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Anon88
Struggled to post tonight, hopefully there isn’t loads of duplicate posts come through.

Basically these are two that I think are nothing noteworthy but after seeing the first one next to an ammonite I found in the same stream in Cambridgeshire, I thought I may as well ask if anyone else sees similarities with texture etc? It can’t be from an ammonite surely, or it would be a really large specimen?

the second - some sort of mineralisation process?

thanks for any help Click image for larger version - Name: 2DDFC389-56C3-437A-B7CF-2595003C9B90.jpeg, Views: 26, Size: 349.41 KB Click image for larger version - Name: 3A1FD354-8AC2-42C0-80AA-437BEED52979.jpeg, Views: 25, Size: 347.12 KB Click image for larger version - Name: C502D2D7-F0C3-457D-9B21-4A3C8131F68B.jpeg, Views: 25, Size: 164.58 KB Click image for larger version - Name: 65B3D295-D902-4AB6-9881-1F73070D3A5B.jpeg, Views: 27, Size: 321.55 KB Click image for larger version - Name: F184B8BA-E4AE-4780-88D2-BF953753B6C8.jpeg, Views: 23, Size: 194.24 KB
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Barrow Museum
The huge tubercle is almost certainly from a large ammonite; maybe Peltoceras or Aspidoceras - both from Upper Jurassic clay formations that are prevalent in the till around your stomping ground.  The ammonite accompanying it has me baffled.  It looks like a phosphate cast from the Gault Clay, but I wonder if it might be from earlier in the the Lower Cretaceous - perhaps the Spilsby Sandstone, which has  a basal layer with fossils like this in it.  Can't say I have seen anything from the Upper Jurassic like this, and I've seen a lot of it!  A clearer view of the venter (keel) might give the game away.  Someone out there will probably recognise it and suggest a name.
The other fragment doesn't look fossil to me.
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prep01
Knowing the location would AWAYS help a lot!
Colin Huller
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Anon88

image.jpg  Hi BM,

see below photograph. This one was found in a stream near Boxworth, at a point where the formation changes from Kimmeridge Clay to Ampthill clay but I’m picking over the shingle exposed by the stream.

I tend to find small ammonites fragment, this one is the largest I’ve found here. I’m thinking about sending it to be prepared, not sure if the centre will be intact.

Interesting to know that the initial fragment is from an ammonite, must have been extremely large!

thanks for the responses


image.jpg 

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Barrow Museum
Is it possible that the bigger ammonite, in your last photo, has or had a sharp keel?  If so, then I would suggest it is Goodhallites, a Lower Cretaceous, Gault Clay genus.  It typically occurs in a phosphate nodule bed near the base of the Upper Gault Clay (in the so-called Varicosum Subzone) in the Bedfordshire area, so I suppose the same might apply to Cambridgeshire.  It would have been brought to its present locality by Quaternary ice.  This phosphate nodule bed was once dug from Buckinghamshire to Cambridgeshire and probably beyond for "Coprolites" (ie the phosphate nodules) from which super phosphate fertilizer could be made.  It was apparently a more valuable industry at the beginning of the 20th century than Cornish tin mining.

The partial ammonite (photographed with with the two black indeterminate imprints) again is difficult to ID, as I cannot see the form of its venter.  It reminds me of something from the "Lower Lias", such as Euagassiceras, which must also have been ice-transported.
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