8423-5 The Sisters (Bowen Range)

This information has been developed from the publications:

Sites of Geological and Geomorphological Significance in Central Gippsland (1981) by Neville Rosengren, M.S McRae-Williams and S.M Kraemers.
Sites of Geological and Geomorphological Significance in the Gippsland Lakes Catchment (1984) by Neville Rosengren.
Sites of Geological and Geomorphological Significance in East Gippsland, Victoria (1981) by Neville Rosengren, M.S McRae-Williams

Geological heritage sites, including sites of geomorphological interest and volcanic heritage sites, are under regular revision by the Geological Society of Australia, especially in the assessment of significance and values. Reference should be made to the most recent reports. See the Earth Science Heritage section of the Geological Society of Australia website for details of geological heritage reports, and a bibliography.

Location:	640025. 15 kilometres north-east of Omeo.	The Sisters, syenite stocks.
Abstract:	Exposures of Triassic Granite Porphyry in prominent peaks.
Access:	Walk from Coughlan Road.
Ownership:	Predominantly Crown Land with a small enclave of privately owned land.
Geology:	The dominant rock type of The Sisters is a pale coloured, medium grained quartz-feldspar (granite porphyry) composed of larger feldspar and quartz crystals enclosed in a matrix composed essentially of the same minerals in micrographic intergrowth. Syenitic rocks, which are transitional in type between the porphyritic syenite of The Brothers and the quartz-feldspar porphyry occur to the north of The Sisters peak. A number of included blocks of metamorphosed Mount Tambo Group sediments occur west of the saddle connecting The Sisters peak to Mt Pleasant. These consist of hornfels (which may in part be derived from the low grade schists of the Omeo metamorphic complex) metamorphosed conglomerates and grits.
Geomorphology:	The Sisters rise to greater than 1200 m in three prominent peaks above a gently undulating topography cut in Ordovician sediments and fault controlled alluvial basins. The granite porphyry is resistant to erosion and down cutting by tributaries, particularly Scrubby Creek, has deeply dissected the southern slopes of the range.
Significance:	Regional. Abundant exposure of the granite porphyry, inclusions of metamorphosed Tambo River Group sediments, and contact metamorphism of these sediments to the east of the peaks are of particular geological interest. The rocks are part of the youngest acid intrusive complex in Victoria.
Management:	Because of the area covered by the site the value of the geological features is unlikely to be seriously reduced by localized disturbance e.g. road works, or extractive industries.
References:	Crohn, P.W. 1950. 'The geology, petrology and physiography of the Omeo District, North-Eastern Victoria', Proc. R. Soc. Vict., 62 :1-70 Vandenberg, A.H.M. and O’Shea, P.J. 1980. 'Explanatory Notes on the Bairnsdale 1:250,00 geological map', Rep. geol. Surv. Vict., No.65.

Site 8423-5

Page top