An island off an island off an island; welcome to Maria! I recently jumped aboard the opportunity to go on a weekend field excursion run by Geological Association of Australia (GSA) and the university to this wonderful little island off the east coast of Tasmania, Australia.
The whole island is a protected national park, and not only is it home to copious colonies of cute Tassie animals like wombats, kangaroos and Tasmanian devils, but it also contains some of the most beautiful and stunning geology you can find here in Tasmania! Ranging from ‘Painted’ to ‘Fossil’ Cliffs, I’ll give a brief background on why the rocks are just so spectacular on Maria Island.
Tasmanian time travel?
Progressing up from the oldest and lowest rock units, underlying Maria island are folded and metamorphosed sedimentary and igneous rocks, referred to as the Mathina Supergroup. The age of these rocks range from Silurian to Devonian (~500 to 360 million years; Ma), and they are exposed as vertical cliffs on the north coast of island (best seen by boat). The Mathina basement rocks are abruptly cut off by what is known as the “great” unconformity of Tasmania (Corbett et al., 2014). Above the unconformity are flat-lying Permian (~280 Ma) mudstones, known as the Parmeener Supergroup. Thus, what this ‘great’ unconformity is is a missing (i.e. eroded away) ~100 Ma period in the geological record.
Fossil Cliffs
The Permian Parmeener group is host to the Fossil Cliffs; an extraordinary fossiliferous sequence of impure limestone, siltstone, and mudstone (Hughes, 1957; Reid, 2004). These beds are locally up to 110 metres thick and full of marine fossils such as bivalves (e.g. Eurydesma), brachiopods (e.g. Trigonotreta) and bryozoans (e.g. Fenstellids) just to name a few!
Disrupting the fossil beds are large rounded ice-rafted debris, interpreted as glacial derived dropstones (Johnston, 1888). What is so unique about Fossil Cliffs is not only the shear abundance of the fossils, but what they represent… This site is one of the rarest in the world (e.g. so rare that David Attenborough was here) as the fossil-rich limestone represents a productive sub-polar cold-water shallow marine environment, where melting glaciers dropped large rocks onto the sea floor (Hughes, 1957; Reid, 2004; Corbett et al., 2014).
Painted Cliffs
Now progressing through time (and to the west of Maria Island) we move out of marine rocks into massive- and cross-bedded quartz sandstones of the Upper Permain Parmeener group. These rocks are exposed along the shore and known as the Painted Cliffs, and it’s obvious why once you see them. The sandstones have stunning patterns of red, orange and yellow bands and rings, which are a form of iron-oxide staining known as liesegang. The patterns are the result of repeated precipitation of colloidal iron from groundwater solutions (Clarke and Baillie, 1984). The groundwater flow is concentrated along an interplay between major fracture or joints and bedding layers within the sandstone, and thus is why they appear symmetrical in some localities.
Where did the iron in groundwater come from to produce these remarkable patterns? The answer may be from one of the youngest geological units. The top of Maria Island is comprised of two prominent hills known as Bishop and Clerk and Mt. Maria. These, along with being excellent day hikes, are composed by the profuse Jurassic aged (~ 180 Ma) dolerite that caps most of the peaks of Tasmania (Corbett et al., 2014). The weathering of these iron-rich dolerite rocks may have contributed to the iron-oxide staining on the Painted Cliffs.
Final thoughts
For such a little island, Maria hosts an immense amount of geological diversity. In a couple days you can travel through Tasmanian geological time, with visiting rocks that are both scientifically interesting and visually beautiful… that is, if you can get away from taking picture of all the wild animals roaming in this island national park! Maria Island is stunning and definitely worth the trip over when you’re on the not-so-little-island of Tasmania.
-Stephanie
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Stephanie:
I’ve visited Maria Island a number of times (including the Painted Cliffs area) but have never seen the bright red and yellow ochre bands in your photos. Can you describe how to get there? The background in your photos doesn’t look anything like the Painted Cliffs bay. Is it further around the corner or have I got the location completely wrong?
Thanks
Trevor Whitton
Thanks from Independence, MO!
We were watching an episode of the TV show “Vet Gone Wild” where the starring vet/host visits Maria Island. Trying to find more information, I stumbled across your site/blog. Thanks for all your wonderful sharing!
That’s cool! Glad they highlighted Maria Island on the show and that you found my blog out of curiosity 🙂 Hope you enjoyed it and thanks for the comment, cheers! Stephanie
thank you forsharing very helpful
You’re welcome 🙂
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Great site! Beautiful pics. Many Thanks.
Thank you very much for the compliments and for reading my blog, cheers 🙂
HI
i would just like to thank you the information you have written has really helped me with my geology assignment and i can’t wait to visit the cliffs next month! 🙂 🙂 🙂
You’re most welcome! Glad I could be of some help with the geology assignment 😉 I hope you get a chance to visit the painted and fossil cliffs on the island next month! Cheers!
I went to Maria island about 20 yrs ago and no one told us anything about this beautiful sandstone. I did enjoy the emus on the beach, the amazing shells on the beach on the isthmus between the two islands, and the old homestead on the small part of the island. It was awesome out there and I still talk about it. I wish I had known about the sandstone…..
Hi Jay, that’s awesome you went to Maria Island. I don’t recall any emus there when I went, but I had a look on the internet and apparently they were there at one point! Maybe you can get a chance to return one day, and if you do now you know about the beautiful sandstone haha. Cheers! 🙂
Hi Stephanie. I took a tour of Maria Island yesterday and, like you, was impressed by the range of geology in such a small space. I’m a retired geo and one of the things I do now is present courses on geology to U3A, in the Batemans Bay area of NSW where I live. Geologically, there is a great deal in common between the two areas (basement of deformed Palaeozoic metagreywacke, exposed angular uncf with fossiliferous Permian seds of the lower Sydney Basin sequence incl dropstones etc, Mesozoic intrusives – oh and great coastal scenery too!). So with your permission I’d like to use some of your pics to make up a presentation in a series I am contemplating, to be called ‘Geological Journeys’ to give to my class later this year. Love what you are doing with your blog. A lot of folk are interested in geology but there is not a lot of accurate info digestible by the layperson, so keep it up!
Hi Stewart,
Glad to hear you enjoyed Maria Island as much as I did! I didn’t realize there was so much in common near the Batemans Bay area of NSW with Maria Island. If I am ever up there I will definitely check it out! And yes, for sure you can use some of my pics for your presentation. Sounds like a really neat thing you are doing and hopefully it will inspire more kids into geology. Thank you for the nice words as well regarding my blog, I will try my best and keep it up 🙂 Best regards!
Stephanie
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Love your blog Stephanie! Jess
Haha, thank you Jess! I look forward to reading your blog when you start it up as well 😉
The colours on those sandstone are incredible, big like !
Indeed! Thank you 🙂
Reblogged this on The Tashina Orogeny and commented:
This is a spectacular blog. This is the kind of blogging I hope to do someday. 🙂
Thank you very much for the nice comment and re-blog!
Awesome geological experience! Thanks, Stephanie, for sharing : )
No worries, glad you liked it and thanks for reading 🙂
Reblogged this on Sig Nordal, Jr. and commented:
Stephanie, your work presented here is truly fascinating. I appreciate your support to our blog, Sig Nordal, Jr.
Very interesting features. How were the colored rocks formed?
Ron
Well the sandstone formed in a non-marine setting via the eventual burial of sand. This was likely a high energy beach environment. The beautiful colours are younger than the formation of the sandstone, and are what I talked about in the blog as liesegang bands. Though the exact progress to form these bands/rings are unknown, it is believe that they formed as a result from repeated precipitation of colloidal iron from groundwater solutions. Thanks for reading and I’m glad you found them interesting!
Fabulous colours !
Thank you! It’s all the rocks, I just snap the photos 😉
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