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  Paleontology
Calcareous Nannofossils of Iran
Author : Fatemeh Hadavi
Publisher date : October 2002
Chapter title : First Chapter - Nannofossils
Data title : Standard Preparation methods

1-AT first, around of sample is completely cleaned by

2- A little amount of sample is cut it is located on lamella.

3- we should pour a distill water drop on lamella . In this stage, a relatively concentrated solution is created.

4- Above solution are scattered by a tooth pick with two flat sides on lamella Mentioned lamella should be dried on an oven rapidly.

5- we should numerate a lamella and locate that reversely on lamella and we should stick by a specific stick .It is necessary to say that this preparation method is very simple and fast . But for getting better results, we need much exercise and experience with wavy movements of toothpick will stretch coarse grains to lamella side. This method is used for preparation of marl and gypsum samples and it is very suitable and it can be used for other lithologies except for hardest sediments.

 

B) Pipette method of preparation

1-      External part of sample is used by a completely cleaned.

2-      The sample is swirled in a thick tissue and then we crush it.

3-      Gained powder is poured in a vessel and we add some distil water to that.

4-      Solution is stirred and a little amount of calgone it added to it and it and we soak that for maximum one hour.

We should ultrasonic system for separation of particles too.

5-      We transfer a small part of solution into other side of vessel and attenuate that with water.

6-      A part of gained solution is poured on lamella with a thickness of 1-2mm lamella is dried on electric oven.

7-      Lam is numerated and joined on that by a reverse lamella stick.

(C) Gravity settling

1-      We should suspend some parts of sample in a vessel as methods which was mentioned above.

2-      We stir solution and it is continued for 1-2 minutes so that coarse grains are deposited.

3-      We transfer upper part of solution into other vessel and we wait for 10-15.

4-      We should exit upper part of this solution and lower part is used for study.

(O) Using centrifuge

1-      We should prepare suspended solution according to above method.

2-      We pour solution in a pipette and then we put it in centrifuge.

3-      We use centrifuge for 15 seconds and with two 350 and then we transfer upper part of solution into other pipette which has been numerated. Coarser grains (coarser than 30 micron) have been eliminated in this stage.

4-      We should increase solution inside of pipette with distil water into 2/3 and then we centrifuge with round of 1000 and for 30 seconds.

Then we put away top part solution in pipette. So, finer grains are exited from samples.

5-      Again we reach pipette volume to 2/3 with water increase and solution is suspended and then we act by use of centrifuge and it is described in row 4 and we continue to top part in completely cleaned pipette.

6-      Deposited solution is poured in pipette on lamella and as we join it at the Top.

E) Preparation for SEM study

1-      We prepare solution by top method.

2-      We attenuate solutions by use of distil water.

3-      We select a round lamella with size of 13mm and then we pour one drop of solution on it by pipette. We put lamella on clock shield and then in oven to dry (in this manner, we can write sample number).

4-      We join lamella on aluminum pod, after drying, in name of EM stub which has been numerated by colloidal silver.

5-      We cover dried sample by gold or palladium with thickness of 500A (coating) and it is reminded that mentioned preparation method is represented at the Top for cleaning of sample from exceed particles. Surface of sedimentary sheets may be observed directly by SEM and in some cases, especially when sediments are full of fossil, there are many interesting aggregations from placolith coccosphere and merolith and hetrococcolithus and subtle hololoccolithus (Bown, 1993).

Apparent shape of nannofossil is sometimes much more uncharacterized rather than its apparent shape in SEM by optical microscope and this problem is just because of presence of organic fine grains and or clay in sediment. In addition to, characterization of stud nannofossils is more difficult and trace of overgrowth and crushing of nannofossils during study via SEM is more distinct; while above traces can not be observed in apparent shape of nannofossils during survey via optical microscope.

Hence we should consider that only some sample with very well preservation are studied by SEM. SEM transmission is used nowadays rarely for routine studies of nannoplanktons.

For acquaintance to preparation method for above microscope, we should refer to report of Hay, 1977.

 


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