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Kara
Joined: 22 Jul 2018
Posts: 120
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 Posted: Aug 14, 2018 11:52 Post subject: Funny breccia |
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Just wanted to show you one funny little rock I've found up north. I guess this is somekind of a breccia, but can't guess the mineral recipe of it. What do you think?
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Kara
Joined: 22 Jul 2018
Posts: 120
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| Posted: Aug 14, 2018 12:23 Post subject: Re: funny breccia |
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Cell phone close-ups: colours aren't right, some contrast added to see the structures.
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Pete Modreski
Site Admin
Joined: 30 Jul 2007
Posts: 669
Location: Denver, Colorado
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| Posted: Aug 14, 2018 12:38 Post subject: Re: funny breccia |
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| Yes, that is a very neat looking and interesting breccia, and, what more can one say? Lots of quartz veining, some red granitic rock and some (some kind of rock) with lots of epidote in it... nice!
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Justin Hickok
Joined: 28 Sep 2017
Posts: 66
Location: Strasburg
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| Posted: Aug 14, 2018 13:13 Post subject: Re: funny breccia |
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Fascinating.
Its what I call "very busy". Wouldn't it be cool to have a two minute video of the life of that specimen?
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Pete Modreski
Site Admin
Joined: 30 Jul 2007
Posts: 669
Location: Denver, Colorado
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| Posted: Aug 14, 2018 13:47 Post subject: Re: funny breccia |
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| Along a similar vein, there is a very nice book, "The Planet in a Pebble", by Jan Zalasiewicz (Oxford Univ. Press), that takes one beach pebble (it's from Wales--kind of a slate, with a white vein (quartz or calcite, I forget which) going through it) and uses this as the basis to retrace the whole history of the earth, and the geochemical methods used to understand it. An enjoyable book to read.
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Justin Hickok
Joined: 28 Sep 2017
Posts: 66
Location: Strasburg
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| Posted: Aug 14, 2018 14:28 Post subject: Re: funny breccia |
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| I'll see if I can get ahold of that, Pete. Thanks.
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Kara
Joined: 22 Jul 2018
Posts: 120
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| Posted: Aug 15, 2018 04:02 Post subject: Re: funny breccia |
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I need to read that book too.
Just realized, I have a perfect " Cambrian Period in one rock " -thingie here. You can see the Gondwana and even Laurentia there, and uni- and multicellular organisms swarming in the Panthalassan Ocean. :)
Ps. Can you tell me something of this rock? I am thinking it is somekind of a metasedimentary quartzite-ish oceanfloor mess, for there are small crystal caves also (third pic). I have no idea really. Help?
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Kevin Schofield
Joined: 05 Jan 2018
Posts: 69
Location: Beacon NY
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| Posted: Aug 15, 2018 09:21 Post subject: Re: funny breccia |
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| Kara wrote: | I need to read that book too.
Just realized, I have a perfect " Cambrian Period in one rock " -thingie here. You can see the Gondwana and even Laurentia there, and uni- and multicellular organisms swarming in the Panthalassan Ocean. :)
Ps. Can you tell me something of this rock? I am thinking it is somekind of a metasedimentary quartzite-ish oceanfloor mess, for there are small crystal caves also (third pic). I have no idea really. Help? |
Hi Kara.
It looks to me as if this at least started out life as a bioclastic limestone, although if you are right about it now being quartzose, it has been subsequently silicified. The second picture in particular, especially when blown up a little, clearly shows elongate shell fragments and a whole bunch of rounded grains of similar sizes, some with indications internal differentiation. They are about the right size to be large ooliths or small oncolites, which would make your rock a shallow-water, possibly infra-tidal limestone. The "crystal caves" are shells that have been partially or wholly dissolved out in which druses have formed. A quick google search reveals that there are Middle Ordovician bioclastic/oolitic limestones in Northern Estonia, so maybe something got transported north?
_________________
Veni, Vidi, Emi |
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Kara
Joined: 22 Jul 2018
Posts: 120
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| Posted: Aug 15, 2018 11:31 Post subject: Re: funny breccia |
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| A zillion times thank you Kevin for the detailed analyze! Very interesting! I'm thrilled! Now I will search every bit of information I can find about these rocks. I have found this near the Varanger Peninsula along the Barents Sea. Wish there were more.
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