[Rockhounds] Salmon Creek poop

[Thomas Yancey]

The case of Salmon Creek concretions is more complex than this. The 
original concretions taken from mud matrix are solid siderite and 
show the classic markings of extrusion on the surface. Internally, 
the siderite is a mosaic of crystals all of similar size and anhedral 
crystal boundaries. Externally they have detailed squeeze surface 
features, but this is not seen internally. Those with a "fractally 
convoluted surface" are composed of iron oxide and are an oxidized 
replacement of the siderite. The mineral replacement process 
'explodes' the siderite, causing the concretions to acquire a heavily 
cracked surface. Intermediate conditions consist of siderite interior 
and iron oxide exterior in the same concretion. Mineral replacement 
makes it difficult to generalize about these concretions. Those that 
have a smoothed surface are usually ones that have been carried in 
the bedload of Salmon Creek and are worn, removing any indications of 
origin. The sediments of this deposit contain both siderite and iron 
oxide concretions, but the iron oxide concretions may be oxidized 
from another mineral (siderite, pyrite, etc.).

Tom Yancey




>They don't, it's a Miocene swamp or lacustrine delta with low grade lignite
>seams and poorly preserved wood. If you see the "raw" concretions before
>they have been worn smooth by the creek,  they aren't casts of anything
>either (unless that something had a fractally convoluted surface). The point
>of the article is that if no other fossilized remains are associated with
>it, then it probably isn't coprolite. See Occam's Razor...
>
>
>Tim Fisher
>Ore-ROCK-On!
>Email address at http://OreRockOn.com
>
>-----Original Message-----
>From: rockhounds-bounces at lists.drizzle.com
>[mailto:rockhounds-bounces at lists.drizzle.com] On Behalf Of Jay Bates
>Sent: Monday, June 01, 2009 12:27 PM
>To: Rockhounds at drizzle.com: A mailing list for rock and gem collectors
>Subject: Re: [Rockhounds] Salmon Creek poop (NOT)
>
>Many petrified woods do not show visible plant material nor traces of
>minerals associated wood. They are called limb casts. I think if the
>coprolites come from the right formation associated with dinosaurs like
>those found in Utah, there is a good possibility they are casts of real
>dino dung. If not, what are they then?  Doubts disprove nothing.
>
>
>pmodreski at aol.com wrote:
>>  That's a great article about coprolites, Tim, thanks for sharing the link.
>>
>>  Aside from the Salmon Creek "coprolites" probably not being real
>coprolites, I talked with Karen Chin once when she gave a lecture about
>coprolites at CU (I mean the lecture was at CU, not the droppings)... and
>she expressed some doubt about whether the warty-looking chalcedony nodules
>found in western Utah and thereabouts and generally known among rockhounds
>as coprolites, also really are.? For a couple of the same reasons: no
>phosphate content, and no visible partly-digested plant or animal fragments
>embedded within them.? I don't think anyone has really subjected those
>Jurassic supposed-coprolites to any in-depth scientific study--Karen said
>she personally had never studied those--and until someone does, I think
>their status will remain questionable; though all the rockhounds recognize
>them and rockshops sell them as?"coprolites".
>>
>>  Pete
>>
>>
>>  -----Original Message-----
>>  From: Tim <nospam at orerockon.com>
>>  To: 'Rockhounds List' <rockhounds at lists.drizzle.com>
>>  Sent: Mon, 1 Jun 2009 8:58 am
>>  Subject: [Rockhounds] Salmon Creek poop (NOT)
>>
>>
>>
>>  http://www.earthmagazine.org/earth/article/68-7d8-8-1c
>>
>>  A very well thought out article on the "coprolites" from Salmon Creek WA.
>>
>>
>>  Tim Fisher
>>  Ore-ROCK-On!
>>  Email address at http://OreRockOn.com <http://orerockon.com/>
>>
>>
>>
>>
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>
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