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Author Topic:   The Story in the Rocks - Southwestern U.S.
Dr Adequate
Member (Idle past 364 days)
Posts: 16113
Joined: 07-20-2006


Message 8 of 121 (777309)
01-28-2016 10:51 PM
Reply to: Message 7 by Tanypteryx
01-28-2016 6:23 PM


Re: The Kayenta Formation & Dinosaur Tracks
I think they told me these were eggs but I have some doubts.
They're some sort of nodule, I'm fairly sure.

This message is a reply to:
 Message 7 by Tanypteryx, posted 01-28-2016 6:23 PM Tanypteryx has replied

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Dr Adequate
Member (Idle past 364 days)
Posts: 16113
Joined: 07-20-2006


Message 15 of 121 (779331)
03-03-2016 12:30 PM
Reply to: Message 14 by edge
03-03-2016 11:33 AM


I read something interesting recently in a very old geology book (by Gideon Mantell, the guy who discovered Iguanadon, so yeah, that old). He said that sandstone could be produced by compaction alone, and adduced the fact that cannonballs shot at sandbags produced sandstone where they impacted. I've not seen this repeated anywhere else, I'd be interested to know if there is any sandstone anywhere that was lithified just by compaction.

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Dr Adequate
Member (Idle past 364 days)
Posts: 16113
Joined: 07-20-2006


Message 17 of 121 (779349)
03-03-2016 4:07 PM
Reply to: Message 16 by Tanypteryx
03-03-2016 2:54 PM


I thought the process that forms sandstone is as much a chemical process that forms a binding matrix ...
Yeah, normally it's cemented, with, as edge says, carbonates, or (IIRC) with iron oxides. But Mantell seemed to think it could just be compacted. If anyone knows of an instance of this happening in nature rather than bombing ranges, let me know. Thanks.
Edited by Dr Adequate, : No reason given.

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Dr Adequate
Member (Idle past 364 days)
Posts: 16113
Joined: 07-20-2006


(1)
Message 21 of 121 (779357)
03-03-2016 4:24 PM
Reply to: Message 19 by Faith
03-03-2016 4:13 PM


As for bombing ranges in Nevada, I understand that the underground caverns formed by the underground nuclear tests of a few decades ago are lined with thick glass, a later stage of what happens to sand under heat and pressure, yes?
Well normally if sand was subjected to both heat and pressure, it would be as a result of being deep underground, and in these circumstances it would cool slowly and give us the crystalline metamorphic rock quartzite. Glass, you will recall, is what you get when molten rock cools quickly, so that there's no time for crystallization.

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