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Bobo the bear
Recently visited Speeton to get more clay for microfossil hunting.
I have soaked in water and filtered with my graduated sieves down to 120 micron 3 times now using about 500 g of clay each time and found zilch.
First time I used detergent which may have been anionic type(slightly acidic) so maybe the Ca carbonate stuff dissolved but next twice just used plain water...Anyone any ideas what I'm doing wrong...supposed to need very little of the clay so i've read to recover the little beasties.
Bobothebear
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Brittle Star
Hi
I have processed clay for many years. I use washing up liquid all of the time, I have always found shells, seeds etc so I do not think this will effect the fossils. I am not familiar with Speeton clay but in my experience you have to be selective in the clay you pick up, I always look for evidence of visible fossils, for example broken shells indicating maybe the sea bed. Knowing about the conditions the clay was deposited in will help.
What do you know about Speeton clay? Is it marine or inland.
JW

 Never ask a star fish for directions
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MicroFossilMan
Marine, lots of ammonites and belemnites.

As Janet is suggesting, it may simply be that your samples don't have many microsfossils in them.
MFM
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Bobo the bear
Brittle Star wrote:
Hi
I have processed clay for many years. I use washing up liquid all of the time, I have always found shells, seeds etc so I do not think this will effect the fossils. I am not familiar with Speeton clay but in my experience you have to be selective in the clay you pick up, I always look for evidence of visible fossils, for example broken shells indicating maybe the sea bed. Knowing about the conditions the clay was deposited in will help.
What do you know about Speeton clay? Is it marine or inland.


Hi, yes I know a little of Speeton clay from the friends of Speeton clay website.
There are 4 bands of Cretaceous clay and some red chalk. After certain scouring conditions the underlying Jurassic Kimmeridge clay is also exposed. At the Southern end are the Chalk cliffs of Flamborough head and the whole has a top layer of Boulder clay so erratics are found on the beach.
I pick the clay to sample where there are lots of Belemnite guards present. I scrape off the surface then dig down. Is the Belemnite zone OK for this purpose do you think?
Yesterdays sample I took were very difficult to dig down as there were so many guards I could only go about half inch before trowel hit one.
The clay is quite sticky and not easy to disperse, how long do you leave in water before filtration and is 120 micron sufficient to hold the beasties?
Bobothebear
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MicroFossilMan
For them that's interested, here's a sketch map showing conditions during the Lower Cretaceous when the Speeton Clays were being laid down. Note how southern England has lagoonal conditions (Purbeck Beds), whereas north of the London (-Brabant) platform there are marine conditions. The Speeton Clay is probably present over north-east and eastern England, but I think it's only at Speeton that there's any good permanent exposure (folk from Lincolnshire might tell me otherwise!). It has been seen occasionally on the north side of the Yorkshire Wolds, and it is seen in boreholes, but otherwise it's on with the wellies and off to Speeton if you want to see deep water lowermost Cretaceous in the UK.
MFM
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Brittle Star
(The clay is quite sticky and not easy to disperse, how long do you leave in water before filtration and is 120 micron sufficient to hold the beasties?)

I generally only use two or three sieves, one to get stones and larger fossils out then my tried and tested 300 microns any sometimes a 180 to test if anything worthwhile getting through. 300 captures forams and mega spores. I dry and break up my clay, then put a layer in old oblong casserole dishes, drizzle washing up liquid all over, then pour boiling water over wait a minute stir and leave 24hts at least stirring occasionally to get rid of air pockets, then sieve, claggy clay may need some encouragement to go through or you can dry and repeat process. You can dry residue naturally or dry in oven for 20 mins.
JW

 Never ask a star fish for directions
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Brittle Star
You mentioned you collected from below a mass burial of Belemnites, this may point to why there were no micro fossils. For what ever reason the Belemnites died on mass and collected in one place, possibly dying after mating as cephalopods do now. Maybe a storm collected them together if this was the case the sediment would not have micro fossils, these in my experience need a calm sea bed where dead creatures float down when they die or are fragments from being chomped on. Accumulating and forming layers on the sea bed, maybe close to a reef where there is abundant life.
Looking for clay with a layer of broken shells is your best bet.
JW

 Never ask a star fish for directions
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Bobo the bear
Thanks JW. I may as well give this stuff one last go then try another part of the clay.
There was an area where I picked up what is probably exogyra or incoceramus with many bits of broken shell around so I guess that is what I should have sampled.
Bobothebear
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Brittle Star
Give it a go. I have picked up stuff myself, lugged it hone and it was a dead loss. As you go along you learn which is good and what is not.

Good luck and pet us know if you find anything next time.
JW

 Never ask a star fish for directions
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