interesting topographic feature

[casper]

Whilst researching for a future fossicking foray I was toggling between satellite and terrain view on google maps and this interesting circular topographic feature caught my eye ....... tektites were common in the alluvial gravels at that location and this looks awfully like an impact crater to me

 

[grubstake]

How large would that feature be?

 

[casper]

How large would that feature be?

......about 2.5km across

 

[UnderEmployedGeo]

That's pretty cool. The tektites are a clue also! I'd love you know where this is. Mind you, not all circular geology features are impact craters...

Check out the Eye of the Sahara https://en.m.wikipedia.org/wiki/Richat_Structure

 

[grubstake]

Whilst researching for a future fossicking foray I was toggling between satellite and terrain view on google maps and this interesting circular topographic feature caught my eye ....... tektites were common in the alluvial gravels at that location and this looks awfully like an impact crater to me

Although they are the result of a meteoritic impact, tektites aren't found co-located with the impact crater. They are blasted into space by the explosive impact and eventually rain back down over a very wide area. While they are inflight, the Earth is turning, so they are much more likely to fall away from their point of origin, than anywhere in its vicinity. Australian tektites (Australites), are from an as yet undetermined impact site somewhere in Indochina.

https://en.wikipedia.org/wiki/Australite

 

[grubstake]

How large would that feature be?

......about 2.5km across

If you have access to a geological map of the area, it might be possible to see whether there is any correlation between the obvious surface features and the underlying rock/s.

 

[Katabatic]

That's pretty cool. The tektites are a clue also! I'd love you know where this is. Mind you, not all circular geology features are impact craters...

Check out the Eye of the Sahara https://en.m.wikipedia.org/wiki/Richat_Structure

Yep....Wilpena Pound is another one that's a bit deceiving:

 

[UnderEmployedGeo]

Whilst researching for a future fossicking foray I was toggling between satellite and terrain view on google maps and this interesting circular topographic feature caught my eye ....... tektites were common in the alluvial gravels at that location and this looks awfully like an impact crater to me

Although they are the result of a meteoritic impact, tektites aren't found co-located with the impact crater. They are blasted into space by the explosive impact and eventually rain back down over a very wide area. While they are inflight, the Earth is turning, so they are much more likely to fall away from their point of origin, than anywhere in its vicinity. Australian tektites (Australites), are from an as yet undetermined impact site somewhere in Indochina.

https://en.wikipedia.org/wiki/Australite

Yes this is an important point about tektites. If people are being accurate in their use of the word of course. Tektites are glassy because of their re-entry burn.

But if there was other ejecta, that would be interesting. Impacts create all manner of interesting rocks. That's how Sudbury in Canada was worked out to be an impact site.

 

[casper]

Whilst researching for a future fossicking foray I was toggling between satellite and terrain view on google maps and this interesting circular topographic feature caught my eye ....... tektites were common in the alluvial gravels at that location and this looks awfully like an impact crater to me

Although they are the result of a meteoritic impact, tektites aren't found co-located with the impact crater. They are blasted into space by the explosive impact and eventually rain back down over a very wide area. While they are inflight, the Earth is turning, so they are much more likely to fall away from their point of origin, than anywhere in its vicinity. Australian tektites (Australites), are from an as yet undetermined impact site somewhere in Indochina.

https://en.wikipedia.org/wiki/Australite

....thank you - I had earlier seen a map of Australia showing "strewn field lanes" and now I better understand it all from your explanation.

 

[casper]

That's pretty cool. The tektites are a clue also! I'd love you know where this is. Mind you, not all circular geology features are impact craters...

Check out the Eye of the Sahara https://en.m.wikipedia.org/wiki/Richat_Structure

Yep....Wilpena Pound is another one that's a bit deceiving:

https://www.prospectingaustralia.co.../1610792285_wilpena-pound-aerial-10129280.jpg

I've been there, a fascinating place erfect:

 

[user 4386]

Any of these?

https://en.wikipedia.org/wiki/List_of_impact_craters_in_Australia

 

[casper]

Any of these?

https://en.wikipedia.org/wiki/List_of_impact_craters_in_Australia

No... and it's not on the list of volcanic craters either - do i get naming rights

 

[grubstake]

Any of these?

https://en.wikipedia.org/wiki/List_of_impact_craters_in_Australia

No... and it's not on the list of volcanic craters either - do i get naming rights

If you're serious about it, this recent ABC article mentions a couple of blokes from WA universities who have expertise in crater verification and may be able to give you some guidance on how to proceed:

Meteorite crater discovered while drilling for gold in outback WA estimated to be 100 million years old:
https://www.abc.net.au/news/2020-09...scovered-in-wa-100-million-years-old/12620970

 

[user 4386]

Any of these?

https://en.wikipedia.org/wiki/List_of_impact_craters_in_Australia

No... and it's not on the list of volcanic craters either - do i get naming rights

You possibly could if you were to demonstrate that it has features of an impact structure and is not just a circular topographic feature - althoughg others would have to choose to name it after you, it is not your choice. Most circular features are not impact structures (yours is a nice shape though and might be worth investigating). First thing would be to overlay it on a geological map and check that there is not some other reason for its existence (e.g. a circular igneous intrusion such as a granite). Next thing is while you are there, keep an eye out for shatter cones and pseudotachylite (glassy) dykes, features characteristic of high-velocity impacts. Also the rare minerals stishovite and coesite (unlikely that you would identify these two minerals in the field).

https://www.bing.com/images/search?...r+cones&form=IGRE&first=1&tsc=ImageBasicHover

https://www.bing.com/images/search?...+photos&form=IGRE&first=1&tsc=ImageBasicHover

http://southafrica.co.za/vredefort-dome-shattercones-shock-metamorphics.html

 

[Gem in I]

Casper's ghost ?????
Let the nominations begin :lol:

 

[casper]

Any of these?

https://en.wikipedia.org/wiki/List_of_impact_craters_in_Australia

No... and it's not on the list of volcanic craters either - do i get naming rights

You possibly could if you were to demonstrate that it has features of an impact structure and is not just a circular topographic feature - although others would have to choose to name it after you, it is not your choice. Most circular features are not impact structures (yours is a nice shape though and might be worth investigating). First thing would be to overlay it on a geological map and check that there is not some other reason for its existence (e.g. a circular igneous intrusion such as a granite). Next thing is while you are there, keep an eye out for shatter cones and pseudotachylite (glassy) dykes, features characteristic of high-velocity impacts. Also the rare minerals stishovite and coesite (unlikely that you would identify these two minerals in the field).

I think we have the answer read on....
"At Mt William (Mafeking) the gold derived from granitic rocks intrusive into the Grampians sandstones and had been concentrated in gravels of Tertiary age over an area of about a square mile, which have yielded over 100,000 worth of gold. The gold was very fine, and much waterworn. Some of the gravel has been re-concentrated by later streams in shallow deposits. The original gravels vary from 30 to 70 feet (9.1 to 21.3m) in thickness, and values are confined to the lower layers. Small auriferous quartz veins have been found in the granitic rock, but are too small to pay for mining."[3]
The small goldfield yielded 1t of gold from alluvial deposits and from quartz veinlets in a weathered I-type[4] granite pluton of Devonian age.[5]

Many thanks GR for you guidance
cheers casper

 

[user 4386]

Yep, it is the Mafeking Granite. not an impact

 

[casper]

Thanks GR 'Tis all the more fascinating now....

cheers Casper