y

COMMONWEALTH OF AUSTRALIA

DEPARTMENT OF NATIONAL DEVELOPMENT

BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS

RECORD No. 1966/141

ISOGAL GRAVITY BASE STATIONS,THURSDAY ISLAND (QUEENSLAND)

AND DARU (TPNG), 1966

by

B.C. BARLOW

The information contained in this report has been obtained bythe Department of National Development as part of the policyof the Commonwealth Government to assist in the explorationand development of mineral resources. It may not be publishedin any form or use in a company prospectus or statement withoutthe permission in writing of the Director, Bureau of MineralResources, Geology and Geophysics.

RECORD No. 1966/141

ISOGAL GRAVITY BASE STATIONS,THURSDAY ISLAND (QUEENSLAND)

AND DARU (TPNG), 1966

by

B.C. BARLOW

The information contained in this report has been obtained bythe Department of National Development as part of the policyof the Commonwealth Government to assist in the explorationand development of mineral resources. It may not be publishedin any form or use in a company prospectus or statement withoutthe permission in writing of the Director, Bureau of MineralResources, Geology and Geophysics.

CONTENTS

Page

1. INTRODUCTION 1

2. TRANSPORTATION. 1

3. GRAVITY METERS AND CALIBRATIONS 1

4. RESULTS 2

50 STATION DESCRIPTIONS 2

6. DATA STORAGE 2

7. ACKNOWLEDGEMENTS 3

8. REFERENCES 3

ILLUSTRATIONS

Plate 1.^Locality map^ (Drawing No. C502-19)

Plate 2.^Station description, Horn Island^ (C502-20)

Plate 3.^Station description, Thursday Island^(C54/B2-21)

Plate 4.^Station description, Daru^ (C54/B2-18)

1966/141

SUMMARY.

Isogal gravity base stations were established at ThursdayIsland (Horn Island) in Queensland and at Daru in the Territory of Papuaand New Guinea in May 1966 in order to provide control for part of a IIMRhelicopter gravity survey and to extend the coverage of the AustralianNational Gravity Network.

Range

Accepted interval (mgal)

Date

No. of readings

MW548 scale divisionsmgal/scale division

S145 scale divisionsmgal/scale division

G20 Intervals computed from. La Coste table (mgal)

Canberra

54.725.5.663-2

499.70.10951

514.30.10641

54.69

Townsville

60.51

14.5.66

3-2

552.70.10949

568.20.10649

60. 55

Canberra

54.7217.5.66

4-3500.20.10939

514.10.10643

54.70

1. INTRODUCTION

During 1964 and 1965 the Australian National Gravity Networkwas considerably strengthened by a number of regional gravity meter surveysreferred to as the 'Isogal' project (Barlow, in preparation). This networkprovides gravity base stations at intervals of about 150 miles throughoutmost of Australia.

Additional Isogal gravity base stations were established atThursday Island (Horn Island) in Queensland, and at Daru in the Territoryof Papua and New Guinea during May 1966 to provide gravity control for thenorthern part of the 1966 BMR contract helicopter gravity survey and tofurther extend the existing coverage.

2. TRANSPORTATION

The forward trip from Canberra to Thursday Island and airties between the aerodromes at Weipa, Thursday Island (Horn Island), andDaru were made in aircraft provided by Helicopter Utilities Pty Ltd.A Bell 47J helicopter provided by Helicopter Utilities Pty Ltd was usedto make a short gravity tie from Horn Island to Thursday Island. Commercialand private transport was used for ground ties and the return trip fromThursday Island to Canberra.

3. GRAVITY METERS AND CALIBRATIONS

Three gravity meters were used for this work: Master Worden548, Sharpe Canadian 145, and La Coste G20. The meters were calibratedat Canberra before the field measurements and afterwards at Townsvilleand Canberra. The gravity meter calibration ranges at these places aredescribed by Barlow (1965). Except for a jump of +0.17 milligal detectedin the La Coste G20 meter during the calibration in Canberra on 5th May,the drifts of all meters were very good. Restate were as follows

The following mean calibration factors were accepted forcalculation of the field work :

Master Worden 548Sharpe 145

- La Coste G20

0.10946 mgal/scale division0.10644 mgal/scale divisionCalibration table supplied by La Coste.

2

4. RESULTS

. The accepted datum for all observed gravity values atThursday Island and Daru is 978 9 302.74 milligals 9 previously establishedat Isogal station 6491.0167 at Weipa airstrip (Barlow 9 in preparation).The resulting °May 1965 Isogal values' are as follows

Informal station name Station number Observed gravity (mgal)

Horn Island airstrip (secondarybase)

6691.9001 978^244.14

Horn Island airstrip (excentre) 6691.1001 244.16

Thursday Island Customs House 240.64

Thursday Island wharf 6691.3001 241.04

Daru airstrip (primary base) 6691.9972 202.62

Daru District Office 6691.0172 202.56

Earlier values at Thai ,Sday:151and and Daru are as followsfile

L.W. Williams (BM458503).of 978,500.1 mgal at Cairns52, (Isogal value 978 9 500.6

Station 6691.0172 918,203.2 mgal byof Tasmania-T.P.Nvalue of 978,214.WA3046(estimated978,2147777

J.E. Shirley (University.G. data). Based on a9 mgal at Port MoresbyIsogal value approximately

5. STATION DESCRIPTIONS

The locations of the new Isogal stations are shown in Plates1-4. Additional descriptive data including photographs, pin—pricked airphotos, and maps are held by the BKR. All stations except 6691.3001 havebeen marked with brass discs, which have also been emplaced at stations6491.9967 and 6491.0167 (both at Weipa).

6. DATA STORAGE

The meter calibration data referred to above are stored inthe BMR calibration files of the relevant meters. Field and drift sheetsare filed in the BMR Isogal naps under the heading "E W1 A", and stationdescriptive data are filed under 'Thursday Island' and 'Daru'.

Station 6691.1001^:^9789 244 . 4 mgal by' .Based oria - valuePen44?-!ATAL8:q2n.mgal).

3

7 0 ACKNOWLEDGEMENTS

Aqnowledgement is made of the assistance given by otherorganisations including

Helicopter Utilities Pty LtdDepartment of Civil Aviation (Horn Island Aero4rome)Department of Customs and Excise (Thursday Island)District Office (Daru)Stol Air Services Pty Ltd (Daru)Ansett—ANA

8. REFERENCES

BARLOW, B.C.

BARLOW, B.C.

1965 Establishment of gravity metercalibration ranges in Australia,1960-61. Bur, Min. Resour. Aust,Rec. 1965/-19.

Australian Isogal gravity survey,1964-65. Bur. Min. Resour. Aust.Rec. (in preparation).

90._

0 OrU

PLATE I

SCALE40 MILES TO 1 INCH

^1:2,534,000

40 30 20 10 0^

40^

80^

120

ESTABLISHMENT OF ISOGAL GRAVITY BASE STATIONS

THURSDAY ISLAND, QLD, AND DARU, TPNG,1966

LOCALITY MAP

Geophysical Branch, Bureau of Mineral Resources, Geology and Geophysics^C54/82-19

TO ACCOMPANY RECORD NO. t966/141

PLATE 2•70._

ofezr

6691.9001( Station Markedwith brass disc)

(:—Noter

6691.1001( Station markedwith brass disc )

Septic

Prince of Wales Island

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L Secondary base

@ E xcentre

THURSDAY ISLAND (HORN ISLAND) QLD

C54/82-20

GRAVITY STATIONSAUSTRALIAN NATIONAL GRAVITY NETWORK

Geophysical Branch ,Bureau of Mineral Resources,Geology and GeophysicsTO ACCOMPANY RECORD NO. 1966/141

PLATE 3^.

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@ Excentre^ •C 54/8 2-21

GRAVITY STATIONSAUSTRALIAN NATIONAL GRAVITY NETWORK

Geophysical Branch ,Bureou of Mineral Resources,Geology and GeophysicsTO ACCOMPANY RECORD NO. 1966/141

DARU TOWNSHIP

Wharf^6691.0172SEE BELOW

----.^---r.^---^---

/"."---- ----\ _I

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rili•

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Air Services PtyLtd Hangar

Footbridge/50Access Bridge -----

. - "STOC I HANGAR

6691.0172(marked with brass discon c ncrete base under

screen)

A Primary base

Secondary base

@Excentre

DARUPAPUA— NEW GUINEA

C54/B2-18

. GRAVITYAUSTRALIAN NATIONAL GRAVITY NETWORK

' •^Pt L..■ ..ew..Geology and GeophysicsTO ACCOMPANY RECORD NO. 1966/141