depositions of sand happen, not reaching to A—the general basis r, r, r, being red marl and sandstone. The surfaces of stratification
r, r, r,—1, 1, 1,—2, 2, 2, &c., are usually spoken of in geological works as marking distinct periods in the deposition of the beds, and the matter at any point on one of the three surfaces is usually supposed to have been contemporaneously deposited. In the diagram referred to, five lines of contemporaneity thus appear to be designated, but this inference is by no means perfectly correct. If the calcareous and arenaceous deposits were supposed to happen in alternate periods, those parts of the former which were furthest from A, on the planes 1, 1, 1, 3, 3, 3, and 5, 5, 5, would be of somewhat later date than the others, though exactly similar in substance, organic contents, &c.; and the like reasoning with reference to the point B, applies to the arenaceous deposits on the planes 2, 2, 2, and 4, 4, 4. Yet the beds a, a′, a″, ​and b, b′, b″, would be correctly described as the deposits of a certain period.
But if the deposits from A and B were continuously and contemporaneously spreading, the lines 1 and 2, 3 and 4, would completely coalesce towards A,—and the lines r and 1, 2, and 3, and 4 and 5 toward B The sandstones would vanish indefinitely towards A, and the limestones towards B: a certain portion of sand would be diffused through the calcareous bed toward A, and some portion of calcareous matter through the sand towards B: the lines of contemporaneity would intersect obliquely the surface of the beds, as in the Diag.(No. 58.)
If the rate of deposition were uniform from each point, there would be only one calcareous and one arenaceous S J (fig. 59.) ', but if from either of these points the
depositions were subject to periodical changes of intensity, this would occasion alternations of calcareous and arenaceous beds more or less distinct, according to the variations of intensity.
From this it may be concluded that the alternations of beds of different nature, proves either cessations or varying intensities of deposition, in one of the deposits; that, consequently, such a system as the oolites must have taken a 'long time for its accumulation and could not possibly have been generated with that rapidity ​which has been ascribed to the deposition of formations, from considerations founded merely on the state of conservation of organic remains.
Organic Remains.—The numerous remains of plants, zoophyta, mollusca, articulosa, and vertebral animals, belonging to the oolitic system, have long been celebrated and represented in many works of merit in England and Germany. Some general considerations arise from a contemplation of them, which deserve attention. The following estimate of the numbers of specific forms in the whole system (exclusive of the wealden formations), drawn up by the author, is at this time undoubtedly below the truth. (Encycl. Metrop. p. 653.)
| Plants — | marine | marine | 4 | — In limestone chiefly | — In limestone chiefly |
| | terrestrial cryptogamous | terrestrial cryptogamous | 39 | $\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$ | In sandstones and shales chiefly. |
| | monocotyledonous | monocotyledonous | 33 | $\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$ | In sandstones and shales chiefly. |
| | gymnospermous | $\left.{\begin{matrix}\ \ \end{matrix}}\right\$ | 4 | $\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$ | In sandstones and shales chiefly. |
| | uncertain | $\left.{\begin{matrix}\ \ \end{matrix}}\right\$ | 4 | $\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$ | In sandstones and shales chiefly. |
| Polyparia — | fibrous | | 75 | $\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$ | Chiefly in limestones, but rarely in the lias. |
| | corticiferous and celluliferous | $\left.{\begin{matrix}\ \\\ \end{matrix}}\right\$ | 44 | $\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$ | Chiefly in limestones, but rarely in the lias. |
| | lamelliferous | $\left.{\begin{matrix}\ \\\ \end{matrix}}\right\$ | 59 | $\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$ | Chiefly in limestones, but rarely in the lias. |
| Kadiaria — | crinoidea | | 31 | | |
| | stellerida | | 17 | | |
| | echinida | | 47 | | Chiefly in limestone, rarely in lias. |
| Conchifera — | plagimyona | | 189 | | |
| | mesomyona | | 134 | | |
| | brachiopoda | | 61 | | |
| Mollusca — | gasteropoda | | 114 | | |
| | cephalopoda | | 273 | | |
| | annulosa | | 55 | | |
| | Crustacea | | 22 | — Chiefly astacidæ | — Chiefly astacidæ |
| | insects | | 20 | — Solenhofen and Stonesfield. | — Solenhofen and Stonesfield. |
| | fishes | | 20 | | |
| | reptiles | | 40 | | |
| | mammalia | | 2 or 3 | | Only in the lower oolite formation at Stonesfield. |
In the wealden formation, are no zoophyta, no cephalopoda—various land plants—some fresh-water bivalves and univalves—a few estuary shells—cyprides, lepidotus, and other fishes—iguanodon, hylsæosaurus plesiosaurus, &c., with various chelonida, both of fresh and salt water.
The most characteristic of the plants are the group of cycadeæ, of which stems in the isle of Portland, and leaves and fruits in Yorkshire, show considerable analogy to the existing forms of the tribe, at the Cape of Good Hope, and in India and Australia. Compared with ​existing races, the polyp aria present some general resemblance, with constant and obvious lesser differences. The sponges are seldom so large as those of the South Seas, and appear most to resemble those of New Holland. It would be difficult to doubt that the radiaria of this system are altogether more like the existing pentacrinus, stellerida, and echinida, than are those of earlier date. The beautiful genus cidaris, in particular, exhibits in many ways a decided analogy to recent tropical species. The mesomyona and brachiopoda, taken together, still predominate over the plagimyona; and cephalopoda are more numerous than any other group of mollusca; thus offering a broad distinction between the system of oolitic and modern life in the sea. The fishes belong mostly to the ganoid division of Agassiz, and are remarkable for the beauty of their preservation in the lias of Dorsetshire, Leicestershire, and Yorkshire. Among the saurians, those which frequented the water predominate in number, but the largest forms were terrestrial (iguanodon, megalosaurus). The natural order of turtles was exceedingly developed in this period. Hugi has found in the Jura formation, about Soleure alone, more than twenty species of emys (fresh water). We are not to imagine the few mammalia, insects, and plants, yet published from these formations, a fair specimen of these races, as they existed on the land during the oolitic period. Doubtless we may believe that the buprestidæ of Stonesfield were not the only beetles that fed its pterodactyls and marsupials: of these latter the few jaws yet found convey only partial information; but it is interesting to know that the earliest mammalia, of which we have yet any trace, were of the marsupial division, now almost characteristic of Australia, the country where yet remain the trigonia, cerithium, isocardia, zamia, tree fern, and other forms of life so analogous to those of the oolitic periods.
The following table will show somewhat of the distribution of remarkable families and genera in the oolitic system, which appears cut off from the cretaceous rocks above by a more decided line than the older formations. ​
| Hamites. Turrilites. | | Cretaceous System. | | |
| Megalosaurus. | Plesiosaurus. Ichtyosaurus. Ammonites. Belemnites. Trigona. Stellerida. Cidaris. | Wealden Formation. | Spirifera. | Clypeus. Apiocrinus. |
| Megalosaurus. | Plesiosaurus. Ichtyosaurus. Ammonites. Belemnites. Trigona. Stellerida. Cidaris. | Upper Oolite Formation. | Spirifera. | Clypeus. Apiocrinus. |
| Megalosaurus. | Plesiosaurus. Ichtyosaurus. Ammonites. Belemnites. Trigona. Stellerida. Cidaris. | Middle Oolite Formation. | Spirifera. | Clypeus. Apiocrinus. |
| Megalosaurus. | Plesiosaurus. Ichtyosaurus. Ammonites. Belemnites. Trigona. Stellerida. Cidaris. | Lower Oolite Formation. | Spirifera. | Clypeus. Apiocrinus. |
| Megalosaurus. | Plesiosaurus. Ichtyosaurus. Ammonites. Belemnites. Trigona. Stellerida. Cidaris. | Lias Formation. | Spirifera. | Clypeus. Apiocrinus. |
During the oolitic period the arctic land was covered by plants like those of hot regions, whose vegetable ruins have locally generated coal beds—adorned by coleopterous, neuropterous, and other insects—among which the flying lizard (pterodactylus) spread his filmy wings. The rivers and shores were watched by saurians more or less amphibious (megalosaurus, iguanodon), or tenanted by reptiles, which by imaginative men have been thought to be the originals of our gavials and crocodiles; while the sea was full of forms of zoophyta, mollusca, articulosa, and fishes. Undoubtedly, the general impression, gathered from a survey of all those monuments of earlier creations, is that they lived in a warm climate; and we might wonder that the result of all inquiry has shown no trace of man or his works, did we not clearly perceive the oolitic fossils to be all very distinct from existing types, and combined in such, different proportions, as to prove that circumstances then prevailed on the globe, materially different from what we now see, and probably incompatible with the existence of those plants and animals, which belong to the creation whereof man is the appointed head.
Geographical Extent.—The oolitic system occupies a considerable surface in England, but is very slightly represented in Scotland (at Brora in Sutherland, in Skye, and other Western Islands), Ireland (about Ballycastle), and in Wales (Aberthaw, Glamorganshire). The lias formation has its western edge continuous, or nearly so, on the surface from the sea-coast near Redcar in Yorkshire to the rival cliffs of Lyme Regis in Dorsetshire. In this long course it passes by Northallerton, Easingwold, and Market Weighton to the confluence of the Trent and Humber; thence due south to Newark; afterwards in a generally south-west course by Belvoir, Leicester, Lutterworth, and Southam to Evesham. From Pershore a long projection of lias runs out northward to Hanbury, but the principal range returns by Tewkesbury, Gloucester, Berkeley, and Sodbury to the Avon at Keynsham. From the Avon to ​the Mendip Hills the distribution of the lias is intricate; south of that chain of limestone, the lias runs out westward between the rivers, and even extends beyond Watchet; from Langport and near Taunton it turns south and (resting on red marl) it passes under the over-extended strata of green sand and chalk. An extraordinary patch of lias occurs in the red marl between Whitchurch and Wem.
Within this long range the lower or Bath oolitic formation is equally continuous, except where unconformable covered by the chalk between the Yorkshire Derwent and the Humber, and in Dorsetshire; and its course may be described as parallel to, and lying on, the eastern side of the lias. Guisborough, Coxwold, Whitwell, South Cave, Lincoln, Grantham, Uppingham, Northampton, Banbury, Stow, Cheltenham, Stroud, Marshfield, Frome, Yeovil, Ilchester, and Bridport, are situated near its western boundary. Parallel to this, and more to the east, is the less continuous range of the coralline oolites, which passes from Scarborough due west to Hambleton, then turns south-east to Malton, beyond which it is concealed beneath the chalk. The argillaceous part of this group (Oxford clay) reappears in Lincolnshire, near Brigg, and passes by Sleaford, Peterborough and Bedford, to Ottmoor near Oxford. From this point the oolitic rocks are added to the series, and the formation fills the vale of Isis to Cricklade, turns south to Chippenham, Calne, and Melksham, and, with some interruption in the oolites, continues by Wincaunton and Sturminster toward Ilminster, where it is covered by the Dorsetshire chalk, but reappears on the south side of it about Weymouth. The Portland oolite formation, represented only by the Kimmeridge clay, fills the vale of Pickering in Yorkshire, borders the chalk and lower green sand of Lincolnshire, from the Humber at Ferraby to Spilsby; underlays a large part of the Fens, and with the Portland oolite fills a considerable breadth in the vale of Aylesbury. Irregularly capped by the same oolite, and sands, the Kimmeridge clay passes by Shotover, Cumner Hurst, Faringdon, ​and Swindon, to Wotton Basset; turns south to Seend and Westbury; appears about Wincaunton and Sturminster, passes under the Dorsetshire chalk, and reappears near Weymouth and in the isle of Portland.
The minute flexures, irregularities, and breaks in the ranges of these formations, can only be understood by consulting a good geological map; but the preceding notices will suffice to show how remarkable is the effect, in the geology of England, of their parallel courses from sea to sea—from Yorkshire to Dorsetshire. In this respect their ranges are of great importance, offering to the inquiring mind a proof of the long succession of quiet processes by which the bed of the sea was gradually filled with a regular series of varying deposits—alternations of chemical and mechanical products—and afterwards, it is almost certain, gradually lifted so as to change with a certain regularity the ancient boundary of the sea. The Wealden formation, in this, as in all else, contrasts very strongly with the truly marine deposits. It makes no part of this parallel series, but lies principally in Kent and Sussex, occupying all the drainage of the Medway above Yalding, the upper branches of the Mole, Wey, Arun, and Adur, and the Ouse. From near Beachy Head to near Hythe and Ashford, the whole breadth of the Weald of Kent and Sussex is formed on these rocks, which are therefore happily named. Detached portions occur in the isle of Purbeck and in the vale of Wardour in Wiltshire, and analogous accumulations near Boulogne and Beauvais.
On the continent of Europe the oolitic rocks appear connected by direction in Normandy with those of England, and the series there is extremely similar and not less fully developed. The figure of the geographical area occupied by these rocks in France and Germany is so singularly ramified as almost to defy description. One portion surrounds the basin of Paris in a course from Caen by Mortagne near Angers, Saumur, Poitiers, Chatelherault, Bourges, Auxerre, Bar le Duc, Mezières, spreading to Luxemburg, Metz, Nancy, and Dijon, ​
Caen, Narbonne. Mezières. Can. Poitiers. Chamberi. Bayonne. Nice. and running south to near Lyons. From near Poitiers branches pass off westward to La Rochelle, and south-eastward to the Cevennes. The north flank of the Pyrenees has a belt of oolitic rocks. Another range passes from near Narbonne due N. E. to Savoy, where it bifurcates; one branch forming the French and Swiss Jura, which, crossing the Rhine above Basle, continues north of the Danube to Ratisbon, and thence turns north to the Mayne at Banz. The other branch keeps the south side of the Rhone, to the Vallais, and thence forward to Vienna forms part of the great chain of the Alps, but is so altered in aspect from ordinary "Jura kalk" as to have been for a long time considered as quite of a different age. The limestone, north of the Carpathians about Krakow, may be looked upon as of the same age.
The south side of the Alps is in like manner bordered by a similar range of the Jura kalk, from the Lago Maggiore, by Lago di Guarda, Belluno, and Lay bach, where it expands greatly, and sends off ridges through Illyria, Dalmatia, Albania, and Greece.
Throughout the greater part of this range, except in France, the minute distinctions of the English formations vanish. In the Swiss and German Jura, and the Alpine borders, the oolitic rocks, though connected with the strata of Normandy, vary greatly from that type, so that in some districts hardly any member but the lias can be perfectly discriminated from the general oolitic mass. This renders very singular the perfect exactness ​with which the argillaceous rocks in the south slope of the Himalaya represent the English lias,—an agreement which, perhaps, by further researches, may be found not less complete than that presented by the lias of Wurtemburg and Franconia, which can hardly be said even to differ from the argillaceous rocks of the Yorkshire coast. (See Geol. Proceedings, for Murchison's notices of the Banz Series, and Voltz on Belemnites, for proof of the identity of the Wurtemburg and Whitby
Spain, the Balearic Islands, and the Apennines, contain the oolitic system, which also appears in the range of the Atlas.
Physical Geography.—The oolitic tracts of England present a broad band of dry limestone surface, rising westward to elevations of 800 and 1100 feet (in Yorkshire 1485 feet), with escarpments commanding very extensive prospects over the undulating plains of lias and red marl. Even where the valleys are abrupt, as about Stroud and Bath, the scenery, though pleasing, appears tame to one acquainted with the older strata. This arises from the comparative softness and easy destructibility of the rocks; for in some parts of the Swiss Jura the harder limestones appear in mighty precipices. The facility of waste has permitted, on the western border of the districts in England, the production of frequent outlines of the limestones on the clays; as Bredon Hill, which stands up in the vale of Gloucester to attest the powerful effects of ancient water.
| Upper oolite. | Middle oolite. | Lower oolite. |
The whole tortuous line of oolitic escarpment from the Humber to the Avon may be regarded as the wasting effect of water on the subjacent red marls and lias clays; but what that water, when and how applied, is a problem of general geology, on which we may enlarge hereafter. ​Each oolitic rock forms an escarpment over the subjacent clays, so that several longitudinal hollows and ridges undulate the area occupied by the oolitic system.
Igneous Rocks.—In Scotland, the Ord of Caithness offers a case of granitic rocks uplifted in a solid form among the oolitic strata, which are in consequence much fractured and displaced. In Yorkshire, the great Whindyke of Cockfield fell crosses the lias and lower oolites, and affects the argillaceous and arenaceous beds considerably, both by induration and debitumenisation.
General Review.—Oolitic System.
Perhaps nothing more clearly demonstrates the frequent dependence of geological phenomena upon causes acting at a distance, than the total dissimilitude of the rocks of the oolitic and saliferous periods; for not the slightest unconformity of dip or direction appears at their line of junction, to mark any local disturbance. The repetition of clay sandstone and oolitic limestone observed at least four times in this system, shows the persistence of the new conditions impressed upon the land and sea, while the very local interpolation of grits, shales, and coal, like those of older periods, may be viewed as the result of a temporary restoration of communication from some particular tracts of land to the oolitiferous sea. If, as appears probable from the thickening of the interpolations towards the north, we suppose that the same land yielded the sandstones, shales, and vegetable basis of coal in the carboniferous and oolitic periods, the change of the land plants in the interval from lepidodendra to cycadites is very remarkable, especially when we take into account the exceptional case stated by De Beaumont, of plants of the true carboniferous era occurring above and below beds containing fossils of the true lias at the Col du Chardonet in Dauphine.
The Wealden formation suggests inquiries of the same order as to the situation and character of the ancient land, from which it has been assumed that a ​great river flowed into the estuary, through forests of large endogenous plants, tenanted by the iguanodon, hylæosaurus, and other large land reptiles. The limited range of the Wealden deposits, their quick termination toward the north-west and south-west, and their expansions, though feeble, to Beauvais and Boulogne, seem to render the supposition of a single river flowing from the west less probable than the concurrence of partial streams from the south and east, with a great current from the north. May we venture to suppose that the primary tracts of the Scandinavian peninsula and Scotland, with other land now sunk beneath the German Ocean, has been the source of most of the arenaceous and argillaceous deposits of the carboniferous, oolitic, and Wealden formations of England? In this point of view, the local strata of Brora, the thick coal series of Bornholm, the oolitic coal tracts of Yorkshire and Westphalia, the Wealden of Boulogne, Beauvais, Sussex, Dorset, Wilts, are all partial and local deposits due to a similar succession of causes, and arising from the same or neighbouring physical regions, as the materials of some of the older coal strata. In Bornholm, coal occurs with marine beds of all geological ages from the transition era to the cretaceous group; and the dependence of its deposits on the waste of the Scandinavian mountains is decided. The dependence of the other deposits on the waste of land in the north is a probable inference; and if we imagine, what is probably true, that the Scottish and Scandinavian coasts were once united, the whole of the phenomena are intelligible as varied deposits on the shores of one limited sea.
The distinction of quantity between the few oolitic and wealden plants, and the vast heaps of vegetable reliquiæ preserved in the older coal strata, is important, and might be explained as an effect of the diminution of the quantity of carbonic acid gas in the atmosphere, did not the uncertainty of our knowledge of the position of the ancient land, and the too local occurrence of the phenomenon, prohibit the application of such general views. It is supposed to be certainly proved (Buckland's ​Bridgwater Treatise), that the dirt bed in the island of Portland contains the remains of trees which really grew on the very spot, and were, by a general and quiet subsidence, overspread by oceanic sediments: the character of the cycadioideæ here buried demands our belief that the climate of the northern lands was then warm. It would be altogether unreasonable to doubt that the same explanation is required by the numerous and varied forms of reptile life, which, with the oolitic era, sprung into such wondrous magnitude: nothing can be more clear than the dependence of the geographical distribution of reptiles upon the feeble power of generating heat in their own bodies, in consequence of the nature of their respiration; for this renders their existence impossible without a certain amount of heat communicated from without. Hence the magnitude, and variety, and activity of reptile life under the tropics; hence the smallness, feebleness, summer life, and winter sleep, of the very few species which occur in the northern regions.
Perhaps we may properly appeal to the fossil corals of the oolitic rocks in support of this conclusion; but it would be ridiculous to quote mollusca or Crustacea for such a purpose; and, with regard to fishes, we must wait for the deliberate decision of M. Agassiz. It is remarkable that something like a gradation of deposits connects the red marls and lias marls of England; sandstones which might be referred either to keuper or to lias occur in Luxemburg and on the Rhine; while in the Alps of Savoy we see the oolites intercalated with green sands, and in Yorkshire and at Havre the Kimmeridge clay appears to join itself with the golt. These transitions are merely examples of the general harmony which connects together the whole system of stratified deposits into Vie varied and locally disturbed series of phenomena.
Cretacous System
Composition.—As in all the older great assemblages of strata, calcareous, argillaceous, and arenaceous rocks ​combine to form the Cretaceous System; but all of these have peculiarities by which they may, upon a great scale, be distinguished from the aqueous products of other periods. The arenaceous rocks are often found in the state of unindurated or even loose sand, the clays are generally soft and marly, the limestones soft and earthy. Peculiar colours also belong to these different members of the group: the sands are often green, sometimes very ochraceous, the clays of a pale greenish blue, the limestones white or red. Variations, however, occur in particular districts. The sands and limestones are usually rather coarsely grained, composed of clear worn quartz grains and pebbles, mixed with some calcareous matter, and coloured by disseminated ochraceous oxide of iron to yellow or brown tints (Woburn, Ryegate), or rendered green by interspersed large or small grains of a peculiar mineral (silicate of iron). This granular mineral is, indeed, eminently characteristic of the lower portions of the cretaceous system, being found commonly in two great groups of "green sands," in an intermediate clay, and in the superincumbent chalk. Nor is its diffusion confined to Europe: it is so abundant in the cretaceous rocks of the New World, as to be used for manure in New Jersey. Fuller's earth and good ochre lie in the lowest arenaceous sands (Woburn, Nutfield, Shotover). Layers of chert nodules occur in the sand, and sometimes beds of chert. In Kent, beds of whitish limestone, of considerable thickness, interlaminate the lower green sands; harder limestone lies in them in Lincolnshire. The clay is usually of a marly or even chalky type, and of a light blue tint (golt of Cambridge), but also of a full blue colour (Folkstone) and somewhat laminar texture; generally it holds small balls and irregular masses of clay indurated by oxide of iron, or crusted over by pyrites. In the Wealden district are some red layers. Green grains are commonly found in it: analysis generally shows it to contain much calcareous matter. Phosphatic grains and nodules cling to the Lower chalk, green sand and golt. ​
But the most peculiar characters belong to the calcareous rocks, which are, of all the limestones known (excepting some in the tertiary deposits), the softest and most earthy. Not that the whole mass is correctly described by the term chalk, as technically applied by geologists; but yet a large proportion of the rock would be so termed even by ordinary observers, from the whiteness and comparative softness of it. In the lower parts, green grains are common; at the base in Lincolnshire and Yorkshire, a red band of from 6 to 12 feet in thickness is traced. Throughout the lower and indeed the greatest part of the chalk in Yorkshire, flint nodules occur in layers; but in the south of England they are nearly confined to the "upper chalk," in which they form layers 4 to 6 feet apart. At Sudbury, flint laminæ occur in the planes of stratification, as at Meudon near Paris.
Stratification.—The clearest possible evidence of regular deposition from water is found in all the rocks of this system, but in few instances are either beds or laminæ traceable so clearly or for such distances as among the older formations. In the green sands, beds are seldom clearly traceable, except where, as in the Isle of Wight and at Folkstone, argillaceous beds occur below and above, and are interpolated among the sands, or where, as at Maidstone, Hythe, and in Lincolnshire, bedded limestones necessarily introduce this structure among the sands. In other cases the layers of chert nodules, or thin chert beds, mark the successive stages of deposition: where none of these causes exist, oblique lamination, and concretionary geodes and other arrangements of oxide of iron, render it almost vain to look for stratification.
The golt clays are sometimes laminated (Speeton, Folkstone), and often, by the courses of small nodules, or by interposed beds of sand, show proofs of successive deposition.
The chalk is only partially bedded, and not at all laminated: its slow, and quiet, and intermitting ​accumulation is, however, perfectly proved by the regular arrangement of the flint nodules, which are so common in its upper part. No layers of sand (or clay?) occur in any part of its thickr:ess. Joints are not, in general, either numerous or regujar in these formations, nor, excepting geodes and shells of oxides of iron, and the nodules of flint and chert, are concretionary structures common among them
Succession of Strata.—The basin of Europe offers generally the same succession of cretaceous deposits, as in the British islands; but there are local variations of importance. Two formations constitute this system in England and Ireland, which may be thus analysed and described:—
| Chalk formation, 600ft. thick. | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\\\ \end{matrix}}\right.$ | g Upper chalk, usually a soft white calcareous mass, with flint nodules at regular intervals: the upper part in the Isle of Wight is of a marly nature. |
| Chalk formation, 600ft. thick. | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\\\ \end{matrix}}\right.$ | f Middle chalk, not very clearly definable; of intermediate character as well as place between the upper and lower chalk. |
| Chalk formation, 600ft. thick. | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\\\ \end{matrix}}\right.$ | e Lower chalk, harder and less white than the Upper, sometimes varied by green grains, generally with fewer flints (red in the North of England). |
| Chalk formation, 600ft. thick. | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\\\ \end{matrix}}\right.$ | d Chalk marl; a soft argillaceous form of chalk. |
| Green sand formation, 600ft. thick. | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\ \end{matrix}}\right.$ | c Upper green sand (Firestone, malm rock, &c.); a mass of sands, occasionally indurated to chalky or cherty sandstone, of green, gray, or white colour; with nodules or laminæ of chert. |
| Green sand formation, 600ft. thick. | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\ \end{matrix}}\right.$ | b Golt (Tetsworth clay, Folkstone clay, &c.); soft bluish marly clay, with green grains. |
| Green sand formation, 600ft. thick. | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\ \end{matrix}}\right.$ | a Lower green sand (iron sand, Shanklin sand); a considerable mass of green, or ferruginous sands, with layers of chert, local beds of golt, rocks of chalky or cherty limestone, and deposits of ochre and fullers' earth. |
In the north of England the upper green sand is totally deficient; nor is it so distinct from the chalk formation in Kent and Sussex as in Berkshire and Wiltshire. In Yorkshire there is no lower green sand, but in Lincolnshire it is greatly developed, and contains useful calcareous beds. In the north of Ireland the series of cretaceous rocks corresponds nearly to the Englis type, the green sand being called mulatto, but the chalk is generally harder. Round the basin of Paris the series ​is also similar, as may be seen by consulting the classification of Cuvier and Brongniart.—About Aix-la-Chapelle, the same formations and groups appear; and the general features, at least, are retained through Westphalia (Essen, Paderborn) and along the plains of northern Germany. On the Elbe, about Dresden and Pirna, the lower green sand is called quadersandstein, the representative of the chalk planerkalk. In the Carpathians is no chalk, the green sand being greatly developed. In the Alps is no chalk, and beds of green sand are intercalated among the upper Jurassic oolites (Salève). But the most remarkable case is the addition of another limestone rock, above the upper chalk, very coarse and sandy in texture, but containing layers of flints, in St. Peter's Mountain, near Maestricht. This rock seems, by its composition and organic contents, to offer an imperfect transition from chalk to the calcaire grossier, one of the next incumbent tertiary strata (Fitton). Murchison and Sedgwick suppose the shelly marls of Gosau to present a somewhat different case of transition from the cretaceous system of the Styrian Alps to the tertiary rocks. The whole cretaceous system of America may be taken together into two great masses,—a chalky, or at least calcareous, mass above, and a green sand mass below. Thus very general analogies appear at very distant points, and the most constant of the formations is the sedimentary or green sand group. (Rogers, in Rep. to Brit. Assoc.)
Organic Remains.—The fossils of the cretaceous system are eminently marine: nearly all the plants which it contains (they are few) are of marine types; and the sponges, stellerida, mollusca, Crustacea, fishes, and reptiles, all appear to have been inhabitants of the ocean. Mammalia are not known in the cretaceous rocks. It appears that (excluding the Maestricht and Gosau beds) nearly the same large proportion of extinct genera, and the same differences of proportionate development of molluscous groups, is traced in the cretaceous as in the oolitic system; so that both the oolitic and cretaceous fossils are reliques of a condition of land ​and sea very different from what we now witness. The fossils of the two systems are, however, very materially different, even in the same natural groups, as sponges, crinoidea, stellerida, echinida, cephalopoda, Crustacea, fishes, and reptiles, in most of which groups the chalk and green sands contain genera never found in any rocks more ancient or more modern; while oolitic and tertiary genera are not found in the cretaceous rocks. There appears no sufficient evidence in the fossils of this system to justify any positive inference as to the character of the climate then prevailing in the northern zones; but we may be sure that the sea was very little disturbed by inundations from the land, otherwise ferns and other land plants, and not fuci, would have been found in the sandy strata.
The condition in which the zoophyta especially are preserved in the chalk and green sands deserves notice. Sponges are silicified in both deposits—possibly from some peculiar affinity which those organic bodies, even in a recent state, appear to possess for silica; but in the same flint nodules which envelope silicified sponges, the crusts of echinodermata and stellerida are found converted to crystallised carbonate of lime, and lamellar shells of the genus gryphæa, and radiated sheaths of belemnites, are not at all changed in texture, and very slightly altered in chemical composition. It is a very common fact that iron pyrites collects around sponges and other organic bodies in the chalk, and, when decomposed, leaves an ochraceous oxide of iron.
Geographical Extent.—In a general sense, the cretaceous system ranges parallel to the oolitic formations from Yorkshire to Dorsetshire, and sends branches from the plains of Hampshire which border on the north and the south the Wealden formation of Kent and Sussex. The green sand formation is, in all parts of England, so closely connected with the chalk (except in Yorkshire, where it is almost deficient, and in Blackdown, Devon), that it appears unnecessary to notice more than the characteristic range of the chalk. This distinguishing feature of English geology overlooks the German Ocean at Flamborough Head, and sweeps in a large curve inland by Birdsall and Pocklington to the Humber, at Hessle; thence it pursues a south-eastward course to Candlesby in Lincolnshire; and, after the interruption of the "Wash," reappears in the cliffs at Hunstanton. Hence to StokeFerry its course is south; but it turns S.W., parallel to the oolities, by Cambridge, Baldock, Wendover, Wallingford, to above Wantage and Devizes. Hence it returns east to the sources of the Kennet, and gives origin to a great ridge (the North Downs) dipping north, and passing by Kingsclere, Guildford, Reigate, Wrotham, and Maidstone to Dover; which corresponds to another great ridge (the South Downs) dipping south, and passing from Beachy Head by Lewes, Steyning, Petersfield, and Alton, to join the North Downs at Farnham. From the sources of the Kennet to Salisbury, and from Farnham to Bishop Waltham, the chalk expands over a vast space in Hampshire; but its proper outcrop is the western boundary of Salisbury Plain, by Lavington, ​Westbury, and Maiden Bradley. The Vale of Wardour is another deep indentation reaching almost to Wilton, from which the chalk returns to Shaftesbury, and then sweeps in a concave arch by Cerne Abbas to Beaminster, and suddenly retires in a narrow eastward course by Abbotsbury and Upway to Corfe Castle. This remarkable ridge of chalk (nearly vertical), reappears in the Isle of Wight at the Needles, and ends at the Culver Cliffs. Detached portions of chalk lie on the green sands of Blackdown; Portsdown and Thanet are detached
In Ireland, a large detached tract of chalk lies under the basalt of Antrim. About Ballycastle, Glenarm Bay, and Larne, and at Belfast, the superposition of the basalt on the chalk is very plainly seen. There is no chalk in Scotland or Wales.
On the continent of Europe, the cretaceous rocks are no where more perfectly developed than in France, where a complete series of the chalk and green sand formations encircles with a broad ring the tertiary basin of Paris; filling large tracts in Artois, Picardy, Normandy, Touraine, and Champagne; bordering the Channel from Boulogne to the mouth of the Seine, and resting every where on an oolitic basis, except on the Belgian frontier about Avesnes and Mons. Here it touches the slaty rocks of the Ardennes, and covers their parallel bands of coal and limestone. It continues north of the Meuse to Maestricht and Aix-la-Chapelle, and reappears beyond the Rhine in a narrow range and argillaceous condition, north of the Westphalian continuation of the Ardennes from Essen to beyond Paderborn. Detached portions occur about Hanover and Brunswick; and from the appearance of it at Grodno, Prentzlow, Luneburg, the isle of Rugen, and many parts in Jutland, Zealand, and Scania, there can be little doubt that chalk ​lies very extensively under the plains of northern Germany. (Heiligoland is formed of wasting green sand.)
The green sand formation is more extensively spread than the chalk, for it is chiefly in this form that we recognise the cretaceous system about Dresden, in the Alps, in the Carpathians, and even the Pyrenees. On the Italian side of the Alps, the chalk is supposed to be represented by the scaglia of Genoa and Lombardy.
In North America, according to Dr. Morton and Professor Rogers, the cretaceous system is largely developed on the Atlantic coast in New Jersey, whence it may be traced locally through Delaware, Maryland, Virginia, North and South Carolina, Georgia Florida, Alabama, Mississippi, Tenessee, Louisiana, Arkansas, and Missouri. In the northern parts of this extensive range, yellow ferruginous and green sands, and some argillaceous beds, constitute the greater part of the system, as in the Carpathians, and are excessively rich in the green silicate of iron; they are covered by friable limestones and calcareous sandstones. Such green sands occur more rarely in the south-western tracts, and are there associated with, and finally superseded by, very thick cretaceous and compact shelly limestones, apparently superior in position, which rise into bold hills. It is curious that, for a great part of this range, the green sands are separated from the primary strata more inland by a narrow belt of tertiary and alluvial deposits. "By specimens brought from time to time from the interior of the continent, it would appear to occur abundantly on the Missouri, far across towards the Rocky Mountains."
Physical Geography.—In England, the range of the chalk is one of the most conspicuous features of the eastern and southern counties, in which it forms a noble chain of hills, still partially left (as, perhaps, they all should have been) open for sheep-pasture. These ​"wolds" or "downs" are covered with a sweet short herbage, generally bare of trees, and singularly dry, even in the valleys, which for miles wind and receive complicated branches, all descending in a regular slope, yet are frequently entirely dry, and, what is most singular, contain no channel, and but little other circumstantial proof of the action of water, by which certainly they were excavated. Both the dry valleys and the bare hills have characteristically smooth and flowing outlines (represented with excellent taste by Fielding), very different from the tabular hills of oolite, and the rugged chains of older rocks. The same characters accompany the chalk in France, The green sand ranges are less characteristic, though in Leith Hill and Hazlemere Forest they rise to nearly 1000 feet in height, and thus rival the chalk, which generally swells to 800 feet, but no where, except at Inkpen Beacon, equals 1011. Copious springs flow from the chalk, over the subjacent golt; or issue on the dip side at low levels: wells sunk in the chalk to some hundred feet yield water, at different levels according to the impediments in the subterranean currents. Where tertiary clays cover the chalk, as in the basin of London, the boring rod no sooner pierces them than strong streams arise, with a temperature much superior to that of the surface, over which they sometimes flow in a constant stream.
Igneous Rocks.—In no part of England is there the smallest trace of igneous rocks associated with the chalk. In Ireland, a very large tract of basaltic rocks occupies the greater part of the drainage of Lough Neagh, and the river which issues from it to Coleraine. If a line be drawn from the mouth of Lough Foyle to Lurgan on Lough Neagh, nearly all the country to the east of it is trap, here and there in the interior, and generally on the coast, exposing chalk, and more locally mulatto, lias, new red sandstone or coal measures. The thickness is in places (Knockhead) supposed to be little short of 1000 feet, and the superficial area 800 miles! What a ​magnificent volcanic eruption is here pictured in its submarine lava currents! For it undoubtedly was a mass or series of expansions of liquid lava poured on the bed of the sea after the deposition of the chalk. It is a series of basaltic and ochraceous beds, some of the former being eminently columnar. Near the Giant's Causeway, the following succession is given by Dr. Richardson:
| 1. Basalt rudely columnar | 60 |
| 2. Red ochre or bole | 9 |
| 3. Basalt rudely prismatic | 60 |
| 4. Basalt columnar | 7 |
| 5. Intermediate between bole and basalt | 9 |
| 6. Basalt coarsely columnar | 10 |
| 7. Basalt columnar; the upper range of pillars at Bengore Head | 54 |
| 8. Basalt irregularly prismatic; in closing the wacke and wood coal of Port Noffer. | 4 |
| 9. Basalt columnar forming the Causeway. | 44 |
| 10. Bole or red ochre. | 22 |
| 11, 12, 13. Basalt, tabular, divided by the layers of bole | 80 |
| 14, 15, 16 Basalt, tabular, with zeolite | 80 |
The stratified rocks on which the basaltic masses rest, are variously altered by the effect of their former heat. Lias is changed, at Portrush, into a hard rock like flinty slate: by the side of basaltic dykes at Fairhead, the coal shales are similarly hardened: red sandstone is indurated at the foot of Lurgethan; and in Rathlin, at Glenarm, &c. the chalk is changed by dykes into a largely crystalline marble.
The quadersandstein (?) of Weinbohla (on the Danube) is overlaid by a syenitic v rock.
In the Pyrenees, cretaceous strata are in contact with granitic and serpentinous rocks, and mineral veins are in consequence introduced among them. (M. Dufrenoy.)
Close of the Secondary Period.—Ensuing Disturbances of the Crust of the Globe.
With the cretaceous system ends the long series of deposits which are, by general consent, ranked as strata of the secondary periods of geology. In reviewing the successive secondary formations, from the red sandstones ​to the green sand, and from the mountain limestone to the chalk, it is impossible not to recognise, on a great scale, the gradual change of the physical conditions of the globe which took place during this period. Mineralogically, the rocks successively deposited deviate more and more from the types of the primary strata; considered as to their zoological and botanical relations, it is evident that the circumstances influencing organic life were undergoing gradual but great changes; and a careful study of the geographical areas over which the secondary strata spread, demonstrates that an equal amount of variation occurred in the relations of land and sea. It may, indeed, be objected, that these conclusions, however true, are almost limited to Europe, North America, and India, since elsewhere the secondary rocks are but imperfectly known; but if the data for reasoning are satisfactory, the geographical area of their application, is ample.
Several distinct mineral types appear predominant in the secondary rocks of Europe, constituting various groups of strata, which may not always be found to combine into exactly the five systems adopted in these pages. The really oceanic types of limestone are three, viz.—
* Chalk,
* Oolite,
* Mountain limestone.
To each of these belong similar concretionary masses of flint or chert, often aggregated round organic bodies and sometimes extended into thin interrupted layers.
The really littoral types of sandstone are various:—
* Green or ferruginous sands.
* Pale coloured calcareous grits.
* Red and white sandstone.
* Red conglomerates.
* Felspathic sandstones.
* Quartzose grits.
Of argillaceous beds are three principal types:—
Not one of all these rocks can be considered as universally coextensive with the secondary series: but it appears from examination, that, in most districts, the conditions under which these various deposits happened, were contemporaneous, or at least succeeded one another in the same order. A very general view of the mineral relations of the rocks would allow us to consider the whole secondary series in two parts,—the lower one characterised by red sandstones and red clays, the upper by blue clays and light coloured sandstones; while in each of these divisions occur carboniferous deposits breaking the uniformity of the series. This arrangement is seen below:—
| Cretaceous group. | $\left.{\begin{matrix}\ \\\ \end{matrix}}\right\$ | Including the coal deposits of the Wealden, Yorkshire, and Bornholm. |
| Oolitic group | $\left.{\begin{matrix}\ \\\ \end{matrix}}\right\$ | Including the coal deposits of the Wealden, Yorkshire, and Bornholm. |
| New red sandstone group. | $\left.{\begin{matrix}\ \\\ \end{matrix}}\right\$ | Including the principal coal deposits of Europe. |
| Old red sandstone group. | $\left.{\begin{matrix}\ \\\ \end{matrix}}\right\$ | Including the principal coal deposits of Europe. |
Nor would such a classification be inapplicable to the calcareous portions of the series, though, as might be expected, these admit of other combinations. Whenever the causes of these successive mineral characters in the secondary rocks shall be known, a great advance will have been made toward a general theory of the stratified crust of the globe.
Turning to the organic remains of the several secondary systems, it is apparent that, within the period of time which elapsed between the deposition of the primary and tertiary strata, two very distinct assemblages of terrestrial plants had flourished and become extinct. The ancient and abundant flora of the carboniferous era, with its lepidodendra, sigillariæ, and calamities, had ​been replaced by new races of zamiae and cycadeæ, which, in their turn, vanished from the northern zones of the globe before the completion of the cretaceous system. The marine zoophyta were changed, though not to the same extent, both as regards the polyparia and crinoidea. One total change had come over the Crustacea,—not a single trilobite being known in the strata more recent than coal: the brachiopodous conchifera, the gasteropodous and cephalopodous mollusca, were equally altered. Two large assemblages of fishes had vanished before the deposition of the chalk; and both on the land and in the sea, gigantic reptile forms had come into being—reproduced themselves to a marvellous extent—and then all perished with the close of the secondary period.
How, then, can they, by whom the magnificent truths of elapsed time and successive creations have been put in clear and strong evidence, how can they be expected to yield to false notions of philosophy, and narrow views of religion, the secure conviction that, in the formation of the crust of the earth, Almighty wisdom was glorified, the permitted laws of nature were in beneficent operation, and thousands of beautiful and active things enjoyed their appointed life, long before man was formed of the dust of the ancient earth, and endowed with a divine power of comprehending the wonders of its construction? It is something worse than philosophical prejudice, to close the eyes of reason on the evidence which the earth offers to the eyes of sense; it is a dangerous theological error to put in unequal conflict a few ill-understood words of the Pentateuch, and the thousands of facts which the finger of God has plainly written in the book of Nature; folly, past all excuse, to suppose that the moral evidence of an eternity of the future shall be weakened by admitting the physical evidence for an immensity of the past.
Since the close of the secondary period, the earth's surface has been greatly altered and the boundaries of ​the ocean entirely changed in the northern zones, on the Mediterranean shores, and on the coasts of India and America. It is difficult to collect very certain evidence of the occurrence of general subterranean movements immediately after the completion of the chalk, though the great extent of sands, and pebbles, and lignitic beds which cover it, and the deep wasting on its surface, as seen beneath those sands and pebbles, leaves no doubt that what had been deep sea was converted to shallow water, and subject to inundations from the land. In many cases, these pebbles appear to be nothing else than broken and rolled flints, derived from the chalk itself; some of the white sands which form part of the tertiary series, when magnified, appear to be fragmentary particles of flint, very slightly worn by attrition; but, upon the whole, the great mass of tertiary deposits in every country can only be understood as derived from the older strata, and, in some cases, transported from considerable distances.
Clear proof of local disturbance of the chalk and older strata, before the production of any tertiary strata, can no where be given in England or Ireland, unless the pebble beds of the former country, and the basaltic eruption of the latter, be admitted in evidence. In the south-east of France De Beaumont ascribes to a late epoch in the cretaceous period the system of dislocations ranging from N. N. W. to S. S. E., which traverses Mont Viso, the French Alps, and the south-west extremity of the Jura. After the cretaceous period occurred the great disruptions of the Pyrenees and Apennines; but there is yet too little known of the geology of the Ghauts and the Alleghanies, to allow us to determine whether these ranges, which are rudely parallel to the same great circle as the Pyrenees and the Apennines, were (as De Beaumont supposes, and his speculation on the relation of age and direction among mountain chains requires) uplifted at the same geological epoch. ​
To determine exactly the geological date of a disruption of the crust of the globe is not easy, even when the case is so simple as that of a common "fault;" when it is to apply to a whole chain of mountains no more difficult problem can be proposed to geological observers. In the present case it is rendered still more perplexing by the change of mineral and organic characters which, on the flanks of the Pyrenees, almost destroys the distinction of secondary and tertiary deposits, and leaves little relation between the Apennine limestone and the chalk of Northern Europe, except what the scaglia of Lombardy has afforded.
As far as regards the British islands, a gradual or interrupted rising of the whole bed of the sea would much better suit the phenomena than one mighty convulsion; and Mr. Lyells views of the gradual rising of the Weald, though, perhaps, not entirely satisfactory in that particular instance, contain an important illustration of the consequences of such an hypothesis.
CAINOZOIC OR TERTIARY STRATA.
Supracretaceous Deposits.—Terrain Tertiaire.—Tertiärgebilde.
Offering a most decided contrast with the secondary and older strata in most of their essential characters, the tertiary strata form a division of the series which may be considered as of more elevated rank than the term "system," in our mode of using it (which is now become common) denotes. But, on the other hand, so many analogies appear among these strata of all ages, that, though with great propriety distinguishable into "formations," they must, for the present at least, be ranked in one general system. ​
Composition.—Arenaceous deposits predominate in most parts of the tertiary system; argillaceous types, however, abound in particular districts; calcareous rocks, marine or of freshwater origin, pure, sandy, shelly, or siliceous, lie in many basins; marls and gypsum are locally accumulated. Marine, freshwater, and terrestrial exuviæ occur in strata of all these descriptions; and so much information is now accumulated concerning them, and so many comparisons have been made between tertiary and modern products, that it is probable the origin of no part of the series of strata is so well understood. The sea, sudden land floods, river currents, lakes, springs, have all contributed to the accumulation of the supracretaceous strata, and left characteristic marks of their action. But confining our views, at this time, to the composition of the masses, those distinctions of the origin of the deposits vanish, for it is not directly by the mineral nature of the strata that their freshwater or marine origin could be known.
The arenaceous rocks are either in the form of conglomerates, holding fragments, pebbles, and enormous boulders of the neighbouring mountains, as the molasse of the northern slope of the Alps; or appear as sand (rarely indurated to sandstone), tinted of many varying hues, as at Alum Bay, in the Isle of Wight, where the effect of the many colours imparted by oxide of iron is of a magical description; left white and colourless, as in the Dorsetshire heaths and forests, and at Fontainbleau; or dyed of a general green, as near Paris, at Reading, Sudbury, &c., by silicate of iron. Beds of rolled pebbles (flints from the chalk) and layers of lignite appear not infrequently among them, and are generally accompanied by sulphuret of iron and clay (Isle of Wight). Mica occurs, but is not plentiful, in these tertiary sands, which convey the impression of much and long abrasion in water, and various exposure to oxygenating processes.
The argillaceous sediments of the tertiary system ​offer also a considerable variety. The principal mass in the vicinity of London is of a dull bluish or brownish tint, not unlike a clay of the oolitic era. The subapennine "marls" are more sandy. Light greenish and bluish marls accompany the limestones of Headon Hill in the Isle of Wight, and occur, with prismatised beds of gypsum, at Montmartre. But the most singular clays are those which accompany the coloured sands of Alum Bay and the neighbourhood of Paris; for these are almost black, or brown, or mottled in the richest manner with red or white, or almost entirely red, so that the same causes of diversity of colour appear to have affected nearly all the deposits of that particular tertiary period.
The tertiary limestones might, perhaps, generally be discriminated from all those of older date by their very inferior degree of induration, though to this certain freshwater limestones (as near Weimar) offer exceptions. The marine calcaire grossier of Paris is a coarse sandy or chalky limestone; the leithakalk of Austria is a coralline rock, somewhat like the English crag; the freshwater limestones of Headon Hill are soft, marly, and full of shells; that of Oeningen marly and laminated; near Weimar are very hard and compact beds, which inclose nodules of flint, like some in Cantal, described by Mr. Lyell; a peculiar siliceous limestone occurs in the basin of Paris.
From all these variations of composition, it is evident that the accumulation of tertiary strata is the fruit of a great diversity of causes, or else a great amount of local influences has modified the effects of the general agencies. It is not merely that some are of marine, and others of fluviatile, or of lacustrine origin: these are, indeed, the leading considerations to guide our inquiries, but local peculiarities of physical geography are also clearly indicated as important conditions in determining the nature of tertiary strata.
Structure.—Stratification.—The whole of the ​tertiary accumulations are plainly stratiform deposits; and they exhibit the different kinds of lamination and bedding which have been so often noticed before, while speaking of older rocks. The molasse of Switzerland, sandstone of Fontainbleau, and sands of the Isle of Wight, are stratified; sometimes, also, parted by oblique or parallel laminæ: the London clay and Headon marls are partially, the Montmartre marl perfectly, laminated: the marine calcaire grossier, and most of the freshwater limestones, are regularly bedded, and the latter very frequently laminated: gypsum occurs at Montmartre, and elsewhere in France, in a bedded mass.
Divisional Planes.—Agreeably to a very general law, which connects the divisional structures with the age of the rocks, and expresses their relative abundance and regularity in terms of their antiquity, we find them less remarkable in the tertiary sands, clays, and marly or chalky limestones, than in any of the older rocks. Joints do certainly exist in them, and especially in the lamellated limestones; and it is probable, from general considerations of the agency of heat in developing these structures, that, near large masses of igneous rocks, as in the Alps, they may be found more numerous. Nor does it appear that many cases of re-arrangement among the particles occur: some oolitic beds occur in the leithakalk; menilite is concentrated in certain marl beds near Paris; flint is collected in nodules in some fresh water limestones; sulphuret of iron gathers round and in the substance of lignite.
Succession and Thickness of the Strata.—Difficulties unfelt with regard to the older systems embarrass the history, or rather the classification, of the tertiary strata. The lower boundary of this system is in general very clearly marked by the peculiar mineral character and remarkable organic remains of the cretaceous rocks; but the upper boundary, the line of distinction between the "tertiary" deposits and those which we may agree to call "modern," is not at all clear. This difficulty arises in various ways: the mineral ​character and circumstances of aggregation of the tertiary rocks are extremely various according to locality; and in this respect so closely resemble formations now in progress, that were the bed of the Adriatic raised to our view, it would, according to the observations of Donati, most closely resemble the subapennine tertiaries; the German Ocean would disclose shelly sand-banks, comparable, perhaps, to the Norfolk crag; and the coral reefs of Bermudas may be thought to resemble the leithakalk of Transylvania. The analogy of tertiary and modern shells and vertebral reliquiæ is also very great,—so great, indeed, that nothing but very refined knowledge can establish differences between them.
When, in addition to these facts, we are further embarrassed by the intermixture of lacustrine, estuary, and marine deposits, which belong naturally to as many distinct series of operations, and certain organic exuviæ which may have unequal degrees of relation to existing types, what wonder if it be sometimes impossible to distinguish tertiary from modern accumulations? The progress of research has, indeed, shown us the necessity of separating from the tertiary class a considerable quantity and variety of superficial accumulations, more or less evidently related in their position to the present features of physical geography; but it has also placed the distinction on its true ground, viz. the difference of organic life in the modern and tertiary periods. This difference, however, is probably of a positive character only in the classes of vertebrated animals, which are chiefly met with in lacustrine sediments; and is with difficulty applied to marine races, which constitute by far the largest portion of tertiary fossils, and are the principal means of linking the history of supracretaceous deposits to those of the older periods, which contain almost no traces of mammalia or birds, and only a very limited number of flu via tile reptilia or lacustrine fishes.
It is hardly to be doubted, that hereafter the mode of studying supracretaceous deposits will be so far changed, ​that the whole series of marine accumulations of every age, from the cretaceous period to the present day, will be grouped together, but distinguished from another equally extended series of lacustrine and fluviatile sediments; the principle of investigation in each case being founded on a rigorous study of the characters of mineral structure, and the organic exuviæ, which are characteristic of the sea, the streams, and the land.
At present, however, not to deviate too far from the method now familiar to geologists, we shall assume that, in spite of the difficulties above noticed, the tertiary strata and modern deposits can be distinguished in particular cases, though not in conformity with any general definition. If the account of the modern deposits be in like manner arranged with reference to the same really influential conditions,—their marine or freshwater origin,—no confusion will, under any circumstances, be caused.
The English series of marine tertiaries is principally exhibited in the basin of Hampshire and the Isle of Wight, in the basin of London, and on the eastern coast, from the mouth of the Thames to that of the Yare; and each of these districts exhibits peculiarities of the component terms. The section of the Isle of Wight, at Alum Bay, one of the most remarkable known in the world, exhibits a great and varied mass of sands and clays, whose planes of stratification, originally horizontal, are now vertical. The whole may be considered as one formation; for, in the lower part, which is principally sandy, argillaceous beds occur, with fossils the same or very similar to those in the upper part. The following is a synopsis of these vertical beds:—
Freshwater Formations above.
In the basin of London, the series is less complete. Mr. Prestwich has determined the place of the London clay in the series to be below the Bagshot sand, and on the parallel of the Bognor beds. (GeoL Proc. 1847.) Hence the following general section:—
In Essex, Suffolk, and Norfolk, the plastic clay group is chiefly represented by the lower green sandy portions, which appear seldom deficient (being found in the Isle of Wight, at Reading, Woolwich, Sudbury, &c). The London clay is seen at Harwich; and a superior marine deposit, the " Crag, " unknown elsewhere in England, appears at Ramsholt, Orford, &c. in two divisions, while a third is added above in the vicinity of Norwich. Thus we have:—
Lower or coralline crag, less ochraceous, almost without pebbles; containing abundance of shells not at all ​worn, at Ramsholt, and abundance of corals not of European forms at Orford, where it is used as a limestone.
Below the Crag deposits of Essex and Suffolk the London clay is seen very extensively in the cliffs, and along the eastern valleys. It is singularly poor in organic remains; now and then a chelonian skeleton appears in the nodules of impure carbonate of lime which yield the 'Roman Cement.' These are now scarce on the shore and in the cliffs, and are obtained by dredging at small distances from the land. In the cliffs at Felixston, faults appear in this clay.
A deposit of tertiary shells in green and irony sands, and in blue clay, occurs at Bridlington in Yorkshire; it probably is of the age of the mammaliferous crag, and is covered by northern drift. The most general view of the English marine tertiaries shows sands to be more extensively diffused than clays; the latter are almost limited to the southern basins; the former are no where wholly deficient, and their lower green portions very characteristic. The calcareous crag is merely a local product.
Turning now to the district where first the genius of Cuvier awakened the philosophical study of the tertiary strata,—the basin of Paris,—we obtain highly interesting results for comparison with the English series and those of the south of France, Italy, and the Danube.
The Parisian series is quintuple, but only two of the terms are marine; two are decidedly of freshwater origin as to the materials (one certainly even lacustrine); the fifth (and lowest) is rather to be viewed as a troubled estuary or river deposit, and may be united with the lower marine formation. The whole stands in general terms according to the example on p. 257.; but we must observe that the several groups are partially mingled with one another by intercalation: there are, in fact, many marine and many freshwater strata, ​
| Upper term. | $\left\{{\begin{matrix}\ \\\\\\\\\\\ \end{matrix}}\right.$ | Epilimnic or upper freshwater formation—the uppermost of all the stratified deposits near Paris; consisting chiefly of siliceous limestone, or burr stone, marl, and marly sands. |
| Upper term. | $\left\{{\begin{matrix}\ \\\\\\\\\\\ \end{matrix}}\right.$ | Upper marine formation—consisting of sandstone, generally white, or partially reddened or ochraceous, and but slightly aggregated, except at Fontainbleau. |
| Lower term. | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\ \end{matrix}}\right.$ | Palæotherian freshwater formation—characterised near Paris by its ossiferous gypsum and marls, siliceous limestones, &c. |
| Lower term. | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\ \end{matrix}}\right.$ | Lower marine formation—consisting principally of limestone (calcaire grossier) of various degrees of coarseness, with laminated flint, marls both calcareous and argillaceous, green sands |
| Lower term. | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\ \end{matrix}}\right.$ | Plastic clay group—an irregular mass of deposits varying with locality, in places yielding plastic clay and sands; in other situations, lignites or pebble beds. |
There is no trace in the basin of Paris of the shelly and gravelly deposits (falun coquillier) of Touraine, which M. J. Desnoyers compares to the English crag, and considers to be more recent than the epilimnic group of the Parisian basin.
It is obvious that the agreement between the Parisian and English tertiaries is merely in the great features of succession: the lower marine formation in England is principally clay in France, limestone: gypsum abounds in the palæotherian freshwater beds of France, but not in England. Yet the basin of the Seine, and that of Hampshire, were connected with the same sea, and subject to very similar successions of marine and fluviatile agencies. The difference of deposits is due to the different materials transported in the currents of the sea.
In the south of France the tertiary deposits of the large basin of the Garonne, contain shells like those of Touraine; the beds of Narbonne and Montpellier more resemble the Parisian series. In M. Dufrenoy's recent memoir, he arranges the tertiaries of the south of France ​in a series of three terms, the upper one of which does not exist at all in the basin of Paris; while, on the other hand, the lower one, well developed near Paris, is only locally seen in the south.
| Upper term | $\left\{{\begin{matrix}\ \\\\\\\ \end{matrix}}\right.$ | Composed principally of beds of pebbles, sands, and coarse sandy clays, which appear all to be eminently detrital formations, so that Elie de Beaumont formerly called them 'Terrain de transport ancien.' Perpignan L offers the best type of these beds. |
| Middle term | $\left\{{\begin{matrix}\ \\\\\\\\\\\\\ \end{matrix}}\right.$ | Comprising a great variety of deposits, partly freshwater and partly marine; freshwater deposits of limestone on hills (Agenois, Provence); sands and pebbles (faluns) on the plains (Landes); sands and marls (molasse) in low hills in Languedoc; conglomerates at Pau; gypsum and lignites at Aix, and in Provence; concretionary limestones (calcaire moellon) at Montpellier. It contains locally sulphur, and generally iron ore. These variations are the result of local circumstances influencing the borders of an oceanic basin. |
| Lower term | $\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$ | Chiefly consists of calcaire grossier, and this is almost confined to the 'Landes' between the A dour and Garonne. The beds of limestone alternate with marls and clays, and rest on the cretaceous rocks. They are full of miliolites. |
The middle term of this series corresponds to the upper term of Paris: it expands greatly in Spain and Switzerland.
In Spain abundance of freshwater deposits occur; in Switzerland the sandy and conglomerate beds (molasse) expand into a vast thickness, include beds of limestone and layers of lignite yielding bones, and extend along the north front of the oolites of the Alps towards Vienna. Here in the basin of Lower Styria, Murchison and Sedgwick give us the following general section of the tertiary series. ​
| Upper group. | $\left\{{\begin{matrix}\ \\\\\\\ \end{matrix}}\right.$ | Calcareous sands and pebble beds, calcareous grits and oolitic limestone in the low ground of Hungary full of shells, as in the highest beds of the basin of Vienna. |
| Upper group. | $\left\{{\begin{matrix}\ \\\\\\\ \end{matrix}}\right.$ | White and blue marl, calcareous grit, white marlstone, and concretionary white limestone: shelly. |
| Middle group. | $\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.$ | Coralline limestone and marl, of a yellowish white colour, very thick and shelly (Leithakalk of Vienna.) |
| Lower group. | $\left\{{\begin{matrix}\\\\\\\\\\\\\ \end{matrix}}\right.$ | Conglomerate, with micaceo-calcareous sand and millstone conglomerate: thick. |
| Lower group. | $\left\{{\begin{matrix}\\\\\\\\\\\\\ \end{matrix}}\right.$ | Blue marly shale, sand, &c., full of shells compared to those of London clay and calcaire grossier. |
| Lower group. | $\left\{{\begin{matrix}\\\\\\\\\\\\\ \end{matrix}}\right.$ | Shale and sandstone, with coal or lignite, containing bones of anthracotheria, gyrogonites, &c. |
| Lower group. | $\left\{{\begin{matrix}\\\\\\\\\\\\\ \end{matrix}}\right.$ | Micaceous sandstones, grits, and conglomerates, made up of the detritus of the primary slaty rocks, on which they rest at high angles of inclination. |
The authors consider the lower group to correspond with the calcaire grossier and Palæotherian deposits; the middle to the English crag, and middle subapennines. According to M. Dufrenoy, the former would rather appear to belong to the middle tertiary period. In his latest memoir on the Alps and Carpathians, Sir R. Murchison expresses the conviction that the flanks of the Alps exhibit a true transition from the younger secondary into the older tertiary strata, and that the older supracretaceous rocks occur abundantly, and well characterized, in the South of Europe, extending thence eastward into Asia. The cretaceous beds, containing inoceramus and ananchytes, are conformed in position to the overlying tertiary rocks characterized by nummulites, and in this latter series we still find gryphæa vesicularis.
The sections of Transylvania, Hungary, and Moravia ​may be reduced to the above general type; the lower beds being more argillaceous.
The Italian tertiaries constitute a triple series, but the lower and upper terms appear only at particular points.
The relation of these tertiary to the subjacent cretaceous groups has again been the subject of an elaborate investigation by Murchison. Taking the limestone of La Spezia and Carrara (of Lower Jurassic age) to be the oldest of the Italian secondaries, we have above the ammonitico rosso and the cretaceous series, this latter being well exhibited on the flanks of the Venetian Alps and about Nice. In these localities they are covered conformably by tertiary accumulations, characterized by nummulites, and devoid of types of secondary fossils. In such sections it is only by the sequence and combinations of the forms of life that the separation of tertiary and secondary strata can be safely attempted, nor can a hard line be drawn where nature has employed the softening pencil.
Geographical Extent, and Physical Geography.—
the regular marine series of deposits: its relation to the existing oceans is therefore a highly interesting subject of inquiry; the more so, as, from the phenomena of alternating marine and freshwater deposits, conclusions have long since been presented by distinguished writers that particular tracts were alternately raised above and sunk below the sea. Cuvier and Brongniart proposed this hypothesis to explain the freshwater interpolations among the marine strata of Paris; and the notion has gradually become a popular part of geological speculation. The solution of an old geological problem requires far more caution than the explanation of a modern geographical phenomenon. For in regard to the older events we are seldom aware of all the essential facts, from which not only the nature of the physical agency is to be ascertained, but the measure of its force, the local centre of its effect, and the sudden or gradual, the continuous or interrupted mode of its application. The geographical relations of tertiary strata must be understood before venturing to adopt or to reject the hypothesis of partial elevation and subsidence.
Before the deposition of the tertiary system, Europe had acquired many of its marking features: the Pyrenees, Brittany, parts of Wales and Scotland, Scandinavia, the Carpathians, Apennines, the mountains of Bohemia, the Vosges, Auvergne, and other tracts, were uplifted above the sea. But these appear to have stood up like unconnected islands, round which the ocean currents passed variously into wide basins like those of the Danube, Paris, &c.; or poured into insulated bays, like what may be termed the Gulf of Bohemia. The direction, force, and materials mixed with these currents, would be materially influenced by the submarine slopes from these insulated ridges, and by other undulations in the bed of the sea; the nature and abundance of the tertiary sediments, and the organic forms which are buried in them, would be greatly dependent on the force and origin of the currents: and thus we see a reason why ​tertiary strata should be so distinctly related to the present configuration of the surface of the earth, and so various both as to mineral character and organic contents, though the basins, as we term them, in which they now appear, were parts of one general ocean. In a few instances, however, the tertiary deposits were almost totally formed in vast lakes or inland seas, as in the valley of the Rhine, from Basle to Bingen.
The relation of tertiary deposits to existing seas will appear from the following classification of the European deposits:—
1. Connected by gradual inclinations with the North Sea.
2. Between the Baltic and the Black Sea.
3. Dependent on the English Channel.
4. Bordering the Atlantic.
5. Bordering the Mediterranean.
Besides these are the following secluded tracts:—
These latter may be viewed as seas wholly drained; the former as merely the raised margins and bays of the actual seas. But this view is imperfect: since the date or during the progress of the tertiary deposits, the partial as well as general uprising of the bed of the sea has materially changed their geographical relations, by separating parts once united, and giving to the detached parts a delusive character of basin-shaped insulated accumulation, which further researches will not justify. For instance, the uprising of the chalk and Wealden tracts between London and Portsmouth has divided the basins of the Solent and the Thames; on a far grander scale, the Alps, raised, at least in part, since all the tertiaries were formed, have given a more complete geographical opposition than originally existed between the tertiaries of the Danube and the Po. It may indeed be supposed, in conformity with Mr. Lyell's views, that the insulation thus attributed to the subsequent rising of mountains, may have been begun by their contemporaneous rising,—a mode of explanation well suited to the case of the difference in the Hampshire and London basins.
Before the production of the earliest tertiaries, inundations from several uplifted ranges of country (as the Pyrenees, Brittany, Auvergne, the Ardennes, and parts of the Jura, sent detritus into the sea of Paris: the London tertiaries are supposed by Mr. Lyell to have been derived from the waste of the previously raised or then rising Weald: oceanic currents would plough the sloping parts of the submarine land; and thus we have a clear explanation of the mixture of marine and fluviatile sediments, as well as the local diversity of their nature, which so remarkably characterises the tertiary strata. The purely lacustrine deposits, with their embedded mammalia, tell a different history. The tertiary land was raised where they occur at the time of the existence of these mammalia; and thus it is often possible to prove that considerable movements of the bed of the sea occurred during the tertiary period. With regard to the age of ​lacustrine and fluviatile deposits, it is to be observed, that when a series of such beds lies inclosed in marine sediments, as the gypsum of Montmartre, the lignites of the Isle of Wight, Zurich, and Styria, they must of course be ranked according to the marine strata with which they are associated; but when, as at Headen Hill in the Isle of Wight, on most of the plateaux round Paris, at Œningin, at Georges Gmünd, the freshwater deposits are uncovered by any but superficial accumulations, how can their true geological age, on the scale of marine formations, be known? No method but one is likely to be at all satisfactory, the study of their embedded organic exuviæ; which therefore is the method now generally adopted. Mr. Conrad and Professor Rogers have thus classed the tertiaries of North America. How far this mode can be safely trusted will be considered in the next section.
Organic Remains.—In general, no contrast can be greater than that offered by comparison of the tertiary with secondary and primary plants, shells, and vertebral reliquiæ—no analogy more striking than between the tertiary and living forms of life. Plants, shells, insects, and even quadrupeds, of the same genera, sometimes even of the same species (as far as naturalists can decide so nice a point), often so similar as to be only distinguishable by minute circumstances, render it doubtful to the inexperienced, whether they are not rather looking upon the buried remains of the present creation, than upon the work of one of those systems which passed away before the birth of man. The number of the species of tertiary fossils is very great, as compared with that of even the rich and well-explored oolites; among them are far more fresh water tribes, and far more terrestrial forms, than among all the older strata taken together; a conclusion which harmonises perfectly with the leading fact of the history of their formation, viz. that before the period of their formation, the great sea of Europe was broken into ​basins between ranges of mountains and masses of land, which in various ways influenced the deposits and supplied some of their organic contents. Yet, upon the whole, the number of terrestrial and freshwater remains is small compared to the marine; a circumstance which, as far as relates to the products of fresh water, is analogous to the present condition of nature. With regard to plants on the land, it has been already shown, (page 70.) that, however numerous these might be, only a few of them would reach the sea, except under particular circumstances of physical geography. The number of land animals already found in tertiary lacustrine, fluviatile, and marine deposits, ought perhaps to strike us by its magnitude, rather than by its inferiority to the catalogue of the living quadrupeds.
Referred to the groups of the basin of Paris, M. Adolphe Brongniart presented, in 1829, the following synopsis of the tertiary plants:—
In the group of plastic clay and lignites :
| Marine plants, noneLand and freshwater plants, chiefly coniferæ, palms, and amentaceæ | 30 or 40 |
| In calcaire grossier and Monte Bolca beds— ||
| Marine plants | 16 |
| Land and freshwater plants | 16 |
| In the palæotherian and epilimnic freshwater beds— ||
| Marine plants, none |
| Land and freshwater plants | 21, |
From the laborious and successful researches of M. Deshayes concerning tertiary mollusca (see Lyell's Geology, vol. iii. first edition), we shall extract some of the leading results.
| The recent species examined by this eminent conchologist amounted to | 4780 |
| The fossil species of the tertiary system alone | 3036 |
| Together | 7816 |
| Of which were found both recent and fossil 426, leaving for the total number of species examined | $\left.{\begin{matrix}\ \ \end{matrix}}\right\$ | 7390 |
| The ratio of the species which are both recent and fossil, to the whole number is | $\left.{\begin{matrix}\ \ \end{matrix}}\right\$ | 5.7 to 100.0 |
The 4780 living species consisted :
| of univalves | $\left.{\begin{matrix}\ \ \end{matrix}}\right\$ | 3616 | or percent | $\left\{{\begin{matrix}\ \ \end{matrix}}\right.$ | 75.6 |
| bivalves | bivalves | 1164 | or percent | $\left\{{\begin{matrix}\ \ \end{matrix}}\right.$ | 24.4 |
| $\left.{\begin{matrix}\ \ \end{matrix}}\right\$ ||
| univalves | $\left.{\begin{matrix}\ \ \end{matrix}}\right\$ | 2098 | ————— | $\left\{{\begin{matrix}\ \ \end{matrix}}\right.$ | 60.1 |
| bivalves | bivalves | 938 | ————— | $\left\{{\begin{matrix}\ \ \end{matrix}}\right.$ | 30.9 |
* Among the shells examined were included 1465 recent, and 259 fossil.
Shells of the land and freshwater, viz. :
| Freshwater species, | living | bivalves | 118 | fossil | 30 |
| | | univalves | 151 | fossil | 151 |
| Land species, | living | univalves | 1196 | fossil | 78 |
| As before observed, the ratio of the number of species, both recent and fossil, to the total number of recent and fossil observed, is | $\left.{\begin{matrix}\ \\\ \end{matrix}}\right\$ | 426 to 7390, or, 5.7 to 100 |
| The ratio of the same to the number of recent species, 4780, is | 8.9 to 100 |
| And to the number of fossil species, 3036, is | 14.0 to 100 |
But this last general average of the number of tertiary species now living, is composed of many very different ratios, by the study of which M. Deshayes has been led to class the tertiary formations upon a new principle. He assumes, as a general truth, that those tertiary deposits which contain the greatest proportion of existing species are of the most recent date; and on the contrary, that those in which the ratio of existing species is smallest are the oldest. Applying this principle to the most important localities of tertiary strata, and grouping together those which have the greatest agreements in ratio of living species, he arrives at the following series of three terms for the whole mass of tertiary strata.
Localities. :
| Upper or most recent group. | $\left\{{\begin{matrix}\ \ \end{matrix}}\right.$ | Sicily; the subapennine beds; the crag. (Perpignan and the Morea agree in their fossils with the subapennine beds. ​ |
| Middle group. | $\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.$ | Bordeaux; Dax; Touraine, Turin; Baden; Vienna; Angers; Ronca. The Viennese and Baden fossils are a general type for Moravia, Hungary, Cracovia, Volhynia, Podolia, and Transylvania. |
| Lower group. | $\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.$ | Paris, London, Hants, Valognes, Belgium. (The fossils of Castel, Gomberto and Pauliac are the same nearly as those of the basin of Paris. |
From each of these localities, the ratio of the species now living has been determined by M. Deshayes as under:—
Upper group. General proportion of living species. 49 per cent. (Allowance being made for occurrence at more than one locality.) :
| Sicily has yielded | 226 | species, of which | 216, | or | 95.0 | per cent, are living. |
| Subapennine | 569 | | 238 | | 41.8 |
| Crag | 111 | | 45 | | 40.1 |
| Middle group. General proportion of living species, 18 per cent. |||||||
| Vienna has yielded | 124 | species, of which | 35, | or | 28.2 | per cent, are living. |
| Baden | 99 | | 26 | | 26.2 |
| Bordeaux and Dax | 594 | | 136 | | 22.9 |
| Touraine | 298 | | 68 | | 227 |
| Turin | 97 | | 17 | | 17.5 |
| Angers | 166 | | 25 | | 15.0 |
| Lower group.—General proportion of living species, 3½ per cent |||||||
| Ronca has yielded | 40 | species, of which | 3, | or, | 7.5 | per cent are living. |
| London | 239 | | 12 | | 5.0 |
| Paris | 1122 | | 38 | | 3.4 |
Mr. Lyell, by independent researches, was induced to class the Sicilian deposits as a separate formation from the rest of the upper group of Deshayes; but in other respects his scheme of nomenclature subjoined is perfectly in accordance with Deshayes' results.
| Newer pleiocene of Lyell | — | Sicilian deposits, with 95 per cent recent species. |
| Elder pleiocene | — | Italian and crag deposits, with 41. |
| Meiocene | — | Vienna, Bordeaux, Turin, &c. 18. |
| Eocene | — | Paris, London, Belgium, 3½. |
The terms are derived from the Greek καινος, recent, combined with ήως, the dawn, μειῶν, less, and πλειῶν, more. ​
I have elsewhere tested the results of M. Deshayes researches in a peculiar manner, and shown that, tried by the relations existing among one another, the classification which he has proposed is well founded: there may be doubts as to the exact discrimination of the species, and the precise proportions of recent forms included among the fossils; but as the whole have been examined by an eminent naturalist, it is probable that, even if the species supposed to be identical were not so, the conclusion of the order of antiquity of the several deposits would be correct. The only thing remaining to be examined, before adopting these conclusions, is, the general principle upon which they all depend. (p. 266.)
This principle is not collected, as an inference, from many observations on the order of tertiary strata, and determinations of the proportion of living species in each, according to its known position in the series; nor is it to be considered in the same light as a mathematical principle, assumed as the basis of certain deductions, which, being compared with phenomena, may serve to test the truth of the assumption; but, in the absence of proof, it is to be admitted or denied upon the following statement of the reasons. In all the series of stratified rocks, the systems of organic nature are found to be different, according to the period: these differences are sometimes gradually, and sometimes abruptly, produced between system and system: in any one clearly defined system, the strata differ as to their organic contents, according to their order of superposition, and the nature of the rock; and, upon the great scale, are characteristic both of geological period and local conditions. Below the tertiary system are no recent species: at the base of that system the lower strata, determined to be such by observation of their position, undoubtedly contain only a very small proportion of recent forms (basin of Paris): in the middle of that system, determined as before, the strata contain about 20 per cent, of recent forms (Bordeaux): in the highest of the system (in ​only one locality, Sicily), the strata contain 95 per cent, of existing forms.
Supposing these statements (which might be fortified by other equally important but more refined results) are thought sufficient to establish the principle, that the affinity of fossils to recent forms, commencing with the geological date of the chalk, has gone on increasing gradually to the close of the tertiary period, and that, therefore, the relative age of tertiary strata is to be judged of by the proportion of recent forms in them, let us inquire what difficulties lie in the way of the practical application of the doctrine.
There is a real difficulty in determining upon what basis to make the required comparison between fossil and recent forms: whether the fossils of a particular region, as, for example, the subapennine countries, should be compared with the whole series of known testacea, or with the shells of the adjoining Mediterranean, to whose products they are extremely similar, and from whose waters they may be thought to have been raised.
In certain cases it appears probable that the strictness of the rule must be relaxed to avoid important errors. For example, the long basin of the Danube, the valley of the Rhine, the basin of Paris, contain a great variety of organic forms, which must have been peculiar to those arms and gulfs of the sea, as we find at this day peculiar shells in almost every partially insulated bay of the sea. But these tertiary tracts having been wholly raised to dry land, all their peculiar shells have perished; and the analogy of the fossil to recent types appears less than would be the case with strata like the subapennine beds, which are yet margined by the sea, out of which they were uplifted.
Peculiar shells live in the German Ocean and English Channel: the crag formation is supposed to contain many now living in these waters; but, had the whole of these seas been obliterated by the rising of their bed, the extensive shelly sand thus brought to the surface would have presented but slight analogies with the general catalogue of ​recent shells from which the peculiar forms were excluded.
These remarks are by no means brought forward to discredit the highly important results of M. Deshayes and Mr. Lyell, but to draw attention to the basis on which they rest, and to induce geologists to follow steadily a plan of observation, which may place the principle assumed on such a foundation as to authorise its being used as the origin of deductions, which may have undoubted influence both in theoretical and positive geology.
Professor Rogers, in his Report on the Tertiary and Secondary Rocks of North America, has adopted the nomenclature of Mr. Lyell, and ranked the deposits on the eastern coast chiefly according to their proportionate numbers of recent forms, as eocene, meiocene, and pleiocene. Both the recent and fossil species of America are, however, almost wholly different from those of Europe: of 210 'eocene' species in America, only 6 belong to Europe; of 195 meiocene and pleiocene shells, only 6 belong to Europe; not more than 32 recent testacea and shelly annulosa are stated by Mr. Conrad to be common to the two sides of the Atlantic.
The number of species of other in vertebral animals buried in tertiary sediments, is very much too small to justify any general inferences; but we may attend to what M. Agassiz has stated concerning the subject of his successful studies.
"The fishes of the tertiary strata are so nearly related to existing forms, that it is often difficult, considering the enormous number (above 8000) of living species, and the imperfect state of preservation of the fossils, to determine exactly their specific relations. In general, I may say that I have not yet found a single species which was perfectly identical with any marine existing fish, except the little species which is found in nodules of clay, of unknown geological age, in Greenland. The species of the Norfolk crag, of the upper subapennine formation, and of the molasse, are mostly referable to ​genera common in tropical regions; such as platax, cartharias, myliobates, &c. In the lower tertiaries of London, the basin of Paris, and Monte Bolca, at least a third of the species belong to genera which are now extinct."
In the chalk, two thirds of the species belong to extinct genera; and in the oolitic system, not a single species can be referred to a living genus!
The same conclusion as to the great general analogy and real specific differences between the fossils of the tertiary series and living races comes with equal force from a consideration of the families of reptiles. Among chelonida, occur freshwater trionyces and emydes, as well as marine cheloniæ and terrestrial testudines: among saurians we have no more the geosaurus, mastodonsaurus, streptospondylus, megalosaurus, ichthyosaurus, plesiosaurus, nor iguanodon; but instead of these extraordinary creatures of the oolitic and saliferous epochs, genuine crocodiles, very nearly agreeing with existing types, appear for the first time, and in considerable variety: decided batrachia show themselves in the freshwater beds of Œningen and the brown coal of the Rhine, and in this latter deposit are accompanied by snakes.
Without stopping to notice the few remains of birds, which are rare even in tertiary formations, we shall pass to consider the very interesting question of the relation of the quadrupeds of the tertiary periods to the present free and domesticated tribes.
In general it is to be remarked, that, concerning the date of some of the fossil animals, especially when they occur in lacustrine deposits not interstratified with marine formations, there is danger of confounding tertiary with diluvial species; but this difficulty applies only to some particular cases, and will be better discussed when we come to speak of the diluvial deposits, to which we shall defer the reasonings we have to offer on fossil mammalia in general. ​
In the following catalogue of remains of mammalia in tertiary strata, chiefly taken from Meyer's Palæologica, extinct genera are marked by an asterisk.
Section A.—In Marine Deposits. :
| Carnivora. |
| Gulo antediluvianus | In sand. Eppelsheim on the Rhine. |
| Canis | In Volhynia, with marine shells. |
| Felis aphanistes | Eppelsheim |
| ogygia | Eppelsheim. |
| prisca | Eppelsheim. |
| Phoca | Hungary. |
| Rodentia. |
| Castor | Crag of Essex. |
| Palaeomys castoroides | Eppelsheim. |
| Hare | Faluns of Touraine. |
| Aulacodon (chelodus) typhus | Eppelsheim. |
| Chalicomys Jageri | Eppelsheim. |
| Myoxus primigenius | Eppelsheim. |
| Spermophilus supercilious | Eppelsheim. |
| Cricetus vulgaris | Eppelsheim. |
| Chloromys | Volhynia. (Also in freshwater deposits.) |
| Pachydermata. |
| Mastodon angustidens | In subapennine formation. In the faluns of Touraine. Eppelsheim. |
| arvernensis | Eppelsheim. |
| Hippopotamus major | In faluns of Touraine. |
| minutus | In faluns of Touraine. |
| undetermined | In molasse, Galicia, and Switzerland. |
| Rhinoceros Schleiermacheri | In sand. Eppelsheim. |
| incisivus | Eppelsheim. |
| leptodon | Wiesbaden. |
| Elephas primigenius | In sandstone, 456 ft. Warsaw. In sandstone at Wieliczka. In molasse, near Estavayer, Switzerland. ​ |
| * Diehobune | In Calcaire grossier near Nanterre. |
| * Dinotherium Bavaricum | France, Bavaria, Eppelsheim. |
| giganteum | Eppelsheim. |
| Equus caballus primigenius | In the faluns of Touraine. In sand. Eppelsheim. |
| mulus primigenius | Eppelsheim. |
| asinus primigenius | Eppelsheim. |
| Sus antiquus | Eppelsheim. |
| palæochaerus | Eppelsheim. |
| ——— | In molasse. Estavayer. |
| * Palæotherium | Under calcaire grossier in the department of Gironde; at Provins; in Touraine; at Zurich. |
| * Lophiodon | Under calcaire grossier at Provins. Eppelsheim. |
| Tapirus priscus | Eppelsheim. |
| Ruminantia |
| Cervus anocerus | Eppelsheim. |
| brachycerus | Eppelsheim. |
| trigonocerus | Eppelsheim. |
| dicranocerus | Eppelsheim. |
| curtocerus | Eppelsheim. |
| Deer | In the faluns of Touraine. |
| Antelope | In molasse. Estavayer. |
| Moschus antiquus | Eppelsheim. |
| Cetacea |
| Manatus fossilis | In Calcaire grossier. East coast of Maryland. |
| Balsena fossilis | Virginia, Wurtemburg, Dauphine, Berne, Montpellier. |
| Sect. B.In Lacustrine and Lignitic Deposits of known Geological Era. ||
| Vespertilic Parisiensis | Gypsum of Montmartre. |
| murinus fossilis | Œningen |
| Nasua | Gypsum of Montmartre. |
| Viverra Parisiensis | Gypsum of Montmartre. |
| Hyæna Parisiensis, Clift | Styrian brown coal. |
| Vulpes vulgaris, Mantell | Œningen (Murchison). ​ |
| Canis | Gypsum of Montmartre. |
| Didelphis Cuvierii | Gypsum of Montmartre. |
| Castor | Brown coal near Zurich. |
| * Anœma Œningensis | Œningen |
| Mus musculus | Œningen |
| Myoxus | Œningen; Montmartre. |
| Sciurus | Montmartre. |
| Lagomys | Œningen |
| * Mastodon tapiroides | Montabusard, near Orleans. |
| turicense | In brown coal near Zurich. |
| * Adapis Parisiensis | Gypsum of Montmartre. |
| Chœropotamus Meisneri | In brown coal near Zurich. |
| * Anthracotherium magnum | Brown coal of Cadibona; marl of Limagne. |
| minus | Cadibona. |
| minimum | Lot et Garonne. |
| Alsaticum | Lobsan. |
| Velaumum 1 and 2 | Puy en Velay. |
| undetermined | Brown coal of Scheineck in Styria. |
| * Anoplotherium commune | Montmartre; Isle of Wight. |
| secundarium | Montmartre. |
| * Xiphodon gracile | Montmartre. |
| * Dichobune leporina | Montmartre. |
| murina | Montmartre. |
| obliqua | Montmartre. |
| * Cainotherium 2 species, Bravard | Puy de Dôme. |
| * Palæotherium magnum | Montmartre. |
| medium | Montmartre. |
| crassum | Montmartre. |
| latum | Montmartre. |
| curtum | Montmartre. |
| minus | Montmartre. |
| minimum | Montmartre. |
| Aurelianense | Orleans; Argenton. |
| Isselanum | Issel. |
| Velaunum | Puy en Velay. |
| * Lophiodon tapirotherium | Issel. |
| occitanicum | Issel. |
| Isselense | Issel; Argenton; Soissons. |
| medium | Argenton. |
| minimum | Argenton. |
| tapiroides | Buchsweiler. |
| buxovillanum | Buchsweiler. |
| giganteum | Montabusard. ​ |
| * Lophiodon Monspessulanum | Montpellier. |
| siberium | In limestone, Government of Orenburg. |
| other species | Laonnois; Argenton; Paris; Frankfort. |
| Cervus capreolus Aurelianensis | Montabusard. |
| Sect. C.—In Lacustrine Deposits of Doubtful Era. ||
| Ursus spelseus | Georges Gmünd. |
| Vulpes | Georges Gmünd. |
| Hyæna, Hehl | Gypsum of Unterturkheim. |
| Mustela | Georges Gmünd. |
| Choeropotamus Soemmeringii | Georges Gmünd. |
| * Palarotherium Aurelianense | Georges Gmünd. |
| * Anoplotherium commune? | Georges Gmünd. |
| * Mastodon minutum | Georges Gmünd. |
| Rhinoceros pygmaeus | Georges Gmünd. |
| Hippopotamus, $\left.{\begin{matrix}\ \ \end{matrix}}\right\$ Bos, | Georges Gmünd. |
| 1. Crassatella aulcata. Sowerby. | $\left.{\begin{matrix}\ \\\\\ \end{matrix}}\right\$ | Chiefly found in the London clay. |
| 2. Venericardia planicostata. Sowerby. | $\left.{\begin{matrix}\ \\\\\ \end{matrix}}\right\$ | Chiefly found in the London clay. |
| 3. Conus scabriculus. Sowerby. | $\left.{\begin{matrix}\ \\\\\ \end{matrix}}\right\$ | Chiefly found in the London clay. |
| 4. Voluta dubia. Brander | $\left.{\begin{matrix}\ \\\\\ \end{matrix}}\right\$ | Chiefly found in the London clay. |
| 5. Fusus contraries. Sowerby. | | From the crag of Suffolk. |
| 6. Fusus bulbiformis. Sowerby. | $\left.{\begin{matrix}\ \\\\\ \end{matrix}}\right\$ | Chiefly found in the London day. |
| 5. Fusus contraries. Sowerby. | $\left.{\begin{matrix}\ \\\\\ \end{matrix}}\right\$ | Chiefly found in the London day. |
| 7. Dentalium striatum. Sowerby. | $\left.{\begin{matrix}\ \\\\\ \end{matrix}}\right\$ | Chiefly found in the London day. |
| 8. Paludina lenta. Sowerby. | $\left.{\begin{matrix}\ \\\\\ \end{matrix}}\right\$ | Chiefly found in the London day. |
Disturbing Movements during and after the Tertiary Period.
In England, two lines of subterranean movement have long been known, by which the tertiary and secondary strata have been raised into anticlinal ridges and sunk into synclinal hollows. They both range east and west, or nearly so; one line, viz. from the Vale of Pewsey by Kingsclere, Farnbam, Guildford, and through the Weald of Sussex to Boulogne, is somewhat parallel to the vale of the Thames; the other, from Weymouth by the isle of Purbeck through the Isle of ​Wight, is nearly parallel to the south coast of England. Thus the lines would converge toward the east somewhere about Boulogne; and diverge westwards, so that, if continuous (which they are not), the northern one would nearly coincide with the south side of the South Wales coal field, and the southern one pass across the southern part of Devonshire. Each of these two lines of dislocation has caused the strata to dip with great steepness to the north (in the Isle of Wight, the beds on this dip are vertical), but the southward dip is in each case moderate. A cross section gives the following appearance:—
| Isle of Wight. | Basin ofHogsback. | Basin of London. |
To disturbances during the tertiary periods, M. de Beaumont ascribes the elevation on a north and south line of the ridges of high land in Corsica and Sardinia: the Western Alps (from the Mediterranean to Mont Blanc) are considered to have been raised after the deposition of the Swiss molasse, in a direction N.N.E. and S.S.W.; and the principal chain of the Alps, from the Valais into Austria, E. ¼ N. E., to be of so recent a date as to have succeeded all the true tertiary deposits, and to have coincided with the dispersion of the great blocks and masses of diluvium on both slopes of the Alps.
Igneous rocks are no where in England associated with the tertiary strata; but in many parts of Europe, as in Central France, the north and south of Italy, Sicily, on the Rhine and in Hungary, volcanic phenomena are even specially abundant among lacustrine tertiaries.
From the activity of Etna and Vesuvius, we pass by ​an easy gradation to the phenomena which mark the former violence of the now silent fires of Auvergne, the Euganean Hills, and Hungary. The relation of these to the basaltic streams of Ireland and Scotland is clear enough as far as relates to the general agency; but the determination of the period when these igneous rocks were formed is difficult. Etna may have begun to burn as soon or even sooner than the now decaying lavas were poured from the craters of Auvergne, the Eifel, and Hungary; and the mere fact of igneous rocks being associated with particular strata, is no criterion of their antiquity. We must therefore endeavour to combine the history of the tertiary volcanic products with those of later and earlier date, in a general discussion of the effects of subterranean heat, which we propose to place after the description of the superficial aqueous deposits, which are intimately related to the tertiary products.
* ↑ Mr. Ormerod estimates the gypseous and saliferous marls of Cheshire at 700 feet, the water stone beds below 400 feet, and the subjacent Bunter 600—Geol. Proc., 1848.
* ↑ Daubeny on Mineral Springs, British Association Reports.
* ↑ The upper part, or slaty, marly limestone, rather than chalk, is called planerkalk; the lower or sandy rock is called quadersandstein: distinctions still clearer in the large area within the Bohemian mountains, where on the course of the Elbe the rocks of this system are widely spread.
* ↑ Rogers, in Report to Brit. Association.
* ↑ Principles of Geology, voL iii. 1st edit.
* ↑ The crag has been investigated with great success by Charlesworth, Wood, Lyeil, Henslow, and Colchester. At the base of the red crag lie the valuable bands of phosphatic nodules.
* ↑ Proceedings of Geol. Soc. 1849.
* ↑ Geol. Proc., 1849. See also the addresses of De la Beche, 1849, and Lyell, 1850, on this subject.
* ↑ There are above 450 species of fossils in the crag, and on the relation of its shells to recent types, Dr. Beck of Copenhagen holds a different opinion from M. Deshayes. See also Mr. Charlesworth on the crag formation, in Phil. Mag. and Annals, 1836.
* ↑ Placed by Deshayes in the middle group, but with hesitation.