Palaeosol Sequences in Floodplain Environments: A Hierarchical Approach
- Médard Thiry and
- Régine Simon-Coinçon
Published Online: 14 APR 2009
Copyright © 1999 The International Association of Sedimentologists
Palaeoweathering, Palaeosurfaces and Related Continental Deposits
How to Cite
Kraus, M. J. and Aslan, A. (1995) Palaeosol Sequences in Floodplain Environments: A Hierarchical Approach, in Palaeoweathering, Palaeosurfaces and Related Continental Deposits (eds M. Thiry and R. Simon-Coinçon), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304190.ch12
- Published Online: 14 APR 2009
- Published Print: 26 MAY 1995
Print ISBN: 9780632053117
Online ISBN: 9781444304190
- macroscale changes involve stratigraphical thicknesses;
- lateral accretion, involving deposition of coarser grained sediment;
- floodplain palaeosols, helping in interpreting past climates;
- soils, integral part of landscape;
- palaeosol-landscape relationships;
- floodplain sedimentation;
- concept of pedofacies
Floodplain soils and palaeosols are considered at four spatial and temporal scales. The processes and factors that influence floodplain systems vary depending on the scales considered. Short-lived, local processes (e.g. a local influx of coarse sediment related to channel crevassing) give rise to small-scale spatial variability, whereas longer-lived autogenic and allogenic processes are responsible for intermediate- and large-scale spatial variability. Various floodplain soils and palaeosols illustrate the different scales and show that recognizing and analysing these different scales are important for evaluating how landscapes evolved over time and for assessing the relative significance of the various autogenic and allogenic controls on landscape evolution in alluvial basins.
Spatial changes in palaeosol properties are commonly studied at the channel/floodplain scale (e.g. catenas and pedofacies that extend hundreds to thousands of metres). At this mesoscale, autogenic processes (e.g. lateral channel migration, crevassing and overbank flooding) that operate over timespans of l–102yr influenced soil formation by controlling both patterns and rates of short-term sediment accumulation and soil hydrology. Embedded within mesoscale changes are microscale changes in soil morphology (tens to hundreds of metres in lateral extent), which formed in response to geological processes that operate over days to months. For example, a flood can locally erode and deposit sediment, producing subtle grain-size and topographical irregularities on the floodplain that influence pedogenesis by creating slightly different drainage conditions.
Macroscale changes involve stratigraphical thicknesses of a few tens of metres and lateral changes over kilometres to several tens of kilometres. Such changes can represent a combination of autogenic and allogenic processes, including avulsion, tectonism and climatically controlled floodplain incision and aggradation. These processes probably operated over intervals of 103–104 yr. Megascale palaeosol variability, which involves hundreds of metres of alluvial deposits and extends over an entire basin, is generally controlled by global or regional climate change, sea-level fluctuations and regional tectonics, processes that influence palaeosol development over 105–107 yr.