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Weathered Lava/basalt Fossil - Scallop


jksmithvegas

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It appears to me that lava flowed over a scallop bed followed by weathering in the surf - i think some mineralization has occured but i cant be positive. Seems a bit rare to me but i don't know anthing about it. Any information would be helpful. Could it have came from Hawaii post-10912-0-63408400-1358921536_thumb.jpgpost-10912-0-63458300-1358921539_thumb.jpgpost-10912-0-35363000-1358921542_thumb.jpgpost-10912-0-31070700-1358921545_thumb.jpgpost-10912-0-67050900-1358921548_thumb.jpgpost-10912-0-44293800-1358921551_thumb.jpgpost-10912-0-18160100-1358921554_thumb.jpg

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AgrilusHunter

Hi jksmithvegas,

Welcome to the Forum! That is a wicked cool fossil and a real showpiece! I think it looks like a scallop also and I'll be interested to see what some of the experts here say about an identification. Why do you think it is volcanic instead of a concretion?

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Was it found in the middle of a round stone? If so, it's likely a concretion that formed around the scallop.

How did you come across it?

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Hi jksmith

That’s pretty cool… but it does look like a concreted scallop shell – ie sedimentary origin. That’s much more likely for the shape you found rather than it having subsequently weathered to that shape, and the way that it has split is very characteristic of sedimentary concretions.

There has been interesting discussion previously on the forum about the potential for fossils of igneous origin and more modern enrobement of organic items by lava here:

http://www.thefossilforum.com/index.php/topic/19457-igneous-fossils/#entry215372

and here:

http://www.thefossilforum.com/index.php/topic/25561-igneous-fossil/page__hl__pompeii#entry279982

When “fossils” occur in igneous rocks such as basalt or volcanic magma they are not true fossils. They are generally casts within a cavity left behind by something organic that has partially or completely incinerated. When true fossils are found in igneous rocks, it’s a rare occurrence and generally relates to volcanic tuff. Although tuff is technically of igneous origin, it’s a consolidated rock formed from volcanic ash and ejecta. In those respects, it’s actually sedimentary – except that the sediments were from atmospheric deposition rather than the more usual water deposition.

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Thank you all for the information. I was able to do some additional research based on your input. This was part of my grandfathers estate and had been passed around in the family. Interestingly I ran across a link for Bandon, Oregon at the mouth of the Coquille River there is a large concentration of concretion fossils throughout the Cape Arago Headlines. My grandfather lived in this area for many years, it seems likely this was where it was found. In all this was a fun and educational journey, again thank you for all your help. I think I will plan a trip there for this summer.

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Painskill said:

"When “fossils” occur in igneous rocks such as basalt or volcanic magma they are not true fossils. They are generally casts within a cavity left behind by something organic that has partially or completely incinerated."

I got to wonder who made the decision that kind of "not-a-fossil" shouldn't be included in the list of ways fossils can form. If something as uncommon as bioimmuration makes the cut then why not casts formed in a lava cavity?

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The definition for fossil I find the most workable is "any evidence of life older than 10k years old." By this definition, there most certainly can be fossils in igneous rock but they are exceedingly rare because evidence of life in this context is usually incinerated. A mold of a tree, or something like the Blue Lake Rhino, since recognizable as evidence of a tree and rhino, are fossils as long as they are at least 10,000 years old. And keep in mind, ash beds are really more of a sedimentary rock than igneous.

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Is a cast in magma or something incinerated by a lava flow not an ichnofossil? That's what I meant by not true fossils. As opposed to something buried in sedimentary ash/ejecta which has mineralised and which I referred to as a true fossil.

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I think ichnofossils are the result of an activity, and that both they and natural casts are true fossils.

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So, in 8,067 years time... what will these be?

post-6208-0-50905700-1358984587_thumb.jpg

Fossils, Ichnofossils or neither?

And what would be the correct term for them until they reach 10,000 years of antiquity? I vote "problematica" (just kidding).

This kinda overspills into the other interesting "What is a Fossil?" thread. Perplexing, isn't it?

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And then there is the Miocene Blue Lake Rhino 'cave' in Washington state. This beast was left as a large mold in the basalt. I believe some bones were found as well.

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And then there is the Miocene Blue Lake Rhino 'cave' in Washington state. This beast was left as a large mold in the basalt. I believe some bones were found as well.

Indeed. I guess if there were bones (I believe you are right) then we would have to regard that as a fossil.

I thought this was interesting too. It was captioned as a (modern) impression in sandy soil left behind after an elephant had taken a nap. I don't have reason to doubt it... but who knows?

post-6208-0-32861500-1358985688_thumb.jpg

How cool would it be if that had filled with muddy sediment and then fossilised. Ultimately you'd have a semi-3D positive mould of an elephant head. That's what I would really call a trace fossil.

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There seems to be a blurry line between 'cast fossil' and 'resting trace fossil'.. which goes to show that ichnofossils should be included under the definition of 'fossil'. I just have a small problem with the arbitrary date of 10 000 years - does that mean that an unaltered Pleistocene shell is a fossil but a similar shell from Holocene layers just above it is not?

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There seems to be a blurry line between 'cast fossil' and 'resting trace fossil'.. which goes to show that ichnofossils should be included under the definition of 'fossil'. I just have a small problem with the arbitrary date of 10 000 years - does that mean that an unaltered Pleistocene shell is a fossil but a similar shell from Holocene layers just above it is not?

Yes, me too. I believe the waters have been muddied (or clarified, depending on how you look at it) by the geologists representing the International Commission on Stratigraphy. They constantly review the geologic timescale of the world’s rocks based on absolute radiometric data, relative comparisons, reversals in the earth’s magnetic field and index fossils to order events in the history of the Earth. They then make proposals for the geologic time scale definitions. As things stand, they regard the Holocene epoch as “recent” - extending from today to 10,000 years ago – and the Pleistocene epoch as the beginning of the age of fossils, extending from 10,000 years to 2.6mya.

That’s where the arbitrary (in palaeontological terms) cut-off point comes from.

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Hi,

In France (thus on the "old continent"), we consider that animals or plants are fossil before the appareance of the human. From their appareance, it is about the "prehistory", and the collect is forbidden. Supposing that we find bear teeth in a french cave which bones are dated after the human appareance (human activity etc...), the authorities consider that the human of this period were able to eat this bear, thus it is forbidden to collect these fossils. They are part of the prehistory and are thus protected.

In the reading of this subject, I thought of Pompéï and in Vesuvius (perhaps what meant the Painshill's pic), as they are human, in France we don't consider them as fossils, in spite of the phenomenon, for the previous period, would have fossilized the present life in this place during the eruption.

Coco

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Rockwood is right: Trace fossils record the activity of an organism. A mold or impression is a body fossil exactly like a fossil bone is. And all of these (molds of long extinct animals, trace fossils, fossil bones) are true fossils.

Is a cast in magma or something incinerated by a lava flow not an ichnofossil? That's what I meant by not true fossils. As opposed to something buried in sedimentary ash/ejecta which has mineralised and which I referred to as a true fossil.

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With or without bones, the Blue Lake Rhino is a true fossil and a body fossil (as opposed to trace fossil). The elephant's head, if found in the geologic record, would also be a body fossil.

Indeed. I guess if there were bones (I believe you are right) then we would have to regard that as a fossil.

I thought this was interesting too. It was captioned as a (modern) impression in sandy soil left behind after an elephant had taken a nap. I don't have reason to doubt it... but who knows?

post-6208-0-32861500-1358985688_thumb.jpg

How cool would it be if that had filled with muddy sediment and then fossilised. Ultimately you'd have a semi-3D positive mould of an elephant head. That's what I would really call a trace fossil.

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A 'cast fossil' would be an ancient, naturally-occurring replica of the outer surface of an organismal body part. A 'resting trace fossil' would be a trace fossil of where a living organism left an impression in soft sediment that was later preserved. Certain fossils can certainly be both (the terms are not mutually exclusive): a sauropod track is a trace fossil (ancient evidence of a walking animal) and a body fossil (the impression of a body part). As for the arbitrariness of the 10k "graduation," I agree it is odd, but it is no less useful that putting the beginning of a day or year where we have put them. An unaltered Pleistocene shell is certainly a fossil. The Holocene one is just 'not a fossil' or 'sub-fossil,' which, as far as I can tell, is never defined. I suspect I am a sub-fossil.

There seems to be a blurry line between 'cast fossil' and 'resting trace fossil'.. which goes to show that ichnofossils should be included under the definition of 'fossil'. I just have a small problem with the arbitrary date of 10 000 years - does that mean that an unaltered Pleistocene shell is a fossil but a similar shell from Holocene layers just above it is not?

Edited by Carl
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The problem I have with this definition is that "human" is not defined. Many use 'human' to mean 'hominid' allowing for humans millions of years old. Others restrict it to 'anatomically modern humans,' which would only go back ~200,000 years. And this definition would not allow there to be any fossil humans, of which I would argue there are plenty.

Hi,

In France (thus on the "old continent"), we consider that animals or plants are fossil before the appareance of the human. From their appareance, it is about the "prehistory", and the collect is forbidden. Supposing that we find bear teeth in a french cave which bones are dated after the human appareance (human activity etc...), the authorities consider that the human of this period were able to eat this bear, thus it is forbidden to collect these fossils. They are part of the prehistory and are thus protected.

In the reading of this subject, I thought of Pompéï and in Vesuvius (perhaps what meant the Painshill's pic), as they are human, in France we don't consider them as fossils, in spite of the phenomenon, for the previous period, would have fossilized the present life in this place during the eruption.

Coco

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Hi,

I just forgot to ask : "when begins the appearance of the human (or of the hominid being, who would be doubtless more just), at which stadium of his evolution ?".

Coco

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Hi,

I just forgot to ask : "when begins the appearance of the human (or of the hominid being, who would be doubtless more just), at which stadium of his evolution ?".

Coco

Hominids (Hominidae) are the “great apes” which includes us, together with chimpanzees, bonobos, gorillas and orang-utans. The family ancestors had differentiated from the the Hylobatidae somewhere between 15 – 20 million years ago. Our most recent common ancestor dates to approximately 14 million years ago.

Hominins (Hominini) as a sub-family are modern humans plus our close relatives (Neanderthals, Denisovans etc)… all of whom are extinct. It then gets complicated. The homo subtribe lineage probably split from the chimpanzee branch somewhere between 5.4 – 6.3 million years ago. There was a 4 million year long period of speciation leading up to that for which the ancestral connections are not established with complete certainty.

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Hi,

Thanks Paintshill for these information. It isn't always easy for foreigners ;)

No problems in France with fossil hominidae, We don't consider that Hominini are fossils. It is here the "prehistory" begin for us.

Coco

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Yes, me too. I believe the waters have been muddied (or clarified, depending on how you look at it) by the geologists representing the International Commission on Stratigraphy. They constantly review the geologic timescale of the world’s rocks based on absolute radiometric data, relative comparisons, reversals in the earth’s magnetic field and index fossils to order events in the history of the Earth. They then make proposals for the geologic time scale definitions. As things stand, they regard the Holocene epoch as “recent” - extending from today to 10,000 years ago – and the Pleistocene epoch as the beginning of the age of fossils, extending from 10,000 years to 2.6mya.

That’s where the arbitrary (in palaeontological terms) cut-off point comes from.

Last number I saw for start of Holocene was (11 700 years ago) if I'm not mistaken, that's about 9700 BC

So a shell buried in 11600 year old sediment is not a fossil, but the same shell in 11800 year old sediment is? I can live with the arbitrary definition but if there is a better definition to be found, we should try and find it. It might be more convoluted but it might make more sense. Like maybe it should be traceable stratigraphically or the matrix should be more consolidated than sand or mud, or some combination of these. I havent thought much about it, but someone said "You know it when you see it" - well this must be definable somehow.

Edited by Wrangellian
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Last number I saw for start of Holocene was (11 700 years ago) if I'm not mistaken, that's about 9700 BC

Yes, I'm out of date... and actually they changed it again in August 2012. The current proposal, which I believe is stil awaiting ratification, is that the Holocene began 11,800 years ago.

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Believe me: I've searched for the perfect definition for decades. Saying a fossil becomes such when it turns 10k years old is really no different from saying your are in the Pleistocene 11,700 years ago but not 11,699 years ago.

Last number I saw for start of Holocene was (11 700 years ago) if I'm not mistaken, that's about 9700 BC

So a shell buried in 11600 year old sediment is not a fossil, but the same shell in 11800 year old sediment is? I can live with the arbitrary definition but if there is a better definition to be found, we should try and find it. It might be more convoluted but it might make more sense. Like maybe it should be traceable stratigraphically or the matrix should be more consolidated than sand or mud, or some combination of these. I havent thought much about it, but someone said "You know it when you see it" - well this must be definable somehow.

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