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zephyr
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PostFri Dec 18, 2020 7:19 pm 
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NorthBen wrote:
A friend fished these out of the Sauk River. Any guesses on rock type and fossil species?

Man, those are some beautiful rocks.    ~z
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Mike Collins
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PostSat Dec 19, 2020 6:41 am 
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NorthBen wrote:

My speculation is that the “harmonica” is a portion of the stem/column of a crinoid. In my own fossil collection I have cuttlebone fossils in that same rock matrix.
https://www.theedkins.co.uk/jo/fossils/crinoid.htm
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NorthBen
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PostSat Dec 19, 2020 6:51 am 
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Another friend-of-a-friend geologist also thought the "harmonica" was a crinoid, with the more circular fossils also being crinoids rotated 90 degrees and viewed head on.

I've seen crinoid fossils in Death Valley several years ago and remember getting the impression they're pretty common as far as fossils go:

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Brushbuffalo
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PostSat Dec 19, 2020 7:03 am 
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Mike Collins wrote:
the “harmonica” is a portion of the stem/column of a crinoid.

Mike and Ben, I initially had 'crinoid' as a possibility in my response, but deleted it.  You guys are more 'paleo' than I am.   wink.gif

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zephyr
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PostSat Dec 19, 2020 9:49 am 
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The stalked forms are known as Sea Lilies, the unstalked ones are Feather Stars.  They are still with us today.  Here's a cool drawing by Ernst Haeckel  via Wikipedia.  ~z


Here's an interesting fossil form.

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mike
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PostSat Dec 19, 2020 2:12 pm 
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One of the most studied rocks in the world.


(file name is an incorrect description)
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Malachai Constant
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PostSat Dec 19, 2020 2:24 pm 
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Lots of Crinoids in Grand Canyon esp North Rim

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Brushbuffalo
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PostSat Dec 19, 2020 5:55 pm 
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mike wrote:

Is that a question?
I am guess it's one of the major unconformities that led to the early study of geology as a science, so it's probably in Europe, maybe in Scotland and studied by Hutton.

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mike
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PostSat Dec 19, 2020 6:32 pm 
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Yes Scotland but not Hutton's Unconformity. Wish I could have visited Siccar Point. This is the Moine Thrust at Knochan Crag. First documented evidence of horizontal movement so not an unconformity as generally described. Oldest rock is thrust on top by tectonic forces as shown by Peach and Horne.
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Anne Elk
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PostSat Dec 19, 2020 10:27 pm 
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This thread got bumped up; I was offline most of August and missed this:
texasbb wrote:
Okay, got a landform question.  What mechanism formed the dozens of tiny little islands here?
Marshy upper end of Swamp Lake, Wallowas
Hi-res

To which
Brushbuffalo wrote:
Based on your pictures, I think you have an example of a bio- geological runaway feedback loop.  Let me explain the theory that I have.

Sediment, mostly gravel, accumulates in a braided stream channel during times of lessening flow velocity. If the little bars remain slightly above average water level, plants are able to become established. These plants trap more sediment thereby increasing the size of the mini islands, which facilitates more plant life on them...a runaway process by trapping more sediment and increasing the island size up to a point limited by erosion.
Key to this is in a gravel- rich stream channel we find that braiding is the dominant pattern, which causes bars to form separated by many divergent/ convergent channels (called ' anastomosing channels' by hydrologists). I have another theory....theory the second. And it's mine.(how about that, Anne Elk?)

But after seeing this -
Google Earth view of the marshy inlet to Swamp Lake
Brush Buffalo wrote:
I agree, it is not clear to me now after seeing that Google Earth image that these little islands are related to a braided stream pattern. The origin is probably at least as much biological as hydrological, but right now I am stumped.

I like the anastamosis idea, BB (what a great word!), and your sediment trapping theory. But the photos reminded me of an arctic land formation I recently discovered wandering around Wikipedia:  Pingo (Another great word!) Obviously there's no permafrost in the Wallowas, but perhaps those little round hummock formations in the anastamoses get further pushed upward by  frost heaving in what looks like shallow, but permanent swamp (see the diagram in the Pingo article), providing more opportunity for plant colonization, contributing to the cycle.  So there you have it: anastamosizing frost-heave pseudo-pingo feedback loops! (Maybe I should stick to brontosaurus theories).  hockeygrin.gif

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puzzlr
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PostSat Dec 19, 2020 11:51 pm 
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This thread is so great. I wish I could contribute! I spend a lot of my time on hikes asking "why" and "how" questions about the land forms around me. Sometimes I know, but mostly just wonder.

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Brushbuffalo
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PostSun Dec 20, 2020 7:10 am 
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Anne Elk wrote:
So there you have it: anastamosizing frost-heave pseudo-pingo feedback loops! (Maybe I should stick to brontosaurus theories).

Anne Elk, I love your theory that you have. And it's yours. (apologies to Monty Python).

I too ruled out pingos due to lack of any probable recent permafrost. However there are relict periglacial features in many areas lacking any recent permafrost, such as 'stone stripes' on hills southeast of Yakima and elsewhere.  But the story gets  more intriguing because even stone stripes, formerly believed to need permafrost to form, now are thought only to require freeze-thaw cycles without permafrost.

The point is that as more observations and analysis occur researchers are able to better understand what is seen in the world. As time goes on and more research is done, earlier ideas are often revised or even rejected if they don't fit the evidence.
Such is the nature of good science.

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Brushbuffalo
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PostSun Dec 20, 2020 7:11 am 
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puzzlr wrote:
Sometimes I know, but mostly just wonder.

Monty, this applies to us professionals too! The difference is that we know enough to come up with multiple working hypotheses instead of just wondering.

Sometimes one of our hypotheses might  be correct.

At other times ( often, if we're honest) we just wonder too!

And finally, Monty, you can contribute( and have, you Middle Fork expert, you!). You go to many places and see much cool stuff. Send it on ( with picture, scale, and location), for us to marvel at and hypothesize about.

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texasbb
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PostSun Dec 20, 2020 3:29 pm 
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Brushbuffalo wrote:
puzzlr wrote:
Sometimes I know, but mostly just wonder.

Monty, this applies to us professionals too! The difference is that we know enough to come up with multiple working hypotheses instead of just wondering.

Which means you experts wonder more than us ignoramuses.  I feel better about myself.  lol.gif
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Anne Elk
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PostMon Jan 18, 2021 11:36 pm 
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Some folks who watch this thread might have missed the one that Kim Brown started in PNW History a while ago about Prof Nick Zentner's entertaining geology presentations.  I just discovered that he's recorded the first two weeks of this year's CWU Geology 101 class, although there's no direct link to the lectures from his website in the Geol 101 tab.

Any of the rock hounds frequenting this thread who are interested in geology "basics" can access them by searching in Youtube for "Geol 101  Zentner".   I just watched "Rocks of North America"   As per his usual, the first 10 minutes of each video are social patter and you can forward to the main part of the talk.  Apparently on campus classes are going to be meeting as of this week - no word if he's going to record those.

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