Intro: Arguably the most famous landscape of Australia, I got to venture into the heart of the outback “red centre” as part of a geology-photography project (AusGeol). Our journey captures multiple meteor impact craters (!!), the famous Uluru (aka Ayer’s rock), Kata Tjuṯa (aka the Olgas), King’s Canyon and more! This post is Part 2 of 2, which goes from Alice Spring to Uluru and back, you can check out my first post here (Capturing Australia’s Outback in 3-D: Part 1), which covers from Darwin to Alice Springs.
The project is part of the University of Tasmania, led by Dr. Michael Roach, with funding from the Australian Government Office for Learning and Teaching and partner institutions. Every captured geological outcrop is made freely available on the website http://www.ausgeol.org/, with an extensive virtual library that has a diverse selection of well-documented examples of important geological features to assist in the development of student geological field skills. For examples of my sites in the N.T. as well as others through Australia, check out the atlas http://www.ausgeol.org/atlas/.
How this was done was using a regular DSLR camera and a UAV (drone) to basically take multiple photos from different angles of a rock outcrop or feature of interest. Then, as long as a GPS point was recorded and a scale with a north direction evident, we can turn these mosaics of images into a 3-D model (using a program called AgiSoft photoscan), or into full spherical panoramas (e.g., Google street-style stuff). Unfortunately drones aren’t allowed in some areas (like around Uluru), so we had to just capture full spherical panoramas or outcrop-scale examples there.
The trip – part 2 (Alice Spring to Uluru and back)
For a brief into the Northern Territory and its geology, check out my first post (Capturing Australia’s Outback in 3-D: Part 1), which has a nice summary of Ahmad and Scrimgeour (2013). Following the adventures in part 1, we headed from Alice Springs and went south toward Ulura, along the Stuart Highway (i.e., #1/#87), into the Amadeus Basin.
Henbury Meteorite Craters
A pretty incredible side trip to the west along the highway is a large hole in the ground called Henbury. This is actually a 180 m wide crater formed 4,000 years ago by a meteor travelling at 40,000 km/hour. Pretty neat eh?! The area is known as the Henbury Meteorite Craters* in the Northern Territory, Australia (*craters because it is a coalescence of multiple small meteorite impacts, rather than just one big one). Below is the 3-D aerial photo I took from a UAV which lets you see the crater quite well. Click on the “play” button to check it out (but wait a few seconds while the HD resolution loads).
Uluru (also known as Ayer’s rock)
Several more hours along the highway you enter the “Red Centre”, and Mt. Connor is there to greet you as a red heron (lots of people are fooled by this initially on the horizon, I was even fooled by it as we drove up from the distance). Nevertheless, in about 100 more kms you reach the true Uluru (also known as Ayer’s rock), Australia’s most famous rock.
Uluru is made up of the Mututjulu Arkose geological unit in the Amadeus Basin Province (i.e., fine- to medium-grained sandstone to arkose). You can see the sub-vertical layers and ribs that have been amplified by years and years of erosion.
Uluru is actually tilted on its side by 90°, and is only the tip of a huge body of rock that continues for possibly 5 to 6 km below the surface! Uluru is the remnant of an 550 million year old sandy fan from an ancient mountain range. The sand was covered by a sea ~ 500 m.y. and the weight compressed the sand to form sandstone. Some millions of years later, after the ancient sea was gone, immense tectonic forces caused areas of Australia to be folded and tilted. Thus what we see today is Uluru tilted 90° from its original position.
The actual colour of Uluru is grey sandstone, but it has turned to orange/red on the surface due to iron in the sandstone that oxidizes (rusts) overtime.
Kata Tjuta (also known as the Olgas)
Beside Uluru are a series of large “bumps” called Kata Tjuṯa (also known as the Olgas). They are the lesser-known cousins of Uluru, and consist of several large outcrops composed of coarse-grained conglomerate (as opposed to the typical fine-grained sandstone of Uluru). Kata Tjuṯa literally meaning “many heads”, and it isn’t hard to imaging seeing the conglomerate domes. They, like Uluru, have been subjected to millions of years of erosion in the Northern Territory “red centre”.
King’s Canyon, Watarrka
Heading north from Uluru is the Watarrka National Park. Herein lies King’s Canyon, which is a stunning sandstone canyon that has the most spectacular cross-beds and ripple marks. There was once a shallow sea ~ 440 million years ago at King’s Canyon. Eventually the sea retreated and land was uplifted, changing the environment to a desert with windswept plains and sand dunes at ~ 400 million years ago. Now what we see exposed along King’s Canyon are remnants of these environments, with the stunning cross-bedded 400 Ma Mereenie sandstone overlying the 440 Ma Carmichael sandstone.
Gosse Bluff (Tnorala)
A (sketchy) 4-wheel drive north up the Mereenie road leds you to the West MacDonnell Ranges. On the way to the ranges is another hole in the ground. Except this one is enormous!! It is known as Gosse Bluff (Tnorala). It is the remains of a giant comet* impact (*note it was a comet, and not a meteorite like Henbury was). Gosse Bluff is a 5 km wide crater which is the remnant inner core of a massive comet impact that occurred ~ 143 million years ago. It is best to see it from way above actually (i.e., Google Earth). Inside the crater is the remnants of this impact, including shatter cones and rocks that have been tilted sub-vertical from their original position due to the impact.
West MacDonnell Range
The West MacDonnell Range features some pretty gorgeous gorges, such as Ormiston Gorge with exposures of the Heavitree quartzite and complex folds and thrust faults. Along the ranges is also the Ochre Pits. These are layered sediments with stunning colours due to oxidation (i.e., exposure to the surface/oxygen) of the fine-grained clays (red = hematite, yellow = limonite and white = kaolinite). Ellery Creek Big Hole offers some neat sedimentary units and structures, such as stromatolite and great examples of de-watering structures in the red sandstone. Lastly, we went to Simpson Gap, just west of Alice Springs. Exposed here is the ever-so-abundant Neoproterozoic Heavitree quartzite rock unconformably overlies the Paleoproterozic metasediments.
Final thoughts: The Northern Territory is a very huge place, and it gives a new meaning to things being “not-far”… For such a flat country, it sure does have some very diverse rocks and landscapes. The red centre has an enchanting aurora, and it is no wonder that Uluru is so famous, it is a glowing statue in a vast, flat plain. Getting to see and capture some of the extraterrestrial impact crater sites was truly “out of this world” (sorry!), and both King’s Canyon and West MacDonnell Range offer stunning exposures.
Overall, being a part of the 3-D photography project was an awesome experience, and hopefully now anyone can at least see and learn a bit more about Australian geology in the Northern Territory.
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