| Abstract: | The application of paleoclimatic interpretation to clay minerals from continental and marine sediments is reviewed and the advantages of this method are indicated. Levels relatively rich in chlorite, illite, palygorskite and quartz are interpreted as corresponding to relatively dry periods, while more humid periods lead to more intensive weathering and consequently to the dominance of clay minerals more advanced in the relative stability scale, such as kaolinite. Smectite is taken to indicate a climate with contrasting seasons and a pronounced dry season.Using this and similar schemes, the paleoclimates of areas adjoining the Mediterranean Basin, North Sea, North Atlantic, Southern Arctic, Equatorial and North-West Pacific, and North Phillipine Sea are reconstructed.Clay minerals in sediments, particularly marine sediments, can be useful indicators of paleoclimatic conditions. While they do not produce direct indications of climatic parameters, they provide integrated records of overall climatic impact. Occasionally, they may be superior to the more conventional paleoclimatic methods, such as pollen or oxygen-isotope analysis.The limitations imposed on the paleoclimatic interpretation of clay minerals in sediments are discussed on the basis of examples. The distinction between authigenic and detrital clay minerals is shown to be problematic, particularly with regard to smectite. The relationship between climatic parameters and clay-mineral formation is complicated by the intervention of extra-climatic factors such as topography, geomorphology, lithology and time. Post-depositional diagenetic changes may not be recognized. Differentiation during transport, due to size sorting or differential flocculation may overlap climate-induced differentiation. The association of clay-mineral assemblages with specific source areas presents difficulties due to dispersal pathways that are affected by type of transport agency, i.e., water, ice or wind. Transport agencies are not constant with time. By an interdisciplinary approach, with the paleoclimatic information derived from clay minerals being correlated with that obtained from the analysis of microfossils and oxygen isotope data, many of these limitations can be overcome. |
