HOBART.Plates iii. to ix.
(ReadJuly 14, 1913.)
Morethan tJiirty years ago Mr. R.
M.Johnston, in a
paper (1) read before this Society, pointed out the great
geological interest of asection exposed on the western side
of Brown's River-road, near
Mr.Johnston's observations hold good
present day, though
haveto be altered. Mr.
havehere a volcanic rock of
the Basalt-aronp overlying sedimentHry rocks, which con-tain an
of these Mr. Johnston sent to the late
wasable to identify
themwith species well-known
fromthe auriferous drifts of Victoria.
would 1e a
mostimportantfact, but the flora, according to
the Baron's determination, is of such an extraordinary nature, thatit wouldbe almost unique, if his determinations
could be accepted as correct.
Manyyears later Messrs.
and White examined
cameto the conclusion that it is a basalt
in which Fayalite, the red variety of Olivine, has replaced
I have frequently studied this section, remarkable in
morethan one way,
cometo the conclusion
that it allows for an intei-pretation quite different
himis of tectonical nature. Mr. Johnston
thinks that the southern pori}ion of the section has been
thrownup, but a careful examination has convinced
that it is not the southern portion thathas moved, but the
northern one; further, there is not an up-throw of the
(1) Notes showing that the Estuary of the Derwent was occupied by a fresh water lake during the Tertiary Period. These Papers and
Proeeedinos, 1881,p. 74-.
(2) Notes on a Favalite Basalt from One Tree Poini..—These Papers and
96 SECTION AT ONE THEE POINT,
southern, but a
down-throwof thenorthena portion.
ends of the leaf beds are turned
upwardsnear the fault,
andthis admits of only one explanation, viz., that
downwardsin relation to the southern one.
If this view be admitted, the interpretation of the section
tak«s a (^lifferenl aspect at once,
down-thrownportion to its original level. I further noticed that theleaf beds ofthe northern portion are considerably thicker than those of the southern one. Therefore
mustassume that, if the portions on either side of thefault
originally formed one continuouslayer, a considerablepart
of the leaf beds
must havedisappeared in the southern
(remaining) portion. This observation holds good, whether
the southern portion is
whetherthe northern portion has slid down, as
Theorigin ofthecurioiisBrecciaseems to
some-whatdoubtful. Mr. Johnston thinks it represents old landslips
whichfell in the "lake."
manyobjections to such a view,
whichI will set forth
This section is perhaps the best illustration of the
moderngeological history of Tasmania,
sequence of strata, as well as its tectonical features, afford
massofinformation regarding the latestphases
of the geological evolution of Tasmania. 1 think it will, therefore,
beadvisable to describe first the section as it
nowstands, then to' discuss its different membei-^, and,
lastly, to deducethose conclusions
which seemto afford an
explanation of thefacts observed.
Thoughnot ecxposed at
OneTree Point, it is pretty
certain that the lowest
wholeseries is a yellowish sandstone, but so far the contact of Sandstone
andBreccia has not been observed (3). It
maybe that thelatter restsimmediately on the Sandstone, orthat
beds of different,
moreargillaceous nature, intervene
Onthe whole this is of little importance as far as the questions here discussed arc concerned, if
always bear in
mindthat the Breccia does not fo-rm th<>
base of the series.
(3) A little further towards Hobart a sandstone of yellowish colour appears from underneath the Breccia. There is no doubt that this
sandstone belongs to tlie LeafBed series, of wlurli it most probably
BY FRITZ NOBTLING, M.A. PH.D. 97
M.Johnston has already noticed that the leaf
bed series asa. whole, wherever they occur, are not found
higher than about 40 feet a,bovethe present sea level,
fromthis psculiai^ deposition he concludes that, excepting
for the south-easterly dip, the leaf bed series is practically
sameposition as it
whenit was deposited.
turtJier assumes that the strata in question are of
andin hisfirstpaper he draws a vivid picture
of the "lake" filling
upthe Dei^vent estuary.
that Mr. Johnston's hypothesis be correct, it requires
(a) Thatthevalley of the
Derwentexisted almost in its presentshape jDievious to the deposition ofthe leaf bed
(I)) Thatthe stratadeposited in this lake gradually
thinouttowardsthe hillranges on either side.
Thefirst proposition assumes that the deep canyon of
wascompleted to about the present day level
in Pre-Eocene times (4). In other words, that the greatest
portion of the
Derwentvalley is geologically of very old
age (5). This is a very fascinating theory, but it mainly
dependson the age of the leaf bed series. There is every reason to believe that the Tertiary strata of Australia are
muchyounger than Eocene; in fact, it is
pro-bable that they are not older than Miocene. Natui^ally
wouldgreatly reduce the age of the valley in
was whosewaters deposited, the leaf beds- This
whichcannot be decidedfor the present,
andw'e have to leave it
an openone, but I
donot think that
Derwentvalley dates back as far as the
Asregards the second proposition,
should expect tliat the leaf bed series gi'adually gets
thinner towards the shore line of the old lake,
ridge, for instance, on the western side.
ThoughI ob-served the leaf bed series on the lower part of the
MountNelson, I have net been able to ascertain
complywith this requirement of the lake
hypothesis or not. If anything can be said from the
ratherunsatisfactoi*}' outcrops itis this, that the thickness
of the leaf beds is not reduced towards the hillside.
(4) For the sake of argument I accept the view that the LeafBeds are of Eocene age, though according to more modern researches this
view is no longer tenable.
(5) Accepting the present view ofthe Eocene age of the Le-afBeds
98 SECTION AT ONE TREE POINT,
particularly his Fig. 2, the section opposite
BayPoint, offer a
mostserious objection to his
leastways they are capable of quite a different
bimin Figure 2, the leaf beds abutting against the Palaeozoicrocks are bent upwards.
effect will never be produced during sedimentation; only
downward movementof the strata can
pro-duce such an eft'ect. Mr. R.
plainly suggests the existence of a trough fault; that is to
say, that the leaf beds were deposited at a
level than they are now,
andthat subsequently the
twogreat faults, one of
whichis running approximately parallel to the
andthat during this downwai'd
wasbroken, the different pieces acquiring the southern
Ofcourse, ifit can be proved that the leaf bedseries
arepreserved in a trough fault, the "lake" hypothesis,
not-withstanding itsseductiveness,has to be abandoned. Before
forthe purposes of this paper I acceptMr. Johnston's lake
hypothesis, because the
mainresults will not be affected
byit. Should, however, future investigations prove that the leaf
nowinside a trough fault,
of theseemingly incongruous features
M.Johnston has already noticed that the leaf
bed series have a very unifoi'm dip towards south,
bya series of faults,
whichrun apparently nearly
parallel in north-west, south-eastern direction. These
faults have produced a feature
knownas stepfaults; thafc
is to say, while one- end of the
stationary, the other
downwards.In the leaf
bedseries apparently the southern
downwards,while the northern
maypoint out that this is a feature frequently obsein^ed in strata preserved in trough faults;
for instance, in the coal basins of Giridih, in Bene^al.
Thesequence of the strata as seenin the above sectioii
isas follows (see Plate iv.):
BY FRITZ NOETLING, M.A., PH.D. 99 1913.
beds-(b) Altered, 4 to 6 feet. (a)
Normal,about 90 feet.
(3) Breccia, about 12 feet.
(2) Leaf beds, normal, about 40 feet.
(1) Breccia, about 80 feet.
(b) Southern part.
Humus,about4 to 5 feet.
ii. Leaf beds.
(a) Altered, about 4 to 5 fe^t. (b)
Normal,about 40 to 42 feet.
(c) Arenaceous, about 18 feet.
i. Breccia, about 130 feet.
Thesequence of strata as given above shows that
the two parts of the section north
andsouth of the fault
Thedifferences are slight only,
maynot bematerial, yet they
haveto be noted.
mostimportant is the appearance of a Breccia
bed in the lower portion of the leaf beds;
the surface it has a thickness cf about 18 feet, but it very
rapidly becomes thinner in the direction of the dip, and
has probably died out completely before reaching- the level
of the road. This conclusively proves that though the deposition of the leaf beds
bylayel's of Breccia.
Inother words, the agencies which produced the Breccia continued to
extent during the deposition cf the leaf beds,
the whole it
wouldappear that the Breccia is older than
the leaf beds.
Theleaf beds are overlaid
bya fairly thick layer of
whichis, however, of small horizontal extension,
andrests unquestionably on altered leaf beds.
Thesouthera portion is
somewhatobscured: the altered
leaf beds foi-m a conspicuous yellow band, which extends
from underneath the Basalt
upto the fault; above this
are about five feet of leaf beds,
whichappear as if they
andseemingly dip in northern
direc-tion; these are followed
bya bed of
a conspicuous dark band.
Theremarkable feature is that the
ap-100 SECTION AT
Pw.S. TAS. plies to the
worked upleaf beds. I shall
Thesouthern portion appears
Undera thick layer of Basalt which, rapidly thins out in northern direction follows a layer of
vesicular Basalt, which rests on altered leaf beds, of
con-spicuous yellow colour, of about 3 to 4 feet in thickness;
below these are the
arenaceous towards the base, resting
onBreccia of gi'eat
thickness-These leaf beds are again observed at sea level, abo<ut
40 to 50 feet below the
Description of the Strata Observed.
A. The Breccia. (PI. v.
M.Johnston has given a
de-scription of this very rock,
well noticed. It is "a motley assortment of coarse
hugeangular blocks principally of the fossiliferous
mud-stone." Thisfeature is exceedingly well
shownin Plate vi.
doubtthe blocks of
far the majority, there occur
manyboulders of Diabase
frequently of large dimensions (See Plate v.). These
boulders are always well rounded,
con-trast with the angular blocks of mudstone.
Atthe northern portion a
mudstoneboulder of fairly
large size is deeply pressed into the underlying leaf beds. (See Plate vi.).
Thedark lines of stratification seen in
the white leaf beds closely follow the contour of tJie
andthis proves conclusively that it
pressed into the leaf beds while these were still in a
havebeen greatly puzzled as to the origin of this
Breccia. It unquestionably closely resembles a
bythe action of glaciers,
andI think that
nobody wouldhesitate to consider it of glacial origin.
Onthe other hand,
haveso far been found,
andI cannot quite
howa glacier could
havepassed over bods
which wereunquestionably in a soft
andpliable state (7)
(6) To judge from Mr. Johnston's figures th^i Breccia could be observed at sea-level in 1881. During
myvisits the Breccia was not
visible, being covered under a layer of debris.
BY FEITZ NOETLING, M.A., TH.D. 101
themfurther than pressing a boulder
into the top layer. Mr. R.
M.Johnston thinks that the
Brecciarepresents the debrisof landslips that fell into the
"lake." This is a very fascinating theory,
convincing at first, but on closer inspection there are
manyobjections to it.
Tobegin with, there are certain
rea/sons against the lake hypothesis, but I will let that pass (8).
mainobjection to the landslip theory is
the composition of the Breccia;
howis it possible that in
a debris produced
bya landslip well
mixedwith angular blocks? In all the landslips I have
seen inthe Himala^^asthe debris consisted of shar]o angular
whichwere, moreover, never
matrix as seen at
OneTree Point. Further, if the
landslip fell into the water one should assume that the
action of the waves started at once the process of sifting.
Instead of preserving its present appearance,
of all sizes are irregularly
mixedup, the heavier blocks
wouldhave eventually settled towards the bottom, leaving the lighter ones near the top. In fact, I cannot imagine
howan entirely unstratified
remainedas such in the
anylength of time.
And,again, if the
debris fell from above,
howis it that only one solitary
block has been observed to be pressed into the underlying
mustbe keptin mind, in a pliable
whenthe Breccia was deposited? If such a
PLvi., fell on the top of a soft
one should imagine that
became imbeddedin it.
But though somelarge boulders
were within an inch or so
fromthe top layer of tlie leaf
beds, they were not pressed into it, as is well seen in Plate
Thewhole appearance of the leaf beds and Breccia
proves that the deposition of the latter on the top of the
musthave been a quiet, rather than a violent,
pro-cess. Further, the Breccia layer in themiddle of the leaf
beds in the northern portion
north; that is to say, towards a direction
were no cliffs
whichthe debris could have fcillen,
wouldnot lay too
muchstress on this.
everything into consideration,this "landslip" hypothesis
af-fords, therefore, such a lot of difficulties, that it is
Forthe present I
amunable to replace it
andthe origin of the Breccia is still a
wecould conclusively prove that it were a
102 SECTION AT ONE TREE POINT,
manyof the present difficulties
argumentsagainst the moraine hypothesis is the present position of the leaf bed series, but were the
view that the leaf bed series rest in a trough fault, that
is to say, are
nowin a lower position than they were
originally, correct, one of the chief objections against the
glacial origin of the Breccia
Theleaf beds represent a series of finely laminated
clay of whitish colour,
whichtowards its base on the
exposed to the air the leaf beds soon crumble away,
this unfortunately renders the presei'\'ation of the fossil
M.Johnston has given a large
figures of plant remains collected
Theassociation of this
flora is rather a curious one; next to such genera like
whichoccurs in cold
andArctic climates, or
whichis essentially a genus preferring a cooler climate, or Quercns
andSalix, also genera existinor in
temperate cooler zones,
Sapo-tacites, or Cassia, genera of essentially a tropical nature. It is very difficult to accept such conflicting evidence as final,
andconsidering the very unsatisfactory state of
preservation, I cannot help thinking that
mistake has been
If it could be
shownthat the tropical genera
been erroneously determined as such,
andthat only genera
indicating a. cool climate occur, the theory of the glacial
origin of the Breccia
wouldgain considerable support.
Ill that case the leaf
hadto be included in the
(9) At the same time it is pretty certain that a good many of the leaveswere fairly macerated when they bi^came deposited in the silt.
(10) During the discussion that followed the reading of this paper Mr, Rodway remarkedthat at thattime wlien Ettingsliausen determined
these leaf-remains, phyto-paheontology was in rather a backward state, a remark with which I heartily agree. When I remember the
unsatis-factory state of our knowledge of fossil i)lant remains, even as late as the end of the seventies or the beginning of the eighties, and when I
consider the great progress made sincf". it is more tlian probable that Ettingshausen's determinations are more or less wrong. Mr. Rodway
statedfossil leaves were usually giventhe names of tliose recent genera with which tliey liad ageneral resemblance,a practice which is entire-ly wrong, because, withoutthe knowledge ofthe fruitsorblossoms,which are farmore important than the leaves, the determination must always remain doubtful. I think that every jjala^ontologist will agree with
BY FRITZ NOETLING, M.A., PH.D. l03
wouldbe cf Post-Pleistocene
age. This view
muchbetter agree with
madealong the north coast of Tasmania. I
repeatedly expressed the opinion that the view of the
Eoceneage of the fossiliferous beds near
Ina,subsequent paper I will
mostprobably contemporaneous with the
stan-nifei-ous dnfts. Considering that Mr. R.
identified one cf the leaves found in the
with one of the
OneTree Point, viz.,
Sapofacifes oiigonevrif^, thesynchronismof the leafbedsin
Wynyardbeds can betaken as
anestablished fact. Granting this, the leaf beds are of
andanother objection against the glacial
origin ofthe Breccia
Ontlie other hand, if it could be proved that the
genera indicating a cooler climate were wrongly
andthe flora werereally one indicating a wai-mer
climate, the glacial origin of the Breccia
quite disposed of, because it
wouldbe quite possible that
instead of one glaciation only there were several
warmerperiods, as in
America. This is a view that
mustnot be entirely
Forthe present this question
mustbe held in
abeyance till a revision of the determination of the flora
has been made, but on the whole I
aminclined to think
that thefinal verdictwill be toconsider the leafbedseries
as of Pleistocene but net of
C. Thf^ BasaJt.
(PI. vii., viii.,
TheBasalt overlying the sedimentaiy rocks shows
somepeculiar features. In the first instance it
hada rather low t-emperature
is conclusively proved
bythe small alteration or
meta-morj^hism the leaf beds sustained.
evi-dence of fritting been observed; all the alterations
pro-duced ai"e a change of colour
fromwhite into yellow,
even this is not always maintained.
of the Basalt is further proved
bythe small alteration of
the included fragments ofrocks through which the
broke. This frequency cf inclusions is another peculiar feature;
someof these are of large size, but unfortunat-ely
haveso fai' not been examined. Mr. Johnston
104 SECTION AT ONE TREE POINT,
"surrounding stratified rocks. "
searched for fragments of the Palseozodc mudstone, I failed
to find them.
Onthe other hand, fragments of schistose
which donot occur
numer-ous. This seems to indicate that the
through beds belonging to the
(11)-Probably the explosions preceding the eruption completely
shattered the overlying Palaeozoic strata,
eventu-ally the eruption of the
magmatook place it only filled
the cauldron-like cavity produced
bythe explosions, en-closing
andenveloping only rocks from greater depths.
Theexamination of these inclusions is another
that awaits solution,
muchinformation as t#
the coimposition of the strata in greater depth
Anotherfeature of the Basaltis its absence of
coluni-nar structure (PI. vii.) ; instead of the customarv
the Basalt is massive,
andrather inclined to part in
hori-zontallayers- This peculiarity
makesit appear asif there
hadbeen several eruptions producing different flows.
anyevidence; the Basalt presents
the appearance of one prciduced
bya single eruption.
Sometimesit shews a vesicular appearance, particularly in contact with the underlying strata.
Butsuch a layer of
vesicular Basalt right in the middle of the massive one is
also seen at the southern
endof the section. I attribute
it to a particularly strong percentage of water in this
par-ticular parti of the
mustnot be taken a^s proof of several eruptions (12).
examina-tion proves that
nowforms only a small portion of the
TheBasalt eruption at
wastherefore not a fissure eruption, but is produced in
harmonyMnth other occurrences
bya single eruption of a
cone-like mass, of
nowa small portion along its
western edge is preserved. (PI. viii.).
microscopical examination of this Basalt,
the complete absence of magnesia.
shownthat the small red grains represent the red variety
of Olivine, Fayalite ; Augite, according to the authors, is
(11) This would indicate that in tho Derwent Valley the Permian series most probably rests directly on Pre-Cambrian Schists.
(12) In tlie great Basalt stream flowing from the plateau of the Dscholan down the valley of the Yaniiuk numerous layers of vesicular Basalt can be observed in the massive ])ortions. These layers, which
BY FRITZ NOETLING, M.A., PH.D. 105
also absent. Accordingly the rock is considered a Basalt
in which Fayalite has replaced Augite
underthese conditions it is correct to term this
rock a "basalt"' appears
somewhatdoubtful to me,
weconsider that it greatly differs in its
fromthe true Olivine Basalt. However, it
wouldbe confusing to introduce a
the terminology has been revised, I prefer to use the
M.Johnston statesthat he obtained
andteeth probably belonging to a small marsupial related
to Hi/pslprymnus in the cooling joints of an older sheet of
have shownabove that
suppose that tliere was
morethan one eruption,
probability that these bones are of
muchlater age, and were
washedinto a cooling joint, has to be taken into serious consideration.
sametime these bones
are very poorly preserved,
anddo not allowfor
determina-tion, except a vague resemblance toa family ofmarsupials,
mightas well be left out altogether.
Butif the possibility that the bones
washedinto the cooling joints could be finally
andMr. Johnston's view
fact, the presence of the
wouldspeak for a very recent age of the Basalt,
severely shake the opinion of its
(PI. iv., viii., and ix.),
Acareful examination of the strata shows that the
leaf beds of the northern portion are slightly bent
wherethey abut against the fault- This is
con-clusive proof that there is no overthrow, as Mr. R.
Johnston assumes; butthat the northern portion has slid
downalong the fault. Therefore, if
position of the strata before their dislocation
the northern portion for about 80 feet,
andplace it ba-ck
in its onginal position.
I have attempted such a reconstruction on Plate ix.,
wesee thatif the
sunkenportion is lifted
andreplaced inits original position a fresh difficultypresents itself. It
shownthat the total thickness of the leaf beds is
muchsmallerinthe southernthan inthe northernportion. Therefore, if the leaf beds of the northern poi-tion are
con-106 SECTION AT ONE TREK POINT,
siderable pox'tion of the latter
musthave been destroyed,
This is quite in
harmonywith the facts of volcanic
activity. Before the eruption of the
magmatook place a considerable portion of the overlying strata is
byexplosions. It isvei^ probablej that the peculiar mass
of leaf bods above
mentionedrepresents a portion of the
destroyed leaf beds
Asthe isolated patch of ve«iciilar Basalt observed in
the northern portion
movesto a higher level than it is
musthaverisen veryrapidlytowards north.
This indicates the form.er existence of a cauldron-like
wassubsequently filledwith Basalt. In other words,the Basalt
formedoriginally a cone, a great portion of
which wassubsequently destroyed.
nowtrace the history of the events
eventually resulted in the present features with the greatestacciu-acy, butforthe
moment wewill refrain
expressing a view as to thegeological time
place- In order to
makethe sequence of events clearer,
work backwardsin descending order, but
upwards fromthe earliest event
weare able totrace.
the supposition that Mr. R.
M.Johnston's lake theory is
andthattbe leaf beds are practically in the
nowas they were
following sequence ofevents:
byerosion of the
nearly its present depth. This
forma-tion of shore deposits, beginning with 2. Sandstone, followed
bythe deposit of
(15) I maybe permitted topointout stillanotuer difficulty; suppos-ing that tlie"amount of the downthrow is more than 8o feet, in other words tliat tlie northern part of the section does not reprr->?ent the
direct'continuation of the southern one. Tliis would naturally mean
that the portions of the section on either side of tlie fault are not contemix>raneous, as lie assumed, but tlmt the southern jjortlon is
older than the northern one. In an undisturbed section we would have, then, the following
In tills case the mass of strata removed above those that are now to beseen wouldbe far greater than here assumed; aU the strata, (4),
BY FRITZ NOETLING, M.A., PH.D. 107
3. Breccia(aperiodof intense denudation),
bythe deposition .of
Wellstratifiedleaf beds. (Tlieagenciesproducingthe
must havecontinued during the formation of the
leaf beds, because layers of Breccia are intercalated in the
.5. Pause in the deposition of sedimentary rocks,
whichthe leaf bed series (including all the beds from
2 to 4) were laid dry. (It is veiy probable that during this
process the leaf bed series acquire the remarkable regular
dip towards south.)
6. Partial destruction ofthe leaf beds
byvolcanic ex-plosions, followed immediately
bythe erujotion of Basaltic
magmaof probably very low temperature.
7. Dislocation of the leaf bed series
byfaults striking in an approximate north-western
andhaving a northern dip, going
with the destruction of the Basalt cone.
8. Period of extensive denudation
anderosion of the
Derwentbelow thepresent sealevel. (Sealevel
lower than at tliepresent day.)
9. Depositionofarenaceous bedson Basaltat
10. Rise of sea to its present level. (Partial filling
Derwentvalley with sea water.)
washconsisting of volcanic
debris, ashes, etc., representing the present
Formationof shell deposits
All these events can be traced with the greatest
must havefollowed each other in the
above order. There can be not theslightest doubt tliat the
whichthe Breccia was deposited in the
lowerparts of the
mustrepresent a period
mostactive denudation in other parts of Tasmania.
Great masses of angulardebris of sedimentary rocks
roundedblocks of Diabase were quickly
andredeposited at convenient places. This period of
byone of comparative rest,
during which a fine silt
impression of delicate leaves floating about in the water.
Occasional relapses of the fonner energetic denudation
108 SECTION AT ONE TREE POINT,
R.S. TA3. inthe deposition of Breccia beds bet-weenthe well stratified leafbeds.
Theclimatic conditions of this period
must have beendifferent
fromthose prevailing at the present day, be-causethe listof plantsgiven
M. Johnston wouldindicate a
somewhatmilder climate than that of the pre-sent day.
However,as I pointed out above, the
deter-minations ofthe species are not
however, appears to be certain, the annual rainfall
nowduring the time
It is impossible to say anything as to the length of
the period that lapsed after the leaf series
upaiid the outburst ofvolcanic action- In all probability
wasnot very long, however.
Itfurther appears thatthedestruction
of the newly-formed Basalt cone
hadbeen built up. This destruction^must again
have taken place during a time of
Derwentcut its channel right through
the leaf series, probably deep into the underlying
beds. Simultaneously the
byfaults; the latter tectonic
movementsdo not appear to
havebeen very energetic,
andthey probably ceased very
soon, while the denudation of the Basalt cone continued.
Until the exact extent of the former cone is
forman idea as to thequantity of matter
must havebeen of great magnitude, because
whatis seen to-day represents only a very small portioR
of the original bulk. (PI. viii.). It is, further, probable that the process of active denudation
cameto a standstill
whenthe level of the sea discontinued to recede,
movementin theopposite directionsetin.
the valley of the Dei-went
upto its present
level; in fact, it almost appears as if it
Thedata for this hypothesis are, however, ver}''
andI do not wish to say
moreon this point.
whenspeaking of the leaf
series in his G-eology of Tasmania, refersitto the Tertiary periodgenerally,but on page 261 hestatesthatin oneofthe
leaf specimens of the Turritella group, near
whichoccursintheleaf beds oftheDerwent, notably at
infra-BY FPvITZ NOETLING, M.A., PH.D. 109
basaltic leaf beds belong to the Palseogene, and aslie
con-siders the fossiliferous beds of Table
Capeto be of
mu&tinfer that he attributes the
sameage to the
bedseries of the Deinvent valley.
cir-cumstancesthe erosion of the old
musthave taken place
in Pre-Eocene times; in other words, it
as far as the Cretaceous period.
Morerecent researches, particularly of Victorian
haveconclusively proved that Tate's views as to
Eoceneage of the Australian Tertiary
longer tenable. All the Tertiaries of Australia are
younger; in fact, it appears very doubtful
Eoceneisrepresented at all in Australia. It is
probable that the Table
Capebeds are of
agethan hitherto assumed,
andconsequentlythe leaf beds
youngerthan Eocene. If
views are correct, they cannot be older than Pleistocene,
assumea Pre-Eocene erosion of the
Derwentvalley if, as I believe, the leaf
bedseries were at
the time of their deposition in a
muchhigher level than they are now,
cameto their present position
whichimmediately preceded the
eruption of the Basalt.
ThePost-Pleistocene period represents, therefore, the
bedseries were raised
andit is probable that eruption of the Basalt took
place during the
im-probable that the latter is
period following the eruption of the Basalt
wasa time of
of the Basalt ccne
anda large portion of the leaf beds.
wastheii at its lowest, or nearly its lowest, this stage
mustrepresent the time
wasconnected with the
endof thePleistocene, long after the glaciers
dis-appeared, a gradual rise of the sea level
previous tofinal separation from the
hadsettled in Tasmania.
the former fauna were a few isolated specimens of gigantic
havenof refuge in
wherethey died out before tliey
Thelast to follow were the aborigines,
andveiy soon after their aiTival the rising sea
110 SECTION AT ONE TREE POINT,
Theabove results have been
ap-pendedtable, which, however, requires a few words of ex-planation.
Thcughthe actual sequence of the strata is
beyonddoubt, the age attributed to the different beds is
opento dispute. It all depends
onthe age of the leaf
Asfar as this is concerned, one fact is cer-tain, that it does not belong to the
weneed not attribute a Pre-Eocene age to a pre-leaf
bed Derweiit valley.
myview as to the Pleistocene
were not correct, the leaf beds are not likely to be oldor
iii. General viewof
V. Diabase boulderin breccia.
vi. Ijrecciaandleaf-beds— boulderpressed into leaf-bed^
vii. Basalt overlyingthe leaf-l^eds.
viii. Section at
BY FRITZ NOETLING, MA., PH.D. Zfa
< 2 D
&p. R. S. Tas., 1913. PLATE III.
p. &. p. R. S. Tas., 1913. PLATE IV.
p.& p. R. S. Tas., 1913. PLATEV.
&p. R. S. Tas.,1913. PLATE VI.
&p. R. S. Tas., 1913 PLATE VII.
p. & p. R. S. Tas., 1913. PLATE VII!
p. & p. R. S. Tas., 1913. PLATE IX.