Oddly shaped bone in pebble from Cap Gris Nez

[pachy-pleuro-whatnot-odon]

Hi all,

 

Found this pebble on the beach close to Audresselles (Cap Gris Nez area, Boulonnais) amidst the heavy rain and wind yesterday. Initially, I thought it was just a piece of odd-looking fossilised plant-material, with a faint thought in the back of my mind that may be it could be a fish skull. When I checked it this morning, I was able to confirm the piece is smooth on the outside, and seems to have what appears to be bone fibres on the inside. In other words, I'm convinced now that it actually is bone, though still have no idea what kind...

 

 

[RJB]

Looks like wood with Turrido borings?

 

RB

[pachy-pleuro-whatnot-odon]

19 minutes ago, RJB said:

Looks like wood with Turrido borings?

 

RB

Turrido? Is that a kind of boring worm? Didn't consider that, but could indeed very well be... Might even be the case if this did turn out to be bone then, though, I guess.

 

Still think this is bone, though, based on the type of grain on the lighter brown parts seen on the last photograph.

[sjaak]

It’s wood with borings filled with sediment. This is a typical for the Jura of the Boulonnais.

[abyssunder]

Our friend suggests terredo borings on diagenetical trasformed substrate. He means Terredolites, if I remember it correctly. The substrate of the borings will define correctly what we are dealing with. If the substate is bonic... I think we go down under .

Edited September 3, 2020 by abyssunder

[pachy-pleuro-whatnot-odon]

8 hours ago, abyssunder said:

Our friend suggests terredo borings on diagenetical trasformed substrate. He means Terredolites, if I remember it correctly. The substrate of the borings will define correctly what we are dealing with. If the substate is bonic... I think we go down under .

Sorry, guessed what he meant, but had never heard of them by that name before, and wasn't able to find any information searching the internet either - possibly because of the wrong spelling (not meant accusatorily). I now found some more in-depth information here thanks to your reference to the Teredolites ichnofacies. It turns out that this is indeed comparable to the modern ship worm Teredo sp.. Thanks for clarifying this for me.

[pachy-pleuro-whatnot-odon]

10 hours ago, sjaak said:

It’s wood with borings filled with sediment. This is a typical for the Jura of the Boulonnais.

I'm still hesitant due to the colour (and arrangement of the fibres, where they are visible), as most of the fossil wood I've found during our recent trip was jet-black and had longer, more regularly arranged fibres. But seeing as your knowledge of the area, Niels, I'll just write this down as a piece of wood with borings then Thanks!

[Fischcrazy]

+1 for Teredo borings. those are Teredolites clavatus. Are these Cretaceous? Kelly 1988 would be a more comprehensive source than Bromley et al. 1984. The 1984 paper discusses these traces in relation to laterally extensive coals as a whole while Kelly compares fossil examples of the tracemakers of this ichnospecies. You would want to compare these with Martesia sp. or Opertochasma sp. rather than Teredo sp.

 

Edited September 4, 2020 by Fischcrazy

[pachy-pleuro-whatnot-odon]

3 hours ago, Fischcrazy said:

Are these Cretaceous?

 

The fossil was found amongst the Jurassic Kimmeridgian deposits of the Boulonnais, although there is an early Cretaceous site nearby with which material is apparently occasionally exchanged...

[sjaak]

On 4-9-2020 at 8:54 AM, pachy-pleuro-whatnot-odon said:

I'm still hesitant due to the colour (and arrangement of the fibres, where they are visible), as most of the fossil wood I've found during our recent trip was jet-black and had longer, more regularly arranged fibres. But seeing as your knowledge of the area, Niels, I'll just write this down as a piece of wood with borings then Thanks!

There is the jet black wood but also this wood. Depends on the sediments. I think you will notice after several visits. Between Boulogne and Wimereux you can find both types. Most wood in the grey rock is soft, you can scratch it with your fingernails.

[pachy-pleuro-whatnot-odon]

1 hour ago, sjaak said:

There is the jet black wood but also this wood. Depends on the sediments. I think you will notice after several visits. Between Boulogne and Wimereux you can find both types. Most wood in the grey rock is soft, you can scratch it with your fingernails.

Yeah, found plenty of that, notwithstanding the low amount of fossils overall. Just didn't realise this type of fossil wood also occurs there. I'm used to seeing either the one type or the other (with jet being the more common type and me being familiar with the sturdier brown type from Lyme Regis only), but not both combined... But thanks for the info!