THE EXISTING FAUNA AND FLORA.
Chronological Relation of the Glacial Period, and the earliest
known Signs of Man's Appearance in Europe.
Series of Tertiary Deposits in Norfolk and Suffolk immediately
antecedent to the Glacial Period.
Gradual Refrigeration of Climate proved by the Marine Shells
of successive Groups.
Marine Newer Pliocene Shells of Northern Character near Woodbridge.
Section of the Norfolk Cliffs.
Norwich Crag.
Forest Bed and Fluvio-marine Strata.
Fossil Plants and Mammalia of the same.
Overlying Boulder Clay and Contorted Drift.
Newer freshwater Formation of Mundesley compared to that of Hoxne.
Great Oscillations of Level implied by the Series of Strata in the
Norfolk Cliffs.
Earliest known Date of Man long subsequent to the existing Fauna
and Flora.
Frequent allusions have been made in the preceding pages to a period
called the glacial, to which no reference is made in the Chronological
Table of Formations given above (Chapter 1). It comprises a long series
of ages, during which the power of cold, whether exerted by glaciers
on the land, or by floating ice on the sea, was greater in the northern
hemisphere, and extended to more southern latitudes than now. [19]
It often happens that when in any given region we have pushed back our
geological investigations as far as we can in search of evidence of the
first appearance of Man in Europe, we are stopped by arriving at what is
called the "boulder clay" or "northern drift." This formation is usually
quite destitute of organic remains, so that the thread of our inquiry
into the history of the animate creation, as well as of man, is abruptly
cut short. The interruption, however, is by no means encountered at the
same point of time in every district. In the case of the Danish peat,
for example, we get no farther back than the Recent period of our
Chronologic Table, and then meet with the boulder clay; and it is the
same in the valley of the Clyde, where the marine strata contain
the ancient canoes before described (Chapter 3), and where nothing
intervenes between that Recent formation and the glacial drift. But we
have seen that, in the neighbourhood of Bedford the memorials of Man can
be traced much farther back into the past, namely, into the Pleistocene
epoch, when the human race was contemporary with the mammoth and many
other species of mammalia now extinct. Nevertheless, in Bedfordshire as
in Denmark, the formation next antecedent in date to that containing
the human implements is still a member of the glacial drift, with its
erratic blocks.
If the reader remembers what was stated in the eighth chapter as to
the absence or extreme scarcity of human bones and works of art in
all strata, whether marine or freshwater, even in those formed in the
immediate proximity of land inhabited by millions of human beings, he
will be prepared for the general dearth of human memorials in glacial
formations, whether Recent, Pleistocene, or of more ancient date. If
there were a few wanderers over lands covered with glaciers, or over
seas infested with ice-bergs, and if a few of them left their bones or
weapons in moraines or in marine drift, the chances, after the lapse
of thousands of years, of a geologist meeting with one of them must be
infinitesimally small.
It is natural, therefore, to encounter a gap in the regular sequence
of geological monuments bearing on the past history of Man, wherever we
have proofs of glacial action having prevailed with intensity, as it has
done over large parts of Europe and North America, in the Pleistocene
period. As we advance into more southern latitudes approaching the 50th
parallel of latitude in Europe, and the 40th in North America, this
disturbing cause ceases to oppose a bar to our inquiries; but even then,
in consequence of the fragmentary nature of all geological annals, our
progress is inevitably slow in constructing anything like a connected
chain of history, which can only be effected by bringing the links of
the chain found in one area to supply the information which is wanting
in another.
The least interrupted series of consecutive documents to which we can
refer in the British Islands, when we desire to connect the Pliocene
with the Pleistocene periods, are found in the counties of Norfolk,
Suffolk, and Essex; and I shall speak of them in this chapter, as they
have a direct bearing on the relations of the human and glacial periods,
which will be the subject of several of the following chapters. The
fossil shells of the deposits in question clearly point to a gradual
refrigeration of climate, from a temperature somewhat warmer than
that now prevailing in our latitudes to one of intense cold; and the
successive steps which have marked the coming on of the increasing cold
are matters of no small geological interest. [20]
It will be seen in the Chronological Table, that next before the
Pleistocene period stands the Pliocene. The shelly and sandy
beds representing these periods in Norfolk and Suffolk are termed
provincially Crag, having under the name been long used in agriculture
to fertilise soils deficient in calcareous matter, or to render them
less stiff and impervious. In Suffolk, the older Pliocene strata called
Crag are divisible into the Coralline and the Red Crags, the former
being the older of the two. In Norfolk, a more modern formation,
commonly termed the "Norwich," or sometimes the "mammaliferous" Crag,
which is referable to the newer Pliocene period, occupies large areas.
We are indebted to Mr. Searles Wood, F.G.S., for an admirable monograph
on the fossil shells of these British Pliocene formations. He has not
himself given us an analysis of the results of his treatise, but the
following tables have been drawn up for me by Mr. S.P. Woodward, the
well-known author of the "Manual of Mollusca, Recent and Fossil" (London
1851-56), in order to illustrate some of the general conclusions to
which Mr. Wood's careful examination of 442 species of mollusca has led.
TABLE 12/1. NUMBER OF KNOWN SPECIES OF MARINE TESTACEA IN THE THREE
ENGLISH PLIOCENE DEPOSITS, CALLED THE NORWICH, THE RED, AND THE
CORALLINE CRAGS.
COLUMN 1: NAME.
COLUMN 2: NUMBER.
Brachiopoda: 6.
Lamellibranchia: 206.
Gasteropoda: 230.
TOTAL: 442.
TABLE 12/2. DISTRIBUTION OF THE ABOVE MARINE TESTACEA.
COLUMN 1: NAME.
COLUMN 2: NUMBER.
Norwich Crag: 81.
Red Crag: 225.
Coralline Crag: 327.
Species common to the Norwich and Red Crag (not in Coralline): 33.
Species common to the Norwich and Coralline (not in Red): 4.
Species common to the Red and Coralline (not in Norwich): 116.
Species common to the Norwich, Red, and Coralline: 19.*
(* These 19 species must be added to the numbers 33, 4, and
116 respectively, in order to obtain the full amount of common
species in each of those cases.)
TABLE 12/3. PROPORTION OF RECENT TO EXTINCT SPECIES.
COLUMN 1: NAME.
COLUMN 2: NUMBER OF RECENT.
COLUMN 3: NUMBER OF EXTINCT.
COLUMN 4: PERCENTAGE OF RECENT.
Norwich Crag: 69: 12: 85%.
Red Crag: 130: 95: 57%.
Coralline Crag: 168: 159: 51%.
TABLE 12/4. RECENT SPECIES NOT LIVING NOW IN BRITISH SEAS.
COLUMN 1: NAME.
COLUMN 2: NUMBER OF NORTHERN.
COLUMN 3: NUMBER OF SOUTHERN.
Norwich Crag: 12: 0.
Red Crag: 8: 16.
Coralline Crag: 2: 27.
In the above list I have not included the shells of the glacial beds of
the Clyde and of several other British deposits of newer origin than the
Norwich Crag, in which nearly all--perhaps all--the species are Recent.
The land and freshwater shells, thirty-two in number, have also been
purposely omitted, as well as three species of London Clay shells,
suspected by Mr. Wood himself to be spurious.
By far the greater number of the living marine species included in these
tables are still inhabitants of the British seas; but even these differ
considerably in their relative abundance, some of the commonest of the
Crag shells being now extremely scarce; as, for example, Buccinopsis
Dalei; and others, rarely met with in a fossil state, being now very
common, as Murex erinaceus and Cardium echinatum.
The last table throws light on a marked alteration in the climate of
the three successive periods. It will be seen that in the Coralline
Crag there are twenty-seven southern shells, including twenty-six
Mediterranean, and one West Indian species (Erato Maugeriae). Of these
only thirteen occur in the Red Crag, associated with three new southern
species, while the whole of them disappear from the Norwich beds. On the
other hand, the Coralline Crag contains only two shells closely
related to arctic forms of the genera Admete and Limopsis. The Red Crag
contains, as stated in the table, eight northern species, all of which
recur in the Norwich Crag, with the addition of four others, also
inhabitants of the arctic regions; so that there is good evidence of
a continual refrigeration of climate during the Pliocene period in
Britain. The presence of these northern shells cannot be explained away
by supposing that they were inhabitants of the deep parts of the sea;
for some of them, such as Tellina calcarea and Astarte borealis, occur
plentifully, and sometimes, with the valves united by their ligament, in
company with other littoral shells, such as Mya arenaria and Littorina
rudis, and evidently not thrown up from deep water. Yet the northern
character of the Norwich Crag is not fully shown by simply saying that
it contains twelve northern species. It is the predominance of certain
genera and species, such as Tellina calcarea, Astarte borealis, Scalaria
groenlandica, and Fusus carinatus, which satisfies the mind of a
conchologist as to the arctic character of the Norwich Crag. In like
manner, it is the presence of such genera as Pyrula, Columbella,
Terebra, Cassidaria, Pholadomya, Lingula, Discina, and others which give
a southern aspect to the Coralline Crag shells.
The cold, which had gone on increasing from the time of the Coralline
to that of the Norwich Crag, continued, though not perhaps without some
oscillations of temperature, to become more and more severe after the
accumulation of the Norwich Crag, until it reached its maximum in what
has been called the glacial epoch. The marine fauna of this last period
contains, both in Ireland and Scotland, Recent species of mollusca now
living in Greenland and other seas far north of the areas where we find
their remains in a fossil state.
The refrigeration of climate from the time of the older to that of the
newer Pliocene strata is not now announced for the first time, as it
was inferred from a study of the Crag shells in 1846 by the late Edward
Forbes.*
(* "Memoirs of the Geological Survey" London 1846 page 391.)
The most southern point to which the marine beds of the Norwich Crag
have yet been traced is at Chillesford, near Woodbridge, in Suffolk,
about 80 miles north-east of London, where, as Messrs. Prestwich and
Searles Wood have pointed out,* they exhibit decided marks of having
been deposited in a sea of a much lower temperature than that now
prevailing in the same latitude. (* "Quarterly Journal of the Geological
Society" volume 5 1849 page 345.) Out of twenty-three shells obtained in
that locality from argillaceous strata 20 feet thick, two only, namely,
Nucula Cobboldiae and Tellina obliqua, are extinct, and not a few of the
other species, such as Leda lanceolata, Cardium groenlandicum, Lucina
borealis, Cyprina islandica, Panopaea norvegica, and Mya truncata,
betray a northern, and some of them an arctic character.
These Chillesford beds are supposed to be somewhat more modern than
any of the purely marine strata of the Norwich Crag exhibited by the
sections of the Norfolk cliffs north-west of Cromer, which I am about
to describe. Yet they probably preceded in date the "Forest Bed" and
fluvio-marine deposits of those same cliffs. They are, therefore, of no
small importance in reference to the chronology of the glacial period,
since they afford evidence of an assemblage of fossil shells with a
proportion of between eight and nine in a hundred of extinct species
occurring so far south as latitude 53 degrees north, and indicating so
cold a climate as to imply that the glacial period commenced before the
close of the Pliocene era.
[Illustration: Figure 27. Succession of Strata]
(FIGURE 27. DIAGRAM TO ILLUSTRATE THE GENERAL SUCCESSION
OF THE STRATA IN THE NORFOLK CLIFFS, EXTENDING SEVERAL MILES
NORTH-WEST AND SOUTH-EAST OF CROMER.
A. Site of Cromer Jetty.
1. Upper Chalk with flints in regular stratification.
2. Norwich Crag, rising from low water at Cromer to the top
of the cliffs at Weybourn, seven miles distant.
3. "Forest Bed," with stumps of trees in situ and remains of
Elephas meridionalis, E. primigenius, E. antiquus, Rhinoceros
etruscus, etc. This bed increases in depth and thickness
eastward. No Crag (Number 2) known east of Cromer Jetty.
3 prime. Fluvio-marine series. At Cromer and eastward, with
abundant lignite beds and mammalian remains, and with cones
of the Scotch and spruce firs and wood. At Runton, north-west
of Cromer, expanding into a thick freshwater deposit, with
overlying marine strata, elsewhere consisting of alternating
sands and clays, tranquilly deposited, some with marine,
others with freshwater shells.
4. Boulder clay of glacial period, with far transported erratics,
some of them polished and scratched, 20 to 80 feet in thickness.
5. Contorted drift.
6. Superficial gravel and sand with covering of vegetable soil.)
The annexed section (Figure 27) will give a general idea of the ordinary
succession of the Pliocene and Pleistocene strata which rest upon the
Chalk in the Norfolk and Suffolk cliffs. These cliffs vary in height
from fifty to above three hundred feet. At the north-western extremity
of the section at Weybourn (beyond the limits of the annexed diagram),
and from thence to Cromer, a distance of 7 miles, the Norwich Crag, a
marine deposit, reposes immediately upon the Chalk. A vast majority
of its shells are of living species such as Cardium edule, Cyprina
islandica, Scalaria groenlandica, and Fusus antiquus, and some few
extinct, as Tellina obliqua, and Nucula Cobboldiae. At Cromer jetty this
formation thins out, as expressed in the diagram at A; and to the south
we find Number 3, or what is commonly called the "Forest Bed," reposing
immediately upon the Chalk, and occupying, as it were, the place
previously held by the marine Crag Number 2. This buried forest has
been traced for more than 40 miles, being exposed at certain seasons
and states of the beach between high and low water mark. It extends from
Cromer to near Kessingland, and consists of the stumps of numerous trees
standing erect, with their roots attached to them, and penetrating in
all directions into the loam or ancient vegetable soil on which they
grew. They mark the site of a forest which existed there for a long
time, since, besides the erect trunks of trees, some of them 2 and 3
feet in diameter, there is a vast accumulation of vegetable matter in
the immediately overlying clays. Thirty years ago, when I first examined
this bed, I saw many trees, with their roots in the old soil, laid open
at the base of the cliff near Happisburgh; and long before my visit,
other observers, and among them the late Mr. J.C. Taylor, had noticed
the buried forest. Of late years it has been repeatedly seen at many
points by Mr. Gunn, and, after the great storms of the autumn of 1861,
by Mr. King. In order to expose the stumps to view, a vast body of sand
and shingle must be cleared away by the force of the waves. [21]
As the sea is always gaining on the land, new sets of trees are brought
to light from time to time, so that the breadth as well as length of the
area of ancient forest land seems to have been considerable. Next above
Number 3, we find a series of sands and clays with lignite (Number
3 prime), sometimes 10 feet thick, and containing alternations of
fluviatile and marine strata, implying that the old forest land, which
may at first have been considerably elevated above the level of the sea,
had sunk down so as to be occasionally overflowed by a river, and
at other times by the salt waters of an estuary. There were probably
several oscillations of level which assisted in bringing about these
changes, during which trees were often uprooted and laid prostrate,
giving rise to layers of lignite. Occasionally marshes were formed and
peaty matter accumulated, after which salt water again predominated, so
that species of Mytilus, Mya, Leda, and other marine genera, lived in
the same area where the Unio, Cyclas, and Paludina had flourished for
a time. That the marine shells lived and died on the spot, and were
not thrown up by the waves during a storm, is proved, as Mr. King has
remarked, by the fact that at West Runton, north-west of Cromer, the Mya
truncata and Leda myalis are found with both valves united and erect in
the loam, all with their posterior or siphuncular extremities uppermost.
This attitude affords as good evidence to the conchologist that those
mollusca lived and died on the spot as the upright position of the trees
proves to the botanist that there was a forest over the Chalk east of
Cromer.
Between the stumps of the buried forest, and in the lignite above them,
are many well-preserved cones of the Scotch and spruce firs, Pinus
sylvestris, and Pinus abies. The specific names of these fossils were
determined for me in 1840, by a botanist of no less authority than
the late Robert Brown; and Professor Heer has lately examined a large
collection from the same stratum, and recognised among the cones of the
spruce some which had only the central part or axis remaining, the rest
having been bitten off, precisely in the same manner as when in our
woods the squirrel has been feeding on the seeds. There is also in the
forest-bed a great quantity of resin in lumps, resembling that gathered
for use, according to Professor Heer, in Switzerland, from beneath
spruce firs.
The following is a list of some of the plants and seeds which were
collected by the Reverend S.W. King, in 1861, from the forest bed at
Happisburgh, and named by Professor Heer:--
PLANTS AND SEEDS OF THE FOREST AND LIGNITE BEDS BELOW THE GLACIAL DRIFT
OF THE NORFOLK CLIFFS.
Pinus sylvestris, Scotch fir.
Pinus abies, spruce fir.
Taxus baccata, yew.
Nuphar luteum, yellow water-lily.
Ceratophyllum demersum, hornwort.
Potamogeton, pondweed.
Prunus spinosus, common sloe.
Menyanthes trifoliata, buckbean.
Nymphaea alba, white water-lily.
Alnus, alder.
Quercus, oak.
Betula, birch.
The insects, so far as they are known, including several species of
Donacia, are, like the plants and freshwater shells, of living species.
It may be remarked, however, that the Scotch fir has been confined in
historical times to the northern parts of the British Isles, and the
spruce fir is nowhere indigenous in Great Britain. The other plants are
such as might now be found in Norfolk, and many of them indicate fenny
or marshy ground.*
(* Mr. King discovered in 1863, in the forest bed, several
rhizomes of the large British fern Osmunda regalis, of such
dimensions as they are known to attain in marshy places.
They are distinguishable from those of other British ferns
by the peculiar arrangement of the vessels, as seen under
the microscope in a cross section.)
When we consider the familiar aspect of the flora, the accompanying
mammalia are certainly most extraordinary. There are no less than three
elephants, a rhinoceros and hippopotamus, a large extinct beaver, and
several large estuarine and marine mammalia, such as the walrus, the
narwhal, and the whale.
The following is a list of some of the species of which the bones have
been collected by Messrs. Gunn and King.
Those marked (asterisk) have been recorded by Professor Owen in his
British Fossil Mammalia. Those marked (dagger) have been recognised by
the same authority in the cabinets of Messrs. Gunn and King, or in
the Norwich Museum; the other three are given on the authority of Dr.
Falconer.
MAMMALIA OF THE FOREST AND LIGNITE BEDS BELOW THE GLACIAL DRIFT OF THE
NORFOLK CLIFFS.
Elephas meridionalis.
(asterisk) Elephas primigenius.
Elephas antiquus.
Rhinoceros etruscus.
(asterisk) Hippopotamus (major?).
(asterisk) Sus scrofa.
(asterisk) Equus (fossilis?).
(asterisk) Ursus (sp.?).
(dagger) Canis lupus.
(dagger) Bison priscus.
(dagger) Megaceros hibernicus.
(asterisk) Cervus capreolus.
(dagger) Cervus tarandus.
(dagger) Cervus Sedgwickii.
(asterisk) Arvicola amphibia.
(asterisk) Castor (Trogontherium) Cuvieri.
(asterisk) Castor europaeus.
(asterisk) Palaeospalax magnus.
(dagger) Trichecus rosmarus, Walrus.
(dagger) Monodon monoceros, Narwhal.
(dagger) Balaenoptera.
Mr. Gunn informs me that the vertebrae of two distinct whales were found
in the fluvio-marine beds at Bacton, and that one of them, shown to
Professor Owen, is said by him to imply that the animal was 60 feet
long. A narwhal's tusk was discovered by Mr. King near Cromer, and
the remains of a walrus. No less than three species of elephant, as
determined by Dr. Falconer, have been obtained from the strata 3 and
3 prime, of which, according to Mr. King, E. meridionalis is the most
common, the mammoth next in abundance, and the third, E. antiquus,
comparatively rare.
The freshwater shells accompanying the fossil quadrupeds, above
enumerated, are such as now inhabit rivers and ponds in England; but
among them, as at Runton, between the "forest bed" and the glacial
deposits, a remarkable variety of the Cyclas amnica occurs (Figure 28),
identical with that which accompanies the Elephas antiquus at Ilford and
Grays in the valley of the Thames.
All the freshwater shells of the beds intervening between the Forest-bed
Number 3, and the glacial formation 4, Figure 27, are of Recent
species. As to the small number of marine shells occurring in the
same fluvio-marine series, I have seen none which belonged to extinct
species, although one or two have been cited by authors. I am in doubt,
therefore, whether to class the forest bed and overlying strata as
Pleistocene, or to consider them as beds of passage between the Pliocene
and Pleistocene periods. The fluvio-marine series usually terminates
upwards in finely laminated sands and clays without fossils, on which
reposes the boulder clay.
[Illustration: Figure 28. Cyclas]
(FIGURE 28. Cyclas (Pisidium) amnica var.?
The two middle figures are of the natural size.)
This formation, Number 4, is of very varying thickness. Its glacial
character is shown, not only by the absence of stratification, and the
great size and angularity of some of the included blocks of distant
origin, but also by the polished and scratched surfaces of such of them
as are hard enough to retain any markings.
Near Cromer, blocks of granite from 6 to 8 feet in diameter have been
met with, and smaller ones of syenite, porphyry, and trap, besides
the wreck of the London Clay, Chalk, Oolite, and Lias, mixed with more
ancient fossiliferous rocks. Erratics of Scandinavian origin occur
chiefly in the lower portions of the till. I came to the conclusion in
1834, that they had really come from Norway and Sweden, after having in
that year traced the course of a continuous stream of such blocks from
those countries to Denmark, and across the Elbe, through Westphalia,
to the borders of Holland. It is not surprising that they should then
reappear on our eastern coast between the Tweed and the Thames, regions
not half so remote from parts of Norway as are many Russian erratics
from the sources whence they came. [22]
[Illustration: Figure 29. Cliff]
(FIGURE 29. CLIFF 50 FEET HIGH BETWEEN BACTON GAP AND MUNDESLEY.
Section through Gravel (top), Sand, Loam and Till (bottom).)
According to the observations of the Reverend J. Gunn and the late Mr.
Trimmer, the glacial drift in the cliffs at Lowestoft consists of
two divisions, the lower of which abounds in the Scandinavian blocks,
supposed to have come from the north-east; while the upper, probably
brought by a current from the north-west, contains chiefly fragments of
Oolitic rocks, more rolled than those of the lower deposit. The united
thickness of the two divisions, without reckoning some interposed
laminated beds, is 80 feet, but it probably exceeds 100 feet near
Happisburgh.*
(* "Quarterly Journal of the Geological Society" volume 7
1851 page 21.)
Although these subdivisions of the drift may be only of local
importance, they help to show the changes of currents and other
conditions, and the great lapse of time which the accumulation of so
varied a series of deposits must have required.
The lowest part of the glacial till, resting on the laminated clays
before mentioned, is very even and regular, while its upper surface
is remarkable for the unevenness of its outline, owing partly, in all
likelihood, to denudation, but still more to other causes presently to
be discussed.
The overlying strata of sand and gravel, Number 5, Figure 27, often
display a most singular derangement in their stratification, which in
many places seems to have a very intimate relation to the irregularities
of outline in the subjacent till. There are some cases, however, where
the upper strata are much bent, while the lower beds of the same
series have continued horizontal. Thus the annexed section (Figure 29)
represents a cliff about 50 feet high, at the bottom of which is till,
or unstratified clay, containing boulders, having an even horizontal
surface, on which repose conformably beds of laminated clay and sand
about 5 feet thick, which, in their turn, are succeeded by vertical,
bent, and contorted layers of sand and loam 20 feet thick, the whole
being covered by flint gravel. The curves of the variously coloured beds
of loose sand, loam, and pebbles, are so complicated that not only may
we sometimes find portions of them which maintain their verticality to a
height of 10 or 15 feet, but they have also been folded upon themselves
in such a manner that continuous layers might be thrice pierced in one
perpendicular boring.
[Illustration: Figures 30 and 31. Strata]
(FIGURE 30. FOLDING OF THE STRATA BETWEEN EAST AND WEST RUNTON.)
(FIGURE 31. SECTION OF CONCENTRIC BEDS WEST OF CROMER.
1. Blue clay.
2. White sand.
3. Yellow Sand.
4. Striped loam and clay.
5. Laminated blue clay.)
At some points there is an apparent folding of the beds round a central
nucleus, as at a, Figure 30, where the strata seem bent round a small
mass of Chalk, or, as in Figure 31, where the blue clay Number 1 is in
the centre; and where the other strata 2, 3, 4, 5 are coiled round it;
the entire mass being 20 feet in perpendicular height. This appearance
of concentric arrangement around a nucleus is, nevertheless, delusive,
being produced by the intersection of beds bent into a convex shape; and
that which seems the nucleus being, in fact, the innermost bed of
the series, which has become partially visible by the removal of the
protuberant portions of the outer layers.
To the north of Cromer are other fine illustrations of contorted drift
reposing on a floor of Chalk horizontally stratified and having a
level surface. These phenomena, in themselves sufficiently difficult
of explanation, are rendered still more anomalous by the occasional
enclosure in the drift of huge fragments of Chalk many yards in
diameter. One striking instance occurs west of Sheringham, where an
enormous pinnacle of Chalk, between 70 and 80 feet in height, is flanked
on both sides by vertical layers of loam, clay, and gravel (Figure 32).
[Illustration: Figure 32. Pinnacle of Chalk]
(FIGURE 32. INCLUDED PINNACLE OF CHALK AT OLD HYTHE POINT,
WEST OF SHERINGHAM.
d. Chalk with regular layers of flints.
c. Layer called "the pan," of Chalk, flints, and marine shells
of Recent species, cemented by oxide of iron.)
This chalky fragment is only one of many detached masses which have
been included in the drift, and forced along with it into their present
position. The level surface of the Chalk in situ (d) may be traced for
miles along the coast, where it has escaped the violent movements to
which the incumbent drift has been exposed.*
(* For a full account of the drift of East Norfolk, see a
paper by the author, "Philosophical Magazine" Number 104 May
1840.)
We are called upon, then, to explain how any force can have been exerted
against the upper masses, so as to produce movements in which the
subjacent strata have not participated. It may be answered that, if we
conceive the till and its boulders to have been drifted to their
present place by ice, the lateral pressure may have been supplied by
the stranding of ice-islands. We learn, from the observations of Messrs.
Dease and Simpson in the polar regions, that such islands, when they
run aground, push before them large mounds of shingle and sand. It
is therefore probable that they often cause great alterations in the
arrangement of pliant and incoherent strata forming the upper part of
shoals or submerged banks, the inferior portions of the same remaining
unmoved. Or many of the complicated curvatures of these layers of loose
sand and gravel may have been due to another cause, the melting on the
spot of ice-bergs and coast ice in which successive deposits of pebbles,
sand, ice, snow, and mud, together with huge masses of rock fallen from
cliffs, may have become interstratified. Ice-islands so constituted
often capsize when afloat, and gravel once horizontal may have assumed,
before the associated ice was melted, an inclined or vertical
position. The packing of ice forced up on a coast may lead to a similar
derangement in a frozen conglomerate of sand or shingle, and, as Mr.
Trimmer has suggested,* alternate layers of earthy matter may have sunk
down slowly during the liquefaction of the intercalated ice so as to
assume the most fantastic and anomalous positions, while the strata
below, and those afterwards thrown down above, may be perfectly
horizontal (see above).
(* "Quarterly Journal of the Geological Society" volume 7
1851 pages 22, 30.)
In most cases where the principal contortions of the layers of gravel
and sand have a decided correspondence with deep indentations in the
underlying till, the hypothesis of the melting of large lumps and masses
of ice once mixed up with the till affords the most natural explanation
of the phenomena. The quantity of ice now seen in the cliffs near
Behring's Straits, in which the remains of fossil elephants are common,
and the huge fragments of solid ice which Meyendorf discovered in
Siberia, after piercing through a considerable thickness of incumbent
soil, free from ice, is in favour of such an hypothesis, the partial
failure of support necessarily giving rise to foldings in the overlying
and previously horizontal layers, as in the case of creeps in coal
mines.*
(* See "Manual of Geology" by the author, page 51.)
In the diagram of the cliffs at page 167, the bent and contorted beds
Number 5, last alluded to, are represented as covered by undisturbed
beds of gravel and sand Number 6. These are usually destitute of organic
remains; but at some points marine shells of Recent species are said to
have been found in them. They afford evidence at many points of repeated
denudation and redeposition, and may be the monuments of a long series
of ages.
MUNDESLEY POST-GLACIAL FRESHWATER FORMATION.
In the range of cliffs above described at Mundesley, about 8 miles
south-east of Cromer, a fine example is seen of a freshwater formation,
newer than all those already mentioned, a deposit which has filled up a
depression hollowed out of all the older beds 3, 4, and 5 of the section
Figure 27.
[Illustration: Figure 33. Newer Freshwater Formation]
(FIGURE 33. SECTION OF THE NEWER FRESHWATER FORMATION I
N THE CLIFFS AT MUNDESLEY, EIGHT MILES SOUTH-EAST OF CROMER,
DRAWN UP BY THE REVEREND S.W. KING.
Height of cliff where lowest, 35 feet above high water.
OLDER SERIES.
1. Fundamental Chalk, below the beach line.
3. Forest bed, with elephant, rhinoceros, stag, etc., and with
tree roots and stumps, also below the beach line.
3 prime. Finely laminated sands and clays, with thin layer of
lignite, and shells of Cyclas and Valvata, and with Mytilus
in some beds.
4. Glacial boulder till.
5. Contorted drift.
6. Gravel overlying contorted drift.
N.B.--Number 2 of the section, Figure 27, is wanting here.
NEWER FRESHWATER BEDS.
A. Coarse river gravel, with shells of Anodon, Valvata, Cyclas,
Succinea, Limnaea, Paludina, etc., seeds of Ceratophyllum
demersum, Nuphar lutea, scales and bones of pike, perch,
salmon, etc., elytra of Donacia, Copris, Harpalus,
and other beetles.
C. Yellow sands.
D. Drift gravel.)
When I examined this line of coast in 1839, the section alluded to
was not so clearly laid open to view as it has been of late years, and
finding at that period not a few of the fossils in the lignite beds
Number 3 prime above the forest bed, identical in species with those
from the post-glacial deposits B C, I supposed the whole to have been of
contemporaneous origin, and so described them in my paper on the Norfolk
cliffs.*
(* "Philosophical Magazine" volume 16 1840 page 345.)
Mr. Gunn was the first to perceive this mistake, which he explained
to me on the spot when I revisited Mundesley in the autumn of 1859 in
company with Dr. Hooker and Mr. King. The last-named geologist has had
the kindness to draw up for me the annexed diagram (Figure 33) of the
various beds which he has recently studied in detail.*
(* Mr. Prestwich has given a correct account of this section
in a paper read to the British Association, Oxford, 1860.
See "The Geologist" volume 4 1861.)
The formations 3, 4, and 5 already described, Figure 27, were evidently
once continuous, for they may be followed for miles north-west and
south-east without a break, and always in the same order. A valley or
river channel was cut through them, probably during the gradual upheaval
of the country, and the hollow became afterwards the receptacle of
the comparatively modern freshwater beds A, B, C, and D. They may well
represent a silted up river-channel, which remained for a time in the
state of a lake or mere, and in which the black peaty mass B accumulated
by a very slow growth over the gravel of the river-bed A. In B we find
remains of some of the same plants which were enumerated as common
in the ancient lignite in 3 prime, such as the yellow water-lily and
hornwort, together with some freshwater shells which occur in the same
fluvio-marine series 3 prime.
[Illustration: Figure 34. Paludina marginata]
(FIGURE 34. Paludina marginata, Michaud (P. minuta, Strickland).
Hydrobia marginata.*
(* This shell is said to have a sub-spiral operculum (not a
concentric one, as in Paludina), and therefore to be
referable to the Hydrobia, a sub-genus of Rissoa. But
this species is always associated with freshwater shells,
while the Rissoae frequent marine and brackish waters.)
The middle figure is of the natural size.)
The only shell which I found not referable to a British species is the
minute Paludina, Figure 34, already alluded to.
When I showed the scales and teeth of the pike, perch, roach, and
salmon, which I obtained from this formation, to M. Agassiz, he thought
they varied so much from their nearest living representatives that they
might rank as distinct species; but Mr. Yarrell doubted the propriety
of so distinguishing them. The insects, like the shells and plants, are
identical, so far as they are known, with living British species. No
progress has yet been made at Mundesley in discovering the contemporary
mammalia.
By referring to the description and section before given of the
freshwater deposit at Hoxne, the reader will at once perceive the
striking analogy of the Mundesley and Hoxne deposits, the latter so
productive of flint implements of the Amiens type. Both of them, like
the Bedford gravel with flint tools and the bones of extinct mammalia,
are post-glacial. It will also be seen that a long series of events,
accompanied by changes in physical geography, intervened between
the "forest bed," Number 3, Figure 27, when the Elephas meridionalis
flourished, and the period of the Mundesley fluviatile beds A, B, C;
just as in France I have shown that the same E. meridionalis belonged to
a system of drainage different from and anterior to that with which the
flint implements of the old alluvium of the Somme and the Seine were
connected.
Before the growth of the ancient forest, Number 3, Figure 33, the
Mastodon arvernensis, a large proboscidian, characteristic of the
Norwich Crag, appears to have died out, or to have become scarce, as no
remains of it have yet been found in the Norfolk cliffs. There was, no
doubt, time for other modifications in the mammalian fauna between the
era of the marine beds, Number 2, Figure 27 (the shells of which imply
permanent submergence beneath the sea), and the accumulation of the
uppermost of the fluvio-marine, and lignite beds, Number 3 prime, which
overlie both Numbers 3 and 2, or the buried forest and the Crag. In the
interval we must suppose repeated oscillations of level, during which
land covered with trees, an estuary with its freshwater shells, and the
sea with its Mya truncata and other mollusca still retaining their erect
position, gained by turns the ascendency. These changes were accompanied
by some denudation followed by a grand submergence of several hundred
feet, probably brought about slowly, and when floating ice aided in
transporting erratic blocks from great distances. The glacial till
Number 4 then originated, and the gravel and sands Number 5 were
afterwards superimposed on the boulder clay, first in horizontal beds,
which became subsequently contorted. These were covered in their turn
by other layers of gravel and sand, Number 6, Figures 27 and 33, the
downward movement still continuing.
The entire thickness of the beds above the Chalk at some points near the
coast, and the height at which they now are raised, are such as to show
that the subsidence of the country after the growth of the forest bed
exceeded 400 feet. The re-elevation must have amounted to nearly as many
feet, as the site of the ancient forest, originally sub-aerial, has been
brought up again to within a few feet of high-water mark. Lastly, after
all these events, and probably during the final process of emergence,
the valley was scooped out in which the newer freshwater strata of
Mundesley, Figure 33, were gradually deposited.
Throughout the whole of this succession of geographical changes, the
flora and invertebrate fauna of Europe appear to have undergone no
important revolution in their specific characters. The plants of the
forest bed belonged already to what has been called the Germanic flora.
The mollusca, the insects, and even some of the mammalia, such as the
European beaver and roebuck, were the same as those now co-existing with
Man. Yet the oldest memorials of our species at present discovered in
Great Britain are post-glacial, or posterior in date to the boulder
clay, Number 4, Figures 27 and 33. The position of the Hoxne flint
implements corresponds with that of the Mundesley beds, from A to D,
Figure 33, and the most likely stratum in which to find hereafter
flint tools is no doubt the gravel A of that section, which has all the
appearance of an old river-bed. No flint tools have yet been observed
there, but had the old alluvium of Amiens or Abbeville occurred in the
Norfolk cliffs instead of the valley of the Somme, and had we depended
on the waves of the sea instead of the labour of many hundred workmen
continued for twenty years, for exposing the flint implements to view,
we might have remained ignorant to this day of the fossil relics brought
to light by M. Boucher de Perthes and those who have followed up his
researches.
Neither need we despair of one day meeting with the signs of Man's
existence in the forest bed Number 3, or in the overlying strata 3
prime, on the ground of any uncongeniality in the climate or incongruity
in the state of the animate creation with the well-being of our species.
For the present we must be content to wait and consider that we have
made no investigations which entitle us to wonder that the bones or
stone weapons of the era of the Elephas meridionalis have failed to come
to light. If any such lie hid in those strata, and should hereafter be
revealed to us, they would carry back the antiquity of Man to a distance
of time probably more than twice as great as that which separates
our era from that of the most ancient of the tool-bearing gravels yet
discovered in Picardy, or elsewhere. But even then the reader will
perceive that the age of Man, though pre-glacial, would be so modern
in the great geological calendar, as given in Chapter 1, that he would
scarcely date so far back as the commencement of the Pleistocene period.