GEOLOGICAL RECONNAISSANCE OF THE Higher ridges range up to 600 feet above the WARBURTON RANGE AREA, Elder Creek level at the mission site, and are flanked WESTERN AUSTRALIA. by, or interbedded with, lower, less-resistant belts of similar trend. Dissection of the hilly belts has By John Sofoulis, BSc. been general with drainages mainly controlled by rock fracture systems, strike and dip features, and INTRODUCTION. lithological diversity. A geological reconnaissance of the Warburton Range area was prompted by the recent marketing In the south-west sector, lower lying breakaway of copper ores extracted from the immediate vicin- and butte features are formed by dissection of the ity of the Warburton Range Aboriginal Missioii. flat-lying Palaeozoic sediments. Earlier geological reconnaissances of the same area were conductkd by Talbot and Clarke (1917) and Outwash Plains. Porman (1932, 1933). Flat alluviated plains skirt or occupy the lower The present report discusses the physiography, lying areas of the hilly belts. These are associated stratigraphy, structure and economic potential of with the sheet drainage of the area, and appear as the area, and also suggests correlations with red loamy outwash plains (or aprons) showing little, a,djacent areas. The report is accompanied by a iL' any outcrop, but frequently mantled by veneers geological compilation based on photo index map of stoney or fragmentary material derived from Talbot, sheet 3/468, scale 1 mile = 1 inch. the upland areas. The geological reconnaissance was carried out These plains support strong stands of mulga during the period October 2nd to 12th, 1961. vegetation and (dependent on gradient) usually present regular dense grove patterns, arcuately ar- LOCATION AND ACCESS. ranged (convex downslope), and up to a half mile The Warburton Range Area is contained within in length. Intergrove areas may be bare or show the "Talbot" international oseries sheet S.G. 52-9 scantier vegetation. In some sectors, the increased delineated by latitudes 26 and 27" south and frequency of mulga banding presents a dense longitudes 126" and 127" 30' east. The locality falls thicket appearance. within a native reservation, and permission to enter Other alluviated and calcreted drainages also in- the area must be obtained from the Department cluded with this unit are separately discussed in of Native Welfare. the water supply report for this area. A native mission Station, operated by the United Aborigines Mission, is located near the junction of Sand Plains. Hughes and Elder Creeks on the north-west foot- Extensive developments of red aeolian sand hills of the Warburton Ranges, and caters for the plains, commonly formed into parallel seif dunes, welfare of the nomadic natives of the region. The appear in the north-east and south-west sectors. Station includes a store, hospital, and school, and Dunes average 30 feet in height, and can vary up is connected to the Flying Doctor radio network to 1 mile in length. General dune orientation is based at Kalgoorlie. A landing strip for light along south-west lines, but directions appear con- aircraft, and water facilities, are available at the fused, anastomising, or chain-like, where adjacent Mission. to upland belts. From t'ne West Australian side, the Warburton area may be reached by travelling eastwards along Some recent sand movements has occurred a graded dirt road from Laverton to Cosmo New- (directed towards the south-west) , but in general, berry Mission (50 miles), and thence north- the Sand plain and dune areas are now fixed by eastwards for a further 300 miles via the southern spinifex and low scrub cover. margin of Lake Throssell. In the south-west sector, sand plain areas locally A graded dirt road running north-eastwards for contain small developments of mulga-covered some 170 miles ccnnects the Warburton Mission lateritic rises and occasional low breakaways, form- with the Giles Weather Station. Forty miles along ing the Tertiary surface as developed over Palaeo- this road, a newly-constructed track branches west- zoic sediments. wards to link with Carnegie Pastoral Station and thence to Wiluna. STRATIGRAPHY. Supplies and mail are carted by the Mission Within the area, metamorphic rocks of sediment- truck which makes a trip monthly to Laverton. The ary and volcanic origins, rise abruptly out of the Giles Weather Station forms the nearest perman- sand plains to form upland areas and prominent ent settlement and has a weekly mail service from ridge belts. On lithological and structural grounds, Alice Springs. Giles is operated jointly by the these rocks bear a strong resemblance to the Nulla- Bureau of Meteorology and Weapons Research, and gine System overlying the undoubted Archean is connected by a graded dirt road running some rocks in the Pilbara and Murchison areas of West 400 miles eastwards via Mulga Park and Mount Davies pastoral Stations to meet the Adelaide to Australia. Alice Springs Highway 10 miles south of Kulgera. In the Warburton region, it is apparent that From this South Australian side, a branch track the metamorphic rocks have been mobilised to also connects to the Warburton area via the Black- form porphyry and granite bodies, and are thus stone Ranges. tentatively relegated to the Lower Proterozoic era. PHYSIOGRAPHY. These rocks form the basement and probably the From a regional aspect, the area has an average source areas for the Palaeozoic beds developed elevation between 1,500 and 2,000 feet above sea marginal to and transgressing the Wa:burton rocks level but shows a gradual fall from north-east to in the west and south-west. south-west. Consequently major drainages are con- trolled by this fall and drain westerly or southerly Younger superficial formations of Cainozoic age to terminate in outwash aprons or become lost in mask a large proportion of the metamorphic and adjacent sand plains areas. Palaeozoic terrains. Dissection of the hilly belts is influenced mainly All of the rocks appear unfossiliferous and by structural and lithological features and, with formation names which are proposed below are the exception of the higher Warburton Range purely tentative, subject to more intensive field ridges, local differences in elevation seldom exceed and petrological study and approval by the West 200 feet. Physiographic units distinguished within Australian Stratigraphical Nomenclature Commit- the area are:- tee. Dissected Hills and Ranges. Lower Proterozoic Metainorphics. Resistant ridges and dissected hills of meta- Distribution and attitudes of the metamorphic morphic rocks comprising the Warburton Ranges rocks indicate a major anticlinal flexure with the form the major positive elements of relief. These eroded core now represented by the various meta- are south-east trending in the north-west sector. morphic belts of the Warburton Range. Higher but alter to an east trend in the south-east sectoi. grades of metamorphism are confined to the axial 16 zone of the anticline, whilst 01; the east flank, From the present investigation, the Townsend upper horizons of the sequence have been further Quartzites appear more or less conformable with mobilised to yield granite and porphyry bodies. the underlying Ainslie Volcanics, but are separated From bottom to top, the formations which can from them by a low angle thrust. Isolated quartzite be distinguished are: outliers frequently appear as conformable strike remnants fused to the underlying Ainslie Volcanics Miller Volcanics (after Miller Hill) .-This name east of the main escarpment. is tentatively proposed for a sequence of some 5 000 to 6,000 feet of fine to medium grained doleritic On the eastern limb, the Townsend Quartzites are and basaltic lavas and extrusi! es appearing along metamorphosed and grade into phyllitic schists, the axial portion of the flexure The sequence also quartz schists, sericite schists, etc., whilst further contains minor intraformational volcanic breccias, east, they have been completely mobilised to yield tuffs, and agglomerates, and thin metasedimentary porphyry and granite masses. In view of this bands (mainly calcareous). mob:lisation, the Townsend Quartzites are prefer- ably grouped with the Lower Proterozoic sequence. Metamorphism has produced massive and schistose rocks of amphibolitic grade, but relic Lower Proterozoic Mobilisations and Igneous In- volcanic and sedimentary textures are frequently trusives. recognised in the relatively unaltered zones. The Miller Volcanics are conformably overlain Mobilisations and igneous intrusives distinguished on both flanks by the Elder Dolomites, and in the within the area are:- axial sector are also intraded by two concordant Warburton Porphyry.-This name is tentatively porphyry sills (Warburton Porphyry). Basal beds Proposed for the massive or foliated fine-grained, of the Miller Volcanics are not exposed. dark grey, brown, or black, quartz-albite porphy- Elder Dolomites (after Elder Creek) .-Thinly ries which intrude the Miller Volcaiiics in the axial bedded dolomitic limestones, associated with rib- zone of the flexure and is also extensively deve- boned, argillaceous and cherty beds, are exposed loped along the eastern limb. on either side of the structure to form the im- Twin concordant porphyry intrusions appearing mediate lower slopes and foothills of the Warbur- on either side of the axis, form prominent ridges, ton Ranges. and are suggestive of two bedded horizons injected This dolomitic sequence is approximately 1,500 along axial crests in sill form. feet thick and is conformably