Southeast Lachlan Ground Gravity Survey
The Geological Survey of Victoria and Geological Survey of New South Wales have collaborated with Geoscience Australia to acquire ground gravity data along the Southeast Lachlan Crustal Transect. The acquisition of this new gravity data supports the processing and interpretation of the 2018 Southeast Lachlan Deep Crustal Seismic Reflection Survey.
The Southeast Lachlan Ground Gravity Survey measures extremely small variations in Earth’s gravity in parts of eastern Victoria and south-east New South Wales.
The ground gravity survey is part of the Geological Survey of Victoria’s Eastern Victoria Geoscience Initiative - a program to develop a greater understanding of Victoria’s underlying geological architecture. The gravity survey adds to Victoria’s geological knowledge base and contribute to future scientific research. It will help Government to make better informed earth resource and land management decisions.
The survey route
The gravity survey follows the route of the Southeast Lachlan Deep Crustal Seismic Reflection Survey which travelled from Swanpool to Tom Groggin and from Benambra to Eden in 2018. The gravity survey includes several small route extensions in Victoria and two additional routes; one from Baddaginnie to Benalla in Victoria and another from Tom Groggin in Victoria, through Cooma to near Badja in NSW.
In Victoria the routes pass through Baddaginnie, Benalla, Tatong, Edi, Merriang South, Myrtleford, Ovens, Rosewhite, Kancoona, Running Creek, Eskdale, Bucheen Creek, Nariel Valley, Tom Groggin, Cobberas, Brumby, Wulgulmerang, Wulgulmerang East, Deddick Valley, Tubbut, Bonang West, Bonang and Bendoc.
The ground gravity survey consists of individual recording sites located 200-400 m apart along the Southeast Lachlan Crustal Transect. The surveyors travelled along public roads and across a small number of private properties.
These routes are marked in green on the below map.
The gravity survey method
Measurements of the Earth’s gravity and a GPS location were recorded at pre-selected sites along the planned route. At each site, the gravity meter (a box containing what is effectively a very sensitive set of scales) is placed on the ground for 1-2 minutes while it measures the strength of Earth’s gravitational “pull” at that location.
By taking measurements at many locations in the survey area, geoscientists can map the differences in Earth’s gravity from place to place. These differences in gravity are associated with the rocks that make up the Earth’s crust and will be used to interpret the position and relationship of different rock types across the Southeast Lachlan Crustal Transect.
The surveyors transport their equipment in light 4WD diesel vehicles. The measurements are passive and do not create any disturbance apart from footprints and /tyre tracks. There is no requirement to disturb fencing or other infrastructure, and traffic is not unduly impacted.
Site selection and property access
Gravity survey sites have been planned along the route taken by the 2018 Southeast Lachlan Deep Crustal Seismic Reflection Survey.
Additional sites have been planned over areas adjacent to the seismic route to understand specific geological features.
Public land managers and private property owners along the route were consulted as part of the survey planning process. Site access and entry conditions are negotiated with individual land owners and managers with permits from the relevant authority obtained where necessary.
Under Victorian laws, geological surveys can be authorised on behalf of the Department of Jobs Precincts and Regions under Section 112(1) of the Mineral Resources (Sustainable Development) Act 1990.
The survey was undertaken by experienced gravity survey contractors and overseen by the Geological Survey of Victoria and Geoscience Australia.
Safety and environment
A detailed risk assessment and mitigation plan was prepared by the contractor to ensure the safety of the surveyors, the public and the environment.
Biosecurity arrangements were in place to avoid the transport of soil and organic material from site to site.
The data gathered during the survey have been processed and are publicly available on this website and the Geoscience Australia website.
Frequently asked questions
A ground gravity survey is one of many low-impact geophysical techniques used by geologists to see beneath the earth’s surface.
A small device (about the size of a small suitcase), called a gravity meter, is used to measure very small variations in the earth’s natural gravity field. Some of these variations are the result of density differences between different types of rocks. This information can then be used to map the distribution of the rocks and other geological features such as naturally occurring faults.
The gravity survey is part of a regional geoscientific program to investigate the large-scale geological architecture of southeast Australia from the surface to approximately 60 kilometres below the Earth’s surface. New fundamental geoscience datasets and applied geoscience research will improve the geological understanding of northeast Victoria and how it has evolved over the past 500 million years.
This research will also result in an improved understanding of the earth resources potential and natural geological hazards of eastern Victoria. Government will be able to make better informed land management decisions to benefit the community, protect State infrastructure and manage earth resources.
The ground gravity survey was carried out in May and June 2019.
The ground gravity survey was carried out along selected private and public roads and tracks around:
- Nariel Valley
- Tom Groggin
Atlas Geophysics Pty Ltd collected the ground gravity survey data. Atlas Geophysics is a specialist contractor with extensive experience in carrying out ground gravity surveys in Victoria and around Australia.
The survey has been commissioned by the Geological Survey of Victoria and the Geological Survey of New South Wales in partnership with Geoscience Australia.
The gravity meters used in this survey work in a similar way to normal scales and contain a mass and a spring. The mass is pulled by the gravitational force of the earth, stretching the spring. By measuring the length of the spring at different locations, the differences in the strength of the local gravity field can be measured.
The ground gravity survey technique does not cause land disturbance beyond that caused by normal vehicle access.
Surveyors travel along existing roads and tracks in light diesel four-wheel-drive vehicles. The gravity meter (a box containing what is effectively a very sensitive set of scales) is placed on the ground for 1-2 minutes to take a measurement, at the same time the surveyor records their location with GPS.
The total time taken at each location is approximately 5 minutes. Apart from footprints and tyre tracks, nothing is left behind. Survey staff work hard to minimise any disruption to landholders and road users.
Under Victorian laws, geological surveys can be authorised on behalf of the Department of Jobs Precincts and Regions under Section 112(1) of the Mineral Resources (Sustainable Development) Act 1990. Victorian land management authorities are also consulted, such as Parks Victoria, the Department of Environment, Land, Water and Planning, VicRoads and local councils.
A detailed risk assessment is prepared to ensure the safety of the surveyors, other road users and the environment. Care is taken to protect flora and fauna, and biosecurity procedures are in place to avoid transport of soil and plant material.
No. A tripod is used to provide a level surface for the gravity meter to take its recordings. No disturbance to the ground is necessary apart from placing the tripod legs firmly onto the surface so that it is stable.
The ground gravity survey has been planned to complement the 2018 seismic reflection survey.
The gravity survey follows the route taken by the 2018 seismic survey. Some additional gravity survey routes were planned to investigate geological features not able to be traversed by the seismic survey.
The aim of the research project is to investigate the geological architecture across southeast Australia from the surface to approximately 60 kilometres below the Earth’s surface by mapping a complete geological cross section of the Earth’s crust.
The survey sites have been chosen by scientists because they are areas where more data is needed to understand the region’s geology and how it has evolved over the past 500 million years.
The data will be incorporated into the existing state and national gravity databases. These databases are used to create gravity variation maps across Australia which show the distribution of different rock types. The survey results will also be used to help build a publicly available, digital three-dimensional (3D) geological model to increase understanding of the region’s geology and to present this information visually.
Yes. The Geological Survey of Victoria and Geoscience Australia have safely carried out ground gravity surveys for more than 50 years in all parts of Victoria using the same techniques to help build up an understanding of Victoria’s geology.
This survey is being conducted to improve scientists’ understanding of the geology of the region and of how it has evolved over time. It is not being carried out to directly explore for minerals in the survey area.
No. This survey is being carried out to better understand the geology of northeast Victoria and how it has evolved over time. The survey area is not prospective for gas and this survey has nothing to do with gas or fracking.
The results of this survey are publicly available on this website and on the Geoscience Australia website.
Page last updated: 30 Nov 2021