RECORD: Darwin, C. R. Geological diary: Concepcion. (3.1835) CUL-DAR35.357-370 Transcribed by Kees Rookmaaker, edited by John van Wyhe (Darwin Online, http://darwin-online.org.uk/)

REVISION HISTORY: Transcribed by Kees Rookmaaker, corrections and editing by John van Wyhe, corrections by Gordon Chancellor 5.2011. RN4

NOTE: This document, part of the largest scientific document composed by Darwin during the voyage of the Beagle, is written mostly in ink. Marginal notes are here integrated into the text. Darwin was in Concepcion 4-6 March 1835. This is covered in the Beagle diary pp. 538-550.

Editorial symbols used in the transcription:
[some text] 'some text' is an editorial insertion
[some text] 'some text' is the conjectured reading of an ambiguous word or passage
[some text] 'some text' is a description of a word or passage that cannot be transcribed
< > word(s) destroyed
<some text> 'some text' is a description of a destroyed word or passage
Text in small red font is a hyperlink or notes added by the editors.

Reproduced with the permission of the Syndics of Cambridge University Library and William Huxley Darwin.

See the introduction to the Geological Diary by Gordon Chancellor.


357

1835 March. Concepcion (1)

[Geolog Trans Juan Fernandez] in Concepcion Bay

The geology of this place, as at Baldivia shows a covering of tertiary strata on ancient slates. The former is as much more abundant here as the micaceous slates were at Baldinia. —

Caldcleugh geology of Concepcion [3 words illeg, in margin] Juan Fernandez1

The form of all the neighbouring country is that of broken denuded plains. I was able during only two days to study examine these formations: one was spent on the island of Quiriquina; here, far the greater part is composed of tertiary sandstones. The stone varies much in its qualities, is always soft, often rather deserves the name of agglomerated sand. (b) like 2576 — it is much marked with ferruginous matter. these bands divide the stone into a concretionary structure.

In the upper parts of the sections often passes into a quite white, very soft fine sandstone & this again is connected with a white aluminous substance. Like what we have described in Chiloe at P Penuy, similarly we meet with much of that peculiar soft ferruginous breccia of white fragments. The identity is perfect between these stones from in each place. —

M. Lesson has cleavage E 10°2

The ferruginous sandstones (c) frequently rest on a hard greenish black sandstone with embedded grains of quartz & broken crystals (2581). — In parts of the island there is much very soft earthy substance of both a brown & red color, which contains white specks, so as to look like a porphyry (2582). All the foregoing substances, which pass into each other without much regularity (a) are capped by a thick bed of bright red, dry friable earth. I should hardly have supposed it a marine deposition if I had not found a layer of recent shells lying on the surface. This without doubt is the same as the

1 Caldcleugh 1825, vol. 1 and Caldcleugh 1834.

2 Duperrey 1826-1830.

357 verso

(a) This is blackened by vegetable matter but to a very short depth. —

(b) In some places there is some greenish impure indurated clay. —

(c) Contained in one place a few pebbles.

47
27
20
60
1200

The 24 ft change since last earthquake insensible because unrecorded

Buckland says ammonite near Concepcion now in Hasler Hospital p. 336 1st ed.1
Broad water direction

Mr Austen Devon paper read before Soc. says I believe gives account of the there becoming up of slate edges2

Mr Thomas in [Journey] review somewhere about November gives similar account3

R.N. p 34 speculations on origin of coal4

Ulloa on elevated shells R.N. p. 1065

NB. The point to which edges of slate are turned, corresponds to point on which old buildings have been thrown

1 Buckland 1836, vol. 1, p. 336 footnote:

The Greensand of New Jersey also contains Ammonites mixed with Hamites and Scaphites, as in the Greensand of England. and Captain Beechey and Lieutenant Belcher found Ammonites on the coast of Chili, in Lat. 36. S. in the Cliffs near Conception; a fragment of one of these Ammonites is preserved in the Museum of Hasler Hospital at Gosport.

2 Austen 1842.

3 Possibly Thomas Park 1828, p. 410:

The mountains bounding the sides of this long valley, as far as I could observe, appear composed of quartzrock and clay-slate alternating with each other, and disposed in strata ranging SSW. and NNE., the dip from 80° to 80° (the direction of the dip not given).

4 Red notebook, p. 39 (published 1980 edition):

I look at the cessation northwards of the Coal in Chili as clearly bearing a relation to present position of <Coal> Forests. These thick beds of Lignite stratified with substances so like the Coal measures in England (Excepting Conglomerates?) [& absence of limestone?] have been collected on the open coast. Perhaps as at Concepcion. favoured by basin formed by outlying rocks; (such as between Mocha & main land). At Carelmapu. — Within Chiloe: —

5 Red notebook, p. 102:

Shells at Concepcion 50 toises above the sea. = talks of them being packed clean. & without earth. — Moreover that such do not occur on the beaches. Perhaps these facts attest a <more> decided elevation of sea's bottom. beds of shells. 2-3 toises thick.— Vol II. p. 252 [Ulloa 1806.]

358

1835 March Concepcion (2)

grand red, mass noticed as overlying & at its base alternating with the whiter stone on much of the coast between this place & Valdivia. — All the sandstone excepting the fine earthy & white sorts contain numerous lines of pebbles; their quantity varies exceedingly. — more commonly in thin layers; they are generally small less than egg. They consist of black compact clay-slates, which pass into dark green or black slightly crystalline rock; some obscurely porphyritic. — The sandstone is traversed by ferruginous hard plates or veins & some few others of yellowish crystallized Carb of Lime. — There are abundant patches of lignite & much silicified wood (2579), it is in the same slate as in Chiloe. — In a light brown micaceous sandstone there were impressions of shells, but too imperfect to be worth bringing (2583) also in a harder stone the figure of Venuses was shown by curved pieces of crystall: carb of lime. Regular concretions are not numerous. we shall presently find them in other localities:

The only shade of difference between this formation & those of Chiloe. Huafo, Mocha &c to the south, is rather a greater abundance of pebbles (& but indeed on East coast of Chiloe there is even more than here). The identity in mineralogical nature silicified wood, lignite &c &c, the general similarity in height, color & structure, the continuity of the cliffs show the absolute uniformity of this formation. —

Capt. Beechey1 appears to have found a greater abundance of shells & bones of cetaceous animals — I hope they are in the collection of the Geological Society: — I know not what reasons he has to call the sandstone secondary. —

1 Beechey 1832.

358 verso

(a) In the subsequent visit of the Beagle Mr Kent procured for me from the cliffs of sandstone at Tomè. (to the North of Linguen) some shells & other organic remains. They are of species, which I do not know: in which respect they agree with those found at the Rapel, nearly to the age of which every reason would incline it would one to attribute. — They occur chiefly in very large, hard, grey calcareous sandstone concretions. Are associated with silicified wood, which has become perforated.

There appears to be one crustaceous animal & a cross like bone of Cephalopidus ???

The presence of bone of cetaceous animals mentioned by Capt. Beechey brings to mind of strata of Coquimbo, which perhaps are rather more modern. —

Specimens 3160 ... 3174

359

1835 March — Concepcion (3)

Proceeding to the North point of the island, we come to great mass of coarse pebbles, angular & rounded composed chiefly of the neighbouring slates & its quartz veins. On the other or west side of island this the upheaval is shown to be a regular conformable bed which separates the finer sedimentary layers (a) from the underlying hard slates.

These latter consist of a black glossy clay slate which either has smooth even laminae (2585) or is harsher & laminae more convoluted (2584). this latter is perhaps the most abundant. — In certain spots (b) there are immense numbers of irregular quartz veins — in the neighbourhead of these the cleavage 359 of the slate is twisted in all directions. There is also some pale brownish green glossy clay slate (2586). — Generally the cleavage here strikes about NW & SE; the angle of the dip is small direction not regular. in one place I found it inclined to the South. In many places in the harbor these hard rocks were exposed on the beach underlying the tertiary plain. — At Fort Galvez there was much of what I have called ampelite blackish [illeg] slate, soiling the fingers 2845, & a glossy green calcareous slate something like (2586).

The cleavage here was most singularly convoluted, so as to render it quite impossible to determine any common direction. — In a horizontal section of 3 or 4 yards a curvature without fracture such as the following ([sketch]) might be observed. In a small vertical section, a horizontal or lateral fault seems to have twisted the inclined laminae. [sketch] S. beds N

359 verso

(a) A fact we have frequently noticed in other places. —

(b) Mr Greenough in essay on stratification (Critical Examination P 78)1 says remarks "near Cherbourgh, between the little cove of Le Poulet & Becquet, a small village on the East of Bretteville, where beds of killas, both plane and curved, are striped by veins of quartz, I could not fail to observe that the curvatures were most sensible in those parts in which the quartz was most abundant"

[sketch]
Fig. 1 slate

[sketch]
fig. 2
slate slate 360

1 Greenough 1819.

360

1835 March Concepcion (4)

so that the upper extremities appear pushed towards the South. — The appearance is very much that represented in De la Beches geology at p 42 as occurring in Cornwall.

This would appear to be the result of mechanical violence; some of the other curvature showed no signs of fracture. —

Near Concepcion large angular blocks of a coarse granite (a) with large white crystals of feldspar are lying about, it is probable the formation is somewhere not distant. — From the close connection of these black slates & the abundant ampelites of the South, I am inclined to believe them all parts of one formation: this would accord with the general vastness of the formations in S. America. — To return to Quiriquina. —

The slates at the extremity of the island in the space of a quarter of a mile are traversed by several dykes: I had so little time I do not believe all are described.

(1:) Is a very narrow dyke. (vide Fig 1) 4 or 5 inches wide is composed of pale slate-colored feldspathic rock. (2587) which is almost decomposed through whole thickness: is nearly vertical & I believe has NW & SE direction (?): bends twice suddenly at rt angles & there is very thin; is seen terminated upwards by a round cap: which may be only a bend, it looked to me like the real end. —

(2:) a dyke running. NW & SE, irregular in its thickness from 10 to 15 ft wide, nearly vertical; leads off is connected with some branches, one of which is shown in Fig (2). is composed of a massive rock of black grey brilliant dolerite (?) (2588) with minute crystals of glassy feldspar. The surrounding slate near both these dykes dip to somewhere near SW; & therefore has not same strike with line of dykes. —

1 de la Beche 1831.

360 verso

(a) Paps of Rio Rio are 900 ft high & composed of true signite

specimen brought me by Mr Stokes

[sketch]

system of dikes top of mountain axes. dike is succession, hence in injection of exis successive

In present earthquake line of vibration clear & distinct

good

The difference of composition showing different periods of injection, it proves interesting [illeg] been done successively [illeg]

NB. Are the tertiary strata are most hardened coarse through elevation of these dikes but the elevation contained in same lines

361

1835 March Concepcion (5)

(3:) about 18 inches wide, composed of feldspathic rock blended with red particles: very smally crystalline (2589): this dyke for some distance was regularly interstratified with the slate & dipped SW, it then suddenly bulged out & lost its parallelism, thus betraying its true nature

(4:) a mass of thin reticulated veins (evidently injected) composed of a stony mottled feldspathic base, with large octagons of quartz & crystals of earthy feldspar (2590). —

(5:) Dyke about 25 ft wide, irregular, chiefly composed of a very curious snow white stony feldspathic rock, containing large octagons of quartz (2592), parts of this were almost in a state of white friable powder. Is not such substance proceeding from volcanos the origin of the white aluminous so beds so abundant (a) on the coast of Patagonia & found likewise on this side of the Andes? Part of this same dyke is constituted of a partially decomposed feldspathic greenstone base with large irregular crystals of feldspar & octagons of quartz (2591). This dyke runs NW & SE on its northern wall the slate dipped very regularly at angle from 20°-30° to the NE by E, & certainly had the appearance of being tilted by the injection of the dyke. From this point to the north point of island the dip of all the slates is about NE.

(6: & 7:) 2 dykes from 10 to 20 ft wide, inclined, nearly of same nature, (2593). & this is similar, but undecomposed, to variety (2591)

(8:) Is again nearly the same: these three dykes run rather to the W of NW & the last indeed nearly E & W. —

361 verso

(a) The effect of weathering appeared to be to stain this white rock. I could not hammering to discover that within these is a more crystalline kind. —

362

1835 March Concepcion (6)

I did not notice that the slate touching these dykes was sensibly altered; in which respect, in their general form, in the mineralogical nature of some of them. I am reminded of those numerous ones which traverse the micaceous schists of the Chonos Isds & Pen: of Tres Montes:

The fact that the northern point alone of the island is composed of the older slates seems probably owing to their elevation by this system of dykes. Their direction is not coincident with the longer axis of the island; we must suppose that this point has been upheaved by an accidental weakness in the slates or by the intersection of several dykes, which had ran in nearly the same line: This pap of hard rock would protect from degradation the linear island behind to the South of it, composed of soft strata, from degradation, as is seen in other parts, & hence the present shape of island may be probably be owing to these two [illeg] separate causes. The dykes to a certain degree, have been influenced in their direction by the NW & SE strike of the cleavage; although certainly they have often broken through the constraint of the laminae. At northern part of Isd the slate dips NE, near to amongst the extreme southern ones it is inclined to an opposite direction about SW. — It would appear like an anticlinal band line; the band where the dykes are most numerous being the axis. — I cannot however feel sure of this, for the cleavage, for instance near the quartz veins, is so much contorted & is certainly not there from violence. — The fact is worthy of attention.

362 verso [blank]

1835 March Concepcion (7)

for in no locality to the South could I find any sort of proof in the older strata of such upheaval. Here the overlying tertiary formation will presently prove such to have been the case & of course it is probable in every locality. — It is manifestly requisite that the laminae of slates should be nearly horizontal, in order to show any small upheaval: the opposite fact accounts for the absence of such proof in the southern islands. Also if we grant that here the cleavage was originally horizontal, we see a reason, why few, (& perhaps at Valdivia) that uniformity in direction, so very remarkable in the greater part of S.America, is here so frequently interrupted. — It may be doubted perhaps whether all the above dykes are of the same age, or whether it is possible that two dykes, so similarly circumstanced, the one composed of dolerite & the other of a white feldspathic stone, could have flowed from the same inferior fluid mass. —

As yet I have said nothing about the stratification of the tertiary formation: in some few places where gravel gravel was abundant I noticed those curved strata which seem to depend on currents, yet generally the beds must have been horizontal, before their upheaval, for amongst the finest sediments single parallel layers rows of flat pebbles show that that amidst undisturbed deposition an occasional current distributed a few pebbles. & there was not the least irregularity to lead to the supposition

363 verso [blank]

364

1835 March Concepcion (8)

of an original inclined position. At the very northern extremity of the island we have the slates & their dykes, immediately to the South & upon them, regular layers of the sandstones &c are inclined at an angle of 30° to the SW by W; now the main dykes & those which are nearest run NW & SE: It is almost certain: their injection has raised the mica slate on which we see the inferior coarse breccia & finer [illeg] strata repose. — & this has tilted them. — I first saw this inclined stratification from the sea, & I immediately recurred to my theory of dykes, advanced at Chiloe. — it was not a little satisfactory to find so perfect an example. — At the foot of these inclined beds there is another ridge of slates; but the intermediate tertiary beds attain a higher elevation than either & traverses right across the island. — To the South of this 2d ridge of old rock I am not sure what is the stratification, but I believe it is also to the SW but at a small angle. At the very southern extreme the dip is to another (a distance of 2-3 miles) point very N by W; the angle is not constant generally about 15°. — in one spot mounting up to 40°. — This is seen also in perhaps owing to concealed paps of mica slate, such as the one on northern point. — [illeg] The tilting must have taken place beneath the sea, for shells are lying on the surface of the beds. — Near Concepcion I saw some hills with inclined strata: also at Linguen

364 verso [blank]

365

1835 March Concepcion (9)

others dipping to the NW ∠23°. In many most parts of the harbor we see horizontal stratification. — Thus we in this neighbourhead the lines of elevations at a distance from each other have not followed any particular direction. —

In connection with this I will mention a fact, noticed in the passage up to this place. — Between the points Rumena & Lavapie, for a length of about 8 miles, the land which had before formed an even plain, became rather higher & much broken. [sketch] NWN SE

The cliffs were of the same apparent constitution;but the strata instead of being horizontal were inclined at ∠40° to the SSE or S. ENE & WSW. — They were very regular. X Three principal ridges were thus composed & might be traced for some distance into the country. — There were others less apparent, I think at least 8 or 9 lines of elevation. — There was no trace of an anticlinal dip. At each extreme (ie. North & South) of this E & W band of disturbance the inclination was less not more perhaps than 20°. —

The form of the land follows the lines of the elevations; & the whole band is remarkable as causing the most projecting headland in the whole coast: Both these facts were noticed likewise at Chiloe: — We thus see in the tertiary period in the four localities, where inclined strata have been observed, viz Chilo P. Tres Montes, Chiloe, Here & Concepcion, that the lines of elevation subterranean violence have followed quite different directions. In a similar manner we know the old mountain ranges, which are

365 verso [blank]

366

1835 March Concepcion (10)

intermediate between the Andes & the Pacific in Chili run N & S whilst in Chonos they follow various transverse directions. —

To return to Concepcion. — At Liguen I visited one of the best of the coal mines, which have been so frequently mentioned by various authors as occurring in the neighbourhead. The coal appears to be rather what is called "Brown coal or lignite", it is of little specific gravity & only one layer has a brilliant fracture. The mine is not now worked; it was found that the coal when placed in hea even small heaps & attention paid to keep water from it, yet on board several vessel the mass spontaneously ignited.

The super-cargo of one of the vessels himself gave me this account. — It is said to contain sulphur & certainly the inferior sorts abound with iron rust. Is the inflammation owing to any union of these two substances? The coal is said not to be serviceable in the blacksmiths forge. —

The cliff where the coal is dug out is about 100 ft high; the upper part is the friable red earth substance mentioned at Quiriquina, beneath which are various soft sandstone in which the beds of lignite lie.

[sketch] 13 12 11 10 9 8 7 6 5 4 3 2 1

The accompanying section is imaginary for I could not see the whole cliff base in any one bed place:

(1) Soft coarse sandstone containing numerous small pebbles of same nature as those described at Quiriquina:

(2) Ferruginous fine grained sandstone. —

(3) Very irregular layer of brown compact not glossy lignite (2574), in many places about a foot thick: it is contained & mingled with a layer of pebbles: in places it is suddenly

366 verso [blank]

367

1835 March Concepcion (11)

truncate, in others as suddenly thins out & dies away. The bed is slightly curvilinear. — This is rather singular because it shows the coal was brought to its present position by a strong current. —

(4) A more compact sandstone, containing large (1-3 ft diameter) sphaerical concretions of a very hard grey fine grained calcareous sandstone. — in one place nearly the whole bed is composed of pure grains of quartz, thus cemented by calcareous matter & is very hard. (2575). — This seems allied to the most general lowest bed in Quiriquina. —

(5) Soft Hard ferruginous sandstone

(6) Main bed of coal. —The earth is now fallen over it, so that I could not examine it. The miner was with me, & said it is nearly a yard thick, lies on a hardish sandstone, is horizontal. — There were abundant fragments lying about of which (2570: 71: 72) are specimens. Every one agrees in stating that this is most abundant & best source traced in the country. — From this the ships were loaded.

(7) Above this there are exceedingly soft sandstone or agglomerated sand (2576), cemented together by curved ferruginous bands (2577). This may represent the common sandstone of the upper part of the cliff. —

(8) A This passes into a compact indurated aluminous bed, with a [illeg] fracture (similar to what is found at Quiriquina) & traversed by what appears to be vegetable fibres. — (2578) non-calcareous

(9) Soft ferruginous laminated shattered lignite, about a foot thick; not worth anything, irregular showing not quite undisturbed deposition. (2573)

(10) Soft sandstone, whiter than before with numerous convoluted water lines: All these

367 verso [blank]

368

1835 March Concepcion (12)

sandstones contain patches of lignite & innumerable thin layers which vary in thickness from that of paper to a sixpence.

(11) An unimportant bed of lignite

(12) sandstone

(13) The red friable earthy substance. —

Where the mine is the strata are nearly horizontal, but not very regular perhaps owing to original deposition.

About 200 yards to the North (a), the all the beds have a regular dip to the NW at an angle of 23°. —

[sketch] NW

From this latter section, owing to upheaval, the three lowest beds are drawn in the section. — the 4th to 10th inclusive are seen at the mine, & the three upper ones a little further back. — It is perhaps owing to the inclination of the strata, that some have considered this formation as corresponding to the secondary epoch of Europe. —

It is almost superfluous to add that this manifestly is part of one formation with Isd of Quiriquina: & I have already pointed out the similarity with all the beds which I have examined to at least as far South as Huafo. —

Perhaps this corresponds to the plains of Patagonia or is rather more modern? — I formerly suspected the sandstone of coast of Chili were rather more ancient: it is not easy to decide with so few fossil remains. —

Close to the town of Talcuana coal has been worked; the structure here does not essentially differ from the above described one. — The sandstones are more simple & uniform in their nature. — The concretions of calcareous sandstone are large & numerous, but the stone is much softer. The coal which I saw is of a much poorer quality. But owing to the ships from the earthquakes

368 verso

(a) I co did not see the junction of the horizontal & inclined layers. —

369

1835 March Concepcion (13)

it is probable I did not see the best layers: it is of little consequence for I believe Mr Caldcleugh in the Geological Trans:1 has accurately described this section. — There were layers of an earthy lignite or rather a laminated carbonaceous earth: The cliff is chiefly remarkable from the abundance of pieces of silicified wood (2580) & patches of lignite, as in Quiriquina distinct from any layer. — The stratification is horizontal or nearly so. —

The recent elevation of the ground in this vicinity has often been mentioned from want of time I could add nothing new. — On the Isd of Quiriquina, I found extensive layers of comminuted recent shells, which judging from the eye must at least have been 400 ft above the sea. — At lower heights the whole slope of the hill side for a space of 1 or 200 ft was coated with such fragments: with them were many perfect Concholepas, Fissurella, Trochus & great Balanus, also fragments of Mytilus retaining their color. — The perfect shells were packed together in & filled by black vegetable earth. — I am assured they are likewise found on the highest hills. —

In the subsequent visit of the Beagle to this point Mr Kent was kind enough to make some observations, on this subject. — Behind Concepcion, on a hill called the Sentinella, at an elevation of 164 ft. (Barom:) there were

1 Unidentified publication.

369 verso [blank]

370

1835 Concepcion (14)

numerous shells packed in black earth; they were brittle & partially bleached consisted of Concholepas, [illeg], common Fissurella & Venus, Turbo, 2 Mytili & Crepidula, a Mactra & other species which I well know. At an elevation of 625 on the top of the hill there were few Turbo, Mytilus & Concholepas. very more brittle & soft than the last; yet Mr Kent rather suspect they may have been carried up. —

In one intermediate spot he also saw a few. —

Shells at a small elevation, such as 20 ft. (Barom) are extremely abundant all along the E & North side of great bay of Tome & Lirguen. — Shells ,much less decomposed than from those at Sentinella. —

There was with the above species the common toothed Buccinum (or Monodon?) Also a piece of the grand Balanus with small Balani growing on inside. — clearly is not edible. — In parts layers masses of the layer mussels or Choros

All the above shells were either on surface or few inches beneath the mould. —

V. Geology of Beecheys Voyage. —1

NB. It has been stated by (Ulloa?)2 that the Choros grows in deep water, now it is notorious in Chiloe. they are procured, either from rocks on coast, or by wading in at low water, or from boats, with a long pole, perhaps 18 ft long at most, which has a treble or quadruple fork at end between which the muscle becomes jammed. —

1 Beechey 1832.

2 Ulloa 1806, vol. 2, pp. 252-3 discusses the Choros.

370 verso

Capt FitzRoy brought me specimens from the Isd of St Mary.

The sandstones generally are soft, more or less, coarse-grained ferruginous & calcareous. particles rounded of quartz & broken crystals. — Also there is a green compact fine grained sandstone, moderately hard. — a concretionary structure, with minute particles of broken crystals. — These is one spot are traversed by vertical veins of white calcareous Spar containing iron pyrites. —

In Arauco near the R. Laraquete Capt FitzRoy noted in a sandstone, a thick stratum of the lignite. — Specific gravity & appearance almost identical with best Cannel coal. — rather more stratified & not quite so conchoidal fracture. — Indeed this is the character of much of the best Concepcion coal or lignite. —

The whole country from Concepcion to South part of Chiloe (in a distance of nearly 500 miles) is carboniferous. — or lignitiferous. —


This document has been accessed 2802 times

Return to homepage

Citation: John van Wyhe, editor. 2002-. The Complete Work of Charles Darwin Online. (http://darwin-online.org.uk/)

File last updated 12 March, 2014