RECORD: Darwin, C. R. Geological diary: Valdivia. (2.1835) CUL-DAR35.343-346 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 5.2011. RN1

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 Valdivia 9-21 February 1835, see the Beagle Diary, pp. 525-536. See the illustrations of Valdivia drawn by FitzRoy and P. G. King in Narrative 1.

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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.


343

1835. Feb.y Valdivia

(a) Proceeding from Chiloe along the coast to this place there is a striking resemblance in the external form to what we have seen on the outer coast of Chiloe. — Nearly the whole is based on a hard slate, doubtless mica schist, which further inland is covered & smoothed over by plains of softer materials. Riding southward from Baldivia, I crossed the crystalline rocks, protected in some few places by clays & gravel, till the at the Mission of Cudico the Llanos were extended before me. — These plains I there saw a pale earthy (i.e coarser grains imbedded with fine dust) not very soft sandstone, divided into horizontal beds. —

The substance is said to be found in all parts of these plains, which extend beyond Osorno & probably are united to those of [Carelmapui].

I heard if lignite in different localities, at P. Estagillos it is said to be very good quality. — At Baldivia itself we meet with some tertiary strata; they consist of more or less coarse & soft sandstone; in one place, the I found numerous, imperfect fossil remains, they consisted of Venus, Mytilus & Solen (2547: 48: 49: 50) 2547: ... :50. I believe of species which now exist. — In another place, there were layers of flattened balls of a yellow soft substance, which possessed a peculiar taste; perhaps these are the altered roots of some large trees (2551) 2551. The sandstone which is attached to the fossils is rather coarser, than what is usually common found, as there are no concretions — no hard veins, no alternations of slaty clay.

343 verso

(a) Looking at the map of S. America, a great change in the form of outline of the coast may be seen to commence at North point of Chiloe: to the South of this the line is broken by infinite Islands & bays; to the North of this we have an inhospitable coast with only 2 or 3 harbors. —

Yet it is pretty certain that both the primitive & tertiary formation in both is identical. —

I have already in my notes about Chili, stated that there was a period. when that coast was must have been equally distinguished by its indentations & islets. —

343A

[sketch by P. G. King]

Entrance to the Valdivia River

Pt. Nieblus Pt. Praja

343A verso [blank]

344

1835 Feb.y — Valdivia

From these reasons & the nature of the organic, I conjecture this a more modern formation than the principal one of Chiloe. — It may be coeval with some of the lower plains of gravel, the structure of which at Chiloe, made me believe to be posterior in formation to the main deposit. — In one place I found the sandstone about 150 ft thick. [sketch] I here noticed rather a curious appearance: a curved layer (A) of softer stone traversed the cliff of sandstone, which in all parts was divided into very regular layers which dipped at about an angle of 45°. —

Generally the tertiary formation may be seen in the harbor forming a fringe (V sketch by Mr King1) round the base of some of the mica slate hills. This border of a plain appears to my eye, exactly the same height (60 ft?) as a similar fact noticed at S.Carlos. — I feel little, that here as well as on the coast of Patagonia, that an upheaval has acted along a whole line of coast (here 150 miles apart) with the same force (a). & that being of unusual energy its effects remain apparent, while all traces of separate lesser ones are soon obliterated. —

With respect to the ancient crystalline rocks. — We find the formation varying much in its mineralogical nature. — The most abundant is mica slate which varys in its color, often being very ferruginous & which contains very many distinct crystals of feldspar (2553). So that in many places it ought

1 Philip Gidley King (1817-1904), Midshipman on the Beagle.

344 verso

(a) I should perhaps add that the beach & its immediate vicinity being of nearly same height, subsequent to there equal upheaval it forms a fringe or plain of similar elevation. —

345

1835 Feby — Valdivia

rather to be called gneiss. — This is the same sort of rock, which I saw in one place at Lowes Harbor. — By immersible passages we have much black mica slate (2552) 2552 & this passes into ampelite. There are some chloritic schists: these latter precisely resemble the common varieties of the islands of the South. — The number of quartz veins is not so numerous, the assumption of so much feldspar marks a decided change in the slate. — The rocks are here auriferous; wit they contain much iron, hence the soil is of a very bright red color. — I believe this formation connects by transition the gneiss of Chili, with the grand mica slate formation of Chiloe & Chonos. (a) —

cleavage

The cleavage is generally well developed, but its direction is most singularly subject to variation: I have no where in S. America. found so little uniformity. — Perhaps in the harbor SW is the most common dip & on the road to Cudico NE: but there are numberless exceptions. —

Nearly all the laminae of slate seem to form parts of very large curves, & hence the irregularities. — In one place I noticed a flat topped arch, on each side of which for some distance the slate had a directly opposite dip. — The general ∠ of inclination is not large; I saw some however with a dip of 50° or 60°. —

The formation is coated in places, as at P. Huechucucuy by a mass of breccia, which is of considerable hardness. —

345 verso

(a) I omitted to state, that in only one place, the road to Cudico, I saw any rock penetrate the mica slate: I there found a slate & colored porphyry abounding with crystals of feldspar; indeed here I did not actually see the rock in situ, but most numerous angular fragments. —

The form of the country of Valdivia, as at Valparaiso is a high sloping platform perhaps 1000 ft or more traversed by numerous valleys. — These crystalline slates may be considered perhaps as part of the formation on East side of Andes. —

346

1835 Feby

Concepcion

Coasting northwards from Baldivia, we see the micaceous slate extending about 30 miles (S. of river of Tolten) where low land commences, which gradually rises into high & white cliffs of a tertiary formation. (a) —

The Island of Mocha is in all probability part of this. — Mr Stokes was kind enough to bring me off a large series of specimens. The stone is a compact fine-grained sandstone, which is slightly calcareous, with parts more crystalline & possessing more carb. of lime. — The shells are but slightly altered. Turritellae are excessively abundant, together with a Murex & Venus. 2562 ... 68 — Both the stone & the fossils are exactly similar to what we meet with at Is of Huafo. — The stone likewise contains patches of lignite. —

The island is level at the top, about 1000 ft Highest point 1240 ft ∠r observ: which would appear to be about equal to the general range on the main-land. — It has formerly in extent been much more extensive: reefs composed of similar rock extend to a distance of 2 or 3 miles. — The channel which separates it from the coast is 20 miles wide but shoal not more than 20 fathom deep. — On the island there is the same rate, which is not met with at Chiloe &c &c. —

The cliffs of same color &c are continued up to the Altos of old Tucapel & from that point up to Concepcion they will be described in the paper in that place. —

About 10 miles South of the Altos & some way in the interior there is a range of hills which probably are of mica slate. — At P. Rumena, the strata are inclined (b), a fact which will be noticed in the [sentence breaks off]

346 verso

(a) The upper part of the cliffs is stained red & appears a change, which corresponds to the usual capping of gravel. in Patagonia & Chiloe. — perhaps owing to the crystalline slates which we now see them give a red soil. — rising into coming more gneiss porphyry =

X of the interior having been raised into the line of tidal degradation; =

(b) paper on Concepcion: the Island of St Mary appears entirely formed of same soft white brown sandstone. —


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

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