Geophysical Bulletin No4.Pdf

DENSITY OF IRISH ROCKS

The densities of 157 rock specimens :in the Geophysics Labora tory of Trinity College, Dublin, have been determined to provide

data for the . evaluation and interpretation of the gravity survey of Ireland. These rock samples have been collected at various times for different purposes, but, in the main, are fairly repre

sentative of the rock types occurring in this country.

The average size of each sample was about 25 ccs. and its density was deter.mined with a Walker Steelyard Balance, weighirigs

being taken in air and in wate~. Most of the samples were imper

vious to water and, apart from ensuring that all air bubbles were eliminated, no special efforts were taken to ensure that they were saturated.. Sandstone specimens, especially of Triassic age, were the most difficult to measw-e since they tended to break down in

water. In these cases the weighing in water was carried out after

the removal of all loosely attached grains and, if a second weigh ing in water was necessitated by further loss of loose grains,

this weighing was carried out after drying in air overnight. This

procedure was repeated until satisfactory readings were obtained. Highly vesicular specimens were boiled in water for five minutes · and allowed to cool in cold water before the weighing in water.

This method, though satisfactory with porous rocks, was inevitably unreliable when applied to specimens which were both vesicular ii

In the table the reference number is that in the catalogue of the Geophysics Laboratory at Trinity College, Dublin. The locality given is intended only as a guide. The geological age of each specimen -is shown but in some cases this is uncertain and indicated by a question mark after the name of the system. In a few instances the age is unknown.

I wish to thank Professor J.H.J. Poole for the use of a Lab- oratory and for permission to use the late Professor J. Joly1s basalt samples, and Professor L. B. Smyth for the loan of the

Steelyard Balance. The work was made possible by a grant from the Meteorological and Geophysical Department of the School of Cosmic Physics in the Dublin Institute for· Advanced Studies.

J. S. JACKSO

' ' 'I I .

......

I I

u u

'-'!U '-'!U

82 82

83 83

.. ..

.75 .75

5/ 5/

2.83 2.83

2.99 2.99

2.81 2.81

2.82 2.82

2.98 2.98

2.75 2.75

2.69 2.69

2.96 2.96

2 2

2.79 2.79

2.68 2.68

2.59 2.59

2.56 2.56

2.68 2.68

2.71 2.71

2.72 2.72

2.70 2.70

I I

-· -·

;. ;.

. .

~ ~

Age Age

us us

~ ~

, ,

? ?

ian ian

iary

vonian vonian cene cene

von

vonian vonian

-· -·

---

......

Cretaceous Cretaceous

Eocene Eocene

Jurassic Jurassic

Carbonifer

Eocene Eocene

Te E

Eocene Eocene

Carboniferous Carboniferous

Eocene Eocene

Carboniferous Carboniferous

Oligocene? Oligocene?

Eocene Eocene

Eocene Eocene Oligocene? Oligocene?

Geological Geological

......

I I

I I I I

I I

......

e e

. .

~ ~

Is. Is.

i:ii i:ii

~ ~

Head, Head,

.. ..

court court

rry rry

Larne Larne

Star Star

p p Quarry Quarry Fair Fair

Qua

Bally-

Belfast Belfast

dyke dyke

e e

Ballyca

Kings

d d

. .

(west) (west)

Causeway Causeway

h h

North North

Point, Point,

Doo, Doo,

Star Star

s s

Head Head

Locality Locality

Hill, Hill,

Ballycastle Ballycastle

near near

Head, Head,

Hill, Hill,

h h

Point,Rathlin Point,Rathlin

ROCKS ROCKS

Maidens Maidens

. .

agh

llyc

allag

: :

!ml

Gorag

Lou

Cave Cave

castle castle

Portrush Portrush

dyke dyke

Beside Beside

Fair Fair near near

Cave Cave

North North

Black Black

Rathlin Rathlin

Ferris Ferris

Ballycastle Ballycastle

Rue Rue

Giant's Giant's

Giant'

The The

IRISH IRISH

. .

} }

n n

.., ..,

d d

OF OF

red) red)

= =

Granite Granite

) )

rboni-

.. ..

(very (very

Lias Lias

Type Type

specimen) specimen)

(

( (

rous rous

weath

ygdaloidal) ygdaloidal)

basalt basalt

dolerite dolerite

shale

DENSITY DENSITY

inster inster

Granite Granite

red) red)

(very (very

Rock Rock

htly htly

stone stone

:!.t :!.t

f f

. .

wry wry

ossi

asalt asalt

(typical (typical

Basalt Basalt

ferous ferous

Newcy Newcy

Homfels Homfels

Hornfels Hornfels

Lim

weath

Chalk Chalk

Tuf

Basalt(a

Olivine Olivine

Basalt Basalt

Dolerite Dolerite

&salt &salt

Basalt Basalt

Columnar Columnar

I I

3 3

• •

34 34

20 20

l5 l5

21 21

4 4

6 6

5 5

8 8

.23 .23

.20 .20

W. W.

B.22 B.22

B.l8 B.l8

B.l3 B.l3

B.l9 B.l9

B.ll B.ll

B.2 B.2

B.6 B.6

B.l B.l

Ref Ref

I I

~ ~

ry ry

~:::: ~::::

'.S '.S

ous ous

eot

Class Class

Ign

Igneous Igneous

Metamorphic Metamorphic

Sedimen

Igneous Igneous

I I

.-""" .-"""

. .

w w

......

-. -.

Cavaii Cavaii

County County

Antrim Antrim

I I

-J'"" -J'""

.. ..

< < · · I\)

u u

g/cm

- 2.~

2.62 2.82 2.67

2.52

2.31 2.60

2.70 2.67 2.62

2.74 2.64 2.58 2.66

2.69 Densi~y

I I

I I I

I I

,./

Age

-•

Geological Tertiary; Tertiary,

.Eocene? .Eocene?

Tertiary, Eocene? (C.M.) Devonian? Carboniferous Carboniferous

Triassic

Devonian Devonian Dalradian Carboniferous

Dalradian? Dalradian Dalradian

I I --- I I I I

I I

·;;

Bridge,

deposit,l

"J" 11 11

Bridge,

Middleton

court

Kingscourt

Kingscourt Kingscourt Kingscourt Ba.llyedmond

near Ballydam,

Locality

Point

court

S.E. Kings Island S. Island

Mountnugent Middleton Middleton N. Middleton

!i=~

(1939), (1939), (1939), Corratober Ardagh, Shot-boring ~. House,near Shot-bor:ing Shot-boring Kings Ballinaclashy Crossdoney, 1m1. Glacifluvial near near near Tory Arranmore Tory Rathcormac, near lml.

near Fanad

I J

I I I I I I I I

IRISH

G.)

ORS)

OF granite

(slightly

(ORS) (

quartz (M.

(NRS) quartz

Type Basalt weathered)

(rolled

Rock

weathered)

DENSITY

Amorphous

Sandstone Limestone Amorphous carbonaceous) f!'~~!~~ly Gannister Grit Granite Sandstone and Sandstone Sandstone

Basalt

Crossdoney

Vesicular

I I

I I I I

I I

!Basalt

B,8 B.9

B_l..':\ B.l2 W.ll W.l2 W.28

B.37

W. W.lO

W.21

B.50

W.l W.l5

B.49 Ref.

I I

.·::.

:;:..;-_

Class

:--..:::~

Igneous

Sedimentary

Igneous

,='---"'_-~

l -

(contd.) Donegal

County

Cork

Cavan

---.--o,

v.> v.>

I I

u u

2.95 2.95

3.00 3.00

g/cm3 g/cm3

2.72 2.72

2.34 2.34

2.71 2.71

2.95 2.95

2.45 2.45

2.99 2.99

2.59 2.59

2.95 2.95

2.23 2.23

2.72 2.72

2.76 2.76 2.60 2.60

2.59 2.59

2.72 2.72

2.45 2.45

2.65 2.65

Density Density

-~.~ -~.~

......

I I

I I I I

I I

~ ~

r···-

Age Age

,, ,,

, ,

_ _

;:=:r;~ ;:=:r;~

-:" -:"

:.....:;, :.....:;,

~ ~

Triassic Triassic

SUurian SUurian

Triassic Triassic

Devonian Devonian Eocene? Eocene?

Triassic Triassic

l'ertiary, l'ertiary,

Dalradian Dalradian

Triassic Triassic

Ordovician Ordovician

Triassic Triassic

Dalradian Dalradian Silurian Silurian

Devonian Devonian

Geological Geological

Dalradian Dalradian

Triassic Triassic

I I

I I I I

I I

School' School'

Hill Hill

Hill Hill Hill Hill

Hill Hill

Lough Lough

(Is.) (Is.)

Treantaboy Treantaboy

Mullaghfin Mullaghfin

near near

Comer, Comer,

Hill Hill

near near

W. W.

(village) (village)

locality locality

Scrabo Scrabo

Fann, Fann, Scrabo Scrabo

Scrabo Scrabo

Treantaboy Treantaboy

Lissinisk Lissinisk

N.E. N.E.

continued continued

Bohemabreena Bohemabreena

Near Near

Rockabill Rockabill

Bohemabreena Bohemabreena

near near

Scrabo Scrabo Bohemabreena Bohemabreena

Near Near

F.den F.den

near near

Scrabo Scrabo

Scrabo Scrabo Quarry Quarry

Quarry Quarry

Scrabo Scrabo Quarry Quarry

Moronay, Moronay,

Scrabo Scrabo

Breen Breen

Moronay, Moronay,

2!mJ.s. 2!mJ.s.

Near Near

!ml. !ml.

I I

I I I I

I I

ROCKS ROCKS

Marl Marl

diorite diorite

Felsite Felsite

NRS) NRS)

(NRS) (NRS)

( (

and and

Schist Schist

Type Type

IRISH IRISH

(weathered) (weathered)

{weathered) {weathered)

OF OF

Rock Rock

Porphyr1tic Porphyr1tic

Slate Slate

Granite Granite

Slate Slate

Granite Granite

Sandstone Sandstone

Grit Grit

Sandstone Sandstone

Mudstone Mudstone

Dolerite Dolerite

Metamorphosed Metamorphosed limestone limestone

Limestone Limestone

Gneiss Gneiss

Diorite Diorite

Porphyritic Porphyritic

• •

I I

DENSITY DENSITY

B.l4 B.l4

B.lO B.lO

B.? B.?

R.39 R.39

8.3 8.3

a.uj a.uj

R.31 R.31

R.24 R.24

R.221 R.221

R.26 R.26

R.l? R.l?

R.5 R.5

R.45 R.45

R.30 R.30

R.6 R.6

R.1.4 R.1.4

R.37 R.37

Ref. Ref.

W.50 W.50

1 1

I I

1 1

I I

Class Class

lletamorphic lletamorphic

·:._ ·:._

Sedimentary Sedimentary

Igneous Igneous

Metamorphic Metamorphic

I I

1 1

I I

~ ~

-"!:

_:; _:;

...:.:-:...::-::;

• •

-. -.

(contd.}" (contd.}"

County County

Dovn Dovn

-:--

Donegal Donegal

I I

;; ;;

......

;-:: ;-::

~- • • DENSITYOF IRISH ROCKS- continued

- Density County Class Ref. Rock Type locality ·GeologicalAge gjcm3 - Dublin Igneous B.24 Rhyolite Blackchurch Ordovician 2.64 (contd.) B.33 Porphyrite Portrane Ordovician 2.86 W.7 Porphyrite Bohernabreena Ordovician 2.95

Sedimentary B.27 Tuff ShennickIs.,Skerries ? 2.~ W.43 Sandstone(ORS) ~. S. of Donabate Devonian 2.67 R.4 11Calp" Southof Rush Carboniferous 2.65 R.lO Conglomerate ShennickIs.,Skerries Carboniferous 2o7S R.l5 Sandstone ShennickIs~,Skerries Carboniferous 2.59 R.l6 Shale ShennickIs.,Skerries Carboniferous 2.$2 I I

R.25 "Lane"Conglomerate BetweenLoughshinny Carboniferous 2.76 i and Skerries ~ R.27 Limestone Loughshinny Carboniferous 2.67 R.29 Conglomerate BetweenLoughshinny Carboniferous 2.69 and Slrerries "' - R.34 Conglomerate Near Rush Carboniferous 2.70 R.36 Limestonewith band BetweenRush Carboniferous 2.6$

.. . . of chert and Loughshinny ... R.3S Gritty Limestone Kate Rock, North Carboniferous 2.67 -. _. of Rush Harbour - . •' 11 11 -. R.40 Carlyanlimestone N. of Rush Harbour Carboniferous 2.71 ... ..;.:_ R.44 11HolJnpatrick" Holmpatrick,SkerriesCarboniferous 2.72 ...... - ·-...... - limestone I '~- " ·~

·--.-- .. --'- ~ -··• _...... _ ...... "'...... -· .. Meta.IOOrphicW.39 Graniticgneiss South Devonian M-·- -,- ,,. - - side of 2.65 - -L' .. ':. ... . G1encreevalley B.16 Slate Bohernabreena Ordovician 2.62 ~·- -.··- - .. .. -- . ~ - . ..._ -.- B.17 Mica-s.chist Bohemabreena Sllurian 2.66 ...... - : ". 7~-·. W.2 Subsequentdo1omitie Howth - ~- - Carboniferous 2.71 - -. - ·-' . . - limestone -- -1="- . - ...: I .. - . - - ·- -- DENSITYOF IRISH ROCKS continued ""'!..~--- -~-"'------· ~ - ._ __ - __. - -· - -- ...._._ -.. 1 ... ·r-.....------·--~-' Density County Class I Ref. I RockType wcality Geological Age I I I g/cm3

Dublin I MetamorphicI W.141 Quartzite IHowth Head ICambrian? {Bray 2.65 ( contd;) Howthseries) R.32 Dolomiticlimestone Lime-kilnCove, Carboniferous t 2.76 near Loughshinny S.E. of Rush R.351 "Rush"Slate Carboniferous I2.70 Galway I Igneous I B.23 Porphyritic Galway Bama Pre-Cambrian, 2.66 granite Dalradian? B.26 I Porphyritic Galway Inishlackan, Pre-Gambrian, I 2.6B granite Roundstone Dalradian? B.39 I Microgranite Roundstone Pre-Gambrian, I 2.60 u (slightly kaolinised) ·: Dalradian? B.4l I Gabbro BetweenBallynahinch Pre-cambrian, I 2.92 and Roundstone Dalradian?

MetamorphicI B.421Hornblende-schist I Letterdyfe Mountain, Pre-cambrian, I 2.99 Roundstone Dalradian?· W.lB I Crystalline merble I Ballynahinch, Pre-Gambrian, I 2.72 near Roundstone Dalradian? W.l9 I Serpentine I Barnaoranquarry, Pre-Gambrian, I 2.61 ( "Connemaramarble") OwenglinRiver, Dalradian? near Ballynahinch

Kerry I Igneous I W.45 I Felsite I BennaumoreMountain, I Devonian I 2.62 near LoughGuitane

SedimentaryI B.36 I Sandstone( ORS) I LoughCurrane, I Devonian I 2.69 Waterville W.31 I Sandstone(ORS) I LoughGuitane, I Devoni.an I 2.6B near Killarney I I I VI

0'-

u u

g/cm3 g/cm3

2.73 2.73

2.64 2.64

2.69 2.69

2.68 2.68

2.90 2.90 2.75 2.75

2.76 2.76 2.73 2.73

2.76 2.76 2.72 2.72

2.61 2.61

2.75 2.75

2.61 2.61

2.90 2.90

Density Density

Age Age

? ?

Bala,Ordovician Bala,Ordovician

Ordovician Ordovician

Bala,Ordovician Bala,Ordovician

Ordovician Ordovician Carboniferous Carboniferous

Ordovician Ordovician Ordovician Ordovician

Ordovician Ordovician

Devonian Devonian

Ordovician Ordovician

Silurian Silurian

Geological Geological

ex-

y y

and and

county county

Athy Athy in in

Hill Hill

Suir Suir

Guitane Guitane

left left

Lower(TL) Lower(TL)

Christen-

of of

Rath-

Quarry, Quarry,

Conmons Conmons

on on

near near

W. W.

Kildare Kildare

inmore inmore

.L.) .L.)

Drumdown

River River

church church

Dunquin Dunquin

Alien Alien

.Lough .Lough

near near

continued continued

bmmdary bmmdary

(T (T

south south

hannon hannon

of of

Stars Stars

of of

Locality Locality

of of

Rathpatrick Rathpatrick

due due

.N .N

of of

Har

Dingle Dingle

House House

entry entry

Curraghlane Curraghlane

church, church,

Lower Lower

Near Near

bank bank

patrick patrick

tmJ_. tmJ_.

Ba.llys Ba.llys

Fonstown, Fonstown,

dom dom treme treme

Quarry Quarry

Quarry Quarry Chair Chair

Seven Seven

~.N~E.Grange ~.N~E.Grange

Chair Chair

Parish Parish

between between

Hill Hill

V V

Ballynahow Ballynahow

3!mls 3!mls

Near Near

near near

ROCKS ROCKS

IRISH IRISH

shale shale

(ORS) (ORS)

Type Type

OF OF

micaceous micaceous

Rock Rock

hale hale

Shale Shale

Felsite Felsite

Diorite Diorite

Lime~tone Lime~tone

Felsite Felsite

Limestone Limestone

Andesite Andesite

(weathered) (weathered)

Porphyrite Porphyrite

slla.le slla.le

Micaceous Micaceous

Grit Grit

Gritty Gritty

Sandstone Sandstone

DENSITY DENSITY

35 35

2 2

34 34

.36 .36

.26 .26

.. ..

W.42 W.42

W.32 W.32

W.22 W.22

W.l3 W.l3

W W

B.32 B.32

R.42 R.42

R.41 R.41

R.ll R.ll

Ref. Ref.

W.44 W.44

tary tary

Class Class

Sedimentary Sedimentary

Igneous Igneous

Sedimentary Sedimentary

Igneous Igneous

Sedim

.. ..

...-

......

" "

. .

......

.. ..

I. I.

. .

-· -·

~ ~

'~-~ '~-~

,.-. ,.-.

~-.:. ~-.:.

......

~ ~

......

= =

~~·· ~~··

......

.. ..

.-. .-.

. .

··--·-

contd.) contd.)

.. ..

.• .• ......

---

( (

-..--

Kilkenny Kilkenny

County County

--~ --~

.J,r .J,r

......

. .

......

Kildare Kildare

......

Kerry Kerry

• •

..-

··- J.- ·~·-

~ ~ ,._ ,._

. . ·-

·-

. .

-~· -~·

.•. .•.

~ ~

--.-· --.-·

......

,.. ,..

~ ~

-- -· -·

~ ~

I I

u u

2.71 2.71

2.73 2.73

2.77 2.77 2~71 2~71

2.66 2.66

2"60 2"60

2.73 2.73 2.70 2.70

2.65 2.65

2.76 2.76 2.85 2.85

2.81 2.81

2.65 2.65

2.62 2.62

2.71 2.71

2.70 2.70

I I

Age Age

rous rous

~ ~

Carboniferous Carboniferous

Carboniferous Carboniferous Carboniferous Carboniferous

Carbonif

Carboniferous Carboniferous

Devonian Devonian

Carboniferous Carboniferous

Devonian Devonian

Carboniferous Carboniferous Devonian Devonian

Devonian Devonian

Carboniferous Carboniferous

Devonian Devonian

Geological Geological

I I

e e

of of

town town

(TL) (TL)

town town

~. ~.

(TL) (TL)

Castle Castle

Castl

Castle Castle

t t

Granny Granny

t t

l l

of of

Kilkenny Kilkenny

Lower Lower

uarry,Granny uarry,Granny

Dunld Dunld

Ballynamona, Ballynamona,

House, House, Grannyferry Grannyferry

Strangsmill Strangsmill

immediately immediately

Quarry, Quarry,

continued continued

ogunnel ogunnel

Co. Co.

Waterford Waterford

Co. Co.

Waterford Waterford

Locality Locality

south-wost south-wost

south south

north-west north-west

south south

of of

N. N.

of of

rri

arrigogunnel arrigogunnel

uarry uarry

lml. lml.

~. ~.

imJ.. imJ..

Carrigogunnel Carrigogunnel C

Carrigogunnel Carrigogunnel

hnJ.. hnJ..

House, House,

Carrigogunn

east east

Granny Granny

N. N.

Granny Granny

South South

N. N.

Grannyferry Grannyferry S.E. S.E.

Murtaghstown, Murtaghstown,

South South

lml. lml. Newrath Newrath

Courtnaboghilla Courtnaboghilla

Annaleck Annaleck

I I

ROCKS ROCKS

(ORS) (ORS)

IRISH IRISH

' '

red) red)

ORS) ORS)

Limestone Limestone

(ORS) (ORS)

( (

(ORS) (ORS)

sandstone sandstone

Ash

Type Type

OF OF

weath

siliceous) siliceous)

t t

stone stone Rock Rock

ry ry

lomitic lomitic

Limestone Limestone

Basalt Basalt

Volcanic Volcanic

easal

Limestone Limestone

Sandstone Sandstone

Limestone Limestone

Copglomerate Copglomerate

Conglomerate Conglomerate

Sandstone Sandstone

(very (very

Sandstone Sandstone

Limestone Limestone

(ORS) (ORS)

Micaceous Micaceous

DENSITY DENSITY

I I

l l

28 28

S S

l l

? ?

33 33

9 9

.. ..

.20 .20

.l9 .l9

R R

R.3 R.3

R.l8 R.l8

W.47 W.47

W.41 W.41

W.49 W.49

W.40 W.40

W.38 W.38

Ref. Ref.

I I

o o

tamorphi

Class Class

Igneous Igneous

Sedimentary Sedimentary

(contd.) (contd.)

County County Kilkenny Kilkenny <»

c.t...,

2.91

2.72

2.90

2.97 2.61

2.71

2.95

3.03

2.94

2.79

3.()) 2.47 2.71

2.28

I I

I I 1 I

Age

-Cambrian,

e e

ria

Tertiary,

Eocene Carboniferous

Eocene? Dalradian? Eocene?

Eocene Eocene Carboniferous Eocene Eocene Pr Eocene? Tertiary, Silurian

Carboniferous Pr

Tertiary, Geological

Dalradian?

I I I

·---

...

Bush

Greenore

Graveyard

ocks,

Rocks;

Mt.,

outcrop,

ckmacross e

outh-w

near

rlingford Island

Island

near

continued

ral

Locality

Carlingford

Quarry,

Carrigogunnel

hed

C hed

rnavav

Achill

C Ca

Achill

Littoral n

l~s

Quarry

Jenkinstown Barnavave

n Jenkinstown Bush

Carllngford

Carlingford Grange, Carlingford

Quarry

Castle

Carlingford

Grange,

near

Churchfield

I I

ROCKS

rbl

stone

IRISH

diorite

lim

Type

roua

Euc]:'ite)

(sill)

(Eucrite)

(

Spar

lsic

schist

Rock

-baked

Granophyre")

ornf

Sla Quartzite

Semi Garnetife h Satin

Mica

( Basalt

Porphyritic

Diorite

Gabbro

Limestone

DENSITY

I I

. . 43 .

.47 .4S

.44

W W

B.46

B.45 B B

B.31

B.30

B.29

Ref.

___

_:;:.

ntary

""'~~

tamorphic

Class

edim

~.-::.

......

Metamorphic

•

Igneous

Sedimentary

_.,.

I _,

Mayo

(contd.)

County

""Monaghan

Louth

Limerick

'-0 '-0

u u

U U

6 6

59 59

63 63 01 01

67 67

.. ..

.70 .70

.. ..

.71 .71

.69 .69

.. ..

nsity nsity

g/cm3 g/cm3

3 3

e 2.69 2.69 2

2 2

2.98 2.98 2.65 2.65

2~65 2~65

3.07 3.07

2.55 2.55 2.71 2.71 2 2

2 2

2 2.66 2.66

2.67 2.67

ge ge

us us

? ?

rous rous

ero

ian ian

series) series)

ian ian

vonian vonian

Devonian Devonian

Howth Howth

Cambrian?(Bray-

Devon

Caledon

Devonian Devonian

Ordovic

Pre-Cambrian Pre-Cambrian D

Pre-Cambrian Pre-Cambrian

Carbonif

Pre-Cambrian Pre-Cambrian

Carboniferous Carboniferous

Pre-Cambrian Pre-Cambrian

Carbonif

Geological Geological

y y

d, d,

of of

Mt. Mt.

Bay Bay

N. N.

ay, ay,

tn.) tn.)

err

Gill Gill

d d

(

h h

L. L.

f f

h h (

of of

Kill

lml. lml.

north north

ty ty

.. ..

lml.S. lml.S.

e e

Arklow Arklow

Lou

ap ap

Point Point

Bunowen Bunowen

of of

Doonee Doonee

Killerry Killerry

ly ly

North North

p p

Bay, Bay,

Quay Quay -

ontinu

Ba.llysadare Ba.llysadare

......

ope ope

h, h,

.Bunowen .Bunowen

ill ill

-. -.

Bir, Bir,

slo

w w G

of of

W. W.

Gill Gill

Local

ff ff

near near

llintogher llintogher

l l

N. N.

h h

ore ore

S. S.

h h

h h G

allintogher allintogher

ggag

slope slope

ediat B

Dy Dy

lly lly

uth uth

. .

ml. ml.

East East

Tonduff Tonduff

Nort

Kilm

Wickl

Ca.rnsore Ca.rnsore Bunowen Bunowen

Slishwood, Slishwood,

S. S.

J,ou

~ ~

of of

Loug

Mt., Mt.,

of of

lml. lml.

ROCKS ROCKS

s s

iss iss

a a

gne

ightly ightly

IRISH IRISH

c) c)

chist chist

gnc

s s

· ·

-s

(

c c

' '

d d

e e

) )

rous rous

Type Type

ati

e e

granite granite

and and

ero

iti

ine ine

nde-schist nde-schist

d d

end,c

---

s s

te te

tone tone

Rock Rock

lom

t~ t~

d.m·T d.m·T

grru

r, r,

stone stone

nat

pent

rtzite rtzite

rnetif

t-~

li.

.~~

a.r;.i a.r;.i

ri ri

IJSITY IJSITY

eg;'la

~ :.

e..c:~

ornbl

pegmatite pegmatite

GJ.

weathered

(

VJ'~

Gneis

Gi:"an

hvrnb

c:.

a"'1

Lim

Limestone Limestone

1 1

8 8

5 5 30 30

38 38

35 35 4 4

48 48

4 4

.. ..

.6 .6

- --

W.37 W.37

W B

13 13

G.5 G.5

G.S G.S

G.? G.?

G.2 G.2

G.3 G.3

G.l G.l

R.l2 R.l2

Ref. Ref.

c c

s) s)

ic ic

r.i

;

s s

rph

us us

Ign

amo

Class Class

& &

Igna

Igne

Metamor

(

. .

Sedimentary Sedimentary

-~ -~

......

. .

1 1

. .

,. ,.

..,. ..,.

.. ..

......

..----

..--

.. ..

• •

., .,

• •

._--_ ._--_

~ ~

. .

-~ -~

---· ---·

_..._ _..._

klow klow

•>•• •>••

~ ~

~; ~;

......

...., ....,

x!'o:-d x!'o:-d

......

"'" "'"

......

-· -·

., .,

......

& &

.;-~-

. .

\(i

.. .. ,.. ,..

ligo ligo

County County

·-

~ ~

. .

• •

.. ..

• •

. .

: :

. .

• •

. .

.. ..

...... b

g/c

2.61

2.63 2.69

2.70

3.05

2.78 2.68

3.03

2.70

Densi~y

sta

Age

(Bray-

series)

ian

l.ogical

weathered

evo

Geo

Howth D

Howth

Devonian

Silurian Cambrian?

Cambrian?

Devonian

Cambrian?

the

Head

Br.,

due

(Mtn.)

Valley

Powerscourt

Rocky

Deerpark North

Hole,Bray

concluded

slope

Kilbride

Locality

Nahanagan

Cloghleagh

Hill

unreliable

side

Brandy

Lough N.

Brandy

Glendalough North Manor

Outside Near

Tonduff Glendalough Long

ROCKS

value

the

ffii

vein

(weathered)

Type

that

Shal.e

Shale

Rock

(ferruginous)

Hornblendite Slate

Fault-breccia

Quartzite

Olive

granite

Mica-schist

DENSITY

f>l:lrple

Pegmatitic

Pegmatite

signifies

B.25

B.40

W.24

W.l6 W.l7

W.33

R.47

W.29

w.JJ>

Ref.

column

last

specimen.

the

Class

"u"

Metamorphic

Sedimentary

Igneous

(contd.)

County

Wieklow GEOPHYSICAL BULLETINS

No. 1: THOl"iAS HURPHY, Provisional Results of the Gravity Survey of Central Ireland; Dublin, Narch 1950.

No. 2: THOMAS MURPHY, Provisional Values for Magnetic Declination in Ireland for the Epoch 1950.5; Dublin, February 1951.

No. 3: L. W. POUAK and NUALA 0 1BRIEN, Frequency of the Centres of Closed Low Pressure Systems over the North Atlantic Ocean; Dublin, April 1951.

No. 4: JOHN S. JACKSON, Density of Irish Rocks; Dublin, july 1951.

IN COURSE · OF PRINTING OR IN PREPARATION

L. W. POLLAK, The Clilna.te of Dublin City.

Address:

Meteorological and Geophysical Department, School of Cosmic Physics,

5 Merrion Square, Dublin, Ireland.