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Denman Island, BC, Canada


urbanfossil

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urbanfossil

Took this picture about a year ago. I was exploring the shoreline on Denman Island. Group I was with was calling me back to leave when I saw this between some boulders. Snapped a few pictures because I thought it looked interesting. Wasn't sure if this could be a fossil, or maybe a concretion? Didn't have time to measure or get any closer for better photos, but it was thicker than a forearm and around the same length. 

 

Anyway, this is something I found online about the area if its useful.

"Upper Cretaceous Nanaimo Group of southwest British Columbia is a >4 km-thick succession consisting mostly of deep marine siliciclastics deposited directly on the Insular Superterrane. "

https://fossilhuntress.blogspot.com/2019/09/denman-island-concretion.html

 

Any help is appreciated, always interested in learning something new :)

Thanks,

Jenaya

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If you're talking about that pipe shaped thing in the middle of the photos, then I'm not sure exactly what it is, but I don't think that it's a fossil.

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Deep marine  siliciclastics and coarse conglomerate usually don't mix. Could this be man made material ?

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FossilDAWG

Welcome to the Fossil Forum!

 

I don't recognize that as any sort of fossil I am aware of.  That being said, I can't actually say what it is.  The conglomerate layers in the Nanaimo Group are typically very poor for fossils, as they were deposited in a high energy environment that ground everything to bits.  However on rare occasion a cobble might survive with a fossil inside.  Personally I ignored the conglomerate and focused on the shale beds.  Maybe one of our Vancouver Island members such as @fossisle might have a suggestion.

 

Don

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urbanfossil
6 minutes ago, Rockwood said:

Deep marine  siliciclastics and coarse conglomerate usually don't mix. Could this be man made material ?

I remember trying to spot evidence of concrete/man made material but couldn't find any- so that embedded cylindrical object became intriguing. The exposed bedrock walking down had areas of shale, but i found this on shore where it would have been reached by high tides.

I've attached some pictures from that trip. Coarse conglomerate was scattered around the area but not the primary rock type (example circled in 1st picture).

coarse.jpg

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IMG_20220220_132439154.jpg

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It's looking like something natural. The shape made me wonder if this was a bore hole in concrete. Such holes can be filled with an expanding material (primarily bentonite) which is used as a less violent means of demolishing the structure.

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urbanfossil

just went down a rabbit hole learning about calamites (i know, wrong time period haha). but i was wondering if the object had potentially been hollow and later filled in by sediment?? Interested to hear people's thoughts

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12 minutes ago, urbanfossil said:

i know, wrong time period

You would need to find the source, or sources, of the material in the conglomerate. Plant fossils are sometimes found as reworked elements in it. This one will be tough to identify as such though.

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FossilDAWG

The Nanaimo Group consists of a series of marine shale formations separated by sandstone and coarse conglomerate formations.  The succession ends with the highest beds being entirely conglomerate and sandstone.  On Hornby Island, adjacent to Denman, the highest point on the island is made of the Mount Geoffrey Conglomerate, a massive conglomerate bed a few hundred (or more) feet thick.  On the other hand the shoreline of both Denman and Hornby have not been subject to the kind of development that would result in giant boulders of concrete.  So, I think the rock under discussion is almost certainly natural conglomerate.

 

And yes, the bedrock is Upper Cretaceous and so far too recent for Calamites.  Petrified wood is common in some of the shale formations, and cones have been found in concretions although they are rare.  Neither looks like the specimen in the OP.  At this point I am guessing it might be a cylindrical fragment of a concretion.  Such concretions are common in the shale formations, where they probably formed around burrows made in the sediment of the sea floor.  It is possible for concretions to be eroded out of the sediment and re-deposited in the coarse conglomerate beds as they were forming.

 

Don

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FossilDAWG

BTW nice photos.  Where was this (roughly) on Denman?  I used to really like visiting Denman and Hornby, although I spent most of my time on the latter island.  The last time I visited was at night which gave a very different perspective with the sky full of stars, and the lights from Comox and Texada Island in the distance.

 

Don

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urbanfossil
1 hour ago, FossilDAWG said:

BTW nice photos.  Where was this (roughly) on Denman?  I used to really like visiting Denman and Hornby, although I spent most of my time on the latter island.  The last time I visited was at night which gave a very different perspective with the sky full of stars, and the lights from Comox and Texada Island in the distance.

 

Don

Thanks for the information, I found that very insightful. Too bad the area is poor for findings, I'll have to wait until I can go back home (NWT, Canada) where the fossils are plentiful.

Boyle Point I believe. It was a nice trail with a front row view of the lighthouse. A first time on Denman for me, went during my reading break to help out on a farm. Hopefully I'll find an opportunity to explore Hornby as well.

Cheers

denmanlighthouse.jpg

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I agree with the validity of urbanfossil's photos. I have found concretions and shell bits mixed in with these conglomerates in the same area of Boyle Point.

With no scale associated the only fossil I can come up with would be a Scaphopod,unless of course the object is a foot long.

Rick

 

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urbanfossil
2 hours ago, fossisle said:

I agree with the validity of urbanfossil's photos. I have found concretions and shell bits mixed in with these conglomerates in the same area of Boyle Point.

With no scale associated the only fossil I can come up with would be a Scaphopod,unless of course the object is a foot long.

Rick

 

Hi Rick,

object was over a foot and around the thickness of a forearm. Maybe one day I'll get the chance to go back and get a closer look

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21 hours ago, urbanfossil said:

Hi Rick,

object was over a foot and around the thickness of a forearm. Maybe one day I'll get the chance to go back and get a closer look

Ok,Wow that is massive, not sure what it could be!! Very interesting!!

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On 1/25/2023 at 4:18 PM, FossilDAWG said:

 Petrified wood is common in some of the shale formations, and cones have been found in concretions although they are rare.  Neither looks like the specimen in the OP.  At this point I am guessing it might be a cylindrical fragment of a concretion.  Such concretions are common in the shale formations, where they probably formed around burrows made in the sediment of the sea floor.  It is possible for concretions to be eroded out of the sediment and re-deposited in the coarse conglomerate beds as they were forming.

 

Don

 

 

My first impression was a concretion or limb cast.  If petrified wood is present in the formation, then a limb cast should be considered.  Below are pictures of a large group of some very small limb casts for sale on an on-line auction site that give you an idea of what they can look like.  Limb casts can get very large,

 

 

Picture 2 of 5

 

Picture 3 of 5

 

 

Marco Sr.

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6 hours ago, MarcoSr said:

 

 

My first impression was a concretion or limb cast.  If petrified wood is present in the formation, then a limb cast should be considered.  Below are pictures of a large group of some very small limb casts for sale on an on-line auction site that give you an idea of what they can look like.  Limb casts can get very large,

 

 

Picture 2 of 5

 

Picture 3 of 5

 

 

Marco Sr.

Thanks Marco, that's very interesting. I'm wondering if in that case the centre of the object would be the limb cast? with the lighter outside being sediment it had eroded out of?

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1 hour ago, urbanfossil said:

Thanks Marco, that's very interesting. I'm wondering if in that case the centre of the object would be the limb cast? with the lighter outside being sediment it had eroded out of?

 

I would expect the entire specimen to be a limb cast based upon its rounded shape.  For a limb cast, the wood was destroyed by a natural process (like completely burning away in volcanic ash) and the cavity left was filled by different replacement minerals over time. Sometimes the limb casts have a rind or casing.

 

Marco Sr.

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