ABSTRACT
Paleosols are ancient soils and duricrust layers preserved in the rock record. Calcrete paleosols are recognized from the Pre - cambrian onwards, although most of the older ones are now dolomitic. Ancient laterites and bauxites are also well known. Since
Definition and range of types
SOIL is the thin residual layer developed upon solid bedrock and unconsolidated sediments through the action of physico-chemical and biological processes (pedogenesis). Soil type is dependent principally on climate, vegetation and rock type (Table 13.1). Thin, poorquality soil develops at high latitudes as a result of physical weathering (entisols, inceptisols). More widespread are the soils of temperate climates (spodosols, podzols, and alfisols). Thick, rich soils develop in warm, humid areas (oxisols). Extensive leaching can result in the formation of hard nodular layers of iron and aluminium oxides/hydroxides (laterite and bauxite soils). High rates of
the advent of land plants in Siluro-Devonian times, many of the other types of soil formed. Clayey soils formed beneath coal seams, typically leached of minerals and with marked rootlet traces, are known as seat-earths. Leached sandy soils are known as ganister.
