Latitude -30.198529, Longitude 146.23989
Located in the Outback Region of NSW, nearest town Bourke
Source: Mount Oxley and Coolabah Geological Mapping Project. Project update - December 2011
Mt Oxley is a mesa or tableland of sedimentary rock which dominates the surrounding flat plains of the area. It was well known to the early explorers, Sturt and Hume, who climbed Mount Oxley in 1829 on their expedition to discover the "inland sea". The mountain is known as Oombi Oombi to local aboriginals and was previously an important source of grinding stones.
There is an intriguing mystery associated with Mt Oxley, and it has puzzled people for many years, including early explorer Charles Sturt. Occasionally, around sunset, after a very hot day, booming noises seem to emanate from the mountain. Sturt himself reported:
"distinctly hearing a report as of a great gun discharge twice in the Stony Desert, and once when near Mt Oxley in 1828. It might have been some gaseous explosion, but I never in the interior saw any indications of such phenomenon. It made such a strong impression on all of us and to this day the singularity of such a sound in such a situation is a matter of mystery to me."
A number of small, crater-like rocky formations may be seen in two distinct lines on the top part of the mountain. No conclusive explanation has been offered for the craters and noises but one possible explanation could be the sudden contraction of the rock upon cooling at sunset after exposure to massive heat during a very hot day.
A paper on the subject of the "loud unexplained booming sounds" was published by the pathologist and naturalist (Sir) Dr J. Burton Clelend (1878-1971) M.D. Journal and Proceedings of the Royal Society of New South Wales for 1911, pp. 187-203. Sydney, 1912.: "On the Occurrence of Explosive or Booming Noises (Barigal [etc] Guns) in Central Australia"
This directly referred, in part, to Mt Oxley. It relates a report from another naturalist, Mr D. G. Stead, who wrote "In regard to mysterious rumblings or explosive sounds - when I was on the dry Bogan during August of last year, I stayed for two nights on Mr Barton's station at Mooculta. While there, and while discussing various natural phenomena with Mr Reginald Kirkwood, Mr Barton's manager, the former told me that, not infrequently, at the end of the very hot days just around and a little after sundown were to be heard coming from the direction of Mt Oxley (which I could see from there, and which is a distant about fourteen or fifteen miles) rumbling explosive sounds, sometimes loud, sometimes muffled, according to the state of the atmosphere and the direction of the wind. I suggest that it would probably be caused by bursting rock which had become intensely heated during the day, and was undergoing a rapid cooling process. He agreed that this was extremely probable, but could not say from actual observation. He also told me that the summit of Mt Oxley had numerous peculiar crater-shaped conical depressions: these were only about the summit. This was most interesting to me and I specially noted it in my book at the time. Upon making a close enquiry later, I found similar sounds had been heard coming from Mount Gundabooka, which I have also seen, and which is about forty miles SSW from Oxley. Now both of these short ranges stand up like islands in a veritable 'ocean' of plain country, the radiation from which must be enormous".
There is an unconformity (a contact separating two rock masses of different ages) at the base of Mount Oxley on the northern and eastern sides of the mountain, with steep-dipping slates overlain by conglomerate.
Mt Oxley is 49.5k by road from Bourke; take the Kamilaroi Hwy and head east towards Brewarrina. You can get specific instructions from the visitor centre or the appropriate property owner where to turn off the highway. There are magnificent views from the top of Mt Oxley looking towards Bourke and the mountain ranges further south. At the top are communications towers and, a little to the west via a dirt track, a picnic area with BBQ, shelter, tables and toilets. Telstra has sealed the track on the steep assents. Visitors must ring the owner of the Mt Oxley property to obtain the code to open the gate. There is a small fee for entry to Mt Oxley. Bourke Visitor Centre Ph: (02) 6872 1222. Property owner 0428 723 275