Hi everyone, we use traditional techniques such as simple water soaking or methods using hydrogen peroxide (H202) or washing-soda (Na2CO3) for disintegration and extraction of foraminifera and other microfossils from soft sediments. However, these methods are not possible for very hard carbonate rocks as hydrogen peroxide can't disintegrate them. So, is there any process by which the foraminifera can be extracted from the hard limestone rocks apart from doing petrographic thin sections?
Dear Swagata Chaudhuri please do well to recommend my answer.
The extraction of foraminifera from hard limestone rock samples involves a series of steps to separate these microscopic marine organisms from the rock matrix. Foraminifera are valuable in paleontological and geological research as they provide insights into past environmental conditions. Here's a general procedure, and while I can't provide specific publications, I can guide you through the process. You may find relevant publications by searching for academic papers on foraminifera extraction methods.
Procedure for Extracting Foraminifera from Limestone Rock Samples:
While I can't provide specific publications, you can search for relevant research papers by using keywords like "foraminifera extraction from limestone" or "foraminifera dissolution techniques" in academic databases like PubMed, Google Scholar, or institutional libraries. Look for research articles that discuss the methods used for extracting foraminifera from hard rock samples, as well as any modifications or improvements to the procedure. Researchers often publish their methods in geological and paleontological journals.
Tobias Makuochukwu Onyia Thanks for your answer. I think you may missed my concern. We follow the protocols for the extraction of foraminifera using hydrogen peroxide. I think weak acids may not be useful enough for dissolution as we have already tried.
Try freeze/thaw for 10 times and check whether a bit of the outer parts disaggregate. If yes move on.
You mention weak acids and perhaps you already tried this, but if not, you could test the "cold acetolyse" method with highly concentrated acetic acid, proposed by Lirer (2000- Micropaleontology) and applied by many others. Fragmentation into small pieces may be required.
You may use hot acetolysis: it is very efficient to retrieve isolated forams, ostracodes and any other calcareous microfossiles (echinoderm plates, cirripedes, worm tubes, etc.) from indurated (even hardground) carbonates.
Please refer to Pr F. Lethiers in Revue de Micropaléontologie.
As mentioned by Speijer and Ferre above, I would purchase 99+% acetic acid (not vinegar, which is 70-97% water). You can add water to the acetic acid until the solution is 2-20% water. As the water concentration increases, the rate at which the rock breaks down increases. Similarly, as the temperature of the solution increases, the rate at which the rock breaks down also increases. You can experiment with water concentration and temperature to find what gives you the best preservation.
The rock disintegrates over hours or days. Calcareous forams left in the solution dissolve more slowly than the limestone matrix but also dissolve away, so residues which fall off the rock should be reviewed periodically. The residues can be air-dried in a fumehood and/or treated with a base.
Using acids will more or less dissolve the surface or even more of calcareous shells. That's why we work with the freeze/thaw method as described in Wissing, Herrig, 2001: Arbeitstechniken der Mikropaläontologie.
I use the methodology developed by G.B. Rodrigues, M.H. Bom, G. Fauth (2012), which uses acetic acid.
I add the acid until it covers the sample (previously broken). And I leave it to react for around 2 to 3 days.
I like this methodology because I can use it on several groups of calcareous microfossils.
I think different techniques applied will not completely extract the foraminifera, so thin sections in different orientations are preferred in this case.