Palaeosols and surfaces: what fossil soils tell us about the representation of time in some sedimentary successions

Soils and, hence, palaeosols develop at geomorphic surfaces comprising landscapes. As most develop they reorganize the substrate to create texturally and chemically defined units (horizons) parallel to the land surfaces and some of these horizons become lithified resembling beds. Palaeosols, in many cases do not represent hiatuses but developed during deposition and represent condensation not lost time. The degree of pedogenic reorganization can be used to estimate the temporal significance of the length of soil formation but soils are commonly polygenetic and have not followed a simple, time-related developmental pathway. The complexity of soil development is illustrated with reference to the late Silurian–early Devonian polyphase alluvial palaeosols from South Wales which provide an example of how dynamic changes in sedimentation and erosion have occurred without changes in soil processes. The significance of these polyphase palaeosol profiles is reviewed in the broader context of mid Paleozoic landscape changes.