A guide to preparation protocols in palynology

A comprehensive, illustrated guide to the preparation (i.e. extraction, concentration and microscope slide production) of palynomorphs from samples of sediments, sedimentary rocks and other materials is presented. The traditional technique, based upon mineral acid digestion of the sample matrix, is subdivided into four phases. These are: sampling and pre-preparation; acid digestion; palynomorph concentration; and presentation of palynomorphs for study and archiving of materials. Modifications for preparing Quaternary and modern materials such as acetolysis are outlined, as are methods of preparation which do not use hazardous acids. One of the most effective non-acid preparation techniques uses sodium hexametaphosphate as a clay deflocculant and works well on clay-rich samples which are not intensely lithified. Hydrogen peroxide is another reagent which can be used for this purpose. The contamination of samples by material from other samples or modern pollen can lead to spurious data and interpretations. Strenuous efforts to avoid contamination should be made. Modifications of the traditional preparation technique are described for 14 specific sample materials. For example, many pure limestones only require digestion with hydrochloric acid. Moreover, coal is typically simply oxidised using nitric acid or Schulze's solution then reacted with dilute potassium hydroxide solution to produce organic substances which are then rinsed away using water. Traditional preparation techniques are used for all palynomorph groups irrespective of their biological affinity, however certain of these require some specific modifications. For example chitinozoa and megaspores are substantially larger than acritarchs, dinoflagellate cysts, miospores and pollen, therefore modifications to the technique must be used, principally in the sieve sizes used. Some attempts have been made to automate palynomorph processing. The equipment for this is discussed, together with other technological solutions such as microwave digestion. Eight techniques closely associated with palynological processing and the microscopical observation of palynomorphs such as scanning electron microscopy are also reviewed.