Not going to say possible coprolite again, but maybe?

[Zesus]

Hello again!

Finally took some pictures of the rocks I was referring to in previous posts. These are the reason I asked for help ID previous rocks. I never new what coprolite was until I tried to find a reason why these rocks look the way they do. In person, they look like they contain chunks of  turtle/lizard/fish/eggs/shellfish/etc  type stuff, I believe what is referred to as inclusions.  But it could just be some funky conglomerate. Either way I’m hoping someone can explain why they look the way they do! There’s about 20 or so of these on my property, just grabbed some and snapped some photos.  I wish I had better lighting/camera so detail could be seen.  Thanks for your time in advance! And if you have any thoughts please let me know!

 

Property is located in residential Menlo Park, California (between San Francisco and San Jose), very close to the San Francisquito Creek.

some were just laying on top of the ground, others were below and found when doing some yard work digging. 

 

Easier to to see the individual parts when rocks are wet as the colors pop, as supposed to blending in as a slightly reddish brown mud. Some seem to have a “skin” if you will around them, like a layer that can be rubbed off, allthough i have noticed once i rub it off the inclusions, a couple days later the colors seem to have faded.

Also many of The inclusions that stick out of the rock give the appearance that they have been scratched off or bitten off, possibly just from hitting other rocks as well. The black inclusions are the easiest to see in the photos, however they are only a small fraction of the reptilian/crustacean/fish/ i dont know  shapes that you can see

[Zesus]

[Zesus]

This one i found had a off-whitish layer around it all which can sort of be seen in the second photo however not as white or clear as before, with texture similar to felt almost, where if i rubbed it one way it was smooth, the other way gave a soft resistance/friction. curious because I saw red and green under it i took a piece of sand paper and started to sand it down

 

[Zesus]

if anyone cares to see some more, or more inclusions, i can upload no problem, didnt want to spam, especially if its nothing interesting haha. thanks again in advance for any thoughts!

[GeschWhat]

I think you have conglomerates there. I'm not seeing anything in them that would point toward coprolites. Sorry 

[Miocene_Mason]

I agree with a lack of coprolites. 

( @GeschWhat love the holiday icon!)

[ynot]

The first one looks like a conglomerate.

 

Other than that I see a bunch of stream tumbled metamorphic rock (mostly quartzite) and do not see any fossils in any of these rocks.

[Fossildude19]

I agree.

I'm not seeing any fossils here. 

Keep looking, though.

 

[Zesus]

thanks for the speedy reply Gesch! i think when i saw this photo online it looked very similar to what I see in some of these rocks so i made the assumption

 

 

 

what do you suppose the black figure is in the rock I found? maybe just a weirdly shaped rock?

 

 

 

[ynot]

It is a rock that has a darker mineral content.  This is part of the conglomerate. There are secondary fractures visible that have been filled with a light colored mineral and some geologic deformation.

[Zesus]

ok cool.  sorry please excuse my ignorance, im not trying to be argumentative or anything like that, not in the least haha. hard to get the across in writing short messages, just actually genuinely interested.   How exactly are they different than the cracks in the other photo that has light colored material between its cracks as well?

[ynot]

10 minutes ago, Zesus said:

  How exactly are they different than the cracks in the other photo that has light colored material between its cracks as well?

There is no difference between the two types of cracks other than what mineral infilled the crack. They both occurred after the material was buried in the surrounding material. 

The difference is in the overall structure and shape that We are basing the ID on.

[doushantuo]

Shape or coloration of a piece of rock just by itself can be misleading.

Morphological information,spatial relations between parts of plants and animals ,mineralogy,all kinds of things can change during fossililization.

Various physical and chemical processes taking place in the Earth's crust can cause structures to come into existence that resemble (parts of) fossils.

Which is basically what Tony is saying,also .

 

[ynot]

9 minutes ago, doushantuo said:

Shape or coloration of a piece of rock just by itself can be misleading.

Morphological information,spatial relations between parts of plants and animals ,mineralogy,all kinds of things can change during fossililization.

Various physical and chemical processes taking place in the Earth's crust can cause structures to come into existence that resemble (parts of) fossils.

Which is basically what Tony is saying,also .

 

Uh, yeah - that is what I meant .

[doushantuo]

Notice how the (totally anorganic)porphyroblasts (below) are similar to the things you might find when examining coal maceral,and some of them

resemble eyes.

The spatial and structural detail(surrounding foliation) gives it away as non-biological

On a larger scale resemblances such as these are also possible 

[Sagebrush Steve]

If you live in Menlo Park, California, you are in luck.  The US Geological Survey has a regional office there at 345 Middlefield Road: https://online.wr.usgs.gov/kiosk/mparea3.html

I don’t know for sure but you might be able to take your samples there and get their opinion.  

I believe they will be closing that site eventually and moving to Mountain View but I don’t know the current status.

[GeschWhat]

12 hours ago, Zesus said:

ok cool.  sorry please excuse my ignorance, im not trying to be argumentative or anything like that, not in the least haha. hard to get the across in writing short messages, just actually genuinely interested.   How exactly are they different than the cracks in the other photo that has light colored material between its cracks as well?

Hey, I'm just thrilled you are interested in coprolites! IMHO, they are one of the most undervalued trace fossils. A lot has to do with location. The first thing I consider when trying to determine whether or not something is a coprolite is whether or not there are body fossils found in the same area. I have been trying to obtain coprolite specimens from the your state, but everyone I have acquired, to date, revealed itself to be a burrow once I got it under the microscope. So I am not familiar with coprolites from formations there. Unlike bones and teeth which are mostly mineral to begin with, it takes very special circumstances for poo to fossilize. They would have to be covered in a gentle way prior to decomposition or consumption by fecal feasters (dung beetles, my daughter's dog, etc.). Then they would have to remain undisturbed in this oxygen deprived, protected environment for a long time in order for mineralization to occur. The most common environments for this to occur is in floodplain areas, seabeds or other aqueous environments where there is soft mud or volcanic ash.  I understand why you might think coprolite when looking at your specimens. If I had nickel for every rock I thought/hoped was a coprolite, I'd have my own poo museum by now!

[JohnBrewer]

@GeschWhat hey Lori these look VERY similar to fish coprolites I find in the bone bed at Aust, Gloucestershire in the UK. Did I send any to you? I’m not at home so can’t post an image of one of mine but here’s an example from The Natural History Museum’s website. 

 

 

 

[GeschWhat]

3 hours ago, JohnBrewer said:

@GeschWhat hey Lori these look VERY similar to fish coprolites I find in the bone bed at Aust, Gloucestershire in the UK. Did I send any to you? I’m not at home so can’t post an image of one of mine but here’s an example from The Natural History Museum’s website. 

John, I was thinking the same thing.  You hadn't sent any, but I have quite a bit of material from Aust Cliff, including this beauty. I had thought about posting this earlier, but there is so much glare, and the photo isn't very good. It is that time of year when it is too cold to shoot outside, and only a limited window for taking photos inside when the light is right.