During the period 1991-94, a co-operative study of the early development of the Otway' Basin was
undertaken as part of a National Geoscience Mapping Accord project. The partners in the project
were the Australian Geological Survey Organisation (AGSO), the Geological Survey of Victoria
(GSV), the Department of Mines and Energy, South Australia (MESA), and the Victorian Institute
of Earth and Planetary Sciences (VIEPS) at Monash and La Trobe Universities. As part of the
project, four subsurface horizons were mapped across the onshore parts of the basin using
exploration industry and AGSO seismic data. MESA undertook mapping in the South Australian
sector of the basin, GSV in the central (western Victorian) part of the basin, and AGSO and VIEPS
in the eastern part of the basin. This is the first time such mapping has been published on a basinwide
scale in the Otway Basin.
This Record accompanies a folio of ten 1:500 000 scale maps compiled by AGSO from the data
provided by NGMA partners from the western, central and eastern parts of the onshore basin. Four
of these maps are presented as two-way times (in milliseconds) to four mega-sequence boundaries
together with interpreted structural information. The four mega-sequence boundaries are: -
1) - base Wangerrip Group,
2) - top Eumeralla Formation,
3) - top Crayfish Group,
and 4) - top Palaeozoic basement.
Time thickness (isochron) maps (in milliseconds two-way time) for the Crayfish Group, the
Eumeralla Formation and the Sherbrook Group, complete the horizon mapping. Also included are
maps of seismic line information and tectonic elements, and geophysical maps of gravity and
magnetic data. The maps are designed to improve the overall understanding of Otway Basin
subsurface geometry and tectonic evolution as a guide to possible hydrocarbon resources.
