First trip to the Lincoln Creek formation

[winnph]

I've been planning a fossil hunting outing with my son for the next week or two (weather permitting), and yesterday my wife kindly suggested that I scout out the site before I take our 8 year old on a fossil hunting trip deep into the woods where no cell phones reach.  So, when today turned out to be mostly sunny and pleasant, I hopped in the car and headed to a location that sounded promising on old geologic maps/reports (by Rau in the 1950s-60s, to be precise). And it turns out that (as always) my wife was correct -- the logging company who owns the land has apparently erected a gate blocking vehicle access to the road I was planning to use to get to the site, which was not on any topo maps including the relatively recent FS Topo that encompasses this area. Their sign said it was fine to hike in as long as I didn't remove any "special forestry products." Pretty sure fossils don't qualify!

 

I was originally planning to start with what Rau called "Tl-3," one of the lower (geologically) members of the formation, but in light of having to hike instead of drive, I opted for a closer member, Tl-5. After a short walk on the road, I struck out for the stream I was targeting through the woods. This is the part where I'm pretty sure my son would not be capable of pushing through the underbrush on steep and soggy stream banks, so I'll have to find another site for next time, preferably within easy walking distance of a logging road I'm allowed to drive on.

 

When I reached the first exposure of the formation, I could see clear evidence that I wasn't the first person to visit this site (no surprise there), in the form of piles of debris at the base of the bank and a few clear empty spherical gaps in the outcrop.  But, I had no trouble finding many small concretions (shells or nothing, I assume?), one large misshapen one (maybe not even a proper concretion?), and one nice looking one that I assume contains a crab, so I suspect no one had been there since the most recent tree-falls and rockslides. I scrambled up, down and along the bank for about 45 minutes, collecting any concretions or fossils I saw either exposed or lose, but did not attempt to expose anything new (maybe next time!). I found a very nice piece of fossilized wood in the debris pile, too, which I can only assume previous visitors to the site mistook for ordinary wood.

 

I am tired and dirty and need to do some household chores, so I will save the whacking of concretions for another day, and probably not do the (likely) crab at all until I have the proper tools to prepare it right.

 

First I'll attach the complete collection of finds, then add a few closeups of the wood in the thread below.

 

 

[winnph]

The wood from various angles.

[Fossilis Willis]

Can't wait to see what's in those concs. Be careful on weyerhaeuser land without a permit. You can purchase a recreational permit to access the area, but they still don't want you removing any forest products including fossils. I'm pretty sure some corporate lawyer realized they could charge for access but still technically qualify for tax breaks for providing recreational  opportunities. Just a theory. You can find old posts here on the forum from when they first started restricting access. I too know the struggle of finding good exposures of the LCF.

 

[winnph]

This is Green Diamond land (unless those are the same company?). I took a picture of the sign which doesn't mention permits for anything other than forestry products.

[winnph]

Here's the legal definition, doesn't include any minerals (which they might not even own the rights to), only plant and fungal matter:

https://www.fs.fed.us/forestmanagement/products/sfp/sfp-definitions.shtml

[Fossilis Willis]

From my limited experience green diamond operates more like weyerhaeuser did in the past and is more welcoming as long as you follow there rules. Not sure what they allow as far as rockhounding and fossil hunting. I assumed weyerhaeuser because they own so much of that area. I forget green diamond, rayoneer and a few others have some land throughout that part of southwest washington.

[winnph]

After soaking and drying them to help loosen the outer shell of sandstone many of them still had, I was just very gently tapping the misshapen larger one around the edge to knock off that outer layer and it unexpectedly cracked! There appears to be a tiny bit of something poking through but nothing much revealed yet. Maybe shell? I guess I'll keep working it gently and see if it will split along this plane again and reveal what's below.... fingers crossed!

[winnph]

Turned out to be otherwise empty, so my original "maybe not even a proper concretion" is probably the explanation for why it split so easily and contained nothing of note.

 

But that got my juices flowing, so I pulled out one of the medium-sized ones (scale shown is inches, I need to start using cm...). After some careful working around the edge of this one, I got it to split along a nice plane as well.  Nothing hard-bodied, but after reading about how concretions often preserve soft-bodied creatures, I'm pretty convinced this is a jellyfish.  See, e.g., the "blob" jellyfish frequently found in Mazon Creek concretions: http://www.jsjgeology.net/Mazon-Creek-Lagerstatte.htm

 

Note that it's upside-down here, but I believe those are tentacles extending from the body upwards.  Should I call it a day or crack one more?

[winnph]

OK, I did one more! This time I went with the absolute tiniest one (concretion measures ~2.5 cm diameter).  Once again, I'm fairly confident this is a jellyfish. The first time it cracked right across the tentacles (first photo), which are preserved very well as bumpiness, then I cracked it vertically through the bell (second photo), which shows a very jellyfish-like shape.  These were imaged on my flatbed scanner, hence the weird focus.

 

I really wish I had just cracked it vertically to start, so that we could see the tentacles dangling down, but such is the problem with guessing how to crack spherical concretions! 

 

P.S. I'm sure some naysayers will reply here, please feel free to burst my bubble....

[winnph]

Ok, I'm just gonna keep on crackin.... so drumrolll......

....a bivalve!  I'll be cross-posting in Fossil ID as well, but just putting it here so this thread is a complete record of the finds from this trip. This one was really hard to crack for its size (which, by the way, is 4 cm across the concretion, about 3 cm across the shell horizontally). I'm guessing the high calcium content of the shells made this concretion extra tough.  I'm glad it cracked the "right" way!

[Rockpit]

This looks like a jellyfish to me.

[winnph]

Next up, a collection of tiny tiny shells. I had suspicions about this being multiple items based on the strange shape of the concretion, which looked almost like two ovals intersecting. After the first cracking open with only one tiny shell showing, I bravely (stupidly?) cracked it again, and was able to keep the second crack along the same plane. The middle piece is the actual middle piece, and I'll probably reattach the left piece as its bottom since it doesn't reveal much of note (that could be a tiny fragment of crab?).

[winnph]

12 minutes ago, Rockpit said:

This looks like a jellyfish to me.

 

Could've been! If so, it's already destroyed (I decided to break up all the small pieces in case there was something small but neat hiding in it). 

I will say that apparent difference in color was due to light reflecting off the angles of the break, and it appeared to be a flat gray in person, but I do see what you're describing in the photo, and maybe it broke that way because of a difference in density even if it was the same color.

[winnph]

OK, so this is the last one for today.... it's almost a dud, but if you squint real hard you can make out a tiny shell in the center. I wonder if maybe it's a longer shell and this is just a cross section? In any case, that's enough hammering for one day, time to clean up the shards and dust and such.

 

I'll probably open the rest this weekend, I'm down to just 3 medium concretions and the one large (crab??) one. I know I said I'd save the crab for after I get better tools, but instead I think I'll just save it for last and use the hammer as judiciously as I can.  I've put it through a freeze/thaw cycle in the hopes that'll help the hammering be more effective.

[Monica]

I love that big bivalve - very nice!!! 

[winnph]

I'm really having trouble resisting the urge to ignore my work and get started on this one with my hammer. Thought I'd post a couple closer shots before I give in to my urges....

[FossilsAnonymous]

[winnph]

After about 30 minutes of judicious hammering around the line I'm hoping will be where it cracks, a piece parallel to that popped off the top! My (maybe) crab lost his hat, but so far he's still hiding. The first photo was taken from a weird angle so I'm showing the line that I'm hoping is where it cracks.

 

Rather than keeping at it with a hammer, I figure I'll take advantage of all the tiny fractures I probably have introduced and let the freezer help things along a bit. I didn't soak it first like people usually do. I'll pull it out tonight once it's solid, dry it on the dehumidifier exhaust overnight and try again with the hammer tomorrow.

 

Edit: While cleaning up the mess, I stopped to inspect more closely the piece that was removed and there is a tiny spine of some sort in it! It's originating from the outside of the concretion, not the inside, so I doubt it's part of my specimen, just debris in the sediment, but figured I'd share. Urchin, I presume?

[FossilDAWG]

I hope you do find a crab in there!

 

I have to say I'm skeptical of the "jellyfish" ID.  None of the concretions in this thread look like jellyfish to me, and I have never heard/read of jellyfish being recovered from Lincoln Creek Formation concretions.  The mechanism of deposition of the fossils in the Lincoln Creek is very different from the Francis Creek Shale (turbidity flows vs stagnant/anoxic bays and lagoons) and not very condusive to the preservation of animals that lived in the water column.  The crabs were likely living on the sea floor and were buried by turbidity flows, i.e. mud flows moving down a steep underwater slope.

 

Don

[winnph]

On 4/9/2019 at 12:50 PM, FossilDAWG said:

I have to say I'm skeptical of the "jellyfish" ID.  None of the concretions in this thread look like jellyfish to me, and I have never heard/read of jellyfish being recovered from Lincoln Creek Formation concretions.  The mechanism of deposition of the fossils in the Lincoln Creek is very different from the Francis Creek Shale (turbidity flows vs stagnant/anoxic bays and lagoons) and not very condusive to the preservation of animals that lived in the water column.  The crabs were likely living on the sea floor and were buried by turbidity flows, i.e. mud flows moving down a steep underwater slope.

 

Skepticism is good! I knew when I made the claim that it was a somewhat extraordinary one, and lacks the extraordinary evidence generally needed to support such a claim.  However, in response to your (very valid and probably correct) points, I have this to say:

(1) It's only in the last few years/decade that scientists studying concretions have come to realize just how instantaneously they tend to form (in geological terms), apparently triggered by the decomposition of the animal itself. See this article  and this article summarizing some recent research. This is true whether the concretion forms in shallow lagoons or turbidity flows, or in some other environment.

(2) While most jellyfish live in the water column, some species live or feed in the benthic zone, and it's especially hard to know how many species lived in those environments in past eras.

(3) I would posit that jellyfish remains have been overlooked in Lincoln Creek concretions precisely because they are so difficult to identify as anything but a featureless blob, and because no one has been looking for them.

 

However, I fully accept that there's a very good chance I'm wrong! I plan to keep collecting and documenting the shapes of various featureless blobs I find in these concretions, in the hope that one of them will be more compelling evidence than the ones shown here (which I agree aren't wonderful examples).

 

Edit: Here's the actual article the first Forbes article was summarizing: https://www.nature.com/articles/s41598-018-24205-5

 

Second edit: Also adding a marked up photo showing where I see a jellyfish

[winnph]

Decided to crack one of the remaining smallish ones. This is interesting, I'd say looks like either a fragment of rock, or possibly bone, with mineralization deposits through its interior.

[winnph]

The big one was NOT a crab! Nothing hard-bodied in it. I suspect another jellyfish or similar soft-bodied creature, but it shattered so completely that it's hard to piece together as anything other than an amorphous dark blob. I'm definitely going to need to get some better tools than a hammer....

[Plantguy]

Sorry to hear about the possible crab's demise...concretions are heart breakers but looks like you have some interesting stuff none the less. So in the last smallish one it almost looks like a bunch of spheres chained together...

 

Very interesting. 

Regards, Chris 

[winnph]

20 minutes ago, Plantguy said:

So in the last smallish one it almost looks like a bunch of spheres chained together...

 

Yup! It looks to me like some kind of spherical crystal structure that formed within the brown shard of whatever-it-is, more so than anything biological, but it's definitely an interesting one.

[winnph]

I forgot to mention in this thread that there is one concretion from this batch that I will not be breaking open. I will be grinding it slowly, layer by layer, and attempting to reconstruct a 3D model using software specifically designed for paleontologists to use for this purpose. I assume this will be a longer-term project, hopefully done sometime this summer. I have been posting about it in another thread, so I will keep my updates there: 

 

One thing I would like to point out is the latest images of that specimen show that it has the same thin filament outline like the smallest one did in this thread (one of the ones I suspect might be a jelly), so I have my fingers crossed we'll get a 3D model of something soft-bodied when I'm done. If not, it'll still be an interesting time-waster!