Notes on further proofs of glaciation at low levels

73

NOTES

_ON

_FURTHER

_PEOOFS

_{OF GLACIATION}

_AT

LOW

LEVELS.

By

T. B.

Moore,

_F.E.G.S.

(Read

14th

August,

_1895J

Before

_{giving notes}

_on

my

_{late observations}

_on

_the

_above

subject, I

_{take the}

liberty _to

_{begin with}

_an

_extract

_from

_a

letter

by

_Professor

_E.

_V.

_Lendenfeld,

_of

_the

_University

Czernowilz,

relative _to

my

_paper

_on

_the

_{discovery of the first}

proofs of

land

glaciation _in

_Tasmania.

_The

_views

_{of so able}

an

authority,

who

_was

_the

_{first to discover positive proofs of}

land

glaciation in Australia, will, _T

am

_sure,

_be

_interesting

to

the

Fellows

of the Society.

Professor

_Lendenfeld

_says

:—

_"

_Your

_map

_shows

_{that in}

_the

Tasmanian

hill

country

_delineated

_the

_{character of}

_the

country,

lakes, etc., is exactly _alike

_the

_{character of the}

Niederen

Tauern

in _Carinthia,

_Salzburg,

_and

_{Styrii, at}

_an

elevation of

about

_{2,500 moires. It is}

_very

_{certain that}

there—

in the

Niederen

_Tauern

_{at that elevation}

—

_there

_have

been

glaciers

_a

_{relatively short}

_time

_ago,

_and

_I

_would

_say

_that

in

the

similar

country

in

Tasmania

_glaciers

_must

_{have been}

very recently, _for

_otherwise

_the

_lakelets

_would

_have

_already

been

filled

up

with

_debris.

The

_glaciation

_deducible

_from

your

map

should, I think,

be

_placed

in _a

more

_recent

_period

than

the _{glaciation of the}

_Australian

_Alps.

_As

_{to the glacial}

evidence

itself,

anyone

acquainted

_with

_the

_subject

_must

agree

that

the

character of

_the

_{country' depicted in}

_your

map

is a certain

_proof

_of

_the

_past

_{glaciation of}

_Tasmania."

Now

I will pass

on

_{to discoveries}

_made

_within

_the

_last

_few

months

up

to

_the

first

week

_in

November,

_{1894, of}

_further

proof

of

land

glaciation at

low

levels, in substantiation of

my

paper

on

this subject

read

before the

Eoyal

_{Society last}

August.

Upon

examination

of the

_banks

_of

_the

King

_Eiver,

_which

flows _into

_Macquarie

_Harbour

_between

_Pine

_{Cove and}

_the

settled

_portion

_of

_the

_town

_of

_Strahan,

_I

_discovered

_large

ice-woin

_boulders

_striated

_and

_grooved

_in

_the

_deep

_gorge

_of

the

liver _{situated at the}

_Upper

_Landing

; also similar

glaci-ated

_boulders

_in

_Harvey's

_Creek

_{at a distance of a}

_quarter

_of

a

mile

_from

_its

_junction

_with

_the

_King

_Eiver

_{at the}

_Landing.

The

boulders

are large,

many

_{tons in weight,}

_and

_are

composed

principally of Silurian sandstone.

_The

_planed

surfaces, _grooves,

_and

_{striaa are fairly distinct,}

_proving

beyond

_doubt

_{that as the ice}

_marks

_are

_not

_{obliterated in so}

74

friable

a

rock

that

the

period

of their transposition

by

ice is

of a

very

recent date.

As

there are conclusive proofs

that

the

whole

mountain

chain

comprising

the

West

_Coast

Range

has been

covered

with

a vast sheet of ice,

we

must

conclude

that rivers of ice

have

flowed

down

the

damp,

sunless, slate

gorges

of the

King

River, collecting as

they

went

masses

of

sandstone

from

the

surrounding

heights, _leaving

them

_at a,

altitude of

not

more

than

100ft.

above

sea level in their

present

shape

and

position at

_the

Upper

Landing

and

Harvey's

Creek,

distant

about

four to five miles

from

the

range.

In

the

same

locality,

on

the

_southern

bank

_{of the river,}

150ft.

above

its bed,

a

large

moraine

_occurs,

composed

_of

rocks

brought

from

the

inland

mountains.

Here

we

find

mica

slates, _large

_boulders

_{of greenstone,}

and

many

_other

formations

not

met

with

in the

country

west

of

_the

_coast range.

These

boulders

_and

pebbles

are

embedded

in

a

clay

or slaty matrix,

and

_{have been brought}

down

_the

_{river gorge,}

probably

at the

beginning

_of

_our

_{glacial period, before}

_the

erosion of

_{the present}

_bed

_{of the stream.}

During

the

recent substantial

improvements

to the

Strahan-Lyell

highway,

_a

_very

_interesting

_phenomenon

_of

_our

_glacial

action

_has

_been

_exposed,

_through

_the

_accumulation

_of

rubbish

_{and moss}

_being

_removed

_from

_the

_cuttings

_and

drains

of the _road.

As

_this

phenomenon

is so accessible

on

the

way

to

_the

_greatest

mine

_{in the island,}

_which

many

scientists

and

_{geologists are sure to visit, it is to be}

_hoped

that

more

able

men

_than

_myself

will give

views

as to its age,

origin,

and

_nature.

A

moraine

_commences

_about

_one

_mile

_from

_Strahan,

_and

extends

_{along the}

_{road towards}

Mount

_{Lyell for a}

_mile

_and

three-quarters _in

_width.

A

_{portion of}

_the

_moraine

_near

_the

surface is

composed

_of

yellow

_clay

containing

_a

few

embedded

pebbles

: this rests

on a

recently

formed

conglomerate, with

a

binding

of the

same

coloured

matter, in other parts

the

yellow

colour gives place to

a

conglomeration

of

pebbles

in

a

blue

slaty _or

_clayey

_nature.

The

texture of

_the

_binding

_{material or "till"} is fine

and

of

rock-like hardness. It contains pebbles of all sizes,

from

mere

atoms

_up

to

boulders

a foot in

diameter

; the stones are either

rounded,

grooved, or planed,

_and

many

are

covered

with,

scratches

_and

scored in various cross directions. All are

of

local origin, as

no

rock

_foreign to

the

West

_Coast

_can

_be

found.

Sheared

_pebbles of

conglomerate

and

_{quartzite, similar}

to those

found

by

Mr.

E. J.

Dunn,

F.Gr.S., anil

myself

in

and

derived

from

the

Devonian

_conglomerate

_round

Mounts

Tyndall

and

_Sedgwick

are

embedded

in the

moraine

_matter.

trace-75

able, the best section of the

_{country can}

_be

_seen.

_Here

_an

outcrop

of the

_bed

_rock

_for

_the

_first

_and

_{only time}

_in

_the

" _{till" is observed, a blue slate lying at}

_an

angle of

₈₀

_degs.,

slightly _distorted,

_but

_{similar in character to}

_the

_binding

material of the glacial

_{conglomerate.}

At

_{this point}

_we

_find

_an

illustration of a " giant's _{kettle," a}

_wide

_{crevasse in the}

_rock

filled

with

" _{till," the outer wall}

_being

_{at the}

_termination

of

the

deposit.

The

_{excavation of}

_the

_{cutting is}

_not

_sufficiently

deep

to

show

_the

_{whole depth}

_{of the filled-up crevasse,}

_nor

_to

allow

me

_{to give}

_an

_{estimate of the}

_probable

_depth

of

the

whole

formation.

During

_former

_{explorations of the}

_country

_I

_found

the

deposit

_two

_{miles further distant, in a north-east}

direction

on

Gould's

_{old track of nearly forty years ago,}

_re-opened

in

18S3

by

the

_Meredith

_Brothers.

_Taking

_this

_and

_other

_enumerated

facts _{into consideration,}

_I

_{arrive at the conclusion}

that

the

tend

of the glaciers

have

been

from

the north-east, _possibly

from

the

highlands

of

Tyndall

and

_Sedgwick,

_which

_{are in that}

direction,

_and

_{that the deposit is a}

_moraine

_profonde,

_and

if

not

_{precisely similar to the}

_boulder

" _till " _{of the}

_more

_ancient

glacial

_epochs

_{of other countries, it is the till of a}

_more

recent _{glacial period in ours.}

_The

_moraines

_on

_the

_edge

of Kelly's Basin,

_spoken

_{of in a previous paper, are similar in}

character to the

one

just described, _{with the}

_exception

_{that as}

far as

_{I have observed}

_{the pebbles are all}

_embedded

_{in a}

_yellow

clay.

The

recent

_conglomerate

_or till

on

the

Strahan-Lyell

road

_is

at

_an

_{altitude of 150ft. to 200ft.}

_above

_{sea level. It}

is in

no

way

identical

_with

_{the ancient}

_{permo-carboniferous}

_glacial

conglomerate found

_by

_Mr.

_Dunn

_near

_Mount

_Eead,

_{nor with}

tho^e

referred to in

my

_{former paper on}

West

_Coast

Glacia-tion as occurring _at

Mount

_Sedgwick

_and

_near

_Zeehan.

_The

recent find is

composed

_of rocks

belonging

_{to the district,}

principally slates, dioride,

_{conglomerate,}

_and

_quartzite,

_which

are

_embedded

_{in a}

_matrix

_derived

_from

_the

_wearing

_down

_and

grinding

_{action of the ice over the local slate rocks, the general}

formation

_found

_{in the}

_lower

_{lands of this territory.}

The

ancient

_conglomerate

_contains

_not

_only

_pebbles

_but

large _{sized boulders quite foreign to the}

_country

; it is

more

consolidated, also of a

much

harder

_character,

_and

_the

_binding

material is of a gritty

sedimentary

_nature,

_showing

_that

_the

deposits

_were

_formed

_under

_water

_and

_have

_a

_different

_age

_and

origin.

After

the _{discovery of the Kelly's}

_Basin

_moraines

_and

_the

huge

_ice-marked

_boulders

_{in the vicinity of}

_Farm

_Cove,

_I

was,

convinced

_that

_our

_glaciers

_had

_in

_some

_instances

_descended

_to

sea _level,

_and

_{since the finding of further proofs}

in the

low-levels _{at a considerable distance}

76

highlands, the

most

sceptical

must

now

allow that the

descent

of these to sea level

has

been

general.

Let

us

now

consider the evidence

we

have

regarding

the

age

of

our

glaciation. Professor

E.

Y.

Lendenfeld's

deductions

are, that the glaciation of the

Tyndall

and

Sedgwick

country

appears

to

belong

to a

more

recent period

than

the glaciation

of the

Australian

Alps. If this is

allowed

we

have

two

glacial

epochs

in Australasia, or

one

long continuous

period besides

the

ice

age

of

the

Permo-carboniferous

era.

In

Western

Tasmania

our

land

glacial action

has

not

been

earlier

than

the

Pliocene

period, or

we

should

find

some

evidences in

the

palaeogene deposits

round

the

shores of

Macquarie Harbour,

especially in the region of the

ice-marked

and

worn

boulders

near

Farm

Cove.

Let

us

assume

that the glacial action in

the

highlands

is of a

more

recent date

than

that of the deposits

lately described,

accounted

for in this

way:

that

the

refrigeration of the climate

was

more

intense at

the

commencement

and

middle

of

our

glacial

epoch than

towards

its close.

During

the intense period the ice

has

not

wholly

covered

the land,

but

has

extended

far

down

into the low-lying

valleys,

and

glaciers

have

descended

even

to sea level, or in

cases nearly so, as

proved

by

the

moraines

at Kelly's Basin,

Parm

Cove,

King

River,

and

Strahan.

Towards

the

end

_

of

our

glacial

epoch

the climate

has

become

milder

and

the ice

has

retired

from

the

lower

valleys, still leaving a vast sheet

on

the

highlands,

which

by

subsequent

local flows

caused

the

more

recent striatums, etc.,

on

the

bed

rocks,

and

on

melting

left the extensive

moraines

in close

proximity

to the

mountain

peaks.

The

Australian

Alps

being

further

from

Antarctic

influence

in a

warmer

latitude

than

our

West

Coast, possibly the refri-geration of the climate there

has not

been

so intense.

For,

according

to

Professor

Lendenfeld

and

other authorities,

the

glaciers

have

been

local,

being

confined to

mountains

higher

than

our

own,

and

the rocks

now

show

less

marked

signs of ice influence

than

those in

our

islands.

This

would

point to

the

fact that the

age

of glacial action in

the Australian

Alps

may

correspond with

the

more

intense period of

our

glacial era, for

assuming

that

the

climate

on

the

continent

was

milder,

the

ice sheets

would

therefore

be

confinod to the

higher

mountains,

and would

probably

have

melted

when

our

rivers of ice

and

glaciers

disappeared

from

the lowlands.

After

the

disap-pearance

of all ice

from

Australia, the

highlands

of

Western

Tasmania would

still

be

covered,

causing

the recent glaciation

at

the

close of

our

glacial epoch.

Perhaps

by

some

I

may

be

considered

an

infatuated

enthu-siast

who

has

recorded

actual facts of observation carefully ;

77

the

_{discovery of fresh proofs of glacial}

_phenomena,

_that

_the

age

and

intensity _of

our

Glacial

Period

will

be

_determined.

Trusting

my

recent discoveries

may

throw

more

_light

_on

_so

interesting a subject,

and

that

some

eminent

authority,

_not

_too biassed

by

past theories,

may

_examine

them

_and

_{give his views,}

either negatively or in

_concurrence

_with

my

_{statements, as to}

the

existence of

_boulder

till in the

lowlands

of

the

West

Coast

of

_Tasmania.

Illustrative

_{specimens forwarded}

_{for the}

_Tasmanian

Museum

from

_boulder

till, Strahan, Lyell-road, _viz.:

—

No. 1)

2

\

3

_y

A

series of

coloured conglomerates.

41

5J

6

Binding

materials of

conglomerate.

7

Scored

pebbles

from

above

conglomerate.