Dear Julie, This is indeed a delicate task and a real problem also in some Late Quaternary sedimentary settings as demonstrated by SEM (Hammarlund and Buchardt, 1996). If the sediments are sufficiently soft, freeze-drying followed by dry-sieving might be an option as descripbed for example by Hammarlund et al. (2002, 2003). These papers are available through my ResearchGate profile.

Dear Julie, Consider only one phase of carbonate through binocular microscope and micro-drill the targeted parts only. Otherl phases of carbonate diagenetic products are also must microdrilled separately. Stained chips (alzarin Red S) may also useful as differentiation tool between carbonate phases.

Dear Julie, It is important what kind of sediments do you have. Is it solid rock or loose sediments. I suspect the second option to be correct. You may of course sieve the sediments and check the micromorphology of the carbonate grains using SEM as Dan Hammarlund has suggested. You may also choose one kind of carbonate material and analyse it (if available from the sediments). A wide range of options are possible: ostracods, molluscs, charophyte incrustations or oospores. It is also possible to run parallel analyses of two kinds of material e.g. bulk samples and charophytes. Such an approach was used in numerous studies. Remember that most of lacustrine carbonates are in fact biogenic. Also the fine fraction is usually a consequence of the photosynthetic activity of phytoplankton in the epilimnion. You may see Pełechaty et al. 2010 or Apolinarska et al. 2011 for some brief descriptions.

You may of course sieve the sediments and check the micromorphology of the carbonate grains using SEM If the sediments are sufficiently soft, freeze-drying followed by dry-sieving might be an option as descripbed for example by Hammarlund et al. I am afraid it is not possible to completely separate from sediment .

Dear all,

I thank you very much for all your contributions. Thank you for giving references, as it gives my new pathways to explore.

The sediments are not loose, but break very easily, it is very powdery and most of the time, finely laminated. It is very fine grained (clay and silt size for the silica grains) and no shell is visible to the naked eye or with a hand lens. Each sample have been divided in 2 sub samples, receiving a different treatment: one sub sample was put in a freezer at -18 and the other put in the oven at 50 for 24 hours.

Would freeze-drying one of the sub sample give me enough loose sediments to dry sieve them? If yes, which is the best sub sample to use? The oven dried or the frozen one?

I will carefully look into each of your proposed solution. I thank you all for broadening my horizon.