|Kata Tjuta, Anangu for "many heads"|
|Basic stratigraphic cross-section of|
Uluru and Kata Tjuta
Back in the Neoproterozoic, the Petermann mountain range was more formidable than it is today, due in major part to the Petermann orogeny. However, the Neoproterozoic/early Paleozoic climate was more temperate, so its peaks were being denuded by precipitation at a greater rate than the more subdued Holocene landscape is by current aeolian forces. Alluvial fans were created along the flanks of the Petermann foothills, each differing slightly in lithology, but not in origin. These fans formed a piedmont range that was a major part of Petermann foreland basins, such as the Amadeus, Georgina, Ngalia, and Officer basins of then central Australia. The fan material developed sequentially into flysch once a eustatic change in sea level occurred in the late Cambrian, covering the region in a shallow sea. Continuing weight of added sediment + the weight of the increasingly deepening sea was enough pressure to lithify the alluvial fans/flysch into arkosic sandstone (Uluru) & conglomerate (Kata Tjuta), each portion representing a different fan thus a slightly different lithology, all connected together during the melding of adjacent sedimentary units. If we could remove the overburden of sand & schist members, we likely could find the area where the conglomerate and sandstone grade into each other.
|Google Earth snapshot of Central Australian plain, with Kata Tjuta @ left and Uluru @ right (VE = 3x)|
Coordinates for centerpoint = 25° 18.710'S 130° 53.730'E
The finer features of the Olgas have been primarily shaped by precipitation during more temperate paleoclimatic conditions. Freeze-thaw processes acted on joints in the rock, fracturing the surface. Rivulets of creeks and small waterfalls promoted the formation of potholes and gorges. Since granite is a primary ingredient in the Kata Tjuta Mount Currie conglomerate, spheroidal weathering was able to smooth and accentuate a rounded dome shape to the remaining 36 mini-bornhardts by working on the angles & corners. Of course, iron content exposed to the atmosphere colored the veneer of Kata Tjuta to that typical iron oxide rusty-red. Some visible structures noticeable when perusing the rocks include limited tafoni structures among the rock domes. Slickensides are also apparent, indicating displacement of large sheets of the conglomerate during times of acute mass wasting.
As an aside, I stumbled upon an interesting take on the formation of Kata Tjuta when google-searching: Tas Walker's Noachian interpretation of Kata Tjuta. It is a prime example of working backwards with the scientific method, where a proposed theory is the starting point, and evidence to support it is anecdotally surmised to fit that theory. Remember, if a null hypothesis cannot be rejected, and credibility cannot be established through peer review, it is not science, and certainly not geomorphology science. Current [accredited] geomorphology research reveals noticeable increase in relief amplitude of both Uluru and Kata Tjuta inselbergs throughout the Cenozoic, which is atypical of the ideal cycle of erosion (see additional links). Interesting mechanisms must be at play, and a deeper look into the asthenosphere, lithospheric flexure, and the mass dynamics between the overburden and the Mount Currie Conglomerate are called for.
|Thanks to my brother for the above photo of the Olgas, circa 2007|