Help! Mystery ammonite from Folkestone

[Phil]

Hi all,

This rather stunning ammonite was found buried in an outcrop of Gault Clay at Folkestone in Kent. I am not certain what type of ammonite it is, but suspect it is something akin to Hysteroceras. This fossil was apparantly poking out of a clay outcrop amongst the beach sand with just a small piece of keel projecting. This ammonite was certainly discovered in the Upper Gault beds and close the chalk boundary, dating it to the upper Albian, Lower Cretaceous. It has a pronounced keel, and is I think, is pretty much intact.

Any opinions on my ID anyone? I can supply better resolution pics if required.

(Mandy, if you read this, I insist on walking the dogs with you next time if you are to find things like this. In five years I've never found anything this good! Bah. )

 

[AndyS]

Phil,

Are you sure about Albian ? Could it be lower Cenomanian ?
It looks just like a Schloenbachia varians forma subplana to me...

AndyS

 

[Architeuthoceras]

Looks like AndyS hit the nail on the head.

Another one of them polymorphic forms, only someone decided to name all the different forms. Does anyone know how many sub-species or forma types there are?


Some of the others I,ve seen on the web could easily be confused with a form of Forresteria from the Coniacian, for example This One

 

[Phil]

Thanks Andy and Kevin.

I see what you mean about Schloenbachia, it certainly does look similar. The only difficulty I have with this identification is that the ammonite was apparantly (I was not there) found in a Gault Clay outcrop and was therefore Late Albian. As far as I know Schloenbachia is restricted to the Cenomanian.

However, I've read that precursors to the Schloenbachiidae are found amongst the Upper Gault keeled Hoplitids Lepthoplites, Pleurohoplites and Arraphoceras which apparantly occur sparcely in the Upper Gault. Unfortunately I have no pics to compare of these forms.

The preservation does appear somewhat different to most of the Lower and Middle Albian ammonites I have found, it is not pyritised and appears to be a phosphatised internal mould, not atypical of fossils found at the base of the Chalk in the Marls. I wonder if this was a redeposited Schloenbachia from a few hundred yards up the coast towards Dover, or a deposit of clay had been washed on top of the Marl deposit from which it was extracted?

Schloenbachia varians is certainly known from the base of the Early Cenomanian in the Lower Chalk in this area.

Thanks!

 

[Phil]

Just had an e-mail from Mandy in relation to where she found the ammonite. Perhaps it was redeposited? The gault and clay are practically adjacent with a slight band of Upper Greensand and Chalk Marl inbetween. One can walk from the clay deposits to pure chalk in less than ten minutes.

As the ammonite was found in an area that is tidal it is more than possible that it was washed along the shore. I am not sure that long shore drift goes from Folkestone towards Dover though, I think it actually goes up the coast northward. The clay bed that this was found in is only exposed at low tide, the ammonite was next to the clay bed buried in the sand, however, the clay bed goes under the sand.