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Cobar Peneplain - subregions

Subregions of the Cobar Peneplain Bioregion
SubregionGeologyCharacteristic landformsTypical soilsVegetation
Boorindal Plains Quaternary alluvial blanket over weathered Ordovician and Silurian low grade metamorphosed sedimentary rocks, such as phyllite. Undulating plains with wide valleys and occasional low stony rises. Gilgai widespread in depressions and swamps. Red earths and red texture contrast soils with stony lag gravels on slopes. Brown clays and harsh texture contrast soils in depressions and swamps. Dense mulga, ironwood, poplar box and red box with dense shrubs on ridges and slopes. Dense poplar box with lignum, budda, emu bush, narrow-leaf hop bush and grasses on lower slopes and depressions.
Barnato Downs Devonian quartzose sandstones in ridges, finer sedimentary rocks under the plains often covered by a mantle of Quaternary alluvium. Steep ridges and rocky slopes controlled by bedding and joints in bedrock. Relief to 150m, length of ranges up to 40 km. Undulating low ridges and stony rises on softer rocks with a mantle of Quaternary colluvium and alluvium. Sands and minor clay deposits in stream lines. Lakes at Barnato. Thin, discontinuous stony profiles on ridges, thickening downslope to stony, red, texture contrast soils and red earths on the plains. Valleys generally texture contrast soils with calcium carbonate in subsoil, small areas of cracking brown clays or red sands. Mulga, red box and grey mallee on crests, white cypress pine and poplar box on slopes. Red box, mulga, white cypress pine and polar box on plains. Areas of belah rosewood and yarran. Pointed mallee in the south. Woody shrubs widespread.
Canbelego Downs Fine grained Ordovician and Silurian metasedimentary and sedimentary rocks, such as phyllite, slate and chert. Undulating plateau with low stony ridges and stony rises, relief to 20m. Long low angle slopes and wide (>500m) valleys. Some central sandy channels, a few swamps. Shallow red loams or stony loams on crests merging to red earths on slopes, plains and through the valley floors.



Minor sand deposits along streams, yellow texture contrast soils in swamps.

Mulga with green mallee, red box and numerous woody shrubs on ridges and slopes. Poplar box, white cypress pine, yarran shrubs and grasses in the valleys. River red gum and polar box with sedges, lignum and nardoo in swamps and larger creeks.
Nymagee Downs Ordovician to Devonian granites, quartzose sandstones, phyllites, slates and acid volcanics. Quaternary aeolian sands and alluvium. Low hills and ridges with steep slopes. Form controlled by rock type, rounded hills with tors on granite, asymmetric strike ridges in sedimentary rocks. Sandplains from adjacent bioregions lap onto lower slopes. Gritty red and yellow earthy sands on granite. Stony red earths and texture contrast soils on sedimentary rocks. Calcareous red earths in sandplains, minor earths and grey clays in alluvium. Dwyer's mallee gum, white cypress pine, kurrajong, golden wattle on granite crests, poplar box and red box on slopes and creeks. White cypress pine, red box, belah with mallee, western wattle grey box and rosewood on crests and slopes of Sedimentary rocks. Mallee communities on sandplains. Dense poplar box and white cypress pine in creek lines.
Lachlan Plains Devonian quartz sandstone and conglomerate, small areas of granite, and Quaternary colluvial slope mantles and alluvium. Strike ridges of resistant rocks often following fold patterns. Low rounded hills of granite with sparse outcrop. Wide short valleys connecting to Lachlan floodplains. Shallow stony or gritty red earths on crests and slopes, thickening downslope as rubbly mantles often with a texture contrast. Deep sandy alluvial soils in valleys with small areas of grey clay in swamps. Dense currawang, Dwyer's mallee gum and white cypress pine on rocky crests. Same with red ironbark, mallee broombush, hill tea-tree and poplar box on slopes. Poplar box, white cypress pine, mallee, kurrajong, yarran and wilga in valleys. Poplar box and black box in minor swamps.

From Morgan and Terrey 1992

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Page last updated: 18 April 2016