Calcium dissolution and clay flocculant removal in pollen extractions from sediments of the arid Southwest, U.S.A.

Abstract

Pollen extraction from sediments of the arid Southwest often involves a variety of problems, including low concentration and poor preservation of pollen, but particularly the complexing of soil particles and evaporites such as calcium carbonate (calcite) and calcium sulfate (gypsum) with the pollen. The low pollen concentration and particle complexing problems are overcome by extraction of a larger volume of sediment (normally 350–450 cc) than is typical for lakes and bogs of temperate regions. Dilute HCl dissolves the most common evaporite, calcium carbonate, and coarser silicates are then removed by sieving or swirling (Funkhauser and Evitt, 1959), thus concentrating finer silts, clays, clay-sized particles, and pollen. The finer silicates are subsequently removed by HF treatment. However, if the calcium ions are not removed completely, prior to the HF treatment, a precipitate of calcium fluoride forms which obscures pollen in the sample.