I recently got to take part in a neat project, called AusGeol, which provides a repository of digital geological teaching and learning resources that documents the diverse geology of Australia. A colleague and I were assigned the task of visiting the Northern Territory (N.T.) to document (through photography) some interesting and important geological sites. In this 2-part blog post I will be sharing some of the geology of the Northern Territory with regular photos and embed links to the 3-D examples. This is part 1, you can check out part 2 here.
About the project
The work was done 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).
The program 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/.
Brief intro to Northern Territory
The N.T. comprises ~ 13% of the Australian continent. It is underlain by the North Australian Craton, and it is dominantly Palaeoproterozic in age (~ 1.8 billion years old), with some Archean basement ‘inliers’ (Ahmad and Scrimgeour, 2013). Along with the Palaeoproterozoic basins and orogens (i.e., North Australian Platform Cover and Orogenic Domains), there are large Neoproterozoic to Palaeozoic sedimentary basins (i.e., Central Australian Platform Cover and Younger basins). Geological regions of the N.T. are broken into “provinces” or “basins” which are areas with distinct geological characteristics and ages; they are separated from one another by major structures and/or unconformities (Ahmad and Scrimgeour, 2013).
The trip – part 1 (Darwin to Alice Springs)
The Northern Territory is a big place… in total we drove over 4,000 km in ~ 3 weeks! Thus I will only go through some places in these posts, with some of my favorite digital captures! This was largely done going down the Stuart Highway (known as “the track”) until just before Alice Springs, in which several detours were then taken to the west and east.
Katherine Gorge
Starting from the north, not too far south from Darwin, is the Katherine Gorge, a popular destination for tourists as it is quite beautiful and offers lots of hiking, swimming, sightseeing, etc.! Though I didn’t do any of this though (haha), as we had to move fast to cover the N.T., we still managed to capture some of the stunning coarse-grained conglomerates of rounded boulders and cobbles that make up the gorge, as well as views of the banded sandstones along the riverside (~ Paleoproterozic 1.7 billion years old).
Davenport Range
Continuing further south is the Davenport Range. This is best seen from the sky actually, and with “geophysical goggles” on! The range is part of the large Wauchope Fold Belt. It is composed of folded succession of shallow marine sedimentary rocks and volcanics that have gone under greenschist metamorphism. The mafic amphiboles units and very magnetic, which can be seen quite well in an air-magnetic photo!
Devil’s Marbles (Karlu Karlu)
Some odd, round boulders in the middle of the N.T. outback (along the “track”, i.e., Stuart Highway) are known as the Devil’s Marbles (Karlu Karlu). These are a popular stop. The Devil’s Marbles are a “nubbin”. That is, they are residual boulders and blocks from the top “layer” of a large granite body that has undergone exfoliation weathering.
How it form is as follows. Molten magma solidified and formed granite beneath and within thick sandstone layers ~1.7 billion years ago. Joints and cracks formed within the granite when it was uplifted closer to the surface and the sandstone was eroded away. Water penetrated the cracks and preferentially weathered them creating more prominent blocks. The curved, domal surface is a characteristic feature of granites called “onion skin” weathering (for more info on this features, check out my Freycinet, Tasmania or Rio, Brazil posts).
Alieron Station and Reynold’s Range
Nearby the Alieron Station is the Paleoproterozoic Reynold’s Range (part of the Aileron Province), where some pretty spectacular folds and structures are! Some examples included parasitic folds, mixed felsic-mafic orthogneiss, coarse-grained granitic augen gneiss and cordierite granulite!
Harts Range
Next we headed east, pass Mudtank (a famous gem fossicking area), into the Harts Range and Etna dome. Here some of the river-bed sands in the Harts Range are composed of gemstones! That is, they are full of garnet from eroded rocks of the Harts Range Metamorhpic Complex, which is full of garnet-biotite gneiss. Rocks here are part of the Irindina Province and are quite younger (i.e., Neoproterozoic in age) than surrounding provinces.
Ross River D’hala Gorge
Leaving the metamorphic Harts Range, we entered the extensive Amadeus Basin on an east to west transect towards Alice Spring. Rocks here are of a more sedimentary flavor, with the ~ 800 Ma Bitter Springs formations dominating the landscape with beautiful overturned folded mountain faces, and synformal layers of interbedded sandstone/siltstone and dolostone/limestone of the ~500 Ma Goyder Formation, near Ross River D’hala Gorge.
Trephina Gorge, Gaps… and Mordor!
Lastly, we approached Trephina Gorge which is full of the Heavitree quartzite (~ 700 million year old). The Heavitree formation composes a prominent range around Alice Springs and with a handful of narrow openings in the range known as “gaps” (such as the Emily and Jessie Gap and The Gap).
From a high point in Trephina Gorge you can look to the south and see the Mordor Pound (which is a small mafic igneous complex). I really wanted to go to it in person, but apparently “one does not simply walk into Mordor”…
Final thoughts
The journey from Darwin to Alice Spring (with major side detours) offers a surprising diverse range of landscapes and geology for land that is relatively big and flat. This was my first experience in the true Australian outback, and coming from Canada and Tasmania it was definitely something completely different and I’m lucky that I was able to experience this unique Australian landscape and capture it digitally for others along the way. Don’t forget to check out www.ausgeol.org/atlas for more sites in the Northern Territory and throughout Australia, and check out part 2 of this post which will be Alice Spring to Uluru and beyond!
Cheers, Stephanie
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PS – Your Harts Range pics showing garnet were fascinating. So looked area up on Google Earth! Many scattered reddish areas. Don’t know if any were garnet gneiss, or just reddish sandstone, or what, but a most interesting area to view from above. (Also saw part of a road simply labelled “track,” which there was going almost east-west. Was that the one you drove?)
Hi Peter, I just had a look on Google Earth and if the scattered reddish areas are the same as what I think you are looking at then I believe they are just patchy areas of iron-oxide or “red-sand”. The creeks with garnet sand from the garnet gneiss aren’t that common and are a bit tricky to spot, even on the ground. I couldn’t find the road labeled “track”, but the one that I drove on towards the Harts Range was the #12 “Plenty Highway”. Thanks for the questions 🙂 Cheers!
Very impressive and informative. (The writing and the photos, AND the university’s program.) Will have to see if air magnetic photos are available around here. Looking forward to Part 2.
Thanks a lot, I’m glad you enjoyed it and thanks for reading! Part 2 is coming very soon 🙂
Thanks, Stephanie. Amazing as usual and I would love to visit the Outback one day. I like the hat, too. It works for you.
Thanks Gary!
Awesome! Any video coming soon? Is that true that there a lot of crocs there?
Thanks Billy! Yes I do have a video planned for this… but unfortunately it is taking me a while to find time to edit it due to all the end of thesis busy rush. I will get on it soon though 🙂 Yes it is true there are crocs in the Northern Territory, but they are up north near Darwin. I was mostly all south and closer to Alice Springs so I actually didn’t see any!
Thanks for sharing Stephanie! I know these areas from multiple trips to visit friends both in Darwin and Katherine! Love the areas and the outback! I’m curious if you went out to Kata Tjuta? Last time I was in Aus we took the Ghan up to ALice and then a bus tour to Kata Tjuta and the driver was very knowledgeable about the rocks and formation. He asked me to pick up one of the stones as we began our hike, it was about the size of two fists and for its size very heavy. Any idea what kind of rock it would be? I have forgotten what he said it was. What did you think about the flies? ?
Hi Sandy, thanks for reading and the comments 🙂 Yes it is a beautiful area, isn’t it! I did indeed go to Kata Tjuṯa and Uluru, that will actually be in my next post on Part 2 of this trip so keep an eye out for it in a week or so.
Hmm… sorry I’m not sure what the heavy rock would have been… maybe a piece of granite or metamophic rock as they are around the area (they are common boulders or clast within Kata Tjuṯa) and would be heavier than the typical sandstone in the area?
Cheers,
Stephanie
Love your posts Stephanie. I’m hiking in the Red Centre in June so this one’s particularly relevant.
Thanks Margaret! I hope you have a great trip in the Red Centre this June and glad my post can help a bit 🙂 I will post part 2 soon which is Uluru and King’s Canyon so you might find that helpful too! Cheers!
Thanks for sharing these amazing sights made even more so with your insightful commentary.
Thank you Marina 🙂
Absotively posilutely beautiful!! I want to go there ..
Yes it is a very beautiful and unique place indeed. Thanks for reading my blog 🙂