Geoscience Reference
In-Depth Information
water is retained in the depression from
nearby river flows and rainfall
1
River
Alluvial soil
Mineral soil
Waterlogged soils
Waterlogged soils
2
Development of marsh vegetation
River
Water colour pH 2.5 - 4.5
changes to
brownish black
• Organic matter from leaf and tree litter accumulates (fibric in nature)
• Decomposition is slowed down - poor aeration, anoxic conditions
• Microbial degradation is retarded
Alluvial
deposition
slows down
3
Develpment of freshwater swamp forest
River
Peat layer formed after many years
(estimate 2.0 - 4.5 mm per year of peat deposit)
Alluvial soil
Figure 2.10
Peat swamps formation (
after
Leete, 2006).
however, is usually flat. The internal stratification is typically threefold, with a fine-
grained hemic/sapric layer overlying a thick zone of fine- to medium-grained woody
hemic-fibric, over-fine grained hemic, peat. The base of the peat dome is typically dark
gray clay and sand with a thin layer of clayey peat or peaty clay.
Lam (1989) postulates the possible events leading to the development of peat
deposits as a result of sea level changes. The last global glaciations resulted in rapid
denudation and deep incision of the parent rock formations. After the last maximum
glaciations (some 20,000 years BP), sea level rose rapidly and reached a maximum
level 5,500 years BP. This resulted in the transportation and deposition of a large
amount of sediment, which formed deltas and flood plains. Peat swamps were initiated
in the depressions and basins between isolated hills and levees, and in the deltas.
During the initial stage, plants developed in mineral soils. The areas were still under
influence of rivers, with an influx of clastic (mineral) sediments during flood. The
