SOILS AS INDICATORS OF QUATERNARY CLIMATIC-CHANGE IN MIDLATITUDE REGIONS

Soils result from changes to uppermost layers of the earth's crust occurring beneath stable land surfaces. Soil properties are determined by five factors or groups of factors: climate, organisms, relief, parent material and time. Quantitative climatic interpretation of soils depends upon mathematical relationships between individual soil properties and climatic factors (i.e., climofunctions). These are difficult to establish and often cannot be applied to diagenetically modified buried soils, so most climatic interpretations of soils are qualitative or semi-quantitative. Soil features formed by frost action are the most reliable climatic indicators. Most soils continue to develop over time. However, many soil dating techniques provide only a single date some time during the period of soil formation. The beginning and end of a soil development period are best determined by reference to dated deposits over as large an area as possible, but stratigraphical interpretation of soils is still impeded by imprecise definitions and procedures. The soil chronosequences developed in the major loess deposits of Europe and Asia provide the best evidence for climatic change throughout the Quaternary. However, only major (glacial-interglacial) cycles are well expressed. To obtain more detailed evidence of weaker (interstadial) cycles it is necessary to study chronosequences in mid-latitude regions which were generally moister for much of the Quaternary. However these soils are less well preserved and present additional difficulties of interpretation because of greater variation in parent material, relief and time as soil-forming factors.