Yilgarn


 

 

In Western Australia the term Yilgarn has been used in many different ways. Itemised below are four different ways, all relevant to Helena and Aurora Range and the region that it occurs within.

 

Yilgarn is an Aboriginal name for quartz or white stone.  The white quartz bedrock is extensive extending south to just north of Albany and north to Mt Marshall (just south of Bencubbin, well north of Merridin) including most of the Wheatbelt and Great Southern Regions (source: Shire of Yilgarn publication).

 

Yilgarn is also used to identify the Yilgarn Craton.  A large land mass made up of predominantly metamorphic (volcanic rock) including granite, basalt and komatiite. The Yilgarn Craton covers most of the south west and ‘goldfields’ of Western Australia (see map below).  It consists of four greenstone belts. The greenstone belts are complex and occur between the more homogeneous granite and gneiss bodies in the Yilgarn Craton. Helena and Aurora Range is within the Southern Cross Granite-Greenstone Terrane or the Marda-Diemals greenstone belt (Chen and Wyche, 2003).

 

The proposed reserve system including Helena and Aurora Range is referred to as occurring in the Northern Yilgarn, and it appears that this refers to being within the northern half of the Yilgarn Craton.

 

There is also the Shire of Yilgarn (central town and Shire Council in Southern Cross) that includes an area from north-east of Hyden to south-west of Menzies, situated in the Great Western Woodlands. 

 

Helena and Aurora Range occurs in all four of these identified places as do the other banded ironstone formation ranges included within the proposed Mt Manning Reserve system.  Sometimes the area including the Mt Maning Reserve system is simply referred to as the Yilgarn (within the Coolgardie Bioregion), distinguishing it from the goldields (Murchison Bioregion) and wheatbelt.  

 

In summary the BIF ranges within the proposed Mt Manning Reserve (including Helena and Aurora Range) occur in the northern area of the Yilgarn Shire and within the centre of the Yilgarn Craton (Central Yilgarn). 

 

The land use in the central Yilgarn has historically been pastoral with some small scale mining.  The vegetation is pristine, most areas showing minimal effects of grazing by cattle (probably due to low stocking rates).  Several pastoral leases have been purchased by Department of Environment and Conservation*.

 

The vegtation in the Central Yilgarn is distinctive in that on the flats between the BIF ranges are extensive areas of tall open woodlands of Salmon Gums (Eucalyptus salmonophloia) and Gimlets (Eucalyptus salubris), or Eucalyptus longicornis, Eucalyptus transcontinentalis, Eucalyptus formanii, Eucalyptus corrugata and Eucalyptus longissima.  This area and vegetation is distinctive to the Coolgardie Bioregion. As one travels further north the big eucalypt trees start to drop out until eventually, once within the Murchison Bioregion there are few eucalypt trees and Mulga (a tall Acacia tree) dominates.

 

The goldfields proper is within the Murchison Bioregion where tree species are uncommon or very sparse, often restricted to water courses.  The Department of Parks and Wildlife (DPaW)* divides Western Australia into management regions that usually include several different geographical types / landforms.  The BIF ranges within the Yilgarn Craton are predominantly within the Goldfields Region and Midwest Region.  Helena and Aurora Range is within the Goldfields Region of DEC.

 

 

Map showing the Yilgarn Craton in Western Australia (Precambrian; craton in legend)

Source: Basic geological units of Australia, after Addario et al, created in Arcinfo GIS from pblic domain geological mapping data, GFDL free use

 


References

Chen SF and Wyche S (2003)  Geology of the Bungalbin 1:100 000 Sheet. Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes.  Department of Industries and Resources.

Wikipedia website (searched 2012)


  * Department of Environment and Conservation (DEC) was separated into two departments on 1 July 2013; Department of Parks and Wildlife and Department of Environment Regulation.