An assessment of techniques for the deflocculation and removal of clays from sediments used in phytolith analysis

This paper describes an experiment in which a comparison is made between two techniques of deflocculation and clay removal generally used for palynological extraction. In the experiment, methods used commonly for pollen extraction are applied to phytolith extraction. The palynological products of the different preparation techniques are compared by reference to several attributes: the time and efficiency in the preparation method; the weight of residue resulting from each method; the palynological composition; clarity of the palynomorphs on the slides; and measures of differential loss and selection by palynomorph shape and size. The results are compared and discussed in relation to the still-settling technique which is most commonly used for phytolith extraction. It is concluded that centrifugation is a reliable and fast method that can be used to remove clays from fine-grained sediments for the extraction of phytoliths and other silica microfossils. High levels of diversity were recorded for morphotypes across all size classes. It produced superior results to the sieving technique and there is no reason to assume that it cannot be used to produce results comparable with still-settling if calculations of settling times consider the implications of sediment density on fluid viscosity. Adoption of the centrifugation method for clay removal from palynological sediment samples can greatly reduce extraction times and, therefore, it is a recommended procedure.