Chapter IV ON THE FORMATIONS OF THE PAMPAS.

Mineralogical constitution.—Microscopical structure.—Buenos Ayres,

shells embedded in tosca-rock.—Buenos Ayres to the Colorado.—San

Ventana.—Bahia Blanca; M. Hermoso, bones and infusoria of; P. Alta,

shells, bones, and infusoria of; co-existence of the recent shells and

extinct mammifers.—Buenos Ayres to Santa Fé.—Skeletons of

Mastodon.—Infusoria.—Inferior marine tertiary strata, their

age.—Horse’s tooth. BANDA ORIENTAL.—Superficial Pampean

formation.—Inferior tertiary strata, variation of, connected with

volcanic action; Macrauchenia Patachonica at San Julian in Patagonia,

age of, subsequent to living mollusca and to the erratic block period.

SUMMARY.—Area of Pampean formation.—Theories of origin.—Source of

sediment.—Estuary origin.—

Contemporaneous with existing mollusca.—Relations to underlying

tertiary strata.—Ancient deposit of estuary origin.—Elevation and

successive deposition of the Pampean formation.—Number and state of the

remains of mammifers; their habitation, food, extinction, and

range.—Conclusion.—Localities in Pampas at which mammiferous remains

have been found.

The Pampean formation is highly interesting from its vast extent, its

disputed origin, and from the number of extinct gigantic mammifers

embedded in it. It has upon the whole a very uniform character:

consisting of a more or less dull reddish, slightly indurated,

argillaceous earth or mud, often, but not always, including in

horizontal lines concretions of marl, and frequently passing into a

compact marly rock. The mud, wherever I examined it, even close to the

concretions, did not contain any carbonate of lime. The concretions are

generally nodular, sometimes rough externally, sometimes

stalactiformed; they are of a compact structure, but often penetrated

(as well as the mud) by hair-like serpentine cavities, and occasionally

with irregular fissures in their centres, lined with minute crystals of

carbonate of lime; they are of white, brown, or pale pinkish tints,

often marked by black dendritic manganese or iron; they are either

darker or lighter tinted than the surrounding mass; they contain much

carbonate of lime, but exhale a strong aluminous odour, and leave, when

dissolved in acids, a large but varying residue, of which the greater

part consists of sand. These concretions often unite into irregular

strata; and over very large tracts of country, the entire mass consists

of a hard, but generally cavernous marly rock: some of the varieties

might be called calcareous tuffs.

Dr. Carpenter has kindly examined under the microscope, sliced and

polished specimens of these concretions, and of the solid marl-rock,

collected in various places between the Colorado and Santa Fe Bajada.

In the greater number, Dr. Carpenter finds that the whole substance

presents a tolerably uniform amorphous character, but with traces of

incipient crystalline metamorphosis; in other specimens he finds

microscopically minute rounded concretions of an amorphous substance

(resembling in size those in oolitic rocks, but not having a concentric

structure), united by a cement which is often crystalline. In some, Dr.

Carpenter can perceive distinct traces of shells, corals, Polythalamia,

and rarely of spongoid bodies. For the sake of comparison, I sent Dr.

Carpenter specimens of the calcareous rock, formed chiefly of fragments

of recent shells, from Coquimbo in Chile: in one of these specimens,

Dr. Carpenter finds, besides the larger fragments, microscopical

particles of shells, and a varying quantity of opaque amorphous matter;

in another specimen from the same bed, he finds the whole composed of

the amorphous matter, with layers showing indications of

an incipient crystalline metamorphosis: hence these latter specimens,

both in external appearance and in microscopical structure, closely

resemble those of the Pampas. Dr. Carpenter informs me that it is well

known that chemical precipitation throws down carbonate of lime in the

opaque amorphous state; and he is inclined to believe that the

long-continued attrition of a calcareous body in a state of crystalline

or semi-crystalline aggregation (as, for instance, in the ordinary

shells of Mollusca, which, when sliced, are transparent) may yield the

same result. From the intimate relations between all the Coquimbo

specimens, I can hardly doubt that the amorphous carbonate of lime in

them has resulted from the attrition and decay of the larger fragments

of shell: whether the amorphous matter in the marly rocks of the Pampas

has likewise thus originated, it would be hazardous to conjecture.

For convenience’ sake, I will call the marly rock by the name given to

it by the inhabitants, namely, Tosca-rock; and the reddish argillaceous

earth, Pampean mud. This latter substance, I may mention, has been

examined for me by Professor Ehrenberg, and the result of his

examination will be given under the proper localities.

I will commence my descriptions at a central spot, namely, at Buenos

Ayres, and thence proceed first southward to the extreme limit of the

deposit, and afterwards northward. The plain on which Buenos Ayres

stands is from thirty to forty feet in height. The Pampean mud is here

of a rather pale colour, and includes small nearly white nodules, and

other irregular strata of an unusually arenaceous variety of

tosca-rock. In a well at the depth of seventy feet, according to

Ignatio Nunez, much tosca-rock was met with, and at several points, at

one hundred feet deep, beds of sand have been found. I have already

given a list of the recent marine and estuary shells found in many

parts on the surface near Buenos Ayres, as far as three or four leagues

from the Plata. Specimens from near Ensenada, given me by Sir W.

Parish, where the rock is quarried just beneath the surface of the

plain, consist of broken bivalves, cemented by and converted into white

crystalline carbonate of lime. I have already alluded, in the first

chapter, to a specimen (also given me by Sir W. Parish) from the A. del

Tristan, in which shells, resembling in every respect the _Azara

labiata_, d’Orbigny, as far as their worn condition permits of

comparison, are embedded in a reddish, softish, somewhat arenaceous

marly rock: after careful comparison, with the aid of a microscope and

acids, I can perceive no difference between the basis of this rock and

the specimens collected by me in many parts of the Pampas. I have also

stated, on the authority of Sir W. Parish, that northward of Buenos

Ayres, on the highest parts of the plain, about forty feet above the

Plata, and two or three miles from it, numerous shells of the _Azara

labiata_ (and I believe of _Venus sinuosa_) occur embedded in a

stratified earthy mass, including small marly concretions, and said to

be precisely like the great Pampean deposit. Hence we may conclude that

the mud of the Pampas continued to be deposited to within the period of

this existing estuary shell. Although this formation is of such immense

extent, I know of no other instance of the presence of shells in it.

_Buenos Ayres to the Rio Colorado._—With the exception of a few

metamorphic ridges, the country between these two points, a distance of

400 geographical miles, belongs to the Pampean formation, and in the

southern part is generally formed of the harder and more calcareous

varieties. I will briefly describe my route: about twenty-five miles

S.S.W. of the capital, in a well forty yards in depth, the upper part,

and, as I was assured, the entire thickness, was formed of dark red

Pampean mud without concretions. North of the River Salado, there are

many lakes; and on the banks of one (near the Guardia) there was a

little cliff similarly composed, but including many nodular and

stalactiform concretions: I found here a large piece of tessellated

armour, like that of the Glyptodon, and many fragments of bones. The

cliffs on the Salado consist of pale-coloured Pampean mud, including

and passing into great masses of tosca-rock: here a skeleton of the

Megatherium and the bones of other extinct quadrupeds (see the list at

the end of this chapter) were found. Large quantities of crystallised

gypsum (of which specimens were given me) occur in the cliffs of this

river; and likewise (as I was assured by Mr. Lumb) in the Pampean mud

on the River Chuelo, seven leagues from Buenos Ayres: I mention this

because M. d’Orbigny lays some stress on the supposed absence of this

mineral in the Pampean formation.

Southward of the Salado the country is low and swampy, with tosca-rock

appearing at long intervals at the surface. On the banks, however, of

the Tapalguen (sixty miles south of the Salado) there is a large extent

of tosca-rock, some highly compact and even semi-crystalline, overlying

pale Pampean mud with the usual concretions. Thirty miles further

south, the small quartz-ridge of Tapalguen is fringed on its northern

and southern flank, by little, narrow, flat-topped hills of tosca-rock,

which stand higher than the surrounding plain. Between this ridge and

the Sierra of Guitru-gueyu, a distance of sixty miles, the country is

swampy, with the tosca-rock appearing only in four or five spots: this

sierra, precisely like that of Tapalguen, is bordered by horizontal,

often cliff-bounded, little hills of tosca-rock, higher than the

surrounding plain. Here, also, a new appearance was presented in some

extensive and level banks of alluvium or detritus of the neighbouring

metamorphic rocks; but I neglected to observe whether it was stratified

or not. Between Guitru-gueyu and the Sierra Ventana, I crossed a dry

plain of tosca-rock higher than the country hitherto passed over, and

with small pieces of denuded tableland of the same formation, standing

still higher.

The marly or calcareous beds not only come up nearly horizontally to

the northern and southern foot of the great quartzose mountains of the

Sierra Ventana, but interfold between the parallel ranges. The

superficial beds (for I nowhere obtained sections more than twenty feet

deep) retain, even close to the mountains, their usual character: the

uppermost layer, however, in one place included pebbles of quartz, and

rested on a mass of detritus of the same rock. At the very foot of the

mountains, there were some few piles of quartz and tosca-rock detritus,

including land-shells; but at the distance of only half a mile

from these lofty, jagged, and battered mountains, I could not, to my

great surprise, find on the boundless surface of the calcareous plain

even a single pebble. Quartz-pebbles, however, of considerable size

have at some period been transported to a distance of between forty and

fifty miles to the shores of Bahia Blanca.[1]

[1] Schmidtmeyer (“Travels in Chile,” p. 150) states that he first

noticed on the Pampas, very small bits of red granite, when fifty

miles distant from the southern extremity of the mountains of Cordova,

which project on the plain, like a reef into the sea.

The highest peak of the St. Ventana is, by Captain Fitzroy’s

measurement, 3,340 feet, and the calcareous plain at its foot (from

observations taken by some Spanish officers[2]) 840 feet above the

sea-level. On the flanks of the mountains, at a height of three hundred

or four hundred feet above the plain, there were a few small patches of

conglomerate and breccia, firmly cemented by ferruginous matter to the

abrupt and battered face of the quartz—traces being thus exhibited of

ancient sea-action. The high plain round this range sinks quite

insensibly to the eye on all sides, except to the north, where its

surface is broken into low cliffs. Round the Sierras Tapalguen,

Guitru-gueyu, and between the latter and the Ventana we have seen (and

shall hereafter see round some hills in Banda Oriental), that the

tosca-rock forms low, flat-topped, cliff-bounded hills, higher than the

surrounding plains of similar composition. From the horizontal

stratification and from the appearance of the broken cliffs, the

greater height of the Pampean formation round these primary hills ought

not to be altogether or in chief part attributed to these several

points having been uplifted more energetically than the surrounding

country, but to the argillaceo-calcareous mud having collected round

them, when they existed as islets or submarine rocks, at a greater

height, than at the bottom of the adjoining open sea;—the cliffs having

been subsequently worn during the elevation of the whole country in

mass.

[2] “La Plata,” etc., by Sir W. Parish, p. 146.

Southward of the Ventana, the plain extends farther than the eye can

range; its surface is not very level, having slight depressions with no

drainage exits; it is generally covered by a few feet in thickness of

sandy earth; and in some places, according to M. Parchappe,[3] beds of

clay two yards thick. On the banks of the Sauce, four leagues S.E. of

the Ventana, there is an imperfect section about two hundred feet in

height, displaying in the upper part tosca-rock and in the lower part

red Pampean mud. At the settlement of Bahia Blanca, the uppermost plain

is composed of very compact, stratified tosca-rock, containing rounded

grains of quartz distinguishable by the naked eye: the lower plain, on

which the fortress stands, is described by M. Parchappe[4] as composed

of solid tosca-rock; but the sections which I examined appeared more

like a redeposited mass of this rock, with small pebbles and fragments

of quartz. I shall immediately return to the important sections on the

shores of Bahia Blanca. Twenty miles southward of

this place, there is a remarkable ridge extending W. by N. and E. by

S., formed of small, separate, flat-topped, steep-sided hills, rising

between one hundred and two hundred feet above the Pampean plain at its

southern base, which plain is a little lower than that to the north.

The uppermost stratum in this ridge consists of pale, highly

calcareous, compact tosca-rock, resting (as seen in one place) on

reddish Pampean mud, and this again on a paler kind: at the foot of the

ridge, there is a well in reddish clay or mud. I have seen no other

instance of a chain of hills belonging to the Pampean formation; and as

the strata show no signs of disturbance, and as the direction of the

ridge is the same with that common to all the metamorphic lines in this

whole area, I suspect that the Pampean sediment has in this instance

been accumulated on and over a ridge of hard rocks, instead of, as in

the case of the above-mentioned Sierras, round their submarine flanks.

South of this little chain of tosca-rock, a plain of Pampean mud

declines towards the banks of the Colorado: in the middle a well has

been dug in red Pampean mud, covered by two feet of white, softish,

highly calcareous tosca-rock, over which lies sand with small pebbles

three feet in thickness—the first appearance of that vast shingle

formation described in the First Chapter. In the first section after

crossing the Colorado, an old tertiary formation, namely, the Rio Negro

sandstone (to be described in the next chapter), is met with: but from

the accounts given me by the Gauchos, I believe that at the mouth of

the Colorado the Pampean formation extends a little further southwards.

[3] M. d’Orbigny, “Voyage,” Part. Géolog., pp. 47, 48.

[4] _Ibid._

_Bahia Blanca._—To return to the shores of this bay. At Monte Hermoso

there is a good section, about one hundred feet in height, of four

distinct strata, appearing to the eye horizontal, but thickening a

little towards the N.W. The uppermost bed, about twenty feet in

thickness, consists of obliquely laminated, soft sandstone, including

many pebbles of quartz, and falling at the surface into loose sand. The

second bed, only six inches thick, is a hard, dark-coloured sandstone.

The third bed is pale-coloured Pampean mud; and the fourth is of the

same nature, but darker coloured, including in its lower part

horizontal layers and lines of concretions of not very compact pinkish

tosca-rock. The bottom of the sea, I may remark, to a distance of

several miles from the shore, and to a depth of between sixty and one

hundred feet, was found by the anchors to be composed of tosca-rock and

reddish Pampean mud. Professor Ehrenberg has examined for me specimens

of the two lower beds, and finds in them three Polygastrica and six

Phytolitharia.[5] Of these, only one (_Spongolithis

Fustis?_) is a marine form; five of them are identical with

microscopical structures of brackish-water origin, hereafter to be

mentioned, which form a central point in the Pampean formation. In

these two beds, especially in the lower one, bones of extinct

mammifers, some embedded in their proper relative positions and others

single, are very numerous in a small extent of the cliffs. These

remains consist of, first, the head of Ctenomys antiquus, allied to the

living Ctenomys Braziliensis; secondly, a fragment of the remains of a

rodent; thirdly, molar teeth and other bones of a large rodent, closely

allied to, but distinct from, the existing species of Hydrochoerus, and

therefore probably an inhabitant of fresh water; fourth and fifthly,

portions of vertebræ, limbs, ribs, and other bones of two rodents;

sixthly, bones of the extremities of some great megatheroid

quadruped.[6] The number of the remains of rodents gives to this

collection a peculiar character, compared with those found in any other

locality. All these bones are compact and heavy; many of them are

stained red, with their surfaces polished; some of the smaller ones are

as black as jet.

[5] The following list is given in the “Monatsberichten der könig.

Akad. zu Berlin,” April 1845:—

POLYGASTRICA.

Fragilaria rhabdosoma.

Gallionella distans.

Pinnularia?

PHYTOLITHARIA.

Lithodontium Bursa.

Lithodontium furcatum.

Lithostylidium exesum.

Lithostylidium rude.

Lithostylidium Serra.

Spongolithis Fustis?

[6] See “Fossil Mammalia” (p. 109) by Professor Owen, in the “Zoology

of the Voyage of the _Beagle_;” and Catalogue (p. 36) of Fossil

Remains in Museum of Royal College of Surgeons.

Monte Hermoso is between fifty and sixty miles distant in a S.E. line

from the Ventana, with the intermediate country gently rising towards

it, and all consisting of the Pampean formation. What relation, then,

do these beds, at the level of the sea and under it, bear to those on

the flanks of the Ventana, at the height of 840 feet, and on the flanks

of the other neighbouring sierras, which, from the reasons already

assigned, do not appear to owe their greater height to unequal

elevation? When the tosca-rock was accumulating round the Ventana, and

when, with the exception of a few small rugged primary islands, the

whole wide surrounding plains must have been under water, were the

strata at Monte Hermoso depositing at the bottom of a great open sea,

between eight hundred and one thousand feet in depth? I much doubt

this; for if so, the almost perfect carcasses of the several small

rodents, the remains of which are so very numerous in so limited a

space, must have been drifted to this spot from the distance of many

hundred miles. It appears to me far more probable, that during the

Pampean period this whole area had commenced slowly rising (and in the

cliffs, at several different heights we have proofs of the land having

been exposed to sea-action at several levels), and that tracts of land

had thus been formed of Pampean sediment round the Ventana and the

other primary ranges, on which the several rodents and other quadrupeds

lived, and that a stream (in which perhaps the extinct aquatic

Hydrochoerus lived) drifted their bodies into the adjoining sea, into

which the Pampean mud continued to be poured from the north. As the

land continued to rise, it appears that this source of sediment was cut

off; and in its place sand and pebbles were borne down by stronger

currents, and conformably deposited over the Pampean strata.

Punta Alta is situated about thirty miles higher up on the northern

side of this same bay: it consists of a small plain, between twenty and

thirty feet in height, cut off on the shore by a line of low cliffs

about a mile in length, represented in figure No. 15 with its vertical

scale necessarily exaggerated. The lower bed (A) is more extensive than

the upper ones; it consists of stratified gravel or conglomerate,

cemented by calcareo-arenaceous matter, and is divided by curvilinear

layers of pinkish marl, of which some are precisely like tosca-rock,

and some more sandy. The beds are curvilinear, owing to the action of

currents, and dip in different directions; they include an

extraordinary number of bones of gigantic mammifers and many shells.

The pebbles are of considerable size, and are of hard sandstone, and of

quartz, like that of the Ventana: there are also a few well-rounded

masses of tosca-rock.

No. 15

Section of beds with recent shells and extinct mammifers, at Punta Alta

in Bahia Blanca.

[Illustration: Section of beds at Punta Alta in Bahia Blanca.]

The second bed (B) is about fifteen feet in thickness, but towards both

extremities of the cliff (not included in the diagram) it either thins

out and dies away, or passes insensibly into an overlying bed of

gravel. It consists of red, tough clayey mud, with minute linear

cavities; it is marked with faint horizontal shades of colour; it

includes a few pebbles, and rarely a minute particle of shell: in one

spot, the dermal armour and a few bones of a Dasypoid quadruped were

embedded in it: it fills up furrows in the underlying gravel. With the

exception of the few pebbles and particles of shells, this bed

resembles the true Pampean mud; but it still more closely resembles the

clayey flats (mentioned in the First Chapter) separating the

successively rising parallel ranges of sand-dunes.

The bed (C) is of stratified gravel, like the lowest one; it fills up

furrows in the underlying red mud, and is sometimes interstratified

with it, and sometimes insensibly passes into it; as the red mud thins

out, this upper gravel thickens. Shells are more numerous in it than in

the lower gravel; but the bones, though some are still present, are

less numerous. In one part, however, where this gravel and the red mud

passed into each other, I found several bones and a tolerably perfect

head of the Megatherium. Some of the large Volutas, though embedded in

the gravel-bed (C), were filled with the red mud, including great

numbers of the little recent _Paludestrina australis._ These three

lower beds are covered by an unconformable mantle (D) of stratified

sandy earth, including many pebbles of quartz, pumice and phonolite,

land and sea-shells.

M. d’Orbigny has been so obliging as to name for me the twenty species

of Mollusca embedded in the two gravel beds: they consist of:—

Volutella angulata, d’Orbigny, “Voyage” Mollusq. and Pal.

Voluta Braziliana, Sol.

Olicancilleria Braziliensis, d’Orbigny.

Olicancilleria auricularia, d’Orbigny.

Olivina puelchana, d’Orbigny.

Buccinanops cochlidium, d’Orbigny.

Buccinanops globulosum, d’Orbigny.

Colombella sertulariarum, d’Orbigny.

Trochus Patagonicus, and var. of ditto, d’Orbigny.

Paludestrina Australis, d’Orbigny.

Fissurella Patagonica, d’Orbigny.

Crepidula muricata, Lam.

Venus purpurata, Lam.

Venus rostrata, Phillippi.

Mytilus Darwinianus, d’Orbigny.

Nucula semiornata, d’Orbigny.

Cardita Patagonica, d’Orbigny.

Corbula Patagonica (?), d’Orbigny.

Pecten tethuelchus, d’Orbigny.

Ostrea puelchana, d’Orbigny.

A living species of Balanus.

and 23. An Astræ and encrusting Flustra, apparently identical with

species now living in the bay.

All these shells now live on this coast, and most of them in this same

bay. I was also struck with the fact, that the proportional numbers of

the different kinds appeared to be the same with those now cast up on

the beach: in both cases specimens of Voluta, Crepidula, Venus, and

Trochus are the most abundant. Four or five of the species are the same

with the upraised shells on the Pampas near Buenos Ayres. All the

specimens have a very ancient and bleached appearance,[7] and do not

emit, when heated, an animal odour: some of them are changed throughout

into a white, soft, fibrous substance; others have the space between

the external walls, either hollow, or filled up with crystalline

carbonate of lime.

[7] A Bulinus, mentioned in the Introduction to the “Fossil Mammalia”

in the “Zoology of the Voyage of the _ Beagle_” has so much fresher an

appearance, than the marine species, that I suspect it must have

fallen amongst the others, and been collected by mistake.

The remains of the extinct mammiferous animals, from the two gravel

beds have been described by Professor Owen in the “Zoology of the

Voyage of the _Beagle_:” they consist of, 1st, one nearly perfect head

and three fragments of heads of the _ Megatherium Cuvierii_; 2nd, a

lower jaw of _Megalonyx Jeffersonii_; 3rd, lower jaw of _Mylodon

Darwinii_; 4th, fragments of a head of some gigantic Edental quadruped;

5th, an almost entire skeleton of the great _Scelidotherium

leptocephalum_, with most of the bones, including the head, vertebræ,

ribs, some of the extremities to the claw-bone, and even, as remarked

by Professor Owen, the knee-cap, all nearly in their proper relative

positions; 6th, fragments of the jaw and a separate tooth of a Toxodon,

belonging either to _T. Platensis_, or to a second species lately

discovered near Buenos Ayres; 7th, a tooth of _Equus curvidens_; 8th,

tooth of a Pachyderm, closely allied to Palæotherium, of which parts of

the head have been lately sent from Buenos Ayres to the British Museum;

in all probability this pachyderm is identical with the _ Macrauchenia

Patagonica_ from Port S. Julian, hereafter to be referred to. Lastly,

and 9thly, in a cliff of the red clayey bed (B), there was a double

piece, about three feet long and two wide, of the bony armour of a

large Dasypoid quadruped, with the two sides pressed nearly close

together: as the

cliff is now rapidly washing away, this fossil probably was lately much

more perfect; from between its doubled-up sides, I extracted the middle

and ungual phalanges, united together, of one of the feet, and likewise

a separate phalanx: hence one or more of the limbs must have been

attached to the dermal case, when it was embedded. Besides these

several remains in a distinguishable condition, there were very many

single bones: the greater number were embedded in a space 200 yards

square. The preponderance of the Edental quadrupeds is remarkable; as

is, in contrast with the beds of Monte Hermoso, the absence of Rodents.

Most of the bones are now in a soft and friable condition, and, like

the shells, do not emit when burnt an animal odour. The decayed state

of the bones may be partly owing to their late exposure to the air and

tidal-waves. Barnacles, Serpulæ, and corallines are attached to many of

the bones, but I neglected to observe[8] whether these might not have

grown on them since being exposed to the present tidal action; but I

believe that some of the barnacles must have grown on the

Scelidotherium, soon after being deposited, and before being _wholly_

covered up by the gravel. Besides the remains in the condition here

described, I found one single fragment of bone very much rolled, and as

black as jet, so as perfectly to resemble some of the remains from

Monte Hermoso.

[8] After having packed up my specimens at Bahia Blanca, this point

occurred to me, and I noted it; but forgot it on my return, until the

remains had been cleaned and oiled: my attention has been lately

called to the subject by some remarks by M. d’Orbigny.

Very many of the bones had been broken, abraded, and rolled, before

being embedded. Others, even some of those included in the coarsest

parts of the the now hard conglomerate, still retain all their minutest

prominences perfectly preserved; so that I conclude that they probably

were protected by skin, flesh, or ligaments, whilst being covered up.

In the case of the Scelidotherium, it is quite certain that the whole

skeleton was held together by its ligaments, when deposited in the

gravel in which I found it. Some cervical vertebræ and a humerus of

corresponding size lay so close together, as did some ribs and the

bones of a leg, that I thought that they must originally have belonged

to two skeletons, and not have been washed in single; but as remains

were here very numerous, I will not lay much stress on these two cases.

We have just seen that the armour of the Dasypoid quadruped was

certainly embedded together with some of the bones of the feet.

Professor Ehrenberg[9] has examined for me specimens of the finer

matter from in contact with these mammiferous remains: he finds in them

two Polygastrica, decidedly marine forms; and six Phytolitharia, of

which one is probably marine, and the others either of fresh-water or

terrestrial origin. Only one of these eight microscopical bodies is

common to the nine from Monte Hermoso: but five of them are in common

with those from the Pampean mud on the banks of the Parana. The

presence of any fresh-water infusoria, considering the aridity of the

surrounding country, is here remarkable: the most probable explanation

appears to be, that these microscopical organisms were washed out of

the adjoining great Pampean formation during its denudation, and

afterwards redeposited.

[9] “Monatsberichten der Akad. zu Berlin,” April 1845. The list

consists of:—

POLYGASTRICA.

Gallionella sulcata.

Stauroptera aspera? fragm.

PHYTOLITHARIA.

Lithasteriscus tuberculatus.

Lithostylidium Clepsammidium.

Lithostylidium quadratum.

Lithostylidium rude.

Lithostylidium unidentatum.

Spongolithis acicularis.

We will now see what conclusions may be drawn from the facts above

detailed. It is certain that the gravel-beds and intermediate red mud

were deposited within the period, when existing species of Mollusca

held to each other nearly the same relative proportions as they do on

the present coast. These beds, from the number of littoral species,

must have been accumulated in shallow water; but not, judging from the

stratification of the gravel and the layers of marl, on a beach. From

the manner in which the red clay fills up furrows in the underlying

gravel, and is in some parts itself furrowed by the overlying gravel,

whilst in other parts it either insensibly passes into, or alternates

with, this upper gravel, we may infer several local changes in the

currents, perhaps caused by slight changes, up or down, in the level of

the land. By the elevation of these beds, to which period the alluvial

mantle with pumice-pebbles, land and sea-shells belongs, the plain of

Punta Alta, from twenty to thirty feet in height, was formed. In this

neighbourhood there are other and higher sea-formed plains and lines of

cliffs in the Pampean formation worn by the denuding action of the

waves at different levels. Hence we can easily understand the presence

of rounded masses of tosca-rock in this lowest plain; and likewise, as

the cliffs at Monte Hermoso with their mammiferous remains stand at a

higher level, the presence of the one much-rolled fragment of bone

which was as black as jet: possibly some few of the other much-rolled

bones may have been similarly derived, though I saw only the one

fragment, in the same condition with those from Monte Hermoso. M.

d’Orbigny has suggested[10] that all these mammiferous remains may have

been washed out of the Pampean formation, and afterwards redeposited

together with the recent shells. Undoubtedly it is a marvellous fact

that these numerous gigantic quadrupeds, belonging, with the exception

of the _Equus curvidens_, to seven extinct genera, and one, namely, the

Toxodon, not falling into any existing family, should have co-existed

with Mollusca, all of which are still living species; but analogous

facts have been observed in North America and in Europe. In the first

place, it should not be overlooked, that most of the co-embedded shells

have a more ancient and altered appearance than the bones. In the

second place, is it probable that numerous bones not hardened by silex

or any other mineral, could have retained their delicate prominences

and surfaces perfect if they

had been washed out of one deposit, and re-embedded in another:—this

later deposit being formed of large, hard pebbles, arranged by the

action of currents or breakers in shallow water into variously curved

and inclined layers? The bones which are now in so perfect a state of

preservation, must, I conceive, have been fresh and sound when

embedded, and probably were protected by skin, flesh, or ligaments. The

skeleton of the Scelidotherium indisputably was deposited entire: shall

we say that when held together by its matrix it was washed out of an

old gravel-bed (totally unlike in character to the Pampean formation),

and re-embedded in another gravel-bed, composed (I speak after careful

comparison) of exactly the same kind of pebbles, in the same kind of

cement? I will lay no stress on the two cases of several ribs and bones

of the extremities having _apparently_ been embedded in their proper

relative position: but will any one be so bold as to affirm that it is

possible, that a piece of the thin tessellated armour of a Dasypoid

quadruped, at least three feet long and two in width, and now so tender

that I was unable with the utmost care to extract a fragment more than

two or three inches square, could have been washed out of one bed, and

re-embedded in another, together with some of the small bones of the

feet, without having been dashed into atoms? We must then wholly reject

M. d’Orbigny’s supposition, and admit as certain, that the

Scelidotherium and the large Dasypoid quadruped, and as highly

probable, that the Toxodon, Megatherium, etc., some of the bones of

which are perfectly preserved, were embedded for the first time, and in

a fresh condition, in the strata in which they were found entombed.

These gigantic quadrupeds, therefore, though belonging to extinct

genera and families, coexisted with the twenty above-enumerated

Mollusca, the barnacle and two corals, still living on this coast. From

the rolled fragment of black bone, and from the plain of Punta Alta

being lower than that of Monte Hermoso, I conclude that the coarse

sub-littoral deposits of Punta Alta, are of subsequent origin to the

Pampean mud of Monte Hermoso; and the beds at this latter place, as we

have seen, are probably of subsequent origin to the high tosca-plain

round the Sierra Ventana: we shall, however, return, at the end of this

chapter, to the consideration of these several stages in the great

Pampean formation.

[10] “Voyage,” Part. Géolog., p. 49.

_Buenos Ayres to St. Fé Bajada, in Entre Rios._—For some distance

northward of Buenos Ayres, the escarpment of the Pampean formation does

not approach very near to the Plata, and it is concealed by vegetation:

but in sections on the banks of the Rios Luxan, Areco, and Arrecifes, I

observed both pale and dark reddish Pampean mud, with small, whitish

concretions of tosca; at all these places mammiferous remains have been

found. In the cliffs on the Parana, at San Nicolas, the Pampean mud

contains but little tosca; here M. d’Orbigny found the remains of two

rodents (_Ctenomys Bonariensis_ and _Kerodon antiquus_) and the jaw of

a Canis: when on the river I could clearly distinguish in this fine

line of cliffs, “horizontal lines of variation both in tint and

compactness.”[11] The plain northward of this point is very

level, but with some depressions and lakes; I estimated its height at

from forty to sixty feet above the Parana. At the A. Medio the bright

red Pampean mud contains scarcely any tosca-rock; whilst at a short

distance the stream of the Pabon, forms a cascade, about twenty feet in

height, over a cavernous mass of two varieties of tosca-rock; of which

one is very compact and semi-crystalline, with seams of crystallised

carbonate of lime: similar compact varieties are met with on the

Salidillo and Seco. The absolute identity (I speak after a comparison

of my specimens) between some of these varieties, and those from

Tapalguen, and from the ridge south of Bahia Blanca, a distance of 400

miles of latitude, is very striking.

[11] I quote these words from my note-book, as written down on the

spot, on account of the general absence of stratification in the

Pampean formation having been insisted on by M. d’Orbigny as a proof

of the diluvial origin of this great deposit.

At Rosario there is but little tosca-rock: near this place I first

noticed at the edge of the river traces of an underlying formation,

which, twenty-five miles higher up in the estancia of Gorodona,

consists of a pale yellowish clay, abounding with concretionary

cylinders of a ferruginous sandstone. This bed, which is probably the

equivalent of the older tertiary marine strata, immediately to be

described in Entre Rios, only just rises above the level of the Parana

when low. The rest of the cliff at Gorodona, is formed of red Pampean

mud, with, in the lower part, many concretions of tosca, some

stalacti-formed, and with only a few in the upper part: at the height

of six feet above the river, two gigantic skeletons of the _Mastodon

Andium_ were here embedded; their bones were scattered a few feet

apart, but many of them still held their proper relative positions:

they were much decayed and as soft as cheese, so that even one of the

great molar teeth fell into pieces in my hand. We here see that the

Pampean deposit contains mammiferous remains close to its base. On the

banks of the Carcarana, a few miles distant, the lowest bed visible was

pale Pampean mud, with masses of tosca-rock, in one of which I found a

much decayed tooth of the Mastodon: above this bed, there was a thin

layer almost composed of small concretions of white tosca, out of which

I extracted a well preserved, but slightly broken tooth of _Toxodon

Platensis_: above this there was an unusual bed of very soft impure

sandstone. In this neighbourhood I noticed many single embedded bones,

and I heard of others having been found in so perfect a state that they

were long used as gate-posts: the Jesuit Falkner found here the dermal

armour of some gigantic Edental quadruped.

In some of the red mud scraped from a tooth of one of the Mastodons at

Gorodona, Professor Ehrenberg finds seven Polygastrica and thirteen

Phytolitharia,[12] all of them, I believe, with two exceptions, already

known species. Of these twenty, the preponderating number are of

fresh-water origin; only two species of Coscinodiscus and a

Spongolithis show the direct influence of the sea; therefore Professor

Ehrenberg arrives at the important conclusion that the deposit must

have been of brackish-water origin. Of the thirteen Phytolitharia, nine

are met with in the two deposits in Bahia Blanca, where there is

evidence from two other species of Polygastrica that the beds were

accumulated in brackish water. The traces of coral, sponges, and

Polythalamia, found by Dr. Carpenter in the tosca-rock (of which I must

observe the greater number of specimens were from the upper beds in the

southern parts of the formation), apparently show a more purely marine

origin.

[12] “Monatsberichten der könig. Akad. zu Berlin,” April 1845. The

list consists of:—

POLYGASTRICA.

Campylodiscus clypeus.

Coscinodiscus subtilis.

Coscinodiscus al. sp.

Eunotia.

Gallionella granulata.

Himantidium gracile.

Pinnularia borealis.

At _St. Fé Bajada_, in Entre Rios, the cliffs, estimated at between

sixty and seventy feet in height, expose an interesting section: the

lower half consists of tertiary strata with marine shells, and the

upper half of the Pampean formation. The lowest bed is an obliquely

laminated, blackish, indurated mud, with distinct traces of vegetable

remains.[13] Above this there is a thick bed of yellowish sandy clay,

with much crystallised gypsum and many shells of Ostreæ, Pectens, and

Arcæ: above this there generally comes an arenaceous crystalline

limestone, but there is sometimes interposed a bed, about twelve feet

thick, of dark green, soapy clay, weathering into small angular

fragments. The limestone, where purest, is white, highly crystalline,

and full of cavities: it includes small pebbles of quartz, broken

shells, teeth of sharks, and sometimes, as I was informed, large bones:

it often contains so much sand as to pass into a calcareous sandstone,

and in such parts the great _Ostrea Patagonica_[14] chiefly abounds. In

the upper part, the limestone alternates with layers of fine white

sand. The shells included in these beds have been named for me by M.

d’Orbigny: they consist of:—

Ostrea Patagonica, d’Orbigny, “Voyage,” Part. Pal.

Ostrea Alvarezii, d’Orbigny, “Voyage,” Part. Pal.

Pecten Paranensis, d’Orbigny, “Voyage,” Part. Pal.

Pecten Darwinianus, d’Orbigny, “Voyage,” Part. Pal.

Venus Munsterii, d’Orbigny, “Voyage,” Pal.

Arca Bonplandiana, d’Orbigny, “Voyage,” Pal.

Cardium Platense, d’Orbigny, “Voyage,” Pal.

Tellina, probably nov. spec., but too imperfect for description.

PHYTOLITHARIA.

Lithasteriscus tuberculatus.

Lithodontium bursa.

Lithodontium furcatum.

Lithodontium rostratum.

Lithostylidium Amphiodon.

Lithostylidium Clepsammidium.

Lithostylidium Hamus.

Lithostylidium polyedrum.

Lithostylidium quadratum.

Lithostylidium rude.

Lithostylidium Serra.

Lithostylidium unidentatum.

Spongolithis Fustis.

[13] M. d’Orbigny has given (“Voyage,” Part. Géolog., p. 37) a

detailed description of this section, but as he does not mention this

lowest bed, it may have been concealed when he was there by the river.

There is a considerable discrepancy between his description and mine,

which I can only account for by the beds themselves varying

considerably in short distances.

[14] Captain Sulivan, R.N., has given me a specimen of this shell,

which he found in the cliffs at Point Cerrito, between twenty and

thirty miles above the Bajada.

These species are all extinct: the six first were found by M. d’Orbigny

and myself in the formations of the Rio Negro, S. Josef, and other

parts of Patagonia; and therefore, as first observed by M. d’Orbigny,

these beds certainly belong to the great Patagonian formation, which

will be described in the ensuing chapter, and which we shall see must

be considered as a very ancient tertiary one. North of the Bajada, M.

d’Orbigny found, in beds which he considers as lying beneath the strata

here described, remains of a Toxodon, which he has named as a distinct

species from the _T. Platensis_ of the Pampean formation. Much

silicified wood is found on the banks of the Parana (and likewise on

the Uruguay), and I was informed that they come out of these lower

beds; four specimens collected by myself are dicotyledonous.

The upper half of the cliff, to a thickness of about thirty feet,

consists of Pampean mud, of which the lower part is pale-coloured, and

the upper part of a brighter red, with some irregular layers of an

arenaceous variety of tosca, and a few small concretions of the

ordinary kind. Close above the marine limestone, there is a thin

stratum with a concretionary outline of white hard tosca-rock or marl,

which may be considered either as the uppermost bed of the inferior

deposits, or the lowest of the Pampean formation; at one time I

considered this bed as marking a passage between the two formations:

but I have since become convinced that I was deceived on this point. In

the section on the Parana, I did not find any mammiferous remains; but

at two miles distance on the A. Tapas (a tributary of the Conchitas),

they were extremely numerous in a low cliff of red Pampean mud with

small concretions, precisely like the upper bed on the Parana. Most of

the bones were solitary and much decayed; but I saw the dermal armour

of a gigantic Edental quadruped, forming a caldron-like hollow, four or

five feet in diameter, out of which, as I was informed, the almost

entire skeleton had been lately removed. I found single teeth of the

_Mastodon Andium, Toxodon Platensis_, and _Equus curvidens_, near to

each other. As this latter tooth approaches closely to that of the

common horse, I paid particular attention to its true embedment, for I

did not at that time know that there was a similar tooth hidden in the

matrix with the other mammiferous remains from Punta Alta. It is an

interesting circumstance, that Professor Owen finds that the teeth of

this horse approach more closely in their peculiar curvature to a

fossil specimen brought by Mr. Lyell[15] from North America, than to

those of any other species of Equus.

[15] Lyell’s “Travels in North America,” vol. i, p. 164 and “Proc. of

Geolog. Soc.,” vol. iv, p. 39.

The underlying marine tertiary strata extend over a wide area: I was

assured that they can be traced in ravines in an east and west line

across Entre Rios to the Uruguay, a distance of about 135 miles. In a

S.E. direction I heard of their existence at the head of the R. Nankay;

and at P. Gorda in Banda Oriental, a distance of

170 miles, I found the same limestone, containing the same fossil

shells, lying at about the same level above the river as at St. Fe. In

a southerly direction, these beds sink in height, for at another P.

Gorda in Entre Rios, the limestone is seen at a much less height; and

there can be little doubt that the yellowish sandy clay, on a level

with the river, between the Carcarana and S. Nicholas, belongs to this

same formation; as perhaps do the beds of sand at Buenos Ayres, which

lie at the bottom of the Pampean formation, about sixty feet beneath

the surface of the Plata. The southerly declination of these beds may

perhaps be due, not to unequal elevation, but to the original form of

the bottom of the sea, sloping from land situated to the north; for

that land existed at no great distance, we have evidence in the

vegetable remains in the lowest bed at St. Fe; and in the silicified

wood and in the bones of _Toxodon Paranensis_, found (according to M.

d’Orbigny) in still lower strata.

_Banda Oriental._—This province lies on the northern side of the Plata,

and eastward of the Uruguay: it has a gentle undulatory surface, with a

basis of primary rocks; and is in most parts covered up with an

unstratified mass, of no great thickness, of reddish Pampean mud. In

the eastern half, near Maldonado, this deposit is more arenaceous than

in the Pampas, it contains many though small concretions of marl or

tosca-rock, and others of highly ferruginous sandstone; in one section,

only a few yards in depth, it rested on stratified sand. Near Monte

Video this deposit in some spots appears to be of greater thickness;

and the remains of the Glyptodon and other extinct mammifers have been

found in it. In the long line of cliffs, between fifty and sixty feet

in height, called the Barrancas de S. Gregorio, which extend westward

of the Rio S. Lucia, the lower half is formed of coarse sand of quartz

and feldspar without mica, like that now cast up on the beach near

Maldonado; and the upper half of Pampean mud, varying in colour and

containing honeycombed veins of soft calcareous matter and small

concretions of tosca-rock arranged in lines, and likewise a few pebbles

of quartz. This deposit fills up hollows and furrows in the underlying

sand; appearing as if water charged with mud had invaded a sandy beach.

These cliffs extend far westward, and at a distance of sixty miles,

near Colonia del Sacramiento, I found the Pampean deposit resting in

some places on this sand, and in others on the primary rocks: between

the sand and the reddish mud, there appeared to be interposed, but the

section was not a very good one, a thin bed of shells of an existing

Mytilus, still partially retaining their colour. The Pampean formation

in Banda Oriental might readily be mistaken for an alluvial deposit:

compared with that of the Pampas, it is often more sandy, and contains

small fragments of quartz; the concretions are much smaller, and there

are no extensive masses of tosca-rock.

In the extreme western parts of this province, between the Uruguay and

a line drawn from Colonia to the R. Perdido (a tributary of the R.

Negro), the formations are far more complicated. Besides primary rocks,

we meet with extensive tracts and many flat-topped, horizontally

stratified, cliff-bounded, isolated hills of tertiary strata, varying

extraordinarily in mineralogical nature, some identical with the old

marine beds of St. Fé Bajada, and some with those of the much more

recent Pampean formation. There are, also, extensive _low_ tracts of

country covered with a deposit containing mammiferous remains,

precisely like that just described in the more eastern parts of the

province. Although from the smooth and unbroken state of the country, I

never obtained a section of this latter deposit close to the foot of

the higher tertiary hills, yet I have not the least doubt that it is of

quite subsequent origin; having been deposited after the sea had worn

the tertiary strata into the cliff-bounded hills. This later formation,

which is certainly the equivalent of that of the Pampas, is well seen

in the valleys in the estancia of Berquelo, near Mercedes; it here

consists of reddish earth, full of rounded grains of quartz, and with

some small concretions of tosca-rock arranged in horizontal lines, so

as perfectly to resemble, except in containing a little calcareous

matter, the formation in the eastern parts of Banda Oriental, in Entre

Rios, and at other places: in this estancia the skeleton of a great

Edental quadruped was found. In the valley of the Sarandis, at the

distance of only a few miles, this deposit has a somewhat different

character, being whiter, softer, finer-grained, and full of little

cavities, and consequently of little specific gravity; nor does it

contain any concretions or calcareous matter: I here procured a head,

which when first discovered must have been quite perfect, of the

_Toxodon Platensis_, another of a Mylodon,[16] perhaps _M. Darwinii_,

and a large piece of dermal armour, differing from that of the

_Glyptodon clavipes._ These bones are remarkable from their

extraordinarily fresh appearance; when held over a lamp of spirits of

wine, they give out a strong odour and burn with a small flame; Mr. T.

Reeks has been so kind as to analyse some of the fragments, and he

finds that they contain about 7 per cent of animal matter, and 8 per

cent of water.[17]

[16] This head was at first considered by Professor Owen (in the

“Zoology of the _Beagle_’s Voyage”) as belonging to a distinct genus,

namely, Glossotherium.

[17] Liebig (“Chemistry of Agriculture,” p. 194) states that fresh dry

bones contain from 32 to 33 per cent of dry gelatine. See also Dr.

Daubeny, in _Edin. New Phil. Journ._, vol. xxxvii, p. 293.

The older tertiary strata, forming the higher isolated hills and

extensive tracts of country, vary, as I have said, extraordinarily in

composition: within the distance of a few miles, I sometimes passed

over crystalline limestone with agate, calcareous tuffs, and marly

rocks, all passing into each other,—red and pale mud with concretions

of tosca-rock, quite like the Pampean formation,—calcareous

conglomerates and sandstones,—bright red sandstones passing either into

red conglomerate, or into white sandstone,—hard siliceous sandstones,

jaspery and chalcedonic rocks, and numerous other subordinate

varieties. I was unable to mark out the relations of all these strata,

and will describe only a few distinct sections:—in the cliffs between

P. Gorda on the Uruguay and the A. de Vivoras, the upper bed is

crystalline

cellular limestone often passing into calcareous sandstone, with

impressions of some of the same shells as at St. Fé Bajada; at P.

Gorda,[18] this limestone is interstratified with and rests on, white

sand, which covers a bed about thirty feet thick of pale-coloured clay,

with many shells of the great _Ostrea Patagonica_: beneath this, in the

vertical cliff, nearly on a level with the river, there is a bed of red

mud absolutely like the Pampean deposit, with numerous often large

concretions of perfectly characterised white, compact tosca-rock. At

the mouth of the Vivoras, the river flows over a pale cavernous

tosca-rock, quite like that in the Pampas, and this _appeared_ to

underlie the crystalline limestone; but the section was not unequivocal

like that at P. Gorda. These beds now form only a narrow and much

denuded strip of land; but they must once have extended much further;

for on the next stream, south of the S. Juan, Captain Sulivan, R.N.,

found a little cliff, only just above the surface of the river, with

numerous shells of the _Venus Munsterii_, D’Orbigny,—one of the species

occurring at St. Fé, and of which there are casts at P. Gorda: the line

of cliffs of the subsequently deposited true Pampean mud, extend from

Colonia to within half a mile of this spot, and no doubt once covered

up this denuded marine stratum. Again at Colonia, a Frenchman found, in

digging the foundations of a house, a great mass of the _Ostrea

Patagonica_ (of which I saw many fragments), packed together just

beneath the surface, and directly superimposed on the gneiss. These

sections are important: M. d’Orbigny is unwilling to believe that beds

of the same nature with the Pampean formation ever underlie the ancient

marine tertiary strata; and I was as much surprised at it as he could

have been; but the vertical cliff at P. Gorda allowed of no mistake,

and I must be permitted to affirm, that after having examined the

country from the Colorado to St. Fé Bajada, I could not be deceived in

the mineralogical character of the Pampean deposit.

[18] In my “Journal” (p. 171, 1st edit.), I have hastily and

inaccurately stated that the Pampean mud, which is found over the

eastern part of B. Oriental, lies _over_ the limestone at P. Gorda; I

should have said that there was reason to infer that it was a

subsequent or superior deposit.

Moreover, in a precipitous part of the ravine of Las Bocas, a red

sandstone is distinctly seen to overlie a thick bed of pale mud, also

quite like the Pampean formation, abounding with concretions of true

tosca-rock. This sandstone extends over many miles of country: it is as

red as the brightest volcanic scoriæ; it sometimes passes into a coarse

red conglomerate composed of the underlying primary rocks; and often

passes into a soft white sandstone with red streaks. At the Calera de

los Huerfanos, only a quarter of a mile south of where I first met with

the red sandstone, the crystalline white limestone is quarried: as this

bed is the uppermost, and as it often passes into calcareous sandstone,

interstratified with pure sand; and as the red sandstone likewise

passes into soft white sandstone, and is also the uppermost bed, I

believe that these two beds, though so different, are equivalents. A

few leagues southward of these two places, on each side of the low

primary range of S. Juan, there are some flat-topped, cliff-bounded,

separate little hills,

very similar to those fringing the primary ranges in the great plain

south of Buenos Ayres: they are composed—1st, of calcareous tuff with

many particles of quartz, sometimes passing into a coarse conglomerate;

2nd, of a stone undistinguishable on the closest inspection from the

compacter varieties of tosca-rock; and 3rd, of semi-crystalline

limestone, including nodules of agate: these three varieties pass

insensibly into each other, and as they form the uppermost stratum in

this district, I believe that they, also, are the equivalents of the

pure crystalline limestone, and of the red and white sandstones and

conglomerates.

Between these points and Mercedes on the Rio Negro, there are scarcely

any good sections, the road passing over limestone, tosca-rock,

calcareous and bright red sandstones, and near the source of the San

Salvador over a wide extent of jaspery rocks, with much milky agate,

like that in the limestone near San Juan. In the estancia of Berquelo,

the separate, flat-topped, cliff-bounded hills are rather higher than

in the other parts of the country; they range in a N.E. and S.W.

direction; their uppermost beds consist of the same bright red

sandstone, passing sometimes into a conglomerate, and in the lower part

into soft white sandstone, and even into loose sand: beneath this

sandstone, I saw in two places layers of calcareous and marly rocks,

and in one place red Pampean-like earth; at the base of these sections,

there was a hard, stratified, white sandstone, with chalcedonic layers.

Near Mercedes, beds of the same nature and apparently of the same age,

are associated with compact, white, crystalline limestone, including

much botryoidal agate, and singular masses, like porcelain, but really

composed of a calcareo-siliceous paste. In sinking wells in this

district the chalcedonic strata seem to be the lowest. Beds, such as

there described, occur over the whole of this neighbourhood; but twenty

miles further up the R. Negro, in the cliffs of Perika, which are about

fifty feet in height, the upper bed is a prettily variegated

chalcedony, mingled with a pure white tallowy limestone; beneath this

there is a conglomerate of quartz and granite; beneath this many

sandstones, some highly calcareous; and the whole lower two-thirds of

the cliff consists of earthy calcareous beds of various degrees of

purity, with one layer of reddish Pampean-like mud.

When examining the agates, the chalcedonic and jaspery rocks, some of

the limestones, and even the bright red sandstones, I was forcibly

struck with their resemblance to deposits formed in the neighbourhood

of volcanic action. I now find that M. Isabelle, in his “Voyage a

Buenos Ayres,” has described closely similar beds on Itaquy and Ibicuy

(which enter the Uruguay some way north of the R. Negro) and these beds

include fragments of red decomposed true scoriæ hardened by zeolite,

and of black retinite: we have then here good evidence of volcanic

action during our tertiary period. Still further north, near S.

Anna,[19] where the Parana makes a remarkable bend, M. Bonpland found

some singular amygdaloidal rocks, which perhaps may belong to this same

epoch. I may remark that, judging from the size and well-rounded

condition of the blocks of rock in the above-described conglomerates,

masses of primary formation probably existed at this tertiary period

above water: there is, also, according to M. Isabelle, much

conglomerate further north, at Salto.

[19] M. d’Orbigny, “Voyage,” Part. Géolog., p. 29.

From whatever source and through whatever means the great Pampean

formation originated, we here have, I must repeat, unequivocal evidence

of a similar action at a period before that of the deposition of the

marine tertiary strata with extinct shells, at Santa Fé and P. Gorda.

During also the deposition of these strata, we have in the intercalated

layers of red Pampean-like mud and tosca-rock, and in the passage near

S. Juan of the semi-crystalline limestones with agate into tosca

undistinguishable from that of the Pampas, evidence of the same action,

though continued only at intervals and in a feeble manner. We have

further seen that in this district, at a period not only subsequent to

the deposition of the tertiary strata, but to their upheavement and

most extensive denudation, true Pampean mud with its usual characters

and including mammiferous remains, was deposited round and between the

hills or islets formed of these tertiary strata, and over the whole

eastern and low primary districts of Banda Oriental.

No. 16

Section of the lowest plain at Port S. Julian.

[Illustration: Section of the lowest plain at Port S. Julian.]

_Earthy mass, with extinct mammiferous remains, over the porphyritic

gravel at S. Julian, lat. 49° 14′ S., in Patagonia._—This case, though

not coming strictly under the Pampean formation, may be conveniently

given here. On the south side of the harbour, there is a nearly level

plain (mentioned in the First Chapter) about seven miles long, and

three or four miles wide, estimated at ninety feet in height, and

bordered by perpendicular cliffs, of which a section is represented

above.

The lower old tertiary strata (to be described in the next chapter) are

covered by the usual gravel bed; and this by an irregular earthy,

sometimes sandy mass, seldom more than two or three feet in thickness,

except where it fills up furrows or gullies worn not only through the

underlying gravel, but even through the upper tertiary beds. This

earthy mass is of a pale reddish colour, like the less pure varieties

of Pampean mud in Banda Oriental; it includes small calcareous

concretions, like those of tosca-rock but more arenaceous, and other

concretions of a greenish, indurated argillaceous substance: a few

pebbles, also, from the underlying gravel-bed are also included in it,

and these being occasionally arranged in horizontal lines, show that

the mass is of sub-aqueous origin. On the surface and embedded in the

superficial parts, there are numerous shells, partially retaining their

colours, of three or four of the now commonest littoral species. Near

the bottom of one deep furrow (represented in figure No. 16), filled up

with this earthy deposit, I found a large part of the skeleton of the

_Macrauchenia Patachonica_—a gigantic and most extraordinary pachyderm,

allied, according to Professor Owen, to the Palæotherium, but with

affinities to the Ruminants, especially to the American division of the

Camelidæ. Several of the vertebræ in a chain, and nearly all the bones

of one of the limbs, even to the smallest bones of the foot, were

embedded in their proper relative positions: hence the skeleton was

certainly united by its flesh or ligaments, when enveloped in the mud.

This earthy mass, with its concretions and mammiferous remains, filling

up furrows in the underlying gravel, certainly presents a very striking

resemblance to some of the sections (for instance, at P. Alta in B.

Blanca, or at the Barrancas de S. Gregorio) in the Pampean formation;

but I must believe that this resemblance is only accidental. I suspect

that the mud which at the present day is accumulating in deep and

narrow gullies at the head of the harbour, would, after elevation,

present a very similar appearance. The southernmost part of the true

Pampean formation, namely, on the Colorado, lies 560 miles of latitude

north of this point.[20]

[20] In the succeeding chapter I shall have to refer to a great

deposit of extinct mammiferous remains, lately discovered by Captain

Sulivan, R.N., at a point still further south, namely, at the R.

Gallegos; their age must at present remain doubtful.

With respect to the age of the Macrauchenia, the shells on the surface

prove that the mass in which the skeleton was enveloped has been

elevated above the sea within the recent period: I did not see any of

the shells embedded at a sufficient depth to assure me (though it be

highly probable) that the whole thickness of the mass was

contemporaneous with these _individual specimens._ That the

Macrauchenia lived subsequently to the spreading out of the gravel on

this plain is certain; and that this gravel, at the height of ninety

feet, was spread out long after the existence of recent shells, is

scarcely less certain. For, it was shown in the First Chapter, that

this line of coast has been upheaved with remarkable equability, and

that over a vast space both north and south of S. Julian, recent

species of shells are strewed on (or embedded in) the surface of the

250 feet plain, and of the 350 feet plain up to a height of 400 feet.

These wide step-formed plains have been formed by the denuding action

of the coast-waves on the old tertiary strata; and therefore, when the

surface of the 350 feet plain, with the shells on it, first rose above

the level of the sea, the 250 feet plain did not exist, and its

formation, as well as the spreading out of the gravel on its summit,

must have taken place subsequently. So also the denudation and the

gravel-covering of the 90 feet plain must have taken

place subsequently to the elevation of the 250 feet plain, on which

recent shells are also strewed. Hence there cannot be any doubt that

the Macrauchenia, which certainly was entombed in a fresh state, and

which must have been alive after the spreading out of the gravel on the

90 feet plain, existed, not only subsequently to the upraised shells on

the surface of the 250 feet plain, but also to those on the 350 to 400

feet plain: these shells, eight in number (namely, three species of

Mytilus, two of Patella, one Fusus, Voluta, and Balanus), are

undoubtedly recent species, and are the commonest kinds now living on

this coast. At Punta Alta in B. Blanca, I remarked how marvellous it

was, that the Toxodon, a mammifer so unlike to all known genera, should

have co-existed with twenty-three still living marine animals; and now

we find that the Macrauchenia, a quadruped only a little less anomalous

than the Toxodon, also co-existed with eight other still existing

Mollusca: it should, moreover, be borne in mind, that a tooth of a

pachydermatous animal was found with the other remains at Punta Alta,

which Professor Owen thinks almost certainly belonged to the

Macrauchenia.

Mr. Lyell[21] has arrived at a highly important conclusion with respect

to the age of the North American extinct mammifers (many of which are

closely allied to, and even identical with, those of the Pampean

formation), namely, that they lived subsequently to the period when

erratic boulders were transported by the agency of floating ice in

temperate latitudes. Now in the valley of the Santa Cruz, only fifty

miles of latitude south of the spot where the Macrauchenia was

entombed, vast numbers of gigantic, angular boulders, which must have

been transported from the Cordillera on icebergs, lie strewed on the

plain, at the height of 1,400 feet above the level of the sea. In

ascending to this level, several step-formed plains must be crossed,

all of which have necessarily required long time for their formation;

hence the lowest or ninety feet plain, with its superficial bed

containing the remains of the Macrauchenia, must have been formed very

long subsequently to the period when the 1,400 feet plain was beneath

the sea, and boulders were dropped on it from floating masses of

ice.[22] Mr. Lyell’s conclusion, therefore, is thus far confirmed in

the southern hemisphere; and it is the more important, as one is

naturally tempted to admit so simple an explanation, that it was the

ice-period that caused the extinction of the numerous great mammifers

which so lately swarmed over the two Americas.

[21] “Geological Proceedings,” vol. iv, p. 36.

[22] It must not be inferred from these remarks, that the ice-action

ceased in South America at this comparatively ancient period; for in

Tierra del Fuego boulders were probably transported contemporaneously

with, if not subsequently to, the formation of the ninety feet plain

at S. Julian, and at other parts of the coast of Patagonia.

_Summary and concluding remarks on the Pampean formation._—One of its

most striking features is its great extent; I passed continuously over

it from the Colorado to St. Fe Bajada, a distance of 500 geographical

miles; and M. d’Orbigny traced it for 250 miles further north. In

the latitude of the Plata, I examined this formation at intervals over

an east and west line of 300 miles from Maldonado to the R. Carcarana;

and M. d’Orbigny believes it extends 100 miles further inland: from Mr.

Caldcleugh’s travels, however, I should have thought that it had

extended, south of the Cordovese range, to near Mendoza, and I may add

that I heard of great bones having been found high up the R. Quinto.

Hence the area of the Pampean formation, as remarked by M. d’Orbigny,

is probably at least equal to that of France, and perhaps twice or

thrice as great. In a basin, surrounded by gravel-cliff (at a height of

nearly three thousand feet), south of Mendoza, there is, as described

in the Third Chapter, a deposit very like the Pampean, interstratified

with other matter; and again at S. Julian’s, in Patagonia, 560 miles

south of the Colorado, a small irregular bed of a nearly similar nature

contains, as we have just seen, mammiferous remains. In the provinces

of Moxos and Chiquitos (1,000 miles northward of the Pampas), and in

Bolivia, at a height of 4,000 metres, M. d’Orbigny has described

similar deposits, which he believes to have been formed by the same

agency contemporaneously with the Pampean formation. Considering the

immense distances between these several points, and their different

heights, it appears to me infinitely more probable, that this

similarity has resulted not from contemporaneousness of origin, but

from the similarity of the rocky framework of the continent: it is

known that in Brazil an immense area consists of gneissic rocks, and we

shall hereafter see, over how great a length the plutonic rocks of the

Cordillera, the overlying purple porphyries, and the trachytic

ejections, are almost identical in nature.

Three theories on the origin of the Pampean formation have been

propounded:—First, that of a great debacle by M. d’Orbigny; this seems

founded chiefly on the absence of stratification, and on the number of

embedded remains of terrestrial quadrupeds. Although the Pampean

formation (like so many argillaceous deposits) is not divided into

distinct and separate strata, yet we have seen that in one good section

it was striped with horizontal zones of colour, and that in several

specified places the upper and lower parts differed, not only

considerably in colour, but greatly in constitution. In the southern

part of the Pampas the upper mass (to a certain extent stratified)

generally consists of hard tosca-rock, and the lower part of red

Pampean mud, often itself divided into two or more masses, varying in

colour and in the quantity of included calcareous matter. In Western

Banda Oriental, beds of a similar nature, but of a greater age,

conformably underlie and are intercalated with the regularly stratified

tertiary formation. As a general rule, the marly concretions are

arranged in horizontal lines, sometimes united into irregular strata:

surely, if the mud had been tumultuously deposited in mass, the

included calcareous matter would have segregated itself irregularly,

and not into nodules arranged in horizontal lines, one above the other

and often far apart: this arrangement appears to me to prove that mud,

differing slightly in composition, was successively and quietly

deposited. On the theory of a debacle, a prodigious amount of mud,

without a single pebble, is supposed to have been borne over the wide

surface of the Pampas, when under water: on the other hand, over the

whole of Patagonia, the same or another debacle is supposed to have

borne nothing but gravel,—the gravel and the fine mud in the

neighbourhood of the Rios Negro and Colorado having been borne to an

equal distance from the Cordillera, or imagined line of disturbance:

assuredly directly opposite effects ought not to be attributed to the

same agency. Where, again, could a mass of fine sediment, charged with

calcareous matter in a fit state for chemical segregation, and in

quantity sufficient to cover an area at least 750 miles long, and 400

miles broad, to a depth of from twenty to thirty feet to a hundred

feet, have been accumulated, ready to be transported by the supposed

debacle? To my mind it is little short of demonstration, that a great

lapse of time was necessary for the production and deposition of the

enormous amount of mudlike matter forming the Pampas; nor should I have

noticed the theory of a debacle, had it not been adduced by a

naturalist so eminent as M. d’Orbigny.

A second theory, first suggested, I believe, by Sir W. Parish, is that

the Pampean formation was thrown down on low and marshy plains by the

rivers of this country before they assumed their present courses. The

appearance and composition of the deposit, the manner in which it

slopes up and round the primary ranges, the nature of the underlying

marine beds, the estuary and sea-shells on the surface, the overlying

sandstone beds at M. Hermoso, are all quite opposed to this view. Nor

do I believe that there is a single instance of a skeleton of one of

the extinct mammifers having been found in an upright position, as if

it had been mired.

The third theory, of the truth of which I cannot entertain the smallest

doubt, is that the Pampean formation was slowly accumulated at the

mouth of the former estuary of the Plata and in the sea adjoining it. I

have come to this conclusion from the reasons assigned against the two

foregoing theories, and from simple geographical considerations. From

the numerous shells of the _Azara labiata_ lying loose on the surface

of the plains, and near Buenos Ayres embedded in the tosca-rock, we

know that this formation not only was formerly covered by, but that the

uppermost parts were deposited in, the brackish water of the ancient La

Plata. Southward and seaward of Buenos Ayres, the plains were upheaved

from under water inhabited by true marine shells. We further know from

Professor Ehrenberg’s examination of the twenty microscopical organisms

in the mud round the tooth of the Mastodon high up the course of the

Parana, that the bottom-most part of this formation was of

brackish-water origin. A similar conclusion must be extended to the

beds of like composition, at the level of the sea and under it, at M.

Hermoso in Bahia Blanca. Dr. Carpenter finds that the harder varieties

of tosca-rock, collected chiefly to the south, contain marine spongoid

bodies, minute fragments of shells, corals, and Polythalamia; these

perhaps may have been drifted inwards by the tides, from the more open

parts of the sea. The absence of shells, throughout this deposit, with

the exception of the uppermost layers near Buenos Ayres, is a

remarkable fact: can it be explained by the brackish condition of the

water, or by the deep mud at the bottom? I have stated that both the

reddish mud and the concretions of tosca-rock are

often penetrated by minute, linear cavities, such as frequently may be

observed in fresh-water calcareous deposits:—were they produced by the

burrowing of small worms? Only on this view of the Pampean formation

having been of estuary origin, can the extraordinary numbers (presently

to be alluded to) of the embedded mammiferous remains be explained.[23]

[23] It is almost superfluous to give the numerous cases (for

instance, in Sumatra; Lyell’s “Principles,” vol. iii, p. 325, sixth

edit.), of the carcasses of animals having been washed out to sea by

swollen rivers; but I may refer to a recent account by Mr. Bettington

(“Asiatic Soc.,” 1845, June 21st), of oxen, deer, and bears being

carried into the Gulf of Cambray; see also the account in my “Journal”

(2nd edit., p. 133), of the numbers of animals drowned in the Plata

during the great, often recurrent, droughts.

With respect to the first origin of the reddish mud, I will only

remark, that the enormous area of Brazil consists in chief part of

gneissic and other granitic rocks, which have suffered decomposition,

and been converted into a red, gritty, argillaceous mass, to a greater

depth than in any other country which I have seen. The mixture of

rounded grains, and even of small fragments and pebbles of quartz, in

the Pampean mud of Banda Oriental, is evidently due to the neighbouring

and underlying primary rocks. The estuary mud was drifted during the

Pampean period in a much more southerly course, owing probably to the

east and west primary ridges south of the Plata not having been then

elevated, than the mud of the Plata at present is; for it was formerly

deposited as far south as the Colorado. The quantity of calcareous

matter in this formation, especially in those large districts where the

whole mass passes into tosca-rock, is very great: I have already

remarked on the close resemblance in external and microscopical

appearance, between this tosca-rock and the strata at Coquimbo, which

have certainly resulted from the decay and attrition of recent

shells:[24] I dare not, however, extend this conclusion to the

calcareous rocks of the Pampas, more especially as the underlying

tertiary strata in western Banda Oriental show that at that period

there was a copious emission of carbonate of lime, in connection with

volcanic action.

[24] I may add, that there are nearly similar superficial calcareous

beds at King George’s Sound in Australia; and these undoubtedly have

been formed by the disintegration of marine remains (see “Volcanic

Islands,” etc., p. 144). There is, however, something very remarkable

in the frequency of superficial, thin beds of earthy calcareous

matter, in districts where the surrounding rocks are not calcareous.

Major Charters, in a Paper read before the Geographical Society (April

13th, 1840, and abstracted in the _ Athenæum_, p. 317), states that

this is the case in parts of Mexico, and that he has observed similar

appearances in many parts of South Africa. The circumstance of the

uppermost stratum round the ragged Sierra Ventana, consisting of

calcareous or marly matter, without any covering of alluvial matter,

strikes me as very singular, in whatever manner we view the deposition

and elevation of the Pampean formation.

The Pampean formation, judging from its similar composition, and from

the apparent absolute specific identity of some of its mammiferous

remains, and from the generic resemblance of others, belongs over its

vast area—throughout Banda Oriental, Entre Rios, and the wide extent of

the Pampas as far south as the Colorado,—to the same geological epoch.

The mammiferous remains occur at all depths from the top to the bottom

of the deposit; and I may add that nowhere in the Pampas is there any

appearance of much superficial denudation: some bones which I found

near the Guardia del Monte were embedded close to the surface; and this

appears to have been the case with many of those discovered in Banda

Oriental: on the Matanzas, twenty miles south of Buenos Ayres, a

Glyptodon was embedded five feet beneath the surface; numerous remains

were found by S. Muniz, near Luxan, at an average depth of eighteen

feet; in Buenos Ayres a skeleton was disinterred at sixty feet depth,

and on the Parana I have described two skeletons of the Mastodon only

five or six feet above the very base of the deposit. With respect to

the age of this formation, as judged of by the ordinary standard of the

existence of Mollusca, the only evidence within the limits of the true

Pampas which is at all trustworthy, is afforded by the still living

_Azara labiata_ being embedded in tosca-rock near Buenos Ayres. At

Punta Alta, however, we have seen that several of the extinct

mammifers, most characteristic of the Pampean formation, co-existed

with twenty species of Mollusca, a barnacle and two corals, all still

living on this same coast;—for when we remember that the shells have a

more ancient appearance than the bones; that many of the bones, though

embedded in a coarse conglomerate, are perfectly preserved; that almost

all the parts of the skeleton of the Scelidotherium, even to the

knee-cap, were lying in their proper relative positions; and that a

large piece of the fragile dermal armour of a Dasypoid quadruped,

connected with some of the bones of the foot, had been entombed in a

condition allowing the two sides to be doubled together, it must

assuredly be admitted that these mammiferous remains were embedded in a

fresh state, and therefore that the living animals co-existed with the

co-embedded shells. Moreover, the _Macrauchenia Patachonica_ (of which,

according to Professor Owen, remains also occur in the Pampas of Buenos

Ayres, and at Punta Alta) has been shown by satisfactory evidence of

another kind, to have lived on the plains of Patagonia long after the

period when the adjoining sea was first tenanted by its present

commonest molluscous animals. We must, therefore, conclude that the

Pampean formation belongs, in the ordinary geological sense of the

word, to the Recent Period.[25]

[25] M. d’Orbigny believes (“Voyage,” Part. Géolog., p. 81) that this

formation, though “très voisine de la nôtre, est néanmoins de beaucoup

antérieure à notre création.”

At St. Fé Bajada, the Pampean estuary formation, with its mammiferous

remains, conformably overlies the marine tertiary strata, which (as

first shown by M. d’Orbigny) are contemporaneous with those of

Patagonia, and which, as we shall hereafter see, belong to a very

ancient tertiary stage. When examining the junction between these two

formations, I thought that the concretionary layer of marl marked a

passage between the marine and estuary stages. M. d’Orbigny

disputes this view (as given in my “Journal”), and I admit that it is

erroneous, though in some degree excusable, from their conformability

and from both abounding with calcareous matter. It would, indeed, have

been a great anomaly if there had been a true passage between a deposit

contemporaneous with existing species of mollusca, and one in which all

the mollusca appear to be extinct. Northward of Santa Fe, M. d’Orbigny

met with ferruginous sandstones, marly rocks, and other beds, which he

considers as a distinct and lower formation; but the evidence that they

are not parts of the same with an altered mineralogical character, does

not appear to me quite satisfactory.

In Western Banda Oriental, while the marine tertiary strata were

accumulating, there were volcanic eruptions, much silex and lime were

precipitated from solution, coarse conglomerates were formed, being

derived probably from adjoining land, and layers of red mud and marly

rocks, like those of the Pampean formation, were occasionally

deposited. The true Pampean deposit, with mammiferous remains, instead

of as at Santa Fe overlying conformably the tertiary strata, is here

seen at a lower level folding round and between the flat-topped,

cliff-bounded hills, formed by a upheaval and denudation of these same

tertiary strata. The upheaval, having occurred here earlier than at

Santa Fe, may be naturally accounted for by the contemporaneous

volcanic action. At the Barrancas de S. Gregorio, the Pampean deposit,

as we have seen, overlies and fills up furrows in coarse sand,

precisely like that now accumulating on the shores near the mouth of

the Plata. I can hardly believe that this loose and coarse sand is

contemporaneous with the old tertiary and often crystalline strata of

the more western parts of the province; and am induced to suspect that

it is of subsequent origin. If that section near Colonia could be

implicitly trusted, in which, at a height of only fifteen feet above

the Plata, a bed of fresh-looking mussels, of an existing _littoral_

species, appeared to lie between the sand and the Pampean mud, I should

conclude that Banda Oriental must have stood, when the coarse sand was

accumulating, at only a little below its present level, and had then

subsided, allowing the estuary Pampean mud to cover far and wide its

surface up to a height of some hundred feet; and that after this

subsidence the province had been uplifted to its present level.

In Western Banda Oriental, we know, from two unequivocal sections that

there is a mass, absolutely undistinguishable from the true Pampean

deposit, beneath the old tertiary strata. This inferior mass must be

very much more ancient than the upper deposit with its mammiferous

remains, for it lies beneath the tertiary strata in which all the

shells are extinct. Nevertheless, the lower and upper masses, as well

as some intermediate layers, are so similar in mineralogical character,

that I cannot doubt that they are all of estuary origin, and have been

derived from the same great source. At first it appeared to me

extremely improbable, that mud of the same nature should have been

deposited on nearly the same spot, during an immense lapse of time,

namely, from a period equivalent perhaps to the Eocene of Europe to

that of the Pampean formation. But as, at the very commencement of the

Pampean

period, if not at a still earlier period, the Sierra Ventana formed a

boundary to the south,—the Cordillera or the plains in front of them to

the west,—the whole province of Corrientes probably to the north, for,

according to M. d’Orbigny, it is not covered by the Pampean

deposit,—and Brazil, as known by the remains in the caves, to the

north-east; and as again, during the older tertiary period, land

already existed in Western Banda Oriental and near St. Fé Bajada, as

may be inferred from the vegetable debris, from the quantities of

silicified wood, and from the remains of a Toxodon found, according to

M. d’Orbigny, in still lower strata, we may conclude, that at this

ancient period a great expanse of water was surrounded by the same

rocky framework which now bounds the plains of Pampean formation. This

having been the case, the circumstance of sediment of the same nature

having been deposited in the same area during an immense lapse of time,

though highly remarkable, does not appear incredible.

The elevation of the Pampas, at least of the southern parts, has been

slow and interrupted by several periods of rest, as may be inferred

from the plains, cliffs, and lines of sand-dunes (with shells and

pumice-pebbles) standing at different heights. I believe, also, that

the Pampean mud continued to be deposited, after parts of this

formation had already been elevated, in the same manner as mud would

continue to be deposited in the estuary of the Plata, if the mud-banks

on its shores were now uplifted and changed into plains: I believe in

this from the improbability of so many skeletons and bones having been

accumulated at one spot, where M. Hermoso now stands, at a depth of

between eight hundred and one thousand feet, and at a vast distance

from any land except small rocky islets,—as must have been the case, if

the high tosca-plain round the Ventana and adjoining Sierras, had not

been already uplifted and converted into land, supporting mammiferous

animals. At Punta Alta we have good evidence that the gravel-strata,

which certainly belong to the true Pampean period, were accumulated

after the elevation in that neighbourhood of the main part of the

Pampean deposit, whence the rounded masses of tosca-rock were derived,

and that rolled fragment of black bone in the same peculiar condition

with the remains at Monte Hermoso.

The number of the mammiferous remains embedded in the Pampas is, as I

have remarked, wonderful: it should be borne in mind that they have

almost exclusively been found in the cliffs and steep banks of rivers,

and that, until lately, they excited no attention amongst the

inhabitants: I am firmly convinced that a deep trench could not be cut

in any line across the Pampas, without intersecting the remains of some

quadruped. It is difficult to form an opinion in what part of the

Pampas they are most numerous; in a limited spot they could not well

have been more numerous than they were at P. Alta; the number, however,

lately found by Senor F. Muniz, near Luxan, in a central spot in the

Pampas, is extraordinarily great: at the end of this chapter I will

give a list of all the localities at which I have heard of remains

having been discovered. Very frequently the remains consist of almost

perfect

skeletons; but there are, also, numerous single bones, as for instance

at St. Fé. Their state of preservation varies much, even when embedded

near each other: I saw none others so perfectly preserved as the heads

of the Toxodon and Mylodon from the white soft earthy bed on the

Sarandis in Banda Oriental. It is remarkable that in two limited

sections I found no less than five teeth separately embedded, and I

heard of teeth having been similarly found in other parts: may we

suppose that the skeletons or heads were for a long time gently drifted

by currents over the soft muddy bottom, and that the teeth

occasionally, here and there, dropped out?

It may be naturally asked, where did these numerous animals live? From

the remarkable discoveries of MM. Lund and Clausen, it appears that

some of the species found in the Pampas inhabited the highlands of

Brazil: the _Mastodon Andium_ is embedded at great heights in the

Cordillera from north of the equator[26] to at least as far south as

Tarija; and as there is no higher land, there can be little doubt that

this Mastodon must have lived on the plains and valleys of that great

range. These countries, however, appear too far distant for the

habitation of the individuals entombed in the Pampas: we must probably

look to nearer points, for instance to the province of Corrientes,

which, as already remarked, is said not to be covered by the Pampean

formation, and may therefore, at the period of its deposition, have

existed as dry land. I have already given my reasons for believing that

the animals embedded at M. Hermoso and at P. Alta in Bahia Blanca,

lived on adjoining land, formed of parts of the already elevated

Pampean deposit. With respect to the food of these many great extinct

quadrupeds, I will not repeat the facts given in my “Journal” (second

edit., p. 85), showing that there is no correlation between the

luxuriance of the vegetation of a country and the size of its

mammiferous inhabitants. I do not doubt that large animals could now

exist, as far as the amount, not kind, of vegetation is concerned, on

the sterile plains of Bahia Blanca and of the R. Negro, as well as on

the equally, if not more sterile plains of Southern Africa. The

climate, however, may perhaps have somewhat deteriorated since the

mammifers embedded at Bahia Blanca lived there; for we must not infer,

from the continued existence of the same shells on the present coasts,

that there has been no change in climate; for several of these shells

now range northward along the shores of Brazil, where the most

luxuriant vegetation flourishes under a tropical temperature. With

respect to the extinction, which at first fills the mind with

astonishment, of the many great and small mammifers of this period, I

may also refer to the work above cited (second edit., p. 173), in which

I have endeavoured to show, that however unable we may be to explain

the precise cause, we ought not properly to feel more surprised at a

species becoming extinct than at one being rare; and yet we are

accustomed to

view the rarity of any particular species as an ordinary event, not

requiring any extraordinary agency.

[26] Humboldt states that the Mastodon has been discovered in New

Granada: it has been found in Quito. When at Lima, I saw a tooth of a

Mastodon in the possession of Don M. Rivero, found at Playa Chica on

the Maranon, near the Guallaga. Every one has heard of the numerous

remains of Mastodon in Bolivia.

The several mammifers embedded in the Pampean formation, which mostly

belong to extinct genera, and some even to extinct families or orders,

and which differ nearly, if not quite, as much as do the Eocene

mammifers of Europe from living quadrupeds having existed

contemporaneously with mollusca, all still inhabiting the adjoining

sea, is certainly a most striking fact. It is, however, far from being

an isolated one; for, during the late tertiary deposits of Britain, an

elephant, rhinoceros, and hippopotamus co-existed with many recent land

and fresh-water shells; and in North America, we have the best evidence

that a mastodon, elephant, megatherium, megalonyx, mylodon, an extinct

horse and ox, likewise co-existed with numerous land, fresh-water, and

marine recent shells.[27] The enumeration of these extinct North

American animals naturally leads me to refer to the former closer

relation of the mammiferous inhabitants of the two Americas, which I

have discussed in my “Journal,” and likewise to the vast extent of

country over which some of them ranged: thus the same species of the

_Megatherium, Megalonyx, Equus_ (as far as the state of their remains

permits of identification), extended from the Southern United States of

North America to Bahia Blanca, in lat. 39° S., on the coast of

Patagonia. The fact of these animals having inhabited tropical and

temperate regions, does not appear to me any great difficulty, seeing

that at the Cape of Good Hope several quadrupeds, such as the elephant

and hippopotamus, range from the equator to lat. 35° south. The case of

the Mastodon Andium is one of more difficulty, for it is found from

lat. 36° S., over, as I have reason to believe, nearly the whole of

Brazil, and up the Cordillera to regions which, according to M.

d’Orbigny, border on perpetual snow, and which are almost destitute of

vegetation: undoubtedly the climate of the Cordillera must have been

different when the mastodon inhabited it; but we should not forget the

case of the Siberian mammoth and rhinoceros, as showing how severe a

climate the larger pachydermata can endure; nor overlook the fact of

the guanaco ranging at the present day over the hot low deserts of

Peru, the lofty pinnacles of the Cordillera, and the damp forest-clad

land of Southern Tierra del Fuego; the puma, also, is found from the

equator to the Strait of Magellan, and I have seen its footsteps only a

little below the limits of perpetual snow in the Cordillera of Chile.

[27] Many original observations, and a summary on this subject, are

given in Mr. Lyell’s paper in the “Geolog. Proc.,” vol. iv, p. 3 and

in his “Travels in North America,” vol. i, p. 164 and vol. ii, p. 60.

For the European analogous cases see Mr. Lyell’s “Principles of

Geology” (6th edit.), vol. i, p. 37.

At the period, so recent in a geological sense, when these extinct

mammifers existed, the two Americas must have swarmed with quadrupeds,

many of them of gigantic size; for, besides those more particularly

referred to in this chapter, we must include in this same period those

wonderfully numerous remains, some few of them specifically, and others

generically related to those of the Pampas, discovered by

MM. Lund and Clausen in the caves of Brazil. Finally, the facts here

given show how cautious we ought to be in judging of the antiquity of a

formation from even a great amount of difference between the extinct

and living species in any one class of animals;—we ought even to be

cautious in accepting the general proposition, that change in organic

forms and lapse of time are at all, necessarily, correlatives.

_Localities within the region of the Pampas where great bones have been

found._

The following list, which includes every account which I have hitherto

met with of the discovery of fossil mammiferous remains in the Pampas,

may be hereafter useful to a geologist investigating this region, and

it tends to show their extraordinary abundance. I heard of and saw many

fossils, the original position of which I could not ascertain; and I

received many statements too vague to be here inserted. Beginning to

the south:—we have the two stations in Bahia Blanca, described in this

chapter, where at P. Alta, the Megatherium, Megalonyx, Scelidotherium,

Mylodon, Holophractus (or an allied genus), Toxodon, Macrauchenia, and

an Equus were collected; and at M. Hermoso a Ctenomys, Hydrochærus,

some other rodents and the bones of a great megatheroid quadruped.

Close north-east of the S. Tapalguen, we have the Rios ‘Huesos’ (i.e.

_bones_), which probably takes its name from large fossil bones. Near

Villa Nuevo, and at Las Averias, not far from the Salado, three nearly

perfect skeletons, one of the Megatherium, one of the _Glyptodon

clavipes_, and one of some great Dasypoid quadruped, were found by the

agent of Sir W. Parish (see his work “Buenos Ayres,” etc., p. 171). I

have seen the tooth of a Mastodon from the Salado; a little northward

of this river, on the borders of a lake near the G. del Monte, I saw

many bones, and one large piece of dermal armour; higher up the Salado,

there is a place called Monte “Huesos.” On the Matanzas, about twenty

miles south of Buenos Ayres, the skeleton (_vide_ p. 178 of “Buenos

Ayres,” etc., by Sir W. Parish) of a Glyptodon was found about five

feet beneath the surface; here also (see Catalogue of Royal College of

Surgeons) remains of _Glyptodon clavipes, G. ornatus_, and _G.

reticulatus_ were found. Signor Angelis, in a letter which I have seen,

refers to some great remains found in Buenos Ayres, at a depth of

twenty varas from the surface. Seven leagues north of this city the

same author found the skeletons of _Mylodon robustus_ and _Glyptodon

ornatus._ From this neighbourhood he has lately sent to the British

Museum the following fossils:—Remains of three or four individuals of

Megatherium; of three species of Glyptodon; of three individuals of the

_Mastodon Andium_; of Macrauchenia; of a second species of Toxodon,

different from _T. Platensis_; and lastly, of the Machairodus, a

wonderful large carnivorous animal. M. d’Orbigny has lately received

from the Recolate (“Voyage,” Pal., p. 144), near Buenos Ayres, a tooth

of _Toxodon Platensis._

Proceeding northward, along the west bank of the Parana, we come to the

Rio Luxan, where two skeletons of the Megatherium have been found; and

lately, within eight leagues of the town of Luxan, Dr. F. X. Muniz has

collected (_British Packet_, Buenos Ayres, September 25, 1841), from an

average depth of eighteen feet, very numerous remains, of no less than,

as he believes, nine distinct species of mammifers. At Areco, large

bones have been found, which are believed, by the inhabitants, to have

been changed

from small bones, by the water of the river! At Arrecifes, the

Glyptodon, sent to the College of Surgeons, was found; and I have seen

two teeth of a Mastodon from this quarter. At S. Nicolas, M. d’Orbigny

found remains of a Canis, Ctenomys, and Kerodon; and M. Isabelle

(“Voyage,” p. 332) refers to a gigantic Armadillo found there. At S.

Carlos, I heard of great bones. A little below the mouth of the

Carcarana, the two skeletons of Mastodon were found; on the banks of

this river, near S. Miguel, I found teeth of the Mastodon and Toxodon;

and “Falkner” (p. 55) describes the osseous armour of some great

animal; I heard of many other bones in this neighbourhood. I have seen,

I may add, in the possession of Mr. Caldcleugh, the tooth of a

_Mastodon Andium_, said to have been found in Paraguay; I may here also

refer to a statement in this gentleman’s travels (vol. i, p. 48), of a

great skeleton having been found in the province of Bolivia in Brazil,

on the R. de las Contas. The furthest point westward in the Pampas, at

which I have _heard_ of fossil bones, was high up on the banks of R.

Quinto.

In Entre Rios, besides the remains of the Mastodon, Toxodon, Equus, and

a great Dasypoid quadruped near St. Fe Bajada, I received an account of

bones having been found a little S.E. of P. Gorda (on the Parana), and

of an entire skeleton at Matanzas, on the Arroyo del Animal.

In Banda Oriental, besides the remains of the Toxodon, Mylodon, and two

skeletons of great animals with osseous armour (distinct from that of

the Glyptodon), found on the Arroyos Sarandis and Berquelo, M. Isabelle

(“Voyage,” p. 322) says, many bones have been found near the R. Negro,

and on the R. Arapey, an affluent of the Paraguay, in lat. 30° 40′

south. I heard of bones near the source of the A. Vivoras. I saw the

remains of a Dasypoid quadruped from the Arroyo Seco, close to M.

Video; and M. d’Orbigny refers (“Voyage,” Géolog., p. 24), to another

found on the Pedernal, an affluent of the St. Lucia; and Signor

Angelis, in a letter, states that a third skeleton of this family has

been found, near Canelones. I saw a tooth of the Mastodon from Talas,

another affluent of the St. Lucia. The most eastern point at which I

heard of great bones having been found, was at Solis Grande, between M.

Video and Maldonado.