Paleonet: Microfossils in organic-rich mudstones

[Walter.Etter at bs.ch]

Dear paleonetters,

does anybody of you have experience using surfactants for microfossil processing?

The disintegration of mudstones rich in organic material is difficult. Standard procedure with 5-8% peroxide and subsequent washing over a sieve-stack (I use 250*m, 125*m, 63*m) sometimes reduces the amount of sediment to only one quarter (from 200g to 50g) which makes it an almost impossible task to pick the microfossils. For a further reduction of the clayey material various methods were suggested such as cooking in sodium carbonate which leads to a modest but still unsatisfactory reduction.

In the past we used the slightly acidic surfactant <Bradophen> (Benzozoniumchloride) and obtained very good results. Alkaline surfactants, however, were not effective. Since <Bradophen> is no longer available, I tried using <Rewoquat> (Imidazoliniumquat) which is also a slightly acidic surfactant and reduces the residue to less than 10%. But of course we do not know what mechanism is behind that, and if certain microfossils are (at least partially) dissolved. Therefore I highly appreciate any suggestions/recommendations regarding the use of surfactants or other methods for the reduction of the clayey material.

With best wishes for the New Year, Walter

Dr. Walter Etter
Naturhistorisches Museum
Kurator Geowissenschaften
Augustinergasse 2
CH 4001 Basel

Telefon +41 61 266 55 63
Fax +41 61 266 55 46
walter.etter at bs.ch<mailto:walter.etter at bs.ch>
www.nmbs.ch<http://www.nmbs.ch/>

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