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gvallee

Calling geologists - Rocks ID

Question

I'm sure it will be very tricky but can anyone help with the composition of these two rock formations please?

 

Location is Ellery Creek Big Hole, West MacDonnell Ranges, Northern Territory, Australia

 

Thanks in advance.

 

2B2WEB8.jpg

 

2B2WEK5.jpg

 

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I took Geology in college.  Uh, pretty stripey rocks?

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Just now, Johnnie5 said:

I took Geology in college.  Uh, pretty stripey rocks?

 

Spot on. I've got 'stripey' and 'rocks' in my KW. Missed 'Pretty' though...

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Posted (edited)

It is very pretty -- some kind  of banded ironstone perhaps? 🤔

Edited by John Mitchell

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51 minutes ago, John Mitchell said:

It is very pretty -- some kind  of banded ironstone perhaps? 🤔

 

Thank you for looking John. I wouldn't know.

I've been to the place mentioned, Karijini, on another trip. It is very impressive geologically.

The MacDonnell Ranges are mostly sandstone.

I'm clueless about geology.

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1 hour ago, gvallee said:

 

Thank you for looking John. I wouldn't know.

I've been to the place mentioned, Karijini, on another trip. It is very impressive geologically.

The MacDonnell Ranges are mostly sandstone.

I'm clueless about geology.

 

The orange and red stuff look like iron deposits (which can be found in sandstone, I believe) to me, but I'm no geologist, just a former rock hound of sorts.

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3 minutes ago, John Mitchell said:

 

The orange and red stuff look like iron deposits (which can be found in sandstone, I believe) to me, but I'm no geologist, just a former rock hound of sorts.

 

Yep, iron oxide I believe. I might have to just use general keywords. It's mission impossible.

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Posted (edited)

Identifying rocks is not the same as identfiying species of plant or animal as rocks are hugely variable. To identify from scratch, I would always prefer to use a microscope except for the most generic identification. The best way is to check up on the geology of the area and work it out from there. Perhaps the Australian geological survey has map data for that area. That is how I would do it here in Britain or Ireland (check the BGS or GSI map data). 

 

Having said that, the rocks could well be banded ironstones which are a common rock type in very ancient times (e.g. Archaean) and definitely found in Australia  but best bet is to check out the map data maybe with that in mind.

Edited by MDM
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5 hours ago, John Mitchell said:

It is very pretty -- some kind  of banded ironstone perhaps? 🤔

 

 Just noticed this. At a guess I would think this might be correct.

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4 minutes ago, MDM said:

 

 Just noticed this. At a guess I would think this might be correct.

 

As stated, I know absolutely nothing about geology. However, I've been to both sites, Karijini and West MacDonnell Ranges where these two shots were taken. The latter look different. My rocks look like bacon (oh no, not back to another food thread...). But what do I know? I don't think I'll be able to accurately KW, so I think I'll leave it generic. Thanks MDM.

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3 minutes ago, gvallee said:

 

As stated, I know absolutely nothing about geology. However, I've been to both sites, Karijini and West MacDonnell Ranges where these two shots were taken. The latter look different. My rocks look like bacon (oh no, not back to another food thread...). But what do I know? I don't think I'll be able to accurately KW, so I think I'll leave it generic. Thanks MDM.

 

 Yes best to stay generic if you are not sure. Apart from looking at map data, tourist organisations often have leaflets or web info on the geology in non-scientific language so might be worth a look though. 

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1 minute ago, MDM said:

 

 Yes best to stay generic if you are not sure. Apart from looking at map data, tourist organisations often have leaflets or web info on the geology in non-scientific language so might be worth a look though. 

 

I did that extensively. Tour agencies, government park entities etc are not interested in anything else but promoting the destination in general terms. Oh well, we tried. Thanks again.

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No worries 😀

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Opal gone wrong during the formation?🤣

 

Allan

 

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No doubt you've seen the Wikipedia entry about the the MacDonnell ranges (quoted below). It sounds as if they are pretty geologically complex. No mention of "bacon stone", however. 🤠

 

"The ranges are composed of many rock types, but are most famous for their red quartzite peaks and gorges. Other rock types include granite, limestone, sandstone and siltstone.[5] Some of the valleys of the range contain fossil evidence of the inland sea that once covered central Australia."

 

 

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Posted (edited)
34 minutes ago, John Mitchell said:

No doubt you've seen the Wikipedia entry about the the MacDonnell ranges (quoted below). It sounds as if they are pretty geologically complex. No mention of "bacon stone", however. 🤠

 

"The ranges are composed of many rock types, but are most famous for their red quartzite peaks and gorges. Other rock types include granite, limestone, sandstone and siltstone.[5] Some of the valleys of the range contain fossil evidence of the inland sea that once covered central Australia."

 

 

 

Yes there is remarkably little about the geology on any of the tourist info and it doesn't say a lot relevant to this on Wikipedia either (I am very wary of Wikipedia when it comes to scientific articles anyway). Given how interesting the geology is, I am surprised that there is no detailed info on the tourismsites. Geotourism is a big thing these days in Britain and Ireland and there is often good and authoritative info available on signs, leaflets and websites in areas of interesting geology. I even tried to find something about it on scientific sites but it is a bit of a minefield (literally) and I found nothing. 

 

They do have a ring of banded ironstones (certainly the second picture) but could be anything sedimentary with interspersed iron-rich layers. The top one has very strange textures. I would not really hazard a guess. Really one would need to see this in outcrop and not in loose boulders. 

Edited by MDM
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53 minutes ago, MDM said:

 

Yes there is remarkably little about the geology on any of the tourist info and it doesn't say a lot relevant to this on Wikipedia either (I am very wary of Wikipedia when it comes to scientific articles anyway). Given how interesting the geology is, I am surprised that there is no detailed info on the tourismsites. Geotourism is a big thing these days in Britain and Ireland and there is often good and authoritative info available on signs, leaflets and websites in areas of interesting geology. I even tried to find something about it on scientific sites but it is a bit of a minefield (literally) and I found nothing. 

 

They do have a ring of banded ironstones (certainly the second picture) but could be anything sedimentary with interspersed iron-rich layers. The top one has very strange textures. I would not really hazard a guess. Really one would need to see this in outcrop and not in loose boulders. 

 

Yes, a picture of an outcrop would make identification a lot easier. Perhaps someone can run back and take one. 😁

 

P.S. Could those smudgy "strange textures" be the result of weathering -- e.g. oxidation?

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Thanks guys. I had read that there is sandstone and stiltstone in the area.

Here is a picture of the cliff at Ellery Creek Big Hole where these two rocks were taken.

 

2B2WEB5.jpg

 

And nearby Ormiston Gorge.

2B2WEB0.jpg

 

 

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15 minutes ago, gvallee said:

Thanks guys. I had read that there is sandstone and stiltstone in the area.

Here is a picture of the cliff at Ellery Creek Big Hole where these two rocks were taken.

And nearby Ormiston Gorge.

 

 

 

 

Wow! That was fast. Lots of folding going on there. Lovely country. Think I'll leave identification to the expert(s), though.

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Where's the nearest geology department in a university? 

 

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Maybe this helps: The Ochre Pits, several layers of multi-coloured, layered rock.

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6 hours ago, AM Chang said:

Maybe this helps: The Ochre Pits, several layers of multi-coloured, layered rock.

 

Thank you for that AM Chang. I also went to Ochre Pits nearby and luckily there were full descriptions there:

"Yellow ochre is caused by a mixture of clay and iron oxide.
The white colour comes from kaolin and white clay."

 

Perhaps it's the same for my two rocks, who knows.

 

2B29J48.jpg

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Posted (edited)

Sure looks like quartz and no I also skipped Geology in high school and college. But I have plenty of "hey look a pretty rock" sitting around the house. 😉

 

Asymmetrical ripples? Yes to the iron and oxidation stains.

 

You know the territory better, I'm in Wisconsin, near Lake Michigan, we have plenty of plain old quartz, rose quartz and the like. So that's why I targeted Quartz first and then searched around for formations, the mountain range and came upon this.

 

https://minerals.nt.gov.au/__data/assets/pdf_file/0009/259389/Heavitree-Quartzite-Amadeus-Basin.pdf

 

 

 

Edited by Klinger

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19 hours ago, Klinger said:

Sure looks like quartz and no I also skipped Geology in high school and college. But I have plenty of "hey look a pretty rock" sitting around the house. 😉

 

Asymmetrical ripples? Yes to the iron and oxidation stains.

 

You know the territory better, I'm in Wisconsin, near Lake Michigan, we have plenty of plain old quartz, rose quartz and the like. So that's why I targeted Quartz first and then searched around for formations, the mountain range and came upon this.

 

https://minerals.nt.gov.au/__data/assets/pdf_file/0009/259389/Heavitree-Quartzite-Amadeus-Basin.pdf

 

 

 

Thanks for that Klinger. I have decided to remain generic as a precaution. Safer that way. Thanks anyway for your research.

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5 minutes ago, gvallee said:

Thanks for that Klinger. I have decided to remain generic as a precaution. Safer that way. Thanks anyway for your research.

 

Generic is sensible. It is definitely not quartz which is a mineral, not a rock type. Quartzite is a rock that is composed predominantly of quartz and can have various origins. Klinger's document is very interesting but somewhat complex (it looks like a presentation from a conferencel) and not sure how it directly relates to the various photos. There is a lot more than quartzite in the area as the document makes clear. Looks like an amazing place. I'll stick in on the bucket list if I ever make it back out to Australia. 

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