Citation

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Thyer, R.F. & Everingham, I.B., 1956. Gravity survey of the Perth Basin, Western Australia. Bulletin  033. Bureau of Mineral Resources, Geology and Geophysics, Canberra.

Abstract

During 1949 and 1951, whilst investigating possible underground water supplies, staff of the Bureau of Mineral Resources surveyed two east-west gravity traverses near Watheroo Observatory (120 miles north of Perth) and Bullsbrook (20 miles north-north-east of Perth). Results of these investigations suggested the presence of a major fault a few miles to the east of both places and gave evidence of a large thickness of sediments underlying the coastal plains. It was decided, therefore, to extend the gravity investigations to a reconnaissance survey of the whole of the coastal region between Geraldton in the north and Cape Leeuwin in the south, extending inland from the coast for distances of 100 to 150 miles. This bulletin gives results of the survey, which was made in 1951 and 1952 over an area of about 43, 000 square miles and comprised gravity observations at 650 stations. The survey revealed a negative gravity anomaly of large magnitude and areal extent. Bouguer anomaly values, with a minimum of more than 130 milligals, form a trough about 400 miles long and up to 55 miles wide. Steep gravity gradients on the flanks of the anomaly suggest the existence of faults which have resulted in relatively light sediments lying adjacent to denser basement rocks. Such steep gradients indicate that the major part of the anomaly is due to an accumulation of sediments which at their maximum development may be about 30,000 feet thick. The Darling and Dunsborough Faults show up prominently on the gravity pattern, but other faults deduced from geological evidence are not apparent probably because the vertical movement on these faults has been too slight to have affected the gravity pattern. On the other hand, the gravity results indicate the presence of other, faults previously undetected. Two minor synclines are indicated, diverging from the main synclinal axis, and the importance of anticlinal axes associated with these synclines is stressed. The gravity pattern indicates that although the Perth Basin narrows to the north, between converging faults, it continues in that direction, to join the Carnarvon Basin. Recommendations are made for more detailed gravity surveys to be made in certain localities and for seismic surveys of selected traverses across the basin.
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nonGeographicDataset - GA Publication - Bulletin

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license
Creative Commons Attribution 3.0 Australia Licence

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Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

1956

Product Type

nonGeographicDataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Bulletin
gravity
Earth Sciences

Resource Language

English

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utf8

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unclassified

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Unknown

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onLine

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pdf

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Organisation Name
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Canberra
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Country
Australia
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Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

1996-10-29

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

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pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
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