J. Henderiks, P. Ziveri: Treating strongly-lithified rocks ... , p. 51.

Journal of Nannoplanldon Research, 18, 2, 1996.

TREATING STRONGLY- LITHIFIED ROCKS WITH ULTRASONICWAVES
Jorijntje Henderiks & Patrizia Ziveri, Geomarine Center, Vrije Universiteit, De Boe/e/aan 1085,
1081 HV Amsterdam, The Netherlands

A detailed calcareous nannofossil biostratigraphy has been
established for the Cenomanian-Turonian of the Russian
Craton Platform and the Crimean Peninsula, using the Cretaceous nannofossil zonation of Sissingh (1977) and modifications by Perch-Nielsen (1985). Quantitative andsemiquantitative analyses of six sections created abiostratigraphical framework for palaeoenvironmental andpalaeoceanographical interpretations. Results will be discussed in a separate paper, but we would like to make ashort note on the methodology used during this study whichmight be useful to other nannofossil investigators who workwith strongly-indurated rocks.
Strongly-lithified limestones from the Crimean sections proved to be barren ofcoccoliths after normal smearslide preparation. Experiments were performed to obtainsufficient material from these limestones in a quick and easy
way, as opposed to the laborious crushing and centrifuging technique, as described by Taylor & Hamilton ( 1982),
or the crushing and decanting method described by
Monechi & Thierstein (1985). It was found that treatmentof rocks with convergent, high-frequency ultrasonic waves
does not deleterously affect the small nannofossil fraction,and that sufficient nannofossiliferous material can be recovered by this method, if subsequently concentrated bycentrifuging. So-called sonifiers are occasionally used incleaning nannofossil material, but the frequency andstrength of the ultrasonic waves is far less than used forthis study.
Rock samples were placed into plastic bottles whichwere then filled with distilled, buffered water. The bottles
were put under a Branson Sonifier 450. This machine, that
can also be described as a ultrasonic 'disruptor', was operated for four minutes with the maximum output control ( 10)======================~51

and a duty cycle of700/o. To check for the reliability of thismethod in keeping the small fraction intact, a comparisonwas made: smear-slides of a well-preserved, nannofossilrich sample were prepared using both the 'normal' method(from a scratched rock-surface) and from an ultrasonicwaves preparation. No differences between the two preparations could be appreciated under the polarising lightmicroscope, and SEM images showed no differences inpreservation, thus giving support for the non-destructive
nature of this method. Under the SEM, samples treatedwith this method also showed intact coccospheres, giving
additional support for the non-destructive character of themethod with respect to the nannofossil fraction.
Acknowledgements
The enthusiastic support and suggestions made by Peter
Willekes during laboratory procedures are gratefully acknowledged.
REFERENCES
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nannofossil and magnetostratigraphic correlations near
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Perch-Nielsen, K. 1985. Mesozoic calcareous nannofossils. In :H .M. Bolli, J.B. Saunders & K. Perch-Nielsen (Eds).
Plankton Stratigraphy: 329-426. Cambridge University
Press.
Sissingh, W. 1977. Biostratigraphy of Cretaceous calcareous
nannoplankton. Geol. Mijnbouw, 56(1): 37-65.
Taylor, R.J. & Hamilton, G.B. 1982. Techniques. In: A.R. Lord(Ed. ). A Stratigraphical Index ofCa/careous Nannofossils:
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