RECORD: Darwin, C. R. [Coquimbo notes]. (5.1835) CUL-DAR39.152 Transcribed by Kees Rookmaaker, edited by John van Wyhe (Darwin Online,

REVISION HISTORY: Transcribed by Kees Rookmaaker, corrections by John van Wyhe 3.2011. RN3

NOTE: 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 permission of the Syndics of Cambridge University Library and William Huxley Darwin.

See the introduction to the Geological Diary by Gordon Chancellor.


May 31st [1835]

252 ft   This expresses the height of plain where quarries are, their plain, none are higher
30.130 TA 57°
30.400 TA 64°

On road, a little South of the City, there is a small valley in grand plain, in which two quite low plains are seen, on both of these an abundance of recent shells: doubtless correspond to 2 lowest of town of Coquimbo. —

In the main plain just above there is a pap small grained granite associated with some dark hornblendic porphyries. = I found all the Losa, dip as the coarse freestone made of pebbles of shells is called, & overlying tosca dip to, as nearly as possible at 10°. — the ground here in furrows, I suppose elevation? —

Further to East than [quarries], the formation appears horizontal. — The tosca rock, especially the stalactiform kind forms thick veins, as wel as cap to the Losa. = The surface of the tosca, where barometric measurement was made, was covered by fragments of blue Mytilus & pieces of Conchlepas; now Conchlepas is very rare in the tosca, as is Mytilus & never blue: yet shells in tosca are I certainly believe, recent: In the conglomerate, which cover the little [illeg] of plain in Herradura.

151 verso

& which is cemented together by calcareous matter, must be of a date posterior to elevation of upper plain. Hence we have absolute identity with shells on beach, & some with partial color: The Calyptraea striated from the crown is conspicuously common & the common pecten. =

The Losa, on its inferior margin, of no great thickness perhaps 20 ft. blends with & [paints] by calcareous matter, a finely cemented coarse aggregate of broken shells: in parts more or less arenaceous: in some of the sections, these almost consisted of different species of the family of Balanidae, with fragments of the common pecten: in another spot these were associated with great numbers of small oysters (diff. spec: from great). (some of which were yet adhaering to vast contained angular blocks of hornblendic rock)

The shells here are partially silicified altered: there occurred a part of bone in same slate with the hard shelly rock. there were strata of yellow & brown very fine & sometimes aluminous sandstone: oft some beds with much iron rust. —


These & the rock. contained numerous line. & scattered pebbles: (an increase of these is the only difference where Big Oysters were found in a coarse conglomerate). — We see in these strata a mineralogical blending, as well as zoological blending of shells: the small oyster is not known here: also the tosca has not the commonest shells now found here: these specimens 2791—7 were found with Big Oyster & crenated Mytilus. so are though both rare: hence they belong to oldest bed: yet may appear same with my intermediate: a large muscle is common to lowest bed & intermediate:

The pecten is common to all three. —

although I have not specimen. — I do not consider it possible to mark any line of distinction; the shells on surface same as Beach lowest shells most different: a gradation between those:

Lowest beds a compact soft fine grained ferruginous sandstone here without concretions: —

Proof of small valley formed by sea [sketch] vertical old cliff with fringe a yard thick in parts of more recent sticking to it. — : Tosca, all the shells. I know — shelly rock may same (no Quintero [illeg]): Lowest very few I knew. =

This document has been accessed 1886 times

Return to homepage

Citation: John van Wyhe, editor. 2002-. The Complete Work of Charles Darwin Online. (

File last updated 27 November, 2015