RECORD: Darwin, C. R. [Hobart Town field notes]. (2.1836) CUL-DAR40.97-99 Transcribed by Gordon Chancellor (Darwin Online, http://darwin-online.org.uk/)
REVISION HISTORY: Transcribed by Gordon Chancellor, typed by Jan Nicholas. Transcription corrected by Kees Rookmaaker, corrections by John van Wyhe 4.2011. RN1
NOTE: See the annotations in the version of this document published in: Banks, M. R. and D. Leaman eds. 1999. Charles Darwin's Field Notes on the geology of Hobart Town — A modern appraisal. Papers and Proceedings of the Royal Society of Tasmania 133(1): 29-50, Text.
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Reproduced with the permission of the Royal Society of Tasmania, the Syndics of Cambridge University Library and William Huxley Darwin.
Feb 7th  — In the town: Sandstones & Greenstones alternately appear, & perhaps in equal proportion — The strata of sandstone inclined, — In entrance of Harbor observed, a SW dip, not great. — Sandstone generally fine grained, particles of quartz with very little cement, — much fine grained laminated, & mottled pale red — alternate, sandy clay shale —
There are many layers of very thin black carbonaceous matter & some Carbonaceous shale.—
Some Sandstone ferruginous
I am doubtful whether stratification generally = -tal; on account of current cleavage:
Very general resemblance to Sydney — Here Trappean rocks far prevalent, — Basaltic Plateaus columnar — near mouth of Harbor. —
Greenstone, generally well characterised — coarse grained — even containing large cysts of hornblende — in Government domain — a
granitic syenitic greenstone —
Only found one plane of contact, where some sandy shale & ferruginous sandstone were in close proximity to a decomposing greenstone — The strata were highly inclined & dipped from the mass ∠
of 68 or 70 — The shale, judging from fragments altered into a Porcelain rock & the sandstone rendered much harder & compact. —
Thus origin of some of the trappean rock explained = Conical hills over whole country
Fossil shells in district of Launceston. —
Walking coast to South on E side of ferry; greenstones; then in close neighbourhead, a quite white — pottery-like very fine grained sandstone, — in parts rather more sandy in others frequently more aluminous or porcelain like (3447:48) vide description is crossed by many veins ferruginous, which project upwards passes into & overlies a blueish rock, possessing more of the character of clay slate. — These two contain few impressions of Terebratula & a very few rounded pebbles of quartz rock — Siliceous stones, like what will be described & one volcanic looking pebble. —
Strata dip at small ∠ Easterly. — I believe but am not sure, this is coeval with general sandstone. — (NB observed flat at high water line, I remember it is same at Chiloe & Port Famine) New Zealand — There appears to have been a general rise — Shells on sides in beds in very many parts — get deep water in coves; & similarity of productions
between here & Australia, & soundings in channel as if subsidence. —
Water is said to be retiring. — Earthquakes?
Beyond these white beds we find ordinary sandstones with current cleavage & then again appears the greenstone —
Ascending the hills, some hundred ft behind the coast, we met with common greenstone but the commonest rock is a greenstone (3453) — syenite — On the summit there were gently inclined strata of altered rocks — Siliceous white, & blue — Siliceo-porcelain rocks (3449: 3450) & 3451 — Greenstone (?) pap belonging to the axis of the hill?
I must believe from these came the pebbles in the lower beds; otherwise I should think, the same only slightly
metamorphised [sic].— On a neighbouring & higher hill, whole rock a dull red ordinary sandstone — Do the hard rocks belong to a distinct formation?
Tuesday 10th [sic: should be 9th.]
Walked coast South of town. — Greenstones; generally globular concentric structure: in close connection with inclined strata, (but not inclined by this rock) of sandstone conglomerate, containing numerous pebbles of the underlying greenstone;
the white chert with organic impressions &c &c:
alternately covered with softish Sandstones; which however in parts, are firmer & whiter & are quarried — associated with layers of slightly indurated clayey beds & other ferruginous ones: — perhaps inclination from original deposition: — Many of the white pebbles strictly resemble the Porcelain beds of yesterday: —
Still travelling onwards, preponderant quantity
[illeg] generally, what I call syenitic (like 3453). — We then meet with some white softened, rather thinly stratified mass of an aluminous sandstone: (somewhat like those of Chiloe) which rested on a sandstone & it contained some darkish impure clayey beds — on these rested a stratum of compact (few minute vesicular cavities) 3467 blackish basalt, containing numerous atoms of red Olivine.—
(NB in the white beds, there was one stratum brecciated with pieces of same kind with itself: would not these cases be produced by violent Earthquake beneath the spot at time of deposition.)
This basalt had a greenish tinge externally: it was separated from a superior stratum of similar kind, by
(3469) angular bed of Wacke or vesicular clay or tufa, for it wore all these appearances it contained balls & masses of true basalt.
I found by tracing structure, it is decomposed scoriae, clearly separating two streams: These & the lower sandstone beds all dipped S at angle of about 30°. — following for a few 100 yards the basaltic beach, came to cliffs entirely composed of cemented fragments, very vesicular, & possess vesicular cavities linear following sweeping lines, lined with green matter (3468).— Amidst fragments [to] of red jaspery & porcelain rock. — This flat point, now formed of such confused, vesicular rocks probably old crater, now no trace of do — This is the first of the great basaltic columnar streams which we saw at the mouth.— Directly beyond this point, & near, we again had, the greenstone
its appearance externally is quite like that of granite — indeed I believe it is such, but imperfect (V 3455). — Beyond this we have strata full of organic remains, which will be described — Beyond this immediately the granite, which continues for some miles along the coast.— The organic beds appear here the lowest — The Volcano has burst through these. — It may be suspected this granite has been protruded subsequent to the organic beds. = These latter consist of gently inclined Strata of 3 varieties and their intermediate variations — a white cherty rock with grains of quartz.
(3457) — a blue, slightly calcareous, siliceous clay not laminated slate
& a (3458) & a brown rather softer do (3459) — These two latter in places are softer & thinly laminated — all three are composed of impressions of Retepora & other coralline (Mem. Limestone of Argyl) & some few Terebratulae. I saw impressions of one Univalve & a large Bivalve —
Some of the Corallines, pretty silicified,— at most few pebbles of quartz, blue siliceous sandstone & a glassy micaceous clay slate. —
This is evidently same as beds of yesterday; there are specimens from near Launceston identical (3470 3471). — The neighbouring mountain, is in its lower parts thus constituted; these beds are covered to the thickness of some hundred ft, with rather siliceous reddish, yellow, or white sandstone, with granules of quartz (3466), — There however at summit a pap of dubious greenstone (3456) & lower down another of Basalt. —
Thus we see, Reteporae strata, with their sandstone, have been preceded judging by pebbles by siliceous sandstones, (which rocks perhaps were those I yesterday examined) — have been probably upheaved by the syenitic greenstones, otherwise in such close proximity, there would have been pebbles.
These two distinct formations have been
succeeded by other sandstones, clays & shales which alternate with Lavas — & partly amongst which most of the freestone will be classed. — Thus we have sandstone of three distinct ages. — perhaps the most modern in mere fringes. —
A good deal of Resemblance with New Zealand & with Australia.
as in the sandstone conglomerate (most modern) there was white freestone, perhaps some such occurs in parts of this series, & the sandstone in the town must remain of doubtful age.
NB. this most modern sandstone was crossed by ferruginous veins in nests, like older series
I found shells in such quantities 10-30 & 40 ft above high water all along fields; I am tempted to believe upheaval. — Comminuted, difficult to decide not having visited wild parts. Agriculture. — Parts in heaps — Yet very much spread — [symbol here like "Z" with vertical middle limb] on small scale, few pebbles on upper surfaces. —
Strata with impressions, half Slate, chert sandstone — Limestone.— capped by sandstone, reddish [but] did not see stratification: — up to perhaps 12-1400 ft — rest greenstone of one character crystals of hornblende — columnar — large flat surface — grand extensive formation many ditto mountains — enormous blocks, numer
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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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