Suman:

You may try a method (Zolnaj, S. 1979) cited in the following link.

Best

Syed

https://www.researchgate.net/publication/264500360_Late_Cretaceous_(Santonian-Maastrichtian)_Integrated_Coccolith-Globotruncanid_Biostratigraphy_of_Pelagic_Limestones_from_the_Accretionary_Prism_of_Manipur_Northeastern_India

Article Late Cretaceous (Santonian-Maastrichtian) Integrated Coccoli...

Dear Suman, 

I agree with Kenneth here. Could you precise for which purpose exactly and the kind of sediments ? This is very relevant for choosing an appropriate method of preparation. Also, do you intend to do some biostrat work, or investigate quantitative aspects, do you wish to pick the forams for other kind of analysis ? All these questions are relevant prior to choosing a method of preparation. 

I invite you to check for these two relatively recent publications as a start:

Remin, Z., Dubicka, Z., Kozłowska, A., Kuchta, B., 2012. A new method of rock disintegration and foraminiferal extraction with the use of liquid nitrogen [LN2]. Do conventional methods lead to biased paleoecological and paleoenviromental interpretations? Marine Micropaleontology 86–87,  11–14.

Nielsen, Jan Kresten, and Jakobsen, Sten Lennart, 2004. Extraction of Calcareous Macrofossils from the Upper Cretaceous White

Chalk and Other Sedimentary Carbonates in Denmark and Sweden: The Acid-Hot Water Method and the Waterblasting Technique.

Palaeontologia Electronica 7(4):11p

Yes I do agree that theme of the work will be related to the methodology. My objective is to carry out biostratigraphy as well as palaeoecology (picking of forams definitely required).

No the material is very fragile so thin-sectioning is not on the cards. I requested for suggestion of methods apart from thin-sections.

I am not a microfossil expert (rudist bivalves are 'my thing', though their bioclasts can be interesting at the micro-scale), but I think that some of my colleagues have used a combination of some organic wetting agent (I think) and ultrasound to disaggregate friable fine-grained sediments in order to extricate the microfossils.  Not nearly a detailed enough answer, I know, so I'll try to track down exactly what they did and come back to you again.

Best wishes,

Peter Skelton

Dear Suman,

what's a fragile carbonate material? Marls?

There is no methodology difference between Cenozoic and Mesozoic methodology to wash sample for micropaleontological purpose. The problem would be if the forams are fragile. In our lab the technician either use water or diluted peroxide to disaggregate the sample and then wash it through meshes.

Dear Suman,

Gentile dis aggregation might work.  Try soaking a sample for 48 hours in soapy water or diluted hydrogen peroxide.

Hi Suman,

I am foraminifer micropalaeontologist. I am not sure what exactly is your problem as were also some or colleagues who already wrote to you.

In case that the problem is, how to get isolated foraminifers from hard limestones that cannot be washed, there are special methods of selective dissolution of rock in acetic acid (I can send you references).

Best wishes, Miroslav

Dear Suman Sarkar,

If you have level(s) that have clay or marl levels within your sequence, you can sample these level(s) after removing altered part (at list 10 kilos). In Iran we process this sort of sample(s) with light acetic acid or vinegar (half water and half vinegar) for 24 hours (one day and one night). After 24 hours you can wash your sample with water (at list 20 times). Then separate residue form undissolved materials (muddy part should be removed by water carefully). By drying residue and picking materials under microscope you can choose larger benthic foramifera. Finally after picking process you can clean them by ultrasonic bath then  glue them for preparing  thin section or photograph them as you wish.

Best wishes Mehdi     

You need to define what you mean by fragile as, without that, it is difficult to answer the query. Some carbonates can be difficult to disaggregate and obtain clean foraminifera but without further clarification it is not easy to help. I have studied benthic foraminifera from the CRETACEOUS in many parts of India and gave not experienced any difficulties.

Here's a reference that I came across, concerning the application of freeze-thaw methodology, in case it might help you: Kennedy, A.E. and Coe, A.L., 2014, Journal of Micropaleontology, 33, 193-203.

Best regards, Peter Skelton

Hallo,

you may also use liquid nitrogene LN2 and hot water - very simple and efective. compare the publication below

While all the suggestions are sensible and well tried, you need to work up the scale of physical/chemical aggressiveness. Begin with the most benign and then judge the effectiveness. 

If I get your question correctly, i can offer method of disaggregation using Na2SO4 · 10H2O (Glauber's sault or mirabilite). I research the Upper cretaceous foramiferas of Volga refion and I work with different species of marls and chalks. Glauber's sault's method is very successufully. I can send you discription. 

Dear Ilya Ryabov,

I shall be thankful if you send me the description.

Best wishes

Suman

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Dear Prof. Towe,

I am doing the study for biostratigraphy as well as palaeoecology. I already took your suggestion of picking the foraminifera. Thin-sectioning is very difficult since the material is very fragile.

Best regards

Suman

If your samples are fragile (poorly consolidated), you might try some gentle ultrasound disaggregation (I have not personally tried this on pre-Quaternary age rocks).

It is  true that ultrasound can be used to clean fossil samples that have already been partially processed. It might work on fragile material but you would need to experiment with the timing as too long could shatter everything. You would need to do it under deionise