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Paleobiological laboratory techniques

Scientific protocols
of usefulness in
Paleontology and Bioarchaeology

Policarp Hortolà

Microfossil obtaining

A) Sampling

1) Select loose or little consolidated sedimentary rocks:
- marls
- fine grained or little cemented sandstones
- marly limestones
- peats
- lignites...
2) Collect approximately 500 g
3) Use a transparent plastic bag, putting the label on its interior so that it could be read without having to open the bag.

B) Chemical preparation

1) Put a part of the sample on diluted hydrochloric (HCl) or nitric (HNO3) acid, in order to obtain the siliceous fraction: radiolarians, diatoms, spicules of siliceous sponges, spores, pollen...
2) Wash with water and sodium bicarbonate (NaHCO3)
3) Put another part of the sample on diluted soda (NaOH) or potassium (KOH), while hot, to obtain the calcareous fraction: microforaminifers, coccolites, spicules of calcareous sponges, ostracodes...

C) Separation

C.1. Sieve/heavy liquid (microfossils in unconsolidated rocks)
1) Huddle the sieves (from greater mesh, up, to smaller one, down)
2) Put the sample on the upper sieve
3) Pass a running water jet (the microfossils will be concentrated in the intermediate sieves)
4) Dry the washed sediment which contains the microfossils
5) Put a heavy liquid (carbon tetrachloride or bromoform/alcohol of e.w.=2.68) on a crystallizer
6) Powder the sample on the heavy liquid (the microfosils, less dense, will float)

C.2. Ultrasounds (for microfossils in marly or clayey rocks)
1) Mash the rock in fragments of 2-3 mm
2) Sonicate to more than 20 kilocycles/s

Sample selection

1) Take a certain quantity of the previously sifted sample
2) Extend it on a flat surface with a printed reticle
3) With a stereoscopical microscope, make a systematical tracking to gather the different taxa of organisms.

Microfossil mounting

A. For trans-lighting (very small microfossils: small microforaminifers, radiolarians, diatoms, pollen, microspores...)
1) Put the microfossils on a microscope slide
2) Put a drop of Canada balsam above
3) Cover with a cover slide glass

B. For epi-lighting (large microforaminifers and megaspores)
1) Making of the slide: take a rectangular carton plate, and make to it one or more holes of about 2 cm of diameter; afterwards, hit a black or red paper plate by below (which will make of opaque fund)
2) Put the microfossils within the hole(s) of the slide
3) Fix the microfossils at the bottom of the hole(s) with a drop of tragacanth glue.

Macroforaminifer oriented thin-sectioning

1) Prepare a glass according to the measures of the foraminifer
2) Put on it a Canada balsam drop or a small chunk of thermoplastic
3) Heat
4) Fix the foraminifer on the glass
5) Put the microscope slide under a stereoscopic microscope
6) Align the foraminifer according to the desired direction, using a handled needle or a toothpick to manipulate it
7) Include the foraminifer in resin, and leave it to dry
8) Polish the block manually with carborundum (SiC, gray powder) of different thickness (CONTROL CONSTANTLY THE PROCESS WITH THE STEREOSCOPIC MICROSCOPE) until the desired section be obtained
9) Unhook the sample from the glass with acetone
10) Fix the foraminifer in a slide by the polished face (i.e., turned)
11) Polish manually the free face until obtaining a thin section of about 20 µm
12) Clean the sample with ultrasounds
13) Dry
14) Cover with a microscope slide.

Links to advanced techniques

Amino Acid Racemization Dating
Molecular Paleogenetics


Allman, M. & D. F. Lawrence: Geological Laboratory Techniques. London: Blandford Press, 1972.
Briggs, D. E. G. & P. R. Crowther (Eds.): Palaeobiology: A synthesis. Item 6.2: Practical Techniques. Oxford, etc.: Blackwell Scientific Publications, pp. 499-511, 1990 (1992, paperback reissue with corrections).
Dillon, B. D. (Ed.): Practical Archaeology: Field and laboratory techniques and archaeological logistics. Los Angeles: UCLA Institute of Archaeology Publications, 1993 (3rd ed.).
Kummel, B. & D. Raup (Eds.): Handbook of Paleontological Techniques. San Francisco-London: W. H. Freeman and Company, 1965.
Meléndez, B.: Paleontología. Tomo 1: Parte general e invertebrados. Capítulo VII: Paleontología práctica. Madrid: Paraninfo, pp. 199-230, 1982 (3ª ed.).
Richter, A. E.: Manual del coleccionista de fósiles. Item: Preparación. Barcelona: Omega, pp. 24-29, 1989.
Vatan, A.: Manuel de Sédimentologie. Paris: Éditions Technip, pp. 383-385, 1967.

You may find more bibliography on the subject by typing below some keywords and going directly to that search result

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