The Student's Elements of Geology
Sir Charles Lyell
Part 6 out of 14
b. Section of cone showing the position of the seeds.)
Ettingshausen remarked in 1851 that five of the fossil species from Sheppey,
named by Bowerbank (Fossil Fruits and Seeds of London Clay Plates 9 and 10.)
were specimens of the same fruit (see Figure 206), in different states of
preservation; and Mr. Carruthers, having examined the original specimens now in
the British Museum, tells me that all these cones from Sheppey may be reduced to
two species, which have an undoubted affinity to the two existing Australian
genera above mentioned, although their perfect identity in structure can not be
The contiguity of land may be inferred not only from these vegetable
productions, but also from the teeth and bones of crocodiles and turtles, since
these creatures, as Dean Conybeare remarked, must have resorted to some shore to
lay their eggs. Of turtles there were numerous species referred to extinct
genera. These are, for the most part, not equal in size to the largest living
tropical turtles. A sea-snake, which must have been thirteen feet long, of the
genus Palaeophis before mentioned, has also been described by Professor Owen
from Sheppey, of a different species from that of Bracklesham, and called
Palaeophis toliapicus. A true crocodile, also, Crocodilus toliapicus, and
another saurian more nearly allied to the gavial, accompany the above fossils;
also the relics of several birds and quadrupeds. One of these last belongs to
the new genus Hyracotherium of Owen, of the hog tribe, allied to Chaeropotamus,
another is a Lophiodon; a third a pachyderm called Coryphodon eocaenus by Owen,
larger than any existing tapir. All these animals seem to have inhabited the
banks of the great river which floated down the Sheppey fruits. They imply the
existence of a mammiferous fauna antecedent to the period when nummulites
flourished in Europe and Asia, and therefore before the Alps, Pyrenees, and
other mountain-chains now forming the backbones of great continents, were raised
from the deep; nay, even before a part of the constituent rocky masses now
entering into the central ridges of these chains had been deposited in the sea.
SHELLS OF THE LONDON CLAY.
(FIGURE 207. Voluta nodosa, Sowerby. Highgate.)
(FIGURE 208. Phorus extensus, Sowerby. Highgate.)
(FIGURE 209. Rostellaria (Hippocrenes) ampla, Brander. 1/3 of natural size; also
found in the Barton clay.)
(FIGURE 210. Nautilus centralis, Sowerby. Highgate.)
(FIGURE 211. Aturia ziczac, Bronn. Syn. Nautilus ziczac, Sowerby. London clay.
(FIGURE 212. Belosepia sepioidea, De Blainv. London clay. Sheppey.)
(FIGURE 213. Leda amygdaloides, Sowerby. Highgate.)
(FIGURE 214. Cyptodon (Axinus) angulatum, Sowerby. London clay. Hornsey.)
(FIGURE 215. Astropecten crispatus, E. Forbes. Sheppey.)
The marine shells of the London Clay confirm the inference derivable from the
plants and reptiles in favour of a high temperature. Thus many species of Conus
and Voluta occur, a large Cypraea, C. oviformis, a very large Rostellaria
(Figure 209), a species of Cancellaria, six species of Nautilus (Figure 211),
besides other Cephalopoda of extinct genera, one of the most remarkable of which
is the Belosepia (Figure 212). Among many characteristic bivalve shells are Leda
amygdaloides (Figure 213) and Cryptodon angulatum (Figure 214), and among the
Radiata a star-fish, Astropecten (Figure 215.)
These fossils are accompanied by a sword-fish (Tetrapterus priscus, Agassiz),
about eight feet long, and a saw-fish (Pristis bisulcatus, Agassiz), about ten
feet in length; genera now foreign to the British seas. On the whole, about
eighty species of fish have been described by M. Agassiz from these beds of
Sheppey, and they indicate, in his opinion, a warm climate.
In the lower part of the London clay at Kyson, a few miles east of Woodbridge,
the remains of mammalia have been detected. Some of these have been referred by
Professor Owen to an opossum, and others to the genus Hyracotherium. The teeth
of this last-mentioned pachyderm were at first, in 1840, supposed to belong to a
monkey, an opinion afterwards abandoned by Owen when more ample materials for
comparison were obtained.
WOOLWICH AND READING SERIES (C.2, TABLE 16.1.)
This formation was formerly called the Plastic Clay, as it agrees with a similar
clay used in pottery which occupies the same position in the French series, and
it has been used for the like purposes in England. (Prestwich Quarterly
Geological Journal volume 10.)
No formations can be more dissimilar, on the whole, in mineral character than
the Eocene deposits of England and Paris; those of our own island being almost
exclusively of mechanical origin-- accumulations of mud, sand, and pebbles;
while in the neighbourhood of Paris we find a great succession of strata
composed of limestones, some of them siliceous, and of crystalline gypsum and
siliceous sandstone, and sometimes of pure flint used for millstones. Hence it
is often impossible, as before stated, to institute an exact comparison between
the various members of the English and French series, and to settle their
respective ages. But in regard to the division which we have now under
consideration, whether we study it in the basins of London, Hampshire, or Paris,
we recognise as a general rule the same mineral character, the beds consisting
over a large area of mottled clays and sand, with lignite, and with some strata
of well-rolled flint pebbles, derived from the chalk, varying in size, but
occasionally several inches in diameter. These strata may be seen in the Isle of
Wight in contact with the chalk, or in the London basin, at Reading, Blackheath,
and Woolwich. In some of the lowest of them, banks of oysters are observed,
consisting of Ostrea bellovacina, so common in France in the same relative
position. In these beds at Bromley, Dr. Buckland found a large pebble to which
five full-grown oysters were affixed, in such a manner as to show that they had
commenced their first growth upon it, and remained attached to it through life.
(FIGURE 216. Cyrena cuneiformis, Sowerby. Natural size. Woolwich clays.)
(FIGURE 217. Melania (Melanatria) inquinata, Des. Syn. Cerithium melanoides,
Sowerby. Woolwich clays.)
In several places, as at Woolwich on the Thames, at Newhaven in Sussex, and
elsewhere, a mixture of marine and fresh-water testacea distinguishes this
member of the series. Among the latter, Cyrena cuneiformis (see Figure 216) and
Melania inquinata (see Figure 217) are very common, as in beds of corresponding
age in France. They clearly indicate points where rivers entered the Eocene sea.
Usually there is a mixture of brackish, fresh-water, and marine shells, and
sometimes, as at Woolwich, proofs of the river and the sea having successively
prevailed on the same spot. At New Charlton, in the suburbs of Woolwich, Mr. de
la Condamine discovered in 1849, and pointed out to me, a layer of sand
associated with well-rounded flint pebbles in which numerous individuals of the
Cyrena tellinella were seen standing endwise with both their valves united, the
siphonal extremity of each shell being uppermost, as would happen if the
mollusks had died in their natural position. I have described a bank of sandy
mud, in the delta of the Alabama River at Mobile, on the borders of the Gulf of
Mexico, where in 1846 I dug out at low tide specimens of living species of
Cyrena and of a Gnathodon, which were similarly placed with their shells erect,
or in a posture which enables the animal to protrude its siphon upward, and draw
in or reject water at pleasure. (Second Visit to the United States volume 2 page
104.) The water at Mobile is usually fresh, but sometimes brackish. At Woolwich
a body of river-water must have flowed permanently into the sea where the
Cyrenae lived, and they may have been killed suddenly by an influx of pure salt-
water, which invaded the spot when the river was low, or when a subsidence of
land took place. Traced in one direction, or eastward towards Herne Bay, the
Woolwich beds assume more and more of a marine character; while in an opposite,
or south-western direction, they become, as near Chelsea and other places, more
fresh-water, and contain Unio, Paludina, and layers of lignite, so that the land
drained by the ancient river seems clearly to have been to the south-west of the
present site of the metropolis.
FLUVIATILE BEDS UNDERLYING DEEP-SEA STRATA.
Before the minds of geologists had become familiar with the theory of the
gradual sinking of land, and its conversion into sea at different periods, and
the consequent change from shallow to deep water, the fluviatile and littoral
character of this inferior group appeared strange and anomalous. After passing
through hundreds of feet of London clay, proved by its fossils to have been
deposited in deep salt-water, we arrive at beds of fluviatile origin, and
associated with them masses of shingle, attaining at Blackheath, near London, a
thickness of 50 feet. These shingle banks are probably of marine origin, but
they indicate the proximity of land, and the existence of a shore where the
flints of the chalk were rolled into sand and pebbles, and spread over a wide
space. We have, therefore, first, as before stated, evidence of oscillations of
level during the accumulation of the Woolwich series, then of a great
submergence, which allowed a marine deposit 500 thick to be laid over the
antecedent beds of fresh and brackish water origin.
THANET SANDS (C.3 TABLE 16.1).
The Woolwich or plastic clay above described may often be seen in the Hampshire
basin in actual contact with the chalk, constituting in such places the lowest
member of the British Eocene series. But at other points another formation of
marine origin, characterised by a somewhat different assemblage of organic
remains, has been shown by Mr. Prestwich to intervene between the chalk and the
Woolwich series. For these beds he has proposed the name of "Thanet Sands,"
because they are well seen in the Isle of Thanet, in the northern part of Kent,
and on the sea-coast between Herne Bay and the Reculvers, where they consist of
sands with a few concretionary masses of sandstone, and contain, among other
fossils, Pholadomya cuneata, Cyprina morrisii, Corbula longirostris, Scalaria
Bowerbankii, etc. The greatest thickness of these beds is 90 feet.
UPPER EOCENE FORMATIONS OF FRANCE.
The tertiary formations in the neighbourhood of Paris consist of a series of
marine and fresh-water strata, alternating with each other, and filling up a
depression in the chalk. The area which they occupy has been called the Paris
Basin, and is about 180 miles in its greatest length from north to south, and
about 90 miles in breadth from east to west. MM. Cuvier and Brongniart
attempted, in 1810, to distinguish five different groups, comprising three
fresh-water and two marine, which were supposed to imply that the waters of the
ocean, and of rivers and lakes, had been by turns admitted into and excluded
from the same area. Investigations since made in the Hampshire and London basins
have rather tended to confirm these views, at least so far as to show that since
the commencement of the Eocene period there have been great movements of the bed
of the sea, and of the adjoining lands, and that the superposition of deep-sea
to shallow-water deposits (the London Clay, for example, to the Woolwich beds)
can only be explained by referring to such movements. It appears,
notwithstanding, from the researches of M. Constant Prevost, that some of the
minor alternations and intermixtures of fresh-water and marine deposits, in the
Paris basin, may be accounted for without such changes of level, by imagining
both to have been simultaneously in progress, in the same bay of the same sea,
or a gulf into which many rivers entered.
GYPSEOUS SERIES OF MONTMARTRE (A.1, TABLE 16.1).
To enlarge on the numerous subdivisions of the Parisian strata would lead me
beyond my present limits; I shall therefore give some examples only of the most
important formations. Beneath the Gres de Fontainebleau, belonging to the Lower
Miocene period, as before stated, we find, in the neighbourhood of Paris, a
series of white and green marls, with subordinate beds of gypsum. These are most
largely developed in the central parts of the Paris basin, and, among other
places, in the hill of Montmartre, where its fossils were first studied by
The gypsum quarried there for the manufacture of plaster of Paris occurs as a
granular crystalline rock, and, together with the associated marls, contains
land and fluviatile shells, together with the bones and skeletons of birds and
quadrupeds. Several land-plants are also met with, among which are fine
specimens of the fan-palm or palmetto tribe (Flabellaria). The remains also of
fresh-water fish, and of crocodiles and other reptiles, occur in the gypsum. The
skeletons of mammalia are usually isolated, often entire, the most delicate
extremities being preserved; as if the carcasses, clothed with their flesh and
skin, had been floated down soon after death, and while they were still swollen
by the gases generated by their first decomposition. The few accompanying shells
are of those light kinds which frequently float on the surface of rivers,
together with wood.
In this formation the relics of about fifty species of quadrupeds, including the
genera Palaeotherium (see Figure 174), Anoplotherium (see Figure 218), and
others, have been found, all extinct, and nearly four-fifths of them belonging
to the Perissodactyle or odd-toed division of the order Pachydermata, which now
contains only four living genera, namely, rhinoceros, tapir, horse, and hyrax.
With them a few carnivorous animals are associated, among which are the
Hyaenodon dasyuroides, a species of dog, Canis Parisiensis, and a weasel,
Cynodon Parisiensis. Of the Rodentia are found a squirrel; of the Cheiroptera, a
bat; while the Marsupalia (an order now confined to America, Australia, and some
contiguous islands) are represented by an opossum.
Of birds, about ten species have been ascertained, the skeletons of some of
which are entire. None of them are referable to existing species. (Cuvier, Oss.
Foss. tome 3 page 255.) The same remark, according to MM. Cuvier and Agassiz,
applies both to the reptiles and fish. Among the last are crocodiles and
tortoises of the genera Emys and Trionyx.
(FIGURE 218. Xiphodon gracile, or Anoplotherium gracile, Cuvier. Restored
The tribe of land quadrupeds most abundant in this formation is such as now
inhabits alluvial plains and marshes, and the banks of rivers and lakes, a class
most exposed to suffer by river inundations. Among these were several species of
Palaeotherium, a genus before alluded to. These were associated with the
Anoplotherium, a tribe intermediate between pachyderms and ruminants. One of the
three divisions of this family was called by Cuvier Xiphodon. Their forms were
slender and elegant, and one, named Xiphodon gracile (Figure 218), was about the
size of the chamois; and Cuvier inferred from the skeleton that it was as light,
graceful, and agile as the gazelle.
There are three superimposed masses of gypsum in the neighbourhood of Paris,
separated by intervening deposits of laminated marl. In the uppermost of the
three, in the valley of Montmorency, M. Desnoyers discovered in 1859 many
footprints of animals occurring at no less than six different levels. (Sur des
Empreintes de Pas d'Animaux par M. J. Desnoyers. Compte rendu de l'Institut
1859.) The gypsum to which they belong varies from thirty to fifty feet in
thickness, and is that which has yielded to the naturalist the largest number of
bones and skeletons of mammalia, birds, and reptiles. I visited the quarries,
soon after the discovery was made known, with M. Desnoyers, who also showed me
large slabs in the Museum at Paris, where, on the upper planes of
stratification, the indented foot-marks were seen, while corresponding casts in
relief appeared on the lower surfaces of the strata of gypsum which were
immediately superimposed. A thin film of marl, which before it was dried and
condensed by pressure must have represented a much thicker layer of soft mud,
intervened between the beds of solid gypsum. On this mud the animals had
trodden, and made impressions which had penetrated to the gypseous mass below,
then evidently unconsolidated. Tracks of the Anoplotherium with its bisulcate
hoof, and the trilobed footprints of Palaeotherium, were seen of different
sizes, corresponding to those of several species of these genera which Cuvier
had reconstructed, while in the same beds were foot-marks of carnivorous
mammalia. The tracks also of fluviatile, lacustrine, and terrestrial tortoises
(Emys, Trionyx, etc.) were discovered, also those of crocodiles, iguanas,
geckos, and great batrachians, and the footprints of a huge bird, apparently a
wader, of the size of the gastornis, to be mentioned in the sequel. There were
likewise the impressions of the feet of other creatures, some of them clearly
distinguishable from any of the fifty extinct types of mammalia of which the
bones have been found in the Paris gypsum. The whole assemblage, says Desnoyers,
indicate the shores of a lake, or several small lakes communicating with each
other, on the borders of which many species of pachyderms wandered, and beasts
of prey which occasionally devoured them. The tooth-marks of these last had been
detected by palaeontologists long before on the bones and skulls of Paleotheres
entombed in the gypsum.
IMPERFECTION OF THE RECORD.
These foot-marks have revealed to us new and unexpected proofs that the air-
breathing fauna of the Upper Eocene period in Europe far surpassed in the number
and variety of its species the largest estimate which had previously been formed
of it. We may now feel sure that the mammalia, reptiles, and birds which have
left portions of their skeletons as memorials of their existence in the solid
gypsum constituted but a part of the then living creation. Similar inferences
may be drawn from the study of the whole succession of geological records. In
each district the monuments of periods embracing thousands, and probably in some
instances hundreds of thousands of years, are totally wanting. Even in the
volumes which are extant the greater number of the pages are missing in any
given region, and where they are found they contain but few and casual entries
of the physical events or living beings of the times to which they relate. It
may also be remarked that the subordinate formations met with in two
neighbouring countries, such as France and England (the minor Tertiary groups
above enumerated), commonly classed as equivalents and referred to corresponding
periods, may nevertheless have been by no means strictly coincident in date.
Though called contemporaneous, it is probable that they were often separated by
intervals of many thousands of years. We may compare them to double stars, which
appear single to the naked eye because seen from a vast distance in space, and
which really belong to one and the same stellar system, though occupying places
in space extremely remote if estimated by our ordinary standard of terrestrial
CALCAIRE SILICIEUX, OR TRAVERTIN INFERIEUR (A.2 AND 3 TABLE 16.1).
This compact siliceous limestone extends over a wide area. It resembles a
precipitate from the waters of mineral springs, and is often traversed by small
empty sinuous cavities. It is, for the most part, devoid of organic remains, but
in some places contains fresh-water and land species, and never any marine
fossils. The calcaire siliceux and the calcaire grossier usually occupy distinct
parts of the Paris basin, the one attaining its fullest development in those
places where the other is of slight thickness. They are described by some
writers as alternating with each other towards the centre of the basin, as at
Sergy and Osny.
The gypsum, with its associated marls before described, is in greatest force
towards the centre of the basin, where the calcaire grossier and calcaire
silicieux are less fully developed.
GRES DE BEAUCHAMP, OR SABLES MOYENS (A.4 TABLE 16.1).
In some parts of the Paris basin, sands and marls, called the Gres de Beauchamp,
or Sables moyens, divide the gypseous beds from the calcaire grossier proper.
These sands, in which a small nummulite (N. variolaria) is very abundant,
contain more than 300 species of marine shells, many of them peculiar, but
others common to the next division.
MIDDLE EOCENE FORMATIONS OF FRANCE.
CALCAIRE GROSSIER, UPPER AND MIDDLE (B.1 TABLE 16.1).
The upper division of this group consists in great part of beds of compact,
fragile limestone, with some intercalated green marls. The shells in some parts
are a mixture of Cerithium, Cyclostoma, and Corbula; in others Limnea,
Cerithium, Paludina, etc. In the latter, the bones of reptiles and mammalia,
Palaeotherium and Lophiodon, have been found. The middle division, or calcaire
grossier proper, consists of a coarse limestone, often passing into sand. It
contains the greater number of the fossil shells which characterise the Paris
basin. No less than 400 distinct species have been procured from a single spot
near Grignon, where they are imbedded in a calcareous sand, chiefly formed of
comminuted shells, in which, nevertheless, individuals in a perfect state of
preservation, both of marine, terrestrial, and fresh-water species, are mingled
together. Some of the marine shells may have lived on the spot; but the
Cyclostoma and Limnea, being land and fresh-water shells, must have been brought
thither by rivers and currents, and the quantity of triturated shells implies
considerable movement in the waters.
Nothing is more striking in this assemblage of fossil testacea than the great
proportion of species referable to the genus Cerithium (Figures 160 and 161
Chapter 15). There occur no less than 137 species of this genus in the Paris
basin, and almost all of them in the calcaire grossier. Most of the living
Cerithia inhabit the sea near the mouths of rivers, where the waters are
brackish; so that their abundance in the marine strata now under consideration
is in harmony with the hypothesis that the Paris basin formed a gulf into which
several rivers flowed.
(FIGURE 219. Calcarina rarispina, Desh.
a. Natural size.
(FIGURE 220. Spirolina stenostoma, Desh.
a. Natural size.
(FIGURE 221. Triloculina inflata, Desh.
a. Natural size.
In some parts of the calcaire grossier round Paris, certain beds occur of a
stone used in building, and called by the French geologists "Miliolite
limestone." It is almost entirely made up of millions of microscopic shells, of
the size of minute grains of sand, which all belong to the class Foraminifera.
Figures of some of these are given in Figures 219 to 221. As this miliolitic
stone never occurs in the Faluns, or Upper Miocene strata of Brittany and
Touraine, it often furnishes the geologist with a useful criterion for
distinguishing the detached Eocene and Upper Miocene formations scattered over
those and other adjoining provinces. The discovery of the remains of
Palaeotherium and other mammalia in some of the upper beds of the calcaire
grossier shows that these land animals began to exist before the deposition of
the overlying gypseous series had commenced.
LOWER CALCAIRE GROSSIER, OR GLAUCONIE GROSSIERE (B.1 TABLE 16.1).
The lower part of the calcaire grossier, which often contains much green earth,
is characterised at Auvers, near Pontoise, to the north of Paris, and still more
in the environs of Compiegne, by the abundance of nummulites, consisting chiefly
of N. laevigata, N. scabra, and N. Lamarcki, which constitute a large proportion
of some of the stony strata, though these same foraminifera are wanting in beds
of similar age in the immediate environs of Paris.
SOISSONNAIS SANDS, OR LITS COQUILLIERS (B.2 TABLE 16.1).
(FIGURE 222. Nerita conoidea, Lam. Syn. N. Schmidelliana, Chemnitz.)
Below the preceding formation, shelly sands are seen, of considerable thickness,
especially at Cuisse-Lamotte, near Compiegne, and other localities in the
Soissonnais, about fifty miles N.E. of Paris, from which about 300 species of
shells have been obtained, many of them common to the calcaire grossier and the
Bracklesham beds of England, and many peculiar. The Nummulites planulata is very
abundant, and the most characteristic shell is the Nerita conoidea, Lam., a
fossil which has a very wide geographical range; for, as M. d'Archiac remarks,
it accompanies the nummulitic formation from Europe to India, having been found
in Cutch, near the mouths of the Indus, associated with Nummulites scabra. No
less than 33 shells of this group are said to be identical with shells of the
London clay proper, yet, after visiting Cuisse-Lamotte and other localities of
the "Sables inferieurs" of Archiac, I agree with Mr. Prestwich, that the latter
are probably newer than the London clay, and perhaps older than the Bracklesham
beds of England. The London clay seems to be unrepresented in the Paris basin,
unless partially so, by these sands. (d'Archiac Bulletin tome 10 and Prestwich
Quarterly Geological Journal 1847 page 377.)
LOWER EOCENE FORMATIONS OF FRANCE.
ARGILE PLASTIQUE (C.2 TABLE 16.1).
At the base of the tertiary system in France are extensive deposits of sands,
with occasional beds of clay used for pottery, and called "argile plastique."
Fossil oysters (Ostrea bellovacina) abound in some places, and in others there
is a mixture of fluviatile shells, such as Cyrena cuneiformis (Figure 216),
Melania inquinata (Figure 217), and others, frequently met with in beds
occupying the same position in the London Basin. Layers of lignite also
accompany the inferior clays and sands.
Immediately upon the chalk at the bottom of all the tertiary strata in France
there generally is a conglomerate or breccia of rolled and angular chalk-flints,
cemented by siliceous sand. These beds appear to be of littoral origin, and
imply the previous emergence of the chalk, and its waste by denudation. In the
year 1855, the tibia and femur of a large bird equalling at least the ostrich in
size were found at Meudon, near Paris, at the base of the Plastic clay. This
bird, to which the name of Gastornis Parisiensis has been assigned, appears,
from the Memoirs of MM. Hebert, Lartet, and Owen, to belong to an extinct genus.
Professor Owen refers it to the class of wading land birds rather than to an
aquatic species. (Quarterly Geological Journal volume 12 page 204 1856.)
That a formation so much explored for economical purposes as the Argile
plastique around Paris, and the clays and sands of corresponding age near
London, should never have afforded any vestige of a feathered biped previously
to the year 1855, shows what diligent search and what skill in osteological
interpretation are required before the existence of birds of remote ages can be
SABLES DE BRACHEUX (C.3 TABLE 16.1).
The marine sands called the Sables de Bracheux (a place near Beauvais), are
considered by M. Hebert to be older than the Lignites and Plastic clay, and to
coincide in age with the Thanet Sands of England. At La Fere, in the Department
of Aisne, in a deposit of this age, a fossil skull has been found of a quadruped
called by Blainville Arctocyon primaevus, and supposed by him to be related both
to the bear and to the Kinkajou (Cercoleptes). This creature appears to be the
oldest known tertiary mammifer.
NUMMULITIC FORMATIONS OF EUROPE, ASIA, ETC.
Of all the rocks of the Eocene period, no formations are of such great
geographical importance as the Upper and Middle Eocene, as above defined,
assuming that the older tertiary formation, commonly called nummulitic, is
correctly ascribed to this group. It appears that of more than fifty species of
these foraminifera described by D'Archiac, one or two species only are found in
other tertiary formations whether of older or newer date. Nummulites intermedia,
a Middle Eocene form, ascends into the Lower Miocene, but it seems doubtful
whether any species descends to the level of the London clay, still less to the
Argile plastique or Woolwich beds. Separate groups of strata are often
characterised by distinct species of nummulite; thus the beds between the lower
Miocene and the lower Eocene may be divided into three sections, distinguished
by three different species of nummulites, N. variolaria in the upper, N.
laevigata in the middle, and N. planulata in the lower beds. The nummulitic
limestone of the Swiss Alps rises to more than 10,000 feet above the level of
the sea, and attains here and in other mountain chains a thickness of several
thousand feet. It may be said to play a far more conspicuous part than any other
tertiary group in the solid framework of the earth's crust, whether in Europe,
Asia, or Africa. It occurs in Algeria and Morocco, and has been traced from
Egypt, where it was largely quarried of old for the building of the Pyramids,
into Asia Minor, and across Persia by Bagdad to the mouths of the Indus. It has
been observed not only in Cutch, but in the mountain ranges which separate
Scinde from Persia, and which form the passes leading to Caboul; and it has been
followed still farther eastward into India, as far as eastern Bengal and the
frontiers of China.
(FIGURE 223. Nummulites Puschi, D'Archiac. Peyrehorade, Pyrenees.
a. External surface of one of the nummulites, of which longitudinal sections are
seen in the limestone.
b. Transverse section of same.)
Dr. T. Thompson found nummulites at an elevation of no less than 16,500 feet
above the level of the sea, in Western Thibet. One of the species, which I
myself found very abundant on the flanks of the Pyrenees, in a compact
crystalline marble (Figure 223) is called by M. D'Archiac Nummulites Puschi. The
same is also very common in rocks of the same age in the Carpathians. In many
distant countries, in Cutch, for example, some of the same shells, such as
Nerita conoidea (Figure 222), accompany the nummulites, as in France. The
opinion of many observers, that the Nummulitic formation belongs partly to the
cretaceous era, seems chiefly to have arisen from confounding an allied genus,
Orbitoides, with the true Nummulite.
When we have once arrived at the conviction that the nummulitic formation
occupies a middle and upper place in the Eocene series, we are struck with the
comparatively modern date to which some of the greatest revolutions in the
physical geography of Europe, Asia, and Northern Africa must be referred. All
the mountain-chains, such as the Alps, Pyrenees, Carpathians, and Himalayas,
into the composition of whose central and loftiest parts the nummulitic strata
enter bodily, could have had no existence till after the Middle Eocene period.
During that period the sea prevailed where these chains now rise, for nummulites
and their accompanying testacea were unquestionably inhabitants of salt water.
Before these events, comprising the conversion of a wide area from a sea to a
continent, England had been peopled, as I before pointed out, by various
quadrupeds, by herbivorous pachyderms, by insectivorous bats, and by opossums.
Almost all the volcanoes which preserve any remains of their original form, or
from the craters of which lava streams can be traced, are more modern than the
Eocene fauna now under consideration; and besides these superficial monuments of
the action of heat, Plutonic influences have worked vast changes in the texture
of rocks within the same period. Some members of the nummulitic and overlying
tertiary strata called flysch have actually been converted in the central Alps
into crystalline rocks, and transformed into marble, quartz-rock, micha-schist,
and gneiss. (Murchison Quarterly Journal of Geological Society volume 5 and
Lyell volume 6 1850 Anniversary Address.)
EOCENE STRATA IN THE UNITED STATES.
In North America the Eocene formations occupy a large area bordering the
Atlantic, which increases in breadth and importance as it is traced southward
from Delaware and Maryland to Georgia and Alabama. They also occur in Louisiana
and other States both east and west of the valley of the Mississippi. At
Claiborne, in Alabama, no less than 400 species of marine shells, with many
echinoderms and teeth of fish, characterise one member of this system. Among the
shells, the Cardita planicosta, before mentioned (Figure 191), is in abundance;
and this fossil and some others identical with European species, or very nearly
allied to them, make it highly probable that the Claiborne beds agree in age
with the central or Bracklesham group of England, and with the calcaire
grossiere of Paris. (See paper by the Author Quarterly Journal of Geological
Society volume 4 page 12 and Second Visit to the United States volume 2 page
Higher in the series is a remarkable calcareous rock, formerly called "the
nummulite limestone," from the great number of discoid bodies resembling
nummulites which it contains, fossils now referred by A. d'Orbigny to the genus
Orbitoides, which has been demonstrated by Dr. Carpenter to belong to the
foraminifera. (Quarterly Journal of Geological Society volume 6 page 32.) That
naturalist, moreover, is of opinion that the Orbitoides alluded to (O. Mantelli)
is of the same species as one found in Cutch, in the Middle Eocene or nummulitic
formation of India.
Above the orbitoidal limestone is a white limestone, sometimes soft and
argillaceous, but in parts very compact and calcareous. It contains several
peculiar corals, and a large Nautilus allied to N. ziczac; also in its upper bed
a gigantic cetacean, called Zeuglodon by Owen. (See Memoir by R.W. Gibbes
Journal of Academy of Natural Science Philadelphia volume 1 1847.)
The colossal bones of this cetacean are so plentiful in the interior of Clarke
County, Alabama, as to be characteristic of the formation. The vertebral column
of one skeleton found by Dr. Buckley at a spot visited by me, extended to the
length of nearly seventy feet, and not far off part of another backbone nearly
fifty feet long was dug up. I obtained evidence, during a short excursion, of so
many localities of this fossil animal within a distance of ten miles, as to lead
me to conclude that they must have belonged to at least forty distinct
(FIGURE 224. Zeuglodon cetoides, Owen. Basilosaurus, Harlan.
Molar tooth, natural size.)
(FIGURE 225. Zeuglodon cetoides, Owen. Basilosaurus, Harlan.
Professor Owen first pointed out that this huge animal was not reptilian, since
each tooth was furnished with double roots (Figure 224), implanted in
corresponding double sockets; and his opinion of the cetacean nature of the
fossil was afterwards confirmed by Dr. Wyman and Dr. R.W. Gibbes. That it was an
extinct mammal of the whale tribe has since been placed beyond all doubt by
discovery of the entire skull of another fossil species of the same family,
having the double occipital condyles only met with in mammals, and the
convoluted tympanic bones which are characteristic of cetaceans.
UPPER CRETACEOUS GROUP.
Lapse of Time between Cretaceous and Eocene Periods.
Table of successive Cretaceous Formations.
Pisolitic Limestone of France.
Chalk of Faxoe.
Geographical Extent and Origin of the White Chalk.
Chalky Matter now forming in the Bed of the Atlantic.
Marked Difference between the Cretaceous and existing Fauna.
Pot-stones of Horstead.
Vitreous Sponges in the Chalk.
Isolated Blocks of Foreign Rocks in the White Chalk supposed to be ice-borne.
Distinctness of Mineral Character in contemporaneous Rocks of the Cretaceous
Fossils of the White Chalk.
Lower White Chalk without Flints.
Chalk Marl and its Fossils.
Chloritic Series or Upper Greensand.
Coprolite Bed near Cambridge.
Fossils of the Chloritic Series.
Connection between Upper and Lower Cretaceous Strata.
Flora of the Upper Cretaceous Period.
Cretaceous Rocks in the United States.
We have treated in the preceding chapters of the Tertiary or Cainozoic strata,
and have next to speak of the Secondary or Mesozoic formations. The uppermost of
these last is commonly called the chalk or the cretaceous formation, from creta,
the latin name for that remarkable white earthy limestone, which constitutes an
upper member of the group in those parts of Europe where it was first studied.
The marked discordance in the fossils of the tertiary, as compared with the
cretaceous formations, has long induced many geologists to suspect that an
indefinite series of ages elapsed between the respective periods of their
origin. Measured, indeed, by such a standard, that is to say, by the amount of
change in the Fauna and Flora of the earth effected in the interval, the time
between the Cretaceous and Eocene may have been as great as that between the
Eocene and Recent periods, to the history of which the last seven chapters have
been devoted. Several deposits have been met with here and there, in the course
of the last half century, of an age intermediate between the white chalk and the
plastic clays and sands of the Paris and London districts, monuments which have
the same kind of interest to a geologist which certain medieval records excite
when we study the history of nations. For both of them throw light on ages of
darkness, preceded and followed by others of which the annals are comparatively
well-known to us. But these newly-discovered records do not fill up the wide
gap, some of them being closely allied to the Eocene, and others to the
Cretaceous type, while none appear as yet to possess so distinct and
characteristic a fauna as may entitle them to hold an independent place in the
great chronological series.
Among the formations alluded to, the Thanet Sands of Prestwich have been
sufficiently described in the last chapter, and classed as Lower Eocene. To the
same tertiary series belong the Belgian formations, called by Professor Dumont,
Landenian. On the other hand, the Maestricht and Faxoe limestones are very
closely connected with the chalk, to which also the Pisolitic limestone of
France is referable.
CLASSIFICATION OF THE CRETACEOUS ROCKS.
UPPER CRETACEOUS OR CHALK PERIOD.
1. Maestricht Beds and Faxoe Limestone.
2. Upper White Chalk, with flints.
3. Lower White Chalk, without flints.
4. Chalk Marl.
5. Chloritic series (or Upper Greensand).
LOWER CRETACEOUS OR NEOCOMIAN.
1. Marine: Upper Neocomian, see Chapter 18. Fresh-water: Wealden Beds (upper
2. Marine: Middle Neocomian, see Chapter 18. Fresh-water: Wealden Beds (upper
3. Marine: Lower Neocomian, see Chapter 18. Fresh-water: Wealden Beds (upper
The cretaceous group has generally been divided into an Upper and a Lower
series, the Upper called familiarly THE CHALK, and the Lower THE GREENSAND; the
one deriving its name from the predominance of white earthy limestone and marl,
of which it consists in a great part of France and England, the other or lower
series from the plentiful mixture of green or chloritic grains contained in some
of the sands and cherts of which it largely consists in the same countries. But
these mineral characters often fail, even when we attempt to follow out the same
continuous subdivisions throughout a small portion of the north of Europe, and
are worse than valueless when we desire to apply them to more distant regions.
It is only by aid of the organic remains which characterise the successive
marine subdivisions of the formation that we are able to recognise in remote
countries, such as the south of Europe or North America, the formations which
were there contemporaneously in progress. To the English student of geology it
will be sufficient to begin by enumerating those groups which characterise the
series in this country and others immediately contiguous, alluding but slightly
to those of more distant regions. In Table 17.1 it will be seen that I have used
the term Neocomian for that commonly called "Lower Greensand;" as this latter
term is peculiarly objectionable, since the green grains are an exception to the
rule in many of the members of this group even in districts where it was first
studied and named.
(FIGURE 226. Belemnitella mucronata, Maestricht, Faxoe, and White Chalk.
a. Entire specimen, showing vascular impression on outer surface, and
b. Section of same, showing place of phragmocone. (For particulars of structure
see Chapter 18.))
On the banks of the Meuse, at Maestricht, reposing on ordinary white chalk with
flints, we find an upper calcareous formation about 100 feet thick, the fossils
of which are, on the whole, very peculiar, and all distinct from tertiary
species. Some few are of species common to the inferior white chalk, among which
may be mentioned Belemnitella mucronata (Figure 226) and Pecten quadricostatus,
a shell regarded by many as a mere variety of Pecten quinquecostatus (see Figure
270). Besides the Belemnite there are other genera, such as Baculites and
Hamites, never found in strata newer than the cretaceous, but frequently met
with in these Maestricht beds. On the other hand, Voluta, Fasciolaria, and other
genera of univalve shells, usually met with only in tertiary strata, occur.
The upper part of the rock, about 20 feet thick, as seen in St. Peter's Mount,
in the suburbs of Maestricht, abounds in corals and Bryozoa, often detachable
from the matrix; and these beds are succeeded by a soft yellowish limestone 50
feet thick, extensively quarried from time immemorial for building. The stone
below is whiter, and contains occasional nodules of grey chert or chalcedony.
(FIGURE 227. Mosasaurus Camperi. Original more than three feet long.)
(FIGURE 228. Hemipneustes radiatus, Ag. Spatangus radiatus, Lam.
Chalk of Maestricht and white chalk.)
M. Bosquet, with whom I examined this formation (August, 1850), pointed out to
me a layer of chalk from two to four inches thick, containing green earth and
numerous encrinital stems, which forms the line of demarkation between the
strata containing the fossils peculiar to Maestricht and the white chalk below.
The latter is distinguished by regular layers of black flint in nodules, and by
several shells, such as Terebratula carnea (see Figure 246), wholly wanting in
beds higher than the green band. Some of the organic remains, however, for which
St. Peter's Mount is celebrated, occur both above and below that parting layer,
and, among others, the great marine reptile called Mosasaurus (see Figure 227),
a saurian supposed to have been 24 feet in length, of which the entire skull and
a great part of the skeleton have been found. Such remains are chiefly met with
in the soft freestone, the principal member of the Maestricht beds. Among the
fossils common to the Maestricht and white chalk may be instanced the
echinoderm, Figure 228.
I saw proofs of the previous denudation of the white chalk exhibited in the
lower bed of the Maestricht formation in Belgium, about 30 miles S.W. of
Maestricht, at the village of Jendrain, where the base of the newer deposit
consisted chiefly of a layer of well-rolled, black chalk-flint pebbles, in the
midst of which perfect specimens of Thecidea papillata and Belemnitella
mucronata are imbedded. To a geologist accustomed in England to regard rolled
pebbles of chalk-flint as a common and distinctive feature of tertiary beds of
different ages, it is a new and surprising phenomenon to behold strata made up
of such materials, and yet to feel no doubt that they were accumulated in a sea
in which the belemnite and other cretaceous mollusca flourished.
PISOLITIC LIMESTONE OF FRANCE.
Geologists were for many years at variance respecting the chronological
relations of this rock, which is met with in the neighbourhood of Paris, and at
places north, south, east, and west of that metropolis, as between Vertus and
Laversines, Meudon and Montereau. By many able palaeontologists the species of
fossils, more than fifty in number, were declared to be more Eocene in their
appearance than Cretaceous. But M. Hebert found in this formation at Montereau,
near Paris, the Pecten quadricostatus, a well-known Cretaceous species, together
with some other fossils common to the Maestricht chalk and to the Baculite
limestone of the Cotentin, in Normandy. He therefore, as well as M. Alcide
d'Orbigny, who had carefully studied the fossils, came to the opinion that it
was an upper member of the Cretaceous group. It is usually in the form of a
coarse yellowish or whitish limestone, and the total thickness of the series of
beds already known is about 100 feet. Its geographical range, according to M.
Hebert, is not less than 45 leagues from east to west, and 35 from north to
south. Within these limits it occurs in small patches only, resting
unconformably on the white chalk.
(FIGURE 229. Portion of Baculites Faujasii.
Maestricht and Faxoe beds and white chalk.)
(FIGURE 230. Nautilus Danicus, Schl. Faxoe, Denmark.)
The Nautilus Danicus, Figure 230, and two or three other species found in this
rock, are frequent in that of Faxoe, in Denmark, but as yet no Ammonites,
Hamites, Scaphites, Turrilites, Baculites, or Hippurites have been met with. The
proportion of peculiar species, many of them of tertiary aspect, is confessedly
large; and great aqueous erosion suffered by the white chalk, before the
pisolitic limestone was formed, affords an additional indication of the two
deposits being widely separated in time. The pisolitic formation, therefore, may
eventually prove to be somewhat more intermediate in date between the secondary
and tertiary epochs than the Maestricht rock.
CHALK OF FAXOE.
In the island of Seeland, in Denmark, the newest member of the chalk series,
seen in the sea-cliffs at Stevensklint resting on white chalk with flints, is a
yellow limestone, a portion of which, at Faxoe, where it is used as a building
stone, is composed of corals, even more conspicuously than is usually observed
in recent coral reefs. It has been quarried to the depth of more than 40 feet,
but its thickness is unknown. The imbedded shells are chiefly casts, many of
them of univalve mollusca, which are usually very rare in the white chalk of
Europe. Thus, there are two species of Cypraea, one of Oliva, two of Mitra, four
of the genus Cerithium, six of Fusus, two of Trochus, one of Patella, one of
Emarginula, etc.; on the whole, more than thirty univalves, spiral or
patelliform. At the same time, some of the accompanying bivalve shells,
echinoderms, and zoophytes, are specifically identical with fossils of the true
Cretaceous series. Among the cephalopoda of Faxoe may be mentioned Baculites
Faujasii (Figure 229), and Belemnitella mucronata (Figure 226), shells of the
white chalk. The Nautilus Danicus (see Figure 230) is characteristic of this
formation; and it also occurs in France in the calcaire pisolitique of Laversin
(Department of Oise). The claws and entire skull of a small crab, Brachyurus
rugosus (Schlott.), are scattered through the Faxoe stone, reminding us of
similar crustaceans inclosed in the rocks of modern coral reefs. Some small
portions of this coralline formation consist of white earthy chalk.
COMPOSITION, EXTENT AND ORIGIN OF THE WHITE CHALK.
(FIGURE 231. Diagrammatic section from Hertfordshire, in England, to Sens, in
Through London (left), Hythe, Boulogne, Valley of Bray, Paris and Sens (right).)
The highest beds of chalk in England and France consist of a pure, white,
calcareous mass, usually too soft for a building-stone, but sometimes passing
into a more solid state. It consists, almost purely, of carbonate of lime; the
stratification is often obscure, except where rendered distinct by
interstratified layers of flint, a few inches thick, occasionally in continuous
beds, but oftener in nodules, and recurring at intervals generally from two to
four feet distant from each other. This upper chalk is usually succeeded, in the
descending order, by a great mass of white chalk without flints, below which
comes the chalk marl, in which there is a slight admixture of argillaceous
matter. The united thickness of the three divisions in the south of England
equals, in some places, 1000 feet. The section in Figure 231 will show the
manner in which the white chalk extends from England into France, covered by the
tertiary strata described in former chapters, and reposing on lower cretaceous
The area over which the white chalk preserves a nearly homogeneous aspect is so
vast, that the earlier geologists despaired of discovering any analogous
deposits of recent date. Pure chalk, of nearly uniform aspect and composition,
is met with in a north-west and south-east direction, from the north of Ireland
to the Crimea, a distance of about 1140 geographical miles, and in an opposite
direction it extends from the south of Sweden to the south of Bordeaux, a
distance of about 840 geographical miles. In Southern Russia, according to Sir
R. Murchison, it is sometimes 600 feet thick, and retains the same mineral
character as in France and England, with the same fossils, including Inoceramus
Cuvieri, Belemnitella mucronata, and Ostrea vesicularis (Figure 251).
(Figures 232 to 236.-- Organic bodies forming the ooze of the bed of the
Atlantic at great depths.
(FIGURE 232. Globigerina bulloides. Calcareous Rhizopod.)
(FIGURE 233. Actinocyclus. Siliceous Diatomaceae. )
(FIGURE 234. Pinnularia. Siliceous Diatomaceae.)
(FIGURE 235. Eunotia bidens. Siliceous Diatomaceae.)
(FIGURE 236. Spicula of sponge. Siliceous sponge.))
Great light has recently been thrown upon the origin of the unconsolidated white
chalk by the deep soundings made in the North Atlantic, previous to laying down,
in 1858, the electric telegraph between Ireland and Newfoundland. At depths
sometimes exceeding two miles, the mud forming the floor of the ocean was found,
by Professor Huxley, to be almost entirely composed (more than nineteen-
twentieths of the whole) of minute Rhizopods, or foraminiferous shells of the
genus Globigerina, especially the species Globigerina bulloides (see Figure
232.) the organic bodies next in quantity were the siliceous shells called
Polycystineae, and next to them the siliceous skeletons of plants called
Diatomaceae (Figures 233, 234, 235), and occasionally some siliceous spiculae of
sponges (Figure 236) were intermixed. These were connected by a mass of living
gelatinous matter to which he has given the name of Bathybius, and which
contains abundance of very minute bodies termed Coccoliths and Coccospheres,
which have also been detected fossil in chalk.
Sir Leopold MacClintock and Dr. Wallich have ascertained that 95 per cent of the
mud of a large part of the North Atlantic consists of Globigerina shells. But
Captain Bullock, R.N., lately brought up from the enormous depth of 16,860 feet
a white, viscid, chalky mud, wholly devoid of Globigerinae. This mud was
perfectly homogeneous in composition, and contained no organic remains visible
to the naked eye. Mr. Etheridge, however, has ascertained by microscopical
examination that it is made up of Coccoliths, Discoliths, and other minute
fossils like those of the Chalk classed by Huxley as Bathybius, when this term
is used in its widest sense. This mud, more than three miles deep, was dredged
up in latitude 20 degrees 19' N., longitude 4 degrees 36' E., or about midway
between Madeira and the Cape of Good Hope.
The recent deep-sea dredgings in the Atlantic conducted by Dr. Wyville Thomson,
Dr. Carpenter, Mr. Gwyn Jeffreys, and others, have shown that on the same white
mud there sometimes flourish Mollusca, Crustacea, and Echinoderms, besides
abundance of siliceous sponges, forming, on the whole, a marine fauna bearing a
striking resemblance in its general character to that of the ancient chalk.
POPULAR ERROR AS TO THE GEOLOGICAL CONTINUITY OF THE CRETACEOUS PERIOD.
We must be careful, however, not to overrate the points of resemblance which the
deep-sea investigations have placed in a strong light. They have been supposed
by some naturalists to warrant a conclusion expressed in these words: "We are
still living in the Cretaceous epoch;" a doctrine which has led to much popular
delusion as to the bearing of the new facts on geological reasoning and
classification. The reader should be reminded that in geology we have been in
the habit of founding our great chronological divisions, not on foraminifera and
sponges, nor even on echinoderms and corals, but on the remains of the most
highly organised beings available to us, such as the mollusca; these being met
with, as explained in Chapter 9, in stratified rocks of almost every age. In
dealing with the mollusca, it is those of the highest or most specialised
organisation, which afford us the best characters in proportion as their
vertical range is the most limited. Thus the Cephalopoda are the most valuable,
as having a more restricted range in time than the Gasteropoda; and these,
again, are more characteristic of the particular stratigraphical subdivisions
than are the Lamellibranchiate Bivalves, while these last, again, are more
serviceable in classification than the Brachiopoda, a still lower class of
shell-fish, which are the most enduring of all.
When told that the new dredgings prove that "we are still living in the Chalk
Period," we naturally ask whether some cuttle-fish has been found with a
Belemnite forming part of its internal framework; or have Ammonites, Baculites,
Hamites, Turrilites, with four or five other Cephalopodous genera characteristic
of the chalk and unknown as tertiary, been met with in the abysses of the ocean?
Or, in the absence of these long-extinct forms, has a single spiral univalve, or
species of Cretaceous Gasteropod, been found living? Or, to descend still lower
in the scale, has some characteristic Cretaceous genus of Lamellibranchiate
Bivalve, such as the Inoceramus, or Hippurite, foreign to the Tertiary seas,
been proved to have survived down to our time? Or, of the numerous genera of
lamellibranchiates common to the Cretaceous and Recent seas, has one species
been found living? The answer to all these questions is-- not one has been
found. Even of the humblest shell-fish, the Brachiopods, no new species common
to the Cretaceous and recent seas has yet been met with. It has been very
generally admitted by conchologists that out of a hundred species of this tribe
occurring fossil in the Upper Chalk-- one, and one only, Terebratulina striata,
is still living, being thought to be identical with Terebratula caput-serpentis.
Although this identity is still questioned by some naturalists of authority, it
would certainly not surprise us if another lamp-shell of equal antiquity should
be met with in the deep sea.
Had it been declared that we are living in the Eocene epoch, the idea would not
be so extravagant, for the great reptiles of the Upper Chalk, the Mosasaurus,
Pliosaurus, and Pterodactyle, and many others, as well as so many genera of
chambered univalves, had already disappeared from the earth, and the marine
fauna had made a greater approach to our own by nearly the entire difference
which separates it from the fauna of the Cretaceous seas. The Eocene nummulitic
limestone of Egypt is a rock mainly composed, like the more ancient white chalk,
of globigerine mud; and if the reader will refer to what we have said of the
extent to which the nummulitic marine strata, formed originally at the bottom of
the sea, now enter into the framework of mountain chains of the principal
continents, he will at once perceive that the present Atlantic, Pacific, and
Indian Oceans are geographical terms, which must be wholly without meaning when
applied to the Eocene, and still more to the Cretaceous Period; so that to talk
of the chalk having been uninterruptedly forming in the Atlantic from the
Cretaceous Period to our own, is as inadmissible in a geographical as in a
The origin of the layers of flint, whether in the form of nodules, or continuous
sheets, or in veins or cracks not parallel to the stratification, has always
been more difficult to explain than that of the white chalk. But here, again,
the late deep-sea soundings have suggested a possible source of such mineral
matter. During the cruise of the "Bulldog," already alluded to, it was
ascertained that while the calcareous Globigerinae had almost exclusive
possession of certain tracts of the sea-bottom, they were wholly wanting in
others, as between Greenland and Labrador. According to Dr. Wallich, they may
flourish in those spaces where they derive nutriment from organic and other
matter, brought from the south by the warm waters of the Gulf Stream, and they
may be absent where the effects of that great current are not felt. Now, in
several of the spaces where the calcareous Rhizopods are wanting, certain
microscopic plants, called Diatomaceae, above-mentioned (Figures 233-235), the
solid parts of which are siliceous, monopolise the ground at a depth of nearly
400 fathoms, or 2400 feet.
The large quantities of silex in solution required for the formation of these
plants may probably arise from the disintegration of feldspathic rocks, which
are universally distributed. As more than half of their bulk is formed of
siliceous earth, they may afford an endless supply of silica to all the great
rivers which flow into the ocean. We may imagine that, after a lapse of many
years or centuries, changes took place in the direction of the marine currents,
favouring at one time a supply in the same area of siliceous, and at another of
calcareous matter in excess, giving rise in the one case to a preponderance of
Globigerinae, and in the other of Diatomaceae. These last, and certain sponges,
may by their decomposition have furnished the silex, which, separating from the
chalky mud, collected round organic bodies, or formed nodules, or filled
(FIGURE 237. View of a chalk-pit at Horstead, near Norwich, showing the position
of the pot-stones. From a drawing by Mrs. Gunn.)
A more difficult enigma is presented by the occurrence of certain huge flints,
or pot-stones, as they are called in Norfolk, occurring singly, or arranged in
nearly continuous columns at right angles to the ordinary and horizontal layers
of small flints. I visited in the year 1825 an extensive range of quarries then
open on the river Bure, near Horstead, about six miles from Norwich, which
afforded a continuous section, a quarter of a mile in length, of white chalk,
exposed to the depth of about twenty-six feet, and covered by a bed of gravel.
The pot-stones, many of them pear-shaped, were usually about three feet in
height and one foot in their transverse diameter, placed in vertical rows, like
pillars, at irregular distances from each other, but usually from twenty to
thirty feet apart, though sometimes nearer together, as in Figure 237. These
rows did not terminate downward in any instance which I could examine, nor
upward, except at the point where they were cut off abruptly by the bed of
gravel. On breaking open the pot-stones, I found an internal cylindrical nucleus
of pure chalk, much harder than the ordinary surrounding chalk, and not
crumbling to pieces like it, when exposed to the winter's frost. At the distance
of half a mile, the vertical piles of pot-stones were much farther apart from
each other. Dr. Buckland has described very similar phenomena as characterising
the white chalk on the north coast of Antrim, in Ireland. (Geological
Transactions 1st Series volume 4 page 413.)
VITREOUS SPONGES OF THE CHALK.
These pear-shaped masses of flint often resemble in shape and size the large
sponges called Neptune's Cups (Spongia patera, Hardw.), which grow in the seas
of Sumatra; and if we could suppose a series of such gigantic sponges to be
separated from each other, like trees in a forest, and the individuals of each
successive generation to grow on the exact spot where the parent sponge died and
was enveloped in calcareous mud, so that they should become piled one above the
other in a vertical column, their growth keeping pace with the accumulation of
the enveloping calcareous mud, a counterpart of the phenomena of the Horstead
pot-stones might be obtained.
(FIGURE 238. Ventriculites radiatus, Mantell. Syn. Ocellaria radiata. D'Orbigny.
Professor Wyville Thomson, describing the modern soundings in 1869 off the north
coast of Scotland, speaks of the ooze or chalk mud brought from a depth of about
3000 feet, and states that at one haul they obtained forty specimens of vitreous
sponges buried in the mud. He suggests that the Ventriculites of the chalk were
nearly allied to these sponges, and that when the silica of their spicules was
removed, and was dissolved out of the calcareous matrix, it set into flint.
BOULDERS AND GROUPS OF PEBBLES IN CHALK.
The occurrence here and there, in the white chalk of the south of England, of
isolated pebbles of quartz and green schist has justly excited much wonder. It
was at first supposed that they had been dropped from the roots of some floating
tree, by which means stones are carried to some of the small coral islands of
the Pacific. But the discovery in 1857 of a group of stones in the white chalk
near Croydon, the largest of which was syenite and weighed about forty pounds,
accompanied by pebbles and fine sand like that of a beach, has been shown by Mr.
Godwin Austen to be inexplicable except by the agency of floating ice. If we
consider that icebergs now reach 40 degrees north latitude in the Atlantic, and
several degrees nearer the equator in the southern hemisphere, we can the more
easily believe that even during the Cretaceous epoch, assuming that the climate
was milder, fragments of coast ice may have floated occasionally as far as the
south of England.
DISTINCTNESS OF MINERAL CHARACTER IN CONTEMPORANEOUS ROCKS OF THE CRETACEOUS
But we must not imagine that because pebbles are so rare in the white chalk of
England and France there are no proofs of sand, shingle, and clay having been
accumulated contemporaneously even in European seas. The siliceous sandstone
called "upper quader" by the Germans overlies white argillaceous chalk or
"planer-kalk," a deposit resembling in composition and organic remains the chalk
marl of the English series. This sandstone contains as many fossil shells common
to our white chalk as could be expected in a sea-bottom formed of such different
materials. It sometimes attains a thickness of 600 feet, and, by its jointed
structure and vertical precipices, plays a conspicuous part in the picturesque
scenery of Saxon Switzerland, near Dresden. It demonstrates that in the
Cretaceous sea, as in our own, distinct mineral deposits were simultaneously in
progress. The quartzose sandstone alluded to, derived from the detritus of the
neighbouring granite, is absolutely devoid of carbonate of lime, yet it was
formed at the distance only of four hundred miles from a sea-bottom now
constituting part of France, where the purely calcareous white chalk was
forming. In the North American continent, on the other hand, where the Upper
Cretaceous formations are so widely developed, true white chalk, in the ordinary
sense of that term, does not exist.
FOSSILS OF THE WHITE CHALK.
(FIGURE 239. Ananchytes ovatus, Leske. White chalk, upper and lower.
a. Side view.
b. Base of the shell, on which both the oral and anal apertures are placed; the
anal being more round, and at the smaller end.)
(FIGURE 240. Micraster cor-angumum, Leske. White chalk.)
(FIGURE 241. Galerites albogalerus, Lam. White chalk.)
(FIGURE 242. Marsupites Milleri. Mant. White chalk.)
Among the fossils of the white chalk, echinoderms are very numerous; and some of
the genera, like Ananchytes (see Figure 239), are exclusively cretaceous. Among
the Crinoidea, the Marsupites (Figure 242) is a characteristic genus. Among the
mollusca, the cephalopoda are represented by Ammonites, Baculites (Figure 229),
and Belemnites (Figure 226). Although there are eight or more species of
Ammonites and six of them peculiar to it, this genus is much less fully
represented than in each of the other subdivisions of the Upper Cretaceous
(FIGURE 243. Terebratulina striata, Wahlenb. Upper white chalk.)
(FIGURE 244. Rhynchonella octoplicata, Sowerby. (Var. of R. plicatilis). Upper
(FIGURE 245. Magas pumila, Sowerby. Upper white chalk.)
(FIGURE 246. Terebratula carnea, Sowerby. Upper white chalk.)
(FIGURE 247. Terebratula biplicata, Brocch. Upper cretaceous.)
(FIGURE 248. Crania Parisiensis, Duf. Inferior or attached valve. Upper white
(FIGURE 249. Pecten Beaveri, Sowerby. Reduced to one-third diameter. Lower white
chalk and chalk marl. Maidstone.)
(FIGURE 250. Lima spinosa, Sowerby. Syn. Spondylus spinosus. Upper white chalk.)
(FIGURE 251. Ostrea vesicularis. Syn. Gryphaea convexa. Upper chalk and upper
Among the brachiopoda in the white chalk, the Terebratulae are very abundant
(see Figures 243-247). With these are associated some forms of oyster (see
Figure 251), and other bivalves (Figures 249, 250).
(FIGURE 252. Inoceramus Lamarckii. Syn. Catillus Lamarckii. White chalk (Dixon's
Geology Sussex Table 28 Figure 29).)
Among the bivalve mollusca, no form marks the Cretaceous era in Europe, America,
and India in a more striking manner than the extinct genus Inoceramus (Catillus
of Lam.; see Figure 252), the shells of which are distinguished by a fibrous
texture, and are often met with in fragments, having probably been extremely
(Figures 253 to 256. Radiolites Mortoni. Mantell. Houghton, Sussex. White chalk.
Diameter one-seventh natural size. On the side where the shell is thinnest,
there is one external furrow and corresponding internal ridge, a, b, Figures
253, 254; but they are usually less prominent than in these figures. The upper
or opercular valve is wanting.
(FIGURE 253. Two individuals deprived of their upper valves, adhering together.)
(FIGURE 254. Same seen from above.)
(FIGURE 255. Transverse section of part of the wall of the shell, magnified to
show the structure.)
(FIGURE 256. Vertical section of the same.))
Of the singular family called Rudistes by Lamarck, hereafter to be mentioned as
extremely characteristic of the chalk of southern Europe, a single
representative only (Figure 253) has been discovered in the white chalk of
(FIGURE 257. Eschara disticha. White chalk.
a. Natural size.
b. Portion magnified.)
(FIGURE 258. Escharina oceani.
a. Natural size.
b. Part of the same magnified.
(FIGURE 259. A branching sponge in a flint, from the white chalk. From the
collection of Mr. Bowerbank.)
The general absence of univalve mollusca in the white chalk is very marked. Of
bryozoa there is an abundance, such as Eschara and Escharina (Figures 257, 258).
These and other organic bodies, especially sponges, such as Ventriculites
(Figure 238), are dispersed indifferently through the soft chalk and hard flint,
and some of the flinty nodules owe their irregular forms to inclosed sponges,
such as Figure 259, a, where the hollows in the exterior are caused by the
branches of a sponge (Figure 259, b), seen on breaking open the flint.
(FIGURE 260. Palatal tooth of Ptychodus decurrens. Lower white chalk.
(FIGURE 261. Cestracion Phillippi; recent. Port Jackson. Buckland, Bridgewater
Treatise Plate 27 d.))
The remains of fishes of the Upper Cretaceous formations consist chiefly of
teeth belonging to the shark family. Some of the genera are common to the
Tertiary formations, and some are distinct. To the latter belongs the genus
Ptychodus (Figure 260), which is allied to the living Port Jackson shark,
Cestracion Phillippi, the anterior teeth of which (see Figure 261, a) are sharp
and cutting, while the posterior or palatal teeth (b) are flat (Figure 260). But
we meet with no bones of land-animals, nor any terrestrial or fluviatile shells,
nor any plants, except sea-weeds, and here and there a piece of drift-wood. All
the appearances concur in leading us to conclude that the white chalk was the
product of an open sea of considerable depth.
The existence of turtles and oviparous saurians, and of a Pterodactyl or winged
lizard, found in the white chalk of Maidstone, implies, no doubt, some
neighbouring land; but a few small islets in mid-ocean, like Ascension, formerly
so much frequented by migratory droves of turtle, might perhaps have afforded
the required retreat where these creatures laid their eggs in the sand, or from
which the flying species may have been blown out to sea. Of the vegetation of
such islands we have scarcely any indication, but it consisted partly of
cycadaceous plants; for a fragment of one of these was found by Captain Ibbetson
in the Chalk Marl of the Isle of Wight, and is referred by A. Brongniart to
Clathraria Lyellii, Mantell, a species common to the antecedent Wealden period.
The fossil plants, however, of beds corresponding in age to the white chalk at
Aix-la-Chapelle, presently to be described, like the sandy beds of Saxony,
before alluded to, afford such evidence of land as to prove how vague must be
any efforts of ours to restore the geography of that period.
The Pterodactyl of the Kentish chalk, above alluded to, was of gigantic
dimensions, measuring 16 feet 6 inches from tip to tip of its outstretched
wings. Some of its elongated bones were at first mistaken by able anatomists for
those of birds; of which class no osseous remains have as yet been derived from
the white chalk, although they have been found (as will be seen) in the
(FIGURE 262. Coprolites of fish, from the chalk.)
The collector of fossils from the white chalk was formerly puzzled by meeting
with certain bodies which they call larch-cones, which were afterwards
recognised by Dr. Buckland to be the excrement of fish (see Figure 262). They
are composed in great part of phosphate of lime.
LOWER WHITE CHALK.
(FIGURE 263. Baculites anceps, Lam. Lower chalk.)
The Lower White Chalk, which is several hundred feet thick, without flints, has
yielded 25 species of Ammonites, of which half are peculiar to it. The genera
Baculite, Hamite, Scaphite, Turrilite, Nautilus, Belemnite, and Belemnitella,
are also represented.
(FIGURE 264. Ammonites Rhotomagensis. Chalk marl. Back and side view.)
(FIGURE 265. Turrilites costatus, Lam. Lower chalk and chalk marl.
a. Section, showing the foliated border of the sutures of the chambers.)
(FIGURE 266. Scaphites aequalis. Chloritic marl and sand, Dorsetshire.)
The lower chalk without flints passes gradually downward, in the south of
England, into an argillaceous limestone, "the chalk marl," already alluded to.
It contains 32 species of Ammonites, seven of which are peculiar to it, while
eleven pass up into the overlying lower white chalk. A. Rhotomagensis is
characteristic of this formation. Among the British cephalopods of other genera
may be mentioned Scaphites aequalis (Figure 266) and Turrilites costatus (Figure
CHLORITIC SERIES (OR UPPER GREENSAND).
According to the old nomenclature, this subdivision of the chalk was called
Upper Greensand, in order to distinguish it from those members of the Neocomian
or Lower Cretaceous series below the Gault to which the name of Greensand had
been applied. Besides the reasons before given for abandoning this nomenclature,
it is objectionable in this instance as leading the uninitiated to suppose that
the divisions thus named Upper and Lower Greensand are of co-ordinate value,
instead of which the chloritic sand is quite a subordinate member of the Upper
Cretaceous group, and the term Greensand has very commonly been used for the
whole of the Lower Cretaceous rocks, which are almost comparable in importance
to the entire Upper Cretaceous series. The higher portion of the Chloritic
series in some districts has been called chloritic marl, from its consisting of
a chalky marl with chloritic grains. In parts of Surrey, where calcareous matter
is largely intermixed with sand, it forms a stone called malm-rock or firestone.
In the cliffs of the southern coast of the Isle of Wight it contains bands of
calcareous limestone with nodules of chert.
The so-called coprolite bed, found near Farnham, in Surrey, and near Cambridge,
contains nodules of phosphate of lime in such abundance as to be largely worked
for the manufacture of artificial manure. It belongs to the upper part of the
Chloritic series, and is doubtless chiefly of animal origin, and may perhaps be
partly coprolitic, derived from the excrement of fish and reptiles. The late Mr.
Barrett discovered in it, near Cambridge, in 1858, the remains of a bird, which
was rather larger than the common pigeon, and probably of the order Natatores,
and which, like most of the Gull tribe, had well-developed wings. Portions of
the metacarpus, metatarsus, tibia, and femur have been detected, and the
determinations of Mr. Barrett have been confirmed by Professor Owen.
This phosphatic bed in the suburbs of Cambridge must have been formed partly by
the denudation of pre-existing rocks, mostly of Cretaceous age. The fossil
shells and bones of animals washed out of these denuded strata, now forming a
layer only a few feet thick, have yielded a rich harvest to the collector. A
large Rudist of the genus Radiolite, no less than two feet in height, may be
seen in the Cambridge Museum, obtained from this bed. The number of reptilian
remains, all apparently of Cretaceous age, is truly surprising; more than ten
species of Pterodactyl, five or six of Ichthyosaurus, one of Pliosaurus, one of
Dinosaurus, eight of Chelonians, besides other forms, having been recognised.
The chloritic sand is regarded by many geologists as a littoral deposit of the
Chalk Ocean, and therefore contemporaneous with part of the chalk marl, and
even, perhaps, with some part of the white chalk. For, as the land went on
sinking, and the cretaceous sea widened its area, white mud and chloritic sand
were always forming somewhere, but the line of sea-shore was perpetually
shifting its position. Hence, though both sand and mud originated
simultaneously, the one near the land, the other far from it, the sands in every
locality where a shore became submerged might constitute the underlying deposit.
(FIGURE 267. Ostrea columba. Syn. Gryphaea columba. Chloritic sand.)
(FIGURE 268. Ostrea carinata. Chalk marl and chloritic sand. Neocomian.)
(FIGURE 269. Terebrirostra lyra, Sowerby. Chloritic sand.)
(FIGURE 270. Pecten 5-costatus. White chalk and chloritic sand. Neocomian.)
(FIGURE 271. Plagiostoma Hoperi, Sowerby. Syn. Lima Hoperi. White chalk and
Among the characteristic mollusca of the chloritic sand may be mentioned
Terebrirostra lyra (Figure 269), Plagiostoma Hoperi (Figure 271), Pecten
quinque-costatus (Figure 270), and Ostrea columba (Figure 267).
The Cephalopoda are abundant, among which 40 species of Ammonites are now known,
10 being peculiar to this subdivision, and the rest common to the beds
immediately above or below.
(FIGURE 272. Ancyloceras spinigerum, d'Orb. Syn. Hamites spiniger, Sowerby. Near
The lowest member of the Upper Cretaceous group, usually about 100 feet thick in
the S.E. of England, is provincially termed Gault. It consists of a dark blue
marl, sometimes intermixed with green sand. Many peculiar forms of cephalopoda,
such as the Hamite (Figure 272), and Scaphite, with other fossils, characterise
this formation, which, small as is its thickness, can be traced by its organic
remains to distant parts of Europe, as, for example, to the Alps.
Twenty-one species of British Ammonites are recorded as found in the Gault, of
which only eight are peculiar to it, ten being common to the overlying Chloritic
CONNECTION BETWEEN UPPER AND LOWER CRETACEOUS STRATA.-- BLACKDOWN BEDS.
The break between the Upper and Lower Cretaceous formations will be appreciated
when it is stated that, although the Neocomian contains 31 species of Ammonite,
and the Gault, as we have seen, 21, there are only three of those common to both
divisions. Nevertheless, we may expect the discovery in England, and still more
when we extend our survey to the Continent, of beds of passage intermediate
between the Upper and Lower Cretaceous. Even now the Blackdown beds in
Devonshire, which rest immediately on Triassic strata, and which evidently
belong to some part of the Cretaceous series, have been referred by some
geologists to the Upper group, by others to the Lower or Neocomian. They
resemble the Folkestone beds of the latter series in mineral character, and 59
out of 156 of their fossil mollusca are common to them; but they have also 16
species common to the Gault, and 20 to the overlying Chloritic series; and what
is very important, out of seven Ammonites six are found also in the Gault and
Chloritic series, only one being peculiar to the Blackdown beds.
Professor Ramsay has remarked that there is a stratigraphical break; for in
Kent, Surrey, and Sussex, at those few points where there are exposures of
junctions of the Gault and Neocomian, the surface of the latter has been much
eroded or denuded, while to the westward of the great chalk escarpment the
unconformability of the two groups is equally striking. At Blackdown this
unconformability is still more marked, for though distant only 100 miles from
Kent and Surrey, no formation intervenes between these beds and the Trias; all
intermediate groups, such as the Lower Neocomian and Oolite, having either not
been deposited or destroyed by denudation.
FLORA OF THE UPPER CRETACEOUS PERIOD.
As the Upper Cretaceous rocks of Europe are, for the most part, of purely marine
origin, and formed in deep water usually far from the nearest shore, land-plants
of this period, as we might naturally have anticipated, are very rarely met
with. In the neighbourhood of Aix-la-Chapelle, however, an important exception
occurs, for there certain white sands and laminated clays, 400 feet in
thickness, contain the remains of terrestrial plants in a beautiful state of
preservation. These beds are the equivalents of the white chalk and chalk marl
of England, or Senonien of d'Orbigny, although the white siliceous sands of the
lower beds, and the green grains in the upper part of the formation, cause it to
differ in mineral character from our white chalk.
Beds of fine clay, with fossil plants, and with seams of lignite, and even
perfect coal, are intercalated. Floating wood, containing perforating shells,
such as Pholas and Gastrochoena, occur. There are likewise a few beds of a
yellowish-brown limestone, with marine shells, which enable us to prove that the
lowest and highest plant-beds belong to one group. Among these shells are Pecten
quadricostatus, and several others which are common to the upper and lower part
of the series, and Trigonia limbata, d'Orbigny, a shell of the white chalk. On
the whole, the organic remains and the geological position of the strata prove
distinctly that in the neighbourhood of Aix-la-Chapelle a gulf of the ancient
Cretaceous sea was bounded by land composed of Devonian rocks. These rocks
consisted of quartzose and schistose beds, the first of which supplied white
sand and the other argillaceous mud to a river which entered the sea at this
point, carrying down in its turbid waters much drift-wood and the leaves of
plants. Occasionally, when the force of the river abated, marine shells of the
genera Trigonia, Turritella, Pecten, etc., established themselves in the same
area, and plants allied to Zostera and Fucus grew on the bottom.
The fossil plants of this member of the upper chalk at Aix have been diligently
collected and studied by Dr. Debey, and as they afford the only example yet
known of a terrestrial flora older than the Eocene, in which the great divisions
of the vegetable kingdom are represented in nearly the same proportions as in
our own times, they deserve particular attention. Dr. Debey estimates the number
of species as amounting to more than two hundred, of which sixty-seven are
cryptogamous, chiefly ferns, twenty species of which can be well determined,
most of them being in fructification. The scars on the bark of one or two are
supposed to indicate tree-ferns. Of thirteen genera three are still existing,
namely, Gleichenia, now inhabiting the Cape of Good Hope, and New Holland;
Lygodium, now spread extensively through tropical regions, but having some
species which live in Japan and North America; and Asplenium, a cosmopolite
form. Among the phaenogamous plants, the Conifers are abundant, the most common
belonging to a genus called Cycadopteris by Debey, and hardly separable from
Sequoia (or Wellingtonia), of which both the cones and branches are preserved.
When I visited Aix, I found the silicified wood of this plant very plentifully
dispersed through the white sands in the pits near that city. In one silicified
trunk 200 rings of annual growth could be counted. Species of Araucaria like
those of Australia are also found. Cycads are extremely rare, and of
Monocotyledons there are but few. No palms have been recognised with certainty,
but the genus Pandanus, or screw pine, has been distinctly made out. The number
of the Dicotyledonous Angiosperms is the most striking feature in so ancient a
(In this and subsequent remarks on fossil plants I shall often use Dr. Lindley's
terms, as most familiar in this country; but as those of M. A. Brongniart are
much cited, it may be useful to geologists to give a table explaining the
corresponding names of groups so much spoken of in palaeontology.
COLUMN 1. BRONGNIART.
COLUMN 2. LINDLEY.
COLUMN 3. EXAMPLES.
1. Cryptogamous amphigens, or cellular cryptogamic: Thallogens: Lichens, sea-
2. Cryptogamous acrogens: Acrogens: Mosses, equisetums, ferns, lycopodiums--
3. Dicotyledonous gymnosperms: Gymnogens: Conifers and Cycads.
4. Dicotyledonous Angiosperms: Exogens: Compositae, leguminosae, umbelliferae,
cruciferae, heaths, etc. All native European trees except conifers.
5. Monocotyledons: Endogens. Palms, lilies, aloes, rushes, grasses, etc.)
Among them we find the familiar forms of the Oak, Fig, and Walnut (Quercus,
Ficus, and Juglans), of the last both the nuts and leaves; also several genera
of the Myrtaceae. But the predominant order is the Proteaceae, of which there
are between sixty and seventy supposed species, many of extinct genera, but some
referred to the following living forms-- Dryandra, Grevillea, Hakea, Banksia,
Persoonia-- all now belonging to Australia, and Leucospermum, species of which
form small bushes at the Cape.
The epidermis of the leaves of many of these Aix plants, especially of the
Proteaceae, is so perfectly preserved in an envelope of fine clay, that under
the microscope the stomata, or polygonal cellules, can be detected, and their
peculiar arrangement is identical with that known to characterise some living
Proteaceae (Grevillea, for example). Although this peculiarity of the structure
of stomata is also found in plants of widely distant orders, it is, on the
whole, but rarely met with, and being thus observed to characterise a foliage
previously suspected to be proteaceous, it adds to the probability that the
botanical evidence had been correctly interpreted.
An occasional admixture at Aix-la-Chapelle of Fucoids and Zosterites attests,
like the shells, the presence of salt-water. Of insects, Dr. Debey has obtained
about ten species of the families Curculionidae and Carabidae.
The resemblance of the flora of Aix-la-Chapelle to the tertiary and living
floras in the proportional number of dicotyledonous angiosperms as compared to
the gymnogens, is a subject of no small theoretical interest, because we can now
affirm that these Aix plants flourished before the rich reptilian fauna of the
secondary rocks had ceased to exist. The Ichthyosaurus, Pterodactyl, and
Mosasaurus were of coeval date with the oak, the walnut, and the fig.
Speculations have often been hazarded respecting a connection between the rarity
of Exogens in the older rocks and a peculiar state of the atmosphere. A denser
air, it was suggested, had in earlier times been alike adverse to the well-being
of the higher order of flowering plants, and of the quick-breathing animals,
such as mammalia and birds, while it was favourable to a cryptogamic and
gymnospermous flora, and to a predominance of reptile life. But we now learn
that there is no incompatibility in the co-existence of a vegetation like that
of the present globe, and some of the most remarkable forms of the extinct
reptiles of the age of gymnosperms.
If the passage seem at present to be somewhat sudden from the flora of the Lower
or Neocomian to that of the Upper Cretaceous period, the abruptness of the
change will probably disappear when we are better acquainted with the fossil
vegetation of the uppermost beds of the Neocomian and that of the lowest strata
of the Gault or true Cretaceous series.
HIPPURITE LIMESTONE.-- DIFFERENCE BETWEEN THE CHALK OF THE NORTH AND SOUTH OF
(FIGURE 273. Map of part of S.W. France, from the Loire river to the Pyrenees.)
By the aid of the three tests, superposition, mineral character, and fossils,
the geologist has been enabled to refer to the same Cretaceous period certain
rocks in the north and south of Europe, which differ greatly both in their
fossil contents and in their mineral composition and structure.
If we attempt to trace the cretaceous deposits from England and France to the
countries bordering the Mediterranean, we perceive, in the first place, that in
the neighbourhood of London and Paris they form one great continuous mass, the
Straits of Dover being a trifling interruption, a mere valley with chalk cliffs
on both sides. We then observe that the main body of the chalk which surrounds
Paris stretches from Tours to near Poitiers (see Figure 273, in which the shaded
part represents chalk).
Between Poitiers and La Rochelle, the space marked A on the map separates two
regions of chalk. This space is occupied by the Oolite and certain other
formations older than the Chalk and Neocomian, and has been supposed by M. E. de
Beaumont to have formed an island in the Cretaceous sea. South of this space we
again meet with rocks which we at once recognise to be cretaceous, partly from
the chalky matrix and partly from the fossils being very similar to those of the
white chalk of the north: especially certain species of the genera Spatangus,
Ananchytes, Cidarites, Nucula, Ostrea, Gryphaea (Exogyra), Pecten, Plagiostoma
(Lima), Trigonia, Catillus (Inoceramus), and Terebratula. (d'Archiac, Sur la
form. Cretacee du S.-O. de la France Mem. de la Soc. Geol. de France tome 2.)
But Ammonites, as M. d'Archiac observes, of which so many species are met with
in the chalk of the north of France, are scarcely ever found in the southern
region; while the genera Hamite, Turrilite, and Scaphite, and perhaps Belemnite,
are entirely wanting.
(FIGURE 274. Radiolites radiosa, d'Orbigny. White chalk of France.
b. Upper valve of same.)
(FIGURE 275. Radiolites foliaceus, d'Orbigny. Syn. Sphaerulites agarici-formis,
Blainv. White chalk of France.)
(FIGURE 276. Hippurites organisans, Desmoulins. Upper chalk:-- chalk marl of
Pyrenees? (d'Orbigny's Palaeontologie francaise plate 533.)
a. Young individual; when full grown they occur in groups adhering laterally to
b. Upper side of the upper valve, showing a reticulated structure in those
parts, b, where the external coating is worn off.
c. Upper end or opening of the lower and cylindrical valve.
d. Cast of the interior of the lower conical valve.)
On the other hand, certain forms are common in the south which are rare or
wholly unknown in the north of France. Among these may be mentioned many
Hippurites, Sphaerulites, and other members of that great family of mollusca
called Rudistes by Lamarck, to which nothing analogous has been discovered in
the living creation, but which is quite characteristic of rocks of the
Cretaceous era in the south of France, Spain, Sicily, Greece, and other
countries bordering the Mediterranean. The species called Hippurites organisans
(Figure 276) is more abundant than any other in the south of Europe; and the
geologist should make himself well acquainted with the cast of the interior, d,
which is often the only part preserved in many compact marbles of the Upper
Cretaceous period. The flutings on the interior of the Hippurite, which are
represented on the cast by smooth, rounded longitudinal ribs, and in some
individuals attain a great size and length, are wholly unlike the markings on
the exterior of the shell.
CRETACEOUS ROCKS IN THE UNITED STATES.
If we pass to the American continent, we find in the State of New Jersey a
series of sandy and argillaceous beds wholly unlike in mineral character to our
Upper Cretaceous system; which we can, nevertheless, recognise as referable,
palaeontologically, to the same division.
That they were about the same age generally as the European chalk and Neocomian,
was the conclusion to which Dr. Morton and Mr. Conrad came after their
investigation of the fossils in 1834. The strata consist chiefly of green sand
and green marl, with an overlying coralline limestone of a pale yellow colour,
and the fossils, on the whole, agree most nearly with those of the Upper
European series, from the Maestricht beds to the Gault inclusive. I collected
sixty shells from the New Jersey deposits in 1841, five of which were identical
with European species-- Ostrea larva, O. vesicularis, Gryphaea costata, Pecten
quinque-costatus, Belemnitella mucronata. As some of these have the greatest
vertical range in Europe, they might be expected more than any others to recur
in distant parts of the globe. Even where the species were different, the
generic forms, such as the Baculite and certain sections of Ammonites, as also
the Inoceramus (see above, Figure 252) and other bivalves, have a decidedly
cretaceous aspect. Fifteen out of the sixty shells above alluded to were
regarded by Professor Forbes as good geographical representatives of well-known
cretaceous fossils of Europe. The correspondence, therefore, is not small, when
we reflect that the part of the United States where these strata occur is
between 3000 and 4000 miles distant from the chalk of Central and Northern
Europe, and that there is a difference of ten degrees in the latitude of the
places compared on opposite sides of the Atlantic. Fish of the genera Lamna,
Galeus, and Carcharodon are common to New Jersey and the European cretaceous
rocks. So also is the genus Mosasaurus among reptiles.
It appears from the labours of Dr. Newberry and others, that the Cretaceous
strata of the United States east and west of the Appalachians are characterised
by a flora decidedly analogous to that of Aix-la-Chapelle above-mentioned, and
therefore having considerable resemblance to the vegetation of the Tertiary and
LOWER CRETACEOUS OR NEOCOMIAN FORMATION.
Classification of marine and fresh-water Strata.
Folkestone and Hythe Beds.
Similarity of Conditions causing Reappearance of Species after short Intervals.
Upper Speeton Clay.
Middle Speeton Clay.
Lower Speeton Clay.
Fresh-water Character of the Wealden.
Punfield Beds of Purbeck, Dorsetshire.
Fossil Shells and Fish of the Wealden.
Area of the Wealden.
Flora of the Wealden.
We now come to the Lower Cretaceous Formation which was formerly called Lower
Greensand, and for which it will be useful for reasons before explained (Chapter
17) to use the term "Neocomian."
TABLE 18.1. LOWER CRETACEOUS OR NEOCOMIAN GROUP.
COLUMN 1: MARINE.
COLUMN 2: FRESH-WATER.
1. Upper Neocomian-- Greensand of Folkestone, Sandgate, and Hythe, Atherfield
clay, upper part of Speeton clay: Part of Wealden beds of Kent, Surrey, Sussex,
Hants, and Dorset.
2. Middle Neocomian-- Punfield Marine bed, Tealby beds, middle part of Speeton
clay: Part of Wealden beds of Kent, Surrey, Sussex, Hants, and Dorset.
3. Lower Neocomian-- Lower part of Speeton clay: Part of Wealden beds of Kent,
Surrey, Sussex, Hants, and Dorset.
In Western France, the Alps, the Carpathians, Northern Italy, and the Apennines,
an extensive series of rocks has been described by Continental geologists under
the name of Tithonian. These beds, which are without any marine equivalent in
this country, appear completely to bridge over the interval between the
Neocomian and the Oolites. They may, perhaps, as suggested by Mr. Judd, be of
the same age as part of the Wealden series.
FOLKSTONE AND HYTHE BEDS.
(FIGURE 277. Nautilus plicatus, Sowerby, in Fitton's Monog.)
(FIGURE 278. Ancyloceras gigas, d'Orbigny.)
(FIGURE 279. Gervillia anceps, Desh. Upper Neocomian, Surrey.)
(FIGURE 280. Trigonia caudata, Agassiz. Upper Neocomian.)
(FIGURE 281. Terebratula sella, Sowerby. Upper Neocomian, Hythe.)
(FIGURE 282. Diceras Lonsdalii. Upper Neocomian, Wilts.
a. The bivalve shell.
b. Cast of one of the valves enlarged.)
The sands which crop out beneath the Gault in Wiltshire, Surrey, and Sussex are
sometimes in the uppermost part pure white, at others of a yellow and
ferruginous colour, and some of the beds contain much green matter. At
Folkestone they contain layers of calcareous matter and chert, and at Hythe, in
the neighbourhood, as also at Maidstone and other parts of Kent, the limestone
called Kentish Rag is intercalated. This somewhat clayey and calcareous stone
forms strata two feet thick, alternating with quartzose sand. The total
thickness of these Folkestone and Hythe beds is less than 300 feet, and they are
seen to rest immediately on a grey clay, to which we shall presently allude as
the Atherfield clay. Among the fossils of the Folkestone and Hythe beds we may
mention Nautilus plicatus (Figure 277), Ancyloceras (Scaphites) gigas (Figure
278), which has been aptly described as an Ammonite more or less uncoiled;
Trigonia caudata (Figure 280), Gervillia anceps (Figure 279), a bivalve genus
allied to Avicula, and Terebratula sella (Figure 281). In ferruginous beds of
the same age in Wiltshire is found a remarkable shell called Diceras Lonsdalii
(Figure 282), which abounds in the Upper and Middle Neocomian of Southern
Europe. This genus is closely allied to Chama, and the cast of the interior has
been compared to the horns of a goat.
We mentioned before that the Folkstone and Hythe series rest on a grey clay.
This clay is only of slight thickness in Kent and Surrey, but acquires great
dimensions at Atherfield, in the Isle of Wight. The difference, indeed, in
mineral character and thickness of the Upper Neocomian formation near
Folkestone, and the corresponding beds in the south of the Isle of Wight, about
100 miles distant, is truly remarkable. In the latter place we find no limestone
answering to the Kentish Rag, and the entire thickness from the bottom of the
Atherfield clay to the top of the Neocomian, instead of being less than 300 feet
as in Kent, is given by the late Professor E. Forbes as 843 feet, which he
divides into sixty-three strata, forming three groups. The uppermost of these
consists of ferruginous sands, the second of sands and clay, and the third or
lowest of a brown clay, abounding in fossils.
Pebbles of quartzose sandstone, jasper, and flinty slate, together with grains
of chlorite and mica, and, as Mr. Godwin-Austen has shown, fragments and water-
worn fossils of the oolitic rocks, speak plainly of the nature of the pre-
existing formations, by the wearing down of which the Neocomian beds were
formed. The land, consisting of such rocks, was doubtless submerged before the
origin of the white chalk, a deposit which was formed in a more open sea, and in
(FIGURE 283. Perna Mulleti, Desh. One-eighth natural size.
b. Part of hinge-line of upper or right valve.)
Among the shells of the Atherfield clay the biggest and most abundant shell is
the large Perna Mulleti, of which a reduced figure is given in Figure 283.
SIMILARITY OF CONDITIONS CAUSING REAPPEARANCE OF SPECIES.
Some species of mollusca and other fossils range through the whole series, while
others are confined to particular subdivisions, and Forbes laid down a law which
has since been found of very general application in regard to estimating the
chronological relations of consecutive strata. Whenever similar conditions, he
says, are repeated, the same species reappear, provided too great a lapse of
time has not intervened; whereas if the length of the interval has been
geologically great, the same genera will reappear represented by distinct
species. Changes of depth, or of the mineral nature of the sea-bottom, the
presence or absence of lime or of peroxide of iron, the occurrence of a muddy,
or a sandy, or a gravelly bottom, are marked by the banishment of certain
species and the predominance of others. But these differences of conditions
being mineral, chemical, and local in their nature, have no necessary connection
with the extinction, throughout a large area, of certain animals or plants. When
the forms proper to loose sand or soft clay, or to perfectly clear water, or to
a sea of moderate or great depth, recur with all the same species, we may infer
that the interval of time has been, geologically speaking, small, however dense
the mass of matter accumulated. But if, the genera remaining the same, the
species are changed, we have entered upon a new period; and no similarity of
climate, or of geographical and local conditions, can then recall the old
species which a long series of destructive causes in the animate and inanimate
world has gradually annihilated.
SPEETON CLAY, UPPER DIVISION.
(FIGURE 284. Ammonites Deshayesii, Leym. Upper Neocomian.)
On the coast, beneath the white chalk of Flamborough Head, in Yorkshire, an
argillaceous formation crops out, called the Speeton clay, several hundred feet
in thickness, the palaeontological relations of which have been ably worked out
by Mr. John W. Judd, and he has shown that it is separable into three divisions,
the uppermost of which, 150 feet thick, and containing 87 species of mollusca,
decidedly belongs to the Atherfield clay and associated strata of Hythe and
Folkestone, already described. (Judd, Speeton clay, Quarterly Geological Journal
volume 24 1868 page 218.) It is characterised by the Perna Mulleti (Figure 283)
and Terebratula sella (Figure 281), and by Ammonites Deshayesii (Figure 284), a
well-known Hythe fossil. Fine skeletons of reptiles of the genera Pliosaurus and
Teleosaurus have been obtained from this clay. At the base of this upper
division of the Speeton clay there occurs a layer of large Septaria, formerly
worked for the manufacture of cement. This bed is crowded with fossils,
especially Ammonites, one species of which, three feet in diameter, was observed
by Mr. Judd.
(FIGURE 285. Pecten cinctus, Sowerby. (P. crassitesta, Rom.) Middle Neocomian,
England; Middle and Lower Neocomian, Germany. One-fifth natural size.)
(FIGURE 286. Ancyloceras (Crioceras) Duvallei, Leveille. Middle and Lower
Neocomian. One-fifth natural size.)
At Tealby, a village in the Lincolnshire Wolds, there crop out beneath the white
chalk some non-fossiliferous ferruginous sands about twenty-feet thick, beneath
which are beds of clay and limestone, about fifty feet thick, with an
interesting suite of fossils, among which are Pecten cinctus (Figure 285), from
9 to 12 inches in diameter, Ancyloceras Duvallei (Figure 286), and some forty
other shells, many of them common to the Middle Speeton clay, about to be
mentioned. Mr. Judd remarks that as Ammonites clypei-formis and Terebratula
hippopus characterise the Middle Neocomian of the Continent, it is to this stage
that the Tealby series containing the same fossils may be assigned. (Judd
Quarterly Geological Journal 1867 volume 23 page 249.)
The middle division of the Speeton clay, occurring at Speeton below the cement-
bed, before alluded to, is 150 feet thick, and contains about 39 species of
mollusca, half of which are common to the overlying clay. Among the peculiar
shells, Pecten cinctus (Figure 285) and Ancyloceras (Crioceras) Duvallei (Figure
(FIGURE 287. Ammonites Noricus, Schloth. Lower Neocomian, Speeton.)
In the lower division of the Speeton clay, 200 feet thick, 46 species of
mollusca have been found, and three divisions, each characterised by its
peculiar ammonite, have been noticed by Mr. Judd. The central zone is marked by
Ammonites Noricus (see Figure 287). On the Continent these beds are well-known
by their corresponding fossils, the Hils clay and conglomerate of the north of
Germany agreeing with the Middle and Lower Speeton, the latter of which, with
the same mineral characters and fossils as in Yorkshire, is also found in the
little island of Heligoland. Yellow limestone, which I have myself seen near
Neuchatel, in Switzerland, represents the Lower Neocomian at Speeton.
Beneath the Atherfield clay or Upper Neocomian of the S.E. of England, a fresh-
water formation is found, called the Wealden, which, although it occupies a
small horizontal area in Europe, as compared to the White Chalk and the marine
Neocomian beds, is nevertheless of great geological interest, since the imbedded
remains give us some insight into the nature of the terrestrial fauna and flora
of the Lower Cretaceous epoch. The name of Wealden was given to this group
because it was first studied in parts of Kent, Surrey, and Sussex, called the
Weald; and we are indebted to Dr. Mantell for having shown, in 1822, in his
"Geology of Sussex," that the whole group was of fluviatile origin. In proof of
this he called attention to the entire absence of Ammonites, Belemnites,
Brachiopoda, Echinodermata, Corals, and other marine fossils, so characteristic
of the Cretaceous rocks above, and of the Oolitic strata below, and to the
presence in the Weald of Paludinae, Melaniae, Cyrenae, and various fluviatile
shells, as well as the bones of terrestrial reptiles and the trunks and leaves
(FIGURE 288. Section from (left) W.S.W. through Brixton bay, Isle of Wight,
Solent and South Downs to E.N.E. (right).
2. Chalk and Gault.
3. Upper Neocomian (or Lower Greensand).
4. Wealden (Weald Clay and Hastings Sands).)
The evidence of so unexpected a fact as that of a dense mass of purely fresh-
water origin underlying a deep-sea deposit (a phenomenon with which we have
since become familiar) was received, at first, with no small doubt and
incredulity. But the relative position of the beds is unequivocal; the Weald
Clay being distinctly seen to pass beneath the Atherfield Clay in various parts
of Surrey, Kent, and Sussex, and to reappear in the Isle of Wight at the base of
the Cretaceous series, being, no doubt, continuous far beneath the surface, as
indicated by the dotted lines in Figure 288. They are also found occupying the
same relative position below the chalk in the peninsula of Purbeck, Dorsetshire,
where, as we shall see in the sequel, they repose on strata referable to the
The Upper division, or Weald Clay, is, in great part, of fresh-water origin, but
in its highest portion contains beds of oysters and other marine shells which
indicate fluvio-marine conditions. The uppermost beds are not only conformable,
as Dr. Fitton observes, to the inferior strata of the overlying Neocomian, but
of similar mineral composition. To explain this, we may suppose that, as the
delta of a great river was tranquilly subsiding, so as to allow the sea to
encroach upon the space previously occupied by fresh-water, the river still
continued to carry down the same sediment into the sea. In confirmation of this
view it may be stated that the remains of the Iguanodon Mantelli, a gigantic
terrestrial reptile, very characteristic of the Wealden, has been discovered
near Maidstone, in the overlying Kentish Rag, or marine limestone of the Upper
Neocomian. Hence we may infer that some of the saurians which inhabited the
country of the great river continued to live when part of the district had
become submerged beneath the sea. Thus, in our own times, we may suppose the
bones of large alligators to be frequently entombed in recent fresh-water strata
in the delta of the Ganges. But if part of that delta should sink down so as to
be covered by the sea, marine formations might begin to accumulate in the same
space where fresh-water beds had previously been formed; and yet the Ganges
might still pour down its turbid waters in the same direction, and carry seaward
the carcasses of the same species of alligator, in which case their bones might
be included in marine as well as in subjacent fresh-water strata.
(FIGURES 289 AND 290. Tooth of Iguanodon Mantelli.
(FIGURE 289. a, and b.)
(FIGURE 290. A. Partially worn tooth of young individual of the same.
b. Crown of tooth in adult worn down. (Mantell.)))
The Iguanodon, first discovered by Dr. Mantell, was an herbivorous reptile, of
which the teeth, though bearing a great analogy, in their general form and
crenated edges (see Figure 289 a and b), to the modern Iguanas which now
frequent the tropical woods of America and the West Indies, exhibit many
important differences. It appears that they have often been worn by the process
of mastication; whereas the existing herbivorous reptiles clip and gnaw off the
vegetable productions on which they feed, but do not chew them. Their teeth
frequently present an appearance of having been chipped off, but never, like the
fossil teeth of the Iguanodon, have a flat ground surface (see Figure 290, b)
resembling the grinders of herbivorous mammalia. Dr. Mantell computes that the
teeth and bones of this species which passed under his examination during twenty
years must have belonged to no less than seventy-one distinct individuals,
varying in age and magnitude from the reptile just burst from the egg, to one of
which the femur measured twenty-four inches in circumference. Yet,
notwithstanding that the teeth were more numerous than any other bones, it is
remarkable that it was not until the relics of all these individuals had been
found, that a solitary example of part of a jaw-bone was obtained. Soon
afterwards remains both of the upper and lower jaw were met with in the Hastings
beds in Tilgate Forest, near Cuckfield. In the same sands at Hastings, Mr.
Beckles found large tridactyle impressions which it is conjectured were made by
the hind feet of this animal, on which it is ascertained that there were only
three well-developed toes.
(FIGURE 291. Cypris spinigera, Fitton.)
(FIGURE 292. Weald clay with Cyprides.)
Occasionally bands of limestone, called Sussex Marble, occur in the Weald Clay,
almost entirely composed of a species of Paludina, closely resembling the common
P. vivipara of English rivers. Shells of the Cypris, a genus of Crustaceans
mentioned in Chapter 3 as abounding in lakes and ponds, are also plentifully
scattered through the clays of the Wealden, sometimes producing, like plates of
mica, a thin lamination (see Figure 292).
This lower division of the Wealden consists of sand, sandstone, calciferous
grit, clay, and shale; the argillaceous strata, notwithstanding the name,
predominating somewhat over the arenaceous, as will be seen by reference to the
following table, drawn up by Messrs. Drew and Foster, of the Geological Survey
of Great Britain:
TABLE 18.1. SUBORDINATE FORMATIONS IN THE HASTINGS SAND.
COLUMN 1: NAME OF SUBORDINATE FORMATION.
COLUMN 2: MINERAL COMPOSITION OF THE STRATA.
COLUMN 3: THICKNESS IN FEET.
Tunbridge Wells Sand: Sandstone and loam: 150.
Wadhurst Clay: Blue and brown shale and clay, with a little calc-grit: 100.
Ashdown Sand: Hard sand, with some beds of calc-grit: 160.
Ashburnham Beds: Mottled white and red clay, with some sandstone: 330.
The picturesque scenery of the "High Rocks" and other places in the
neighbourhood of Tunbridge Wells is caused by the steep natural cliffs, to which
a hard bed of white sand, occurring in the upper part of the Tunbridge Wells
Sand, mentioned in the above table, gives rise. This bed of "rock-sand" varies
in thickness from 25 to 48 feet. Large masses of it, which were by no means hard
or capable of making a good building-stone, form, nevertheless, projecting rocks
with perpendicular faces, and resist the degrading action of the river because,
says Mr. Drew, they present a solid mass without planes of division. The
calcareous sandstone and grit of Tilgate Forest, near Cuckfield, in which the
remains of the Iguanodon and Hylaeosaurus were first found by Dr. Mantell,
constitute an upper member of the Tunbridge Wells Sand, while the "sand-rock" of
the Hastings cliffs, about 100 feet thick, is one of the lower members of the
same. The reptiles, which are very abundant in this division, consist partly of
saurians, referred by Owen and Mantell to eight genera, among which, besides
those already enumerated, we find the Megalosaurus and Plesiosaurus. The
Pterodactyl also, a flying reptile, is met with in the same strata, and many
remains of Chelonians of the genera Trionyx and Emys, now confined to tropical
(FIGURE 293. Lepidotus Mantelli, Agassiz. Wealden.
a. Palate and teeth.
b. Side view of teeth.
The fishes of the Wealden are chiefly referable to the Ganoid and Placoid
orders. Among them the teeth and scales of Lepidotus are most widely diffused
(see Figure 293). These ganoids were allied to the Lepidosteus, or Gar-pike, of
the American rivers. The whole body was covered with large rhomboidal scales,
very thick, and having the exposed part coated with enamel. Most of the species
of this genus are supposed to have been either river-fish, or inhabitants of the
sea at the mouth of estuaries.
(FIGURE 294. Unio Valdensis, Mant. Isle of Wight and Dorsetshire; in the lower
beds of the Hastings Sands. a, b.)
(FIGURE 295. Underside of slab of sandstone about one yard in diameter.
At different heights in the Hastings Sands, we find again and again slabs of
sandstone with a strong ripple-mark, and between these slabs beds of clay many
yards thick. In some places, as at Stammerham, Horsham, near there, are
indications of this clay having been exposed so as to dry and crack before the
next layer was thrown down upon it. The open cracks in the clay have served as
moulds, of which casts have been taken in relief, and which are, therefore, seen
on the lower surface of the sandstone (see Figure 295).
(FIGURE 296. Sphenopteris gracilis, Fitton. From the Hastings Sands near
a. A portion of the same magnified.)
Near the same place a reddish sandstone occurs in which are innumerable traces
of a fossil vegetable, apparently Sphenopteris, the stems and branches of which
are disposed as if the plants were standing erect on the spot where they
originally grew, the sand having been gently deposited upon and around them; and
similar appearances have been remarked in other places in this formation.
(Mantell Geology of S.E. of England page 244.) In the same division also of the
Wealden, at Cuckfield, is a bed of gravel or conglomerate, consisting of water-
worn pebbles of quartz and jasper, with rolled bones of reptiles. These must
have been drifted by a current, probably in water of no great depth.
From such facts we may infer that, notwithstanding the great thickness of this
division of the Wealden, the whole of it was a deposit in water of a moderate
depth, and often extremely shallow. This idea may seem startling at first, yet
such would be the natural consequence of a gradual and continuous sinking of the
ground in an estuary or bay, into which a great river discharged its turbid
waters. By each foot of subsidence, the fundamental rock would be depressed one
foot farther from the surface; but the bay would not be deepened, if newly-
deposited mud and sand should raise the bottom one foot. On the contrary, such
new strata of sand and mud might be frequently laid dry at low water, or
overgrown for a season by a vegetation proper to marshes.
PUNFIELD BEDS, BRACKISH AND MARINE.
(FIGURE 297. Vicarya Lujani, De Verneuil (Foss. de Utrillas.) Wealden, Punfield.
a. Nearly perfect shell.
b. Vertical section of smaller specimen, showing continuous ridges as in
The shells of the Wealden beds belong to the genera Melanopsis, Melania,
Paludina, Cyrena, Cyclas, Unio (see Figure 294), and others, which inhabit
rivers or lakes; but one band has been found at Punfield, in Dorsetshire,
indicating a brackish state of the water, where the genera Corbula, Mytilus, and
Ostrea occur; and in some places this bed becomes purely marine, containing some
well-known Neocomian fossils, among which Ammonites Deshayesii (Figure 284) may
be mentioned. Others are peculiar as British, but very characteristic of the
Upper and Middle Neocomian of Spain, and among these the Vicarya Lujani (Figure
297), a shell allied to Nerinea, is conspicuous.
By reference to Table 18.1 it will be seen that the Wealden beds are given as
the fresh-water equivalents of the Marine Neocomian. The highest part of them in
England may, for reasons just given, be regarded as Upper Neocomian, while some
of the inferior portions may correspond in age to the Middle and Lower divisions
of that group. In favour of this latter view, M. Marcou mentions that a fish
called Asteracanthus granulosus, occurring in the Tilgate beds, is
characteristic of the lowest beds of the Neocomian of the Jura, and it is well
known that Corbula alata, common in the Ashburnham beds, is found also at the
base of the Neocomian of the Continent.
AREA OF THE WEALDEN.
In regard to the geographical extent of the Wealden, it can not be accurately
laid down, because so much of it is concealed beneath the newer marine
formations. It has been traced about 320 English miles from west to east, from
the coast of Dorsetshire to near Boulogne, in France; and nearly 200 miles from
north-west to south-east, from Surrey and Hampshire to Vassy, in France. If the
formation be continuous throughout this space, which is very doubtful, it does
not follow that the whole was contemporaneous; because, in all likelihood, the
physical geography of the region underwent frequent changes throughout the whole
period, and the estuary may have altered its form, and even shifted its place.
Dr. Dunker, of Cassel, and H. von Meyer, in an excellent monograph on the
Wealdens of Hanover and Westphalia, have shown that they correspond so closely,
not only in their fossils, but also in their mineral characters, with the
English series, that we can scarcely hesitate to refer the whole to one great
delta. Even then, the magnitude of the deposit may not exceed that of many
modern rivers. Thus, the delta of the Quorra or Niger, in Africa, stretches into
the interior for more than 170 miles, and occupies, it is supposed, a space of
more than 300 miles along the coast, thus forming a surface of more than 25,000
square miles, or equal to about one-half of England. (Fitton Geology of Hastings
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