Hello Satoshi,

A look like some agglutinated forams, or some orbitolinids (Orbitolina sp.?: see the stratotypical revision of Pierre Juignet, the 22nd European Micropaleontological Congress published in Revue de Micropaléontologie, and seminal works of Rolf Schroeder -similarly see the online website of Notebooks on Geology).

B could be some large calcispheres (either calcidinoflagellate cysts, or classical Pithonella sphaerica, see seminal works of Jean-Michel Villain, Alphonse Blondeau, Helmut Willems, Helmut Keupp and Peter Zügel).

C looks like a siliceous infilling of a foram (already seen in Normandy and stratotypic area from the "tuffeau").

D looks a siliceous infilling of either a radiolarian (quite improbable) or a planktonic foram like Schackoina sp (more likely).

E looks like also like a siliceous infilling of a benthic agglutinated foram Tritaxia sp.

Hope it will help.

Cheers

Hello Bruno,

Very interesting.

A: In the same samples, most of agglutinated forams show white or transparent color, but A shows black color similar to co-existing radiolarians. At least they are unilocular.

B: I did not know "calcispheres." Aperture is invisible, but Pithonella sphaerica certainly resemble.

C, D, and E could be infilling of foram or radiolaria. I will try to compare them with well-preserved specimens whether they can be inner mold. 

Thank you so much.

Those are radiolarians. It is quite common to find them, most in deep water paleoenvironment.

Thank you, Juan,

I suspected that A might be radiolarians, and its abundance suggest any oceanographic condition related to OAE. But strange thing is that this fossil (or at least its overwhelming/abundant occurrences) has not been reported from Hokkaido by radiolarian researchers as far as I know. 

For C I personally prefer a sponge sclerite. In sponge terminolgy this type of microscleres are termed euasters.

Hello Satoshi,

in my opinion the spherical objects A and B very likely are radiolarians. C, D and probably E too could be sponge sclerites. E additionally resembles a test of an triserial agglutinating foram.

Happy to participate in the microfossil quiz of the day. (A) look like agglutinated forams to me; they are often flattened/compressed. (B) is a calcisphere (Pithonella); see paper by Wendler 2012. Not sure about (C). (D) and (E) are likely to be replaced radiolarians, although (E) may be a diatom. 

Mark Leckie

Hello Satoshi,

I suspect that the objects in fig. A are not radiolarians because too big.  Those in figs. B and C could be radiolarians, but we need SEM pictures to observe the ornamentation of the shell (pores, nodes, etc.). The object in fig. D has a shape similar to a radiolarian (genus Paronaella), but a SEM picture could confirm it. I agree for the diatom in fig. E.

That would be good if I could see the thin section photomicrographs of them.

A. - for me agglutinated forams

c and D are similar to radiolarians

Difficult to say for sure first of all because of the rather poor preseervation and secondly because it seems that the photos have been taken in a liquid, wather probably, that gives this disturbing irisation to all photos. Better to photo the dry specimens and, if possible, get Scan photos. In this situation, my determinations are as follow:

A. Some of them could be radiolarians, but impossible to say what genera.

B. Seem to be the nassellarian species Holocryptocanium barbui, a rather large and common species in the late Albian-Cenomanian. I base my opinion on the fact that some specimens seem to have a small depression corresponding to the apical part of the species marking cephalo-thoracic segment included in the abdomen.

c. Difficult to say.

D. Seems to be the radiolarian genus Paronaella.

E. Due to its tetrahedral shape it could be the radiolarian species Pyramispongia glaskockensis Pessagno, a Cenomanian-Turonian species. 

Hello Satoshi,

nice Cretaceous fossils. Concerning your photographs I think that you have in

A: most probably agglutinated forams.

B: yes, nasselarian radiolarians ... definitively not "calcispheres"/calcareous dinoflagellate cysts.

C + D: also radiolarians,

E: probably radiolarian ... However, this type of triangular shape is also known from diatoms (but then more common and typical for Palaeogene/Neogene forms).

I also recommend to take SEM pictures, which are better for determination at all ...

Best wishes,

Mike

E-  cannot be at all diatom first of all because at this poor preservation and the general assemblage. And many radiolarians of the genus Paronaella have this shape.  

yes ... I agree, its probably more likely a radiolarian ... I only mentioned, that there are some Tertiary/Recent marine diatoms (like Trinacria) that have this type of shape ... More can be seen after SEM of these microfossils ... 

Thank you everyone. I apologize for my late reply.

I cannot show SEM and thin-section soon, but I will provide some additional photos later.

I took all pictures A-E in dry condition. I created them using software "Helicon Focus" from several digital photos taken in different focus depths.

All specimens shown above are, at least, not calcareous. Apparently A do not have aperture, and agglutinated foraminifera like Saccamina included in the same samples show white color. Certainly I also feel A is larger than most of radiolaria and structure is too simple.

Best wishes

I confirmed B does not dissolve in acid.

I added picture of thin section of A and dissected specimen of B. Outer shell of A is not clear, but there are many small pore-like depression on surface, so I feel this is not agglutinated forams but some kind of radiolarians. B clearly shows tiny pores connected inside and outside of the shell.

I am sorry to bother everyone. I will close this session.

I feel that A. is a saccaminid foraminifera and D may also be a foraminiferal specie belonging to Tuberitina genus

Thank you Ranju,

All these fossils are radiolarians in my final answer.

yes, of course they are radiolarians. Good luck.

Thank you so much! Your answer gave me the confidence.

Hi

some of them... Radiolarians.

Cheers

I am not sure about A, but rest are radiolarians for sure. Similar forms are found in deep-sea sediments from Indian Ocean also.