EXTRACTION OF CALCAREOUS MACROFOSSILS FROM THE UPPER CRETACEOUS WHITE CHALK AND OTHER SEDIMENTARY CARBONATES IN DENMARK AND SWEDEN: THE ACID-HOT WATER METHOD AND THE WATERBLASTING TECHNIQUE

ABSTRACT

Improved methods in extracting macrofossils from the Upper Cretaceous White Chalk and other partly lithified calcareous sediments in Denmark and Sweden are presented. Bulk sediment samples may be disaggregated in highly concentrated acetic acid (99-100%) to provide assemblages of cleaned fossils. Because the concentrated acetic acid does not react with carbonates (providing they do not contain any water), the calcareous fossils remain unetched. Adding boiling water, the acid-saturated sediments become rapidly disaggregated by mechanical pressure from the production of carbon dioxide. The procedure is time saving in comparison with the classical Glauber's Salt method. The acid-hot water method is efficient for large bulk samples of limestones that have a high permeability and porosity.

A waterblasting technique is introduced as a cleaning agent in fossil preparation. The pressurized water even leaves fragile skeletal fossils undamaged. Because the technique leaves the fossils in their original position within outcrop surfaces and samples, the technique is readily applicable for biofabric studies. Combined with the acid-hot water method, the waterblasting technique has been employed effectively in preparation of Campanian brachiopods and Maastrichtian bivalves and bryozoans as well as Danian octocorals, asteroids and regular echinoids.

Jan Kresten Nielsen. Geological Museum, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.
Sten Lennart Jakobsen. Geological Museum, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.

KEY WORDS: preparation; carbonates; Cretaceous; Palaeogene; Denmark; Sweden