440
temperature, being slower in cooler climates . ... today the
vast majority of peat is accumulating in cool climates -
mostly between 50° and 70° N. Most tropical rain forests
are not sites of peat accumulation because the organic
matter rapidly deteriorates on the forest floor. The major
area of peat formation in the tropics today occurs in parts
of Southeast Asia where the rainfall is over 2m year-I and
where substantial precipitation occurs throughout the
year. Because evaporation is also a function of temperature, it is wrong to assume that coal is an indicator of high
rainfall; much of the vast peat swamps of Siberia and
Canada receive less than 50 em of precipitation per year . ...
Correlation of palaeolatitides with areas of coal deposition
... shows that coal has been deposited at all latitudes from
the equator to polar regions, with the majority forming in
mid�latitudes . ... Coal itself is not a good palaeoclimatic
indicator, although characteristics of a coal maybe related
to palaeoclimate."
McCabe and Parrish (1992) reviewed the global
distribution of coal in Cretaceous strata. They noted
that coals require nonsaline wetlands for formation.
Continuous wetness is required to permit growth
and the replenishment of the nutrient supply for
plants. Wetness is also a necessary condition for the
anoxic environment required for preservation. They
stated:
"Climate directly influences plant productivity and preservation of plant matter and therefore determines the
amount of. organic accumulation. High water tables, necessary for the accumulation of peat, tend to occur in climates where precipitation exceeds evaporation, especially
where rainfall is evenly distributed throughout the year
(Ziegler and others 1987). Seasonal climates, by contrast,
often lead to such large annual fluctuations in the water
table that organic matter accumulated during the wet season decays during the dry season, and no net accumulation
of organic matter takes place (Ziegler and others 1987)."
McCabe and Parrish (1992) pointed out that an excess of precipitation over evaporation does not necessarily imply high rainfall. Such a condition may
develop in cool climates with modest rainfall.
Very little vegetation cover may suffice to generate coaly layers in a fluvial deposit. Hubert and
Filipov (1989) described the debris-flow-dominated
sediments of Owens Valley, California, an arid area
with scattered scrub vegetation. Many of their sec�
tions contain layers of plant debris, which would
become coaly streaks following compaction and diagenesis. Therefore, climatic interpretations should
not be attempted from the presence of coal unless
the accumulations are substantial.
12.9.2 Paleosols
Pedogenesis takes place on any interfluve surface
not receiving frequent additions of sediment from
What Does Fluvial Lithofacies Reveal About Climate?
overbank flow. Soil types depend on substrate conditions, including chemistry and water saturation,
and undergo continual modification with time. Two
major concepts are useful in understanding the variability of paleosols. A "catena" is a soil unit showing
lateral variations reflecting differences in relief and
drainage, for example, the differences between the
immature soils developing on a well-drained levee
undergoing periodic addition of increments of sediment, the soils of a saturated backswamp, and the
mature soils of an adjacent, well-drained, upland
region (Wright 1992). "M aturity" refers to the state
of completion of the pedogenesis process, and therefore is related to the age of the soil. Bown and Kraus
(1987) pointed out
. that the ·concept of the catena
was introduced primar�lyto encompass variations in
modern soils related to their position on hill.Slopes,
whereas most paleosols of interest to sedimentologists occur within the floodplain, and differences
within and between individual soils depend on
maturation time and the amount of dilution of the
soil with clastic sediment. They found that these
factors depend primarily on proximity to active fluvial channels, and they suggested that a different
terminology is required to accommodate such observational and interpretive differences. They introduced the term <'pedofacies", which they defined to
encompass the «laterally contiguous bodies of sedimentary rock that differ in their contained laterally
contiguous paleosols as a result of theii distance
(during formation) from areas of high sediment accumulation." These ideas are discussed further in
Sect. 7.4.2.
The dependency of soil type on substrate and
groundwater chemistry, on water saturation, and on
the rate of groundwater flow through the soil intra�
duces climatic factors into soil genesis, although care
must be taken to distinguish depositional from
diagenetic conditions. Thus ferric nodules and concretions typically indicate well-drained, oxidized
soils; siderite nodules indicate neutral to alkaline,
waterlogged soils; calcareous nodules indicate welldrained alkaline soils (Retallack 1988). Retallack
(1986) reached several generalized conclusions
based on his studies of the Upper Eocene and Oligocene succession of Badlands National Park, South
Dakota. Several features reflect rainfall and watertable factors. For example, calcic soils characterize
dry subtropical climates, where evapotranspiration
exceeds precipitation for most of the year, and the
depth to the top of the calcic horizon is related to
. mean annual rainfall) becoming deeper in wetter
climates. Clay production in soils increases with
humidity. The type of clay also varies with climate,
temperature, being slower in cooler climates . ... today the
vast majority of peat is accumulating in cool climates -
mostly between 50° and 70° N. Most tropical rain forests
are not sites of peat accumulation because the organic
matter rapidly deteriorates on the forest floor. The major
area of peat formation in the tropics today occurs in parts
of Southeast Asia where the rainfall is over 2m year-I and
where substantial precipitation occurs throughout the
year. Because evaporation is also a function of temperature, it is wrong to assume that coal is an indicator of high
rainfall; much of the vast peat swamps of Siberia and
Canada receive less than 50 em of precipitation per year . ...
Correlation of palaeolatitides with areas of coal deposition
... shows that coal has been deposited at all latitudes from
the equator to polar regions, with the majority forming in
mid�latitudes . ... Coal itself is not a good palaeoclimatic
indicator, although characteristics of a coal maybe related
to palaeoclimate."
McCabe and Parrish (1992) reviewed the global
distribution of coal in Cretaceous strata. They noted
that coals require nonsaline wetlands for formation.
Continuous wetness is required to permit growth
and the replenishment of the nutrient supply for
plants. Wetness is also a necessary condition for the
anoxic environment required for preservation. They
stated:
"Climate directly influences plant productivity and preservation of plant matter and therefore determines the
amount of. organic accumulation. High water tables, necessary for the accumulation of peat, tend to occur in climates where precipitation exceeds evaporation, especially
where rainfall is evenly distributed throughout the year
(Ziegler and others 1987). Seasonal climates, by contrast,
often lead to such large annual fluctuations in the water
table that organic matter accumulated during the wet season decays during the dry season, and no net accumulation
of organic matter takes place (Ziegler and others 1987)."
McCabe and Parrish (1992) pointed out that an excess of precipitation over evaporation does not necessarily imply high rainfall. Such a condition may
develop in cool climates with modest rainfall.
Very little vegetation cover may suffice to generate coaly layers in a fluvial deposit. Hubert and
Filipov (1989) described the debris-flow-dominated
sediments of Owens Valley, California, an arid area
with scattered scrub vegetation. Many of their sec�
tions contain layers of plant debris, which would
become coaly streaks following compaction and diagenesis. Therefore, climatic interpretations should
not be attempted from the presence of coal unless
the accumulations are substantial.
12.9.2 Paleosols
Pedogenesis takes place on any interfluve surface
not receiving frequent additions of sediment from
What Does Fluvial Lithofacies Reveal About Climate?
overbank flow. Soil types depend on substrate conditions, including chemistry and water saturation,
and undergo continual modification with time. Two
major concepts are useful in understanding the variability of paleosols. A "catena" is a soil unit showing
lateral variations reflecting differences in relief and
drainage, for example, the differences between the
immature soils developing on a well-drained levee
undergoing periodic addition of increments of sediment, the soils of a saturated backswamp, and the
mature soils of an adjacent, well-drained, upland
region (Wright 1992). "M aturity" refers to the state
of completion of the pedogenesis process, and therefore is related to the age of the soil. Bown and Kraus
(1987) pointed out
. that the ·concept of the catena
was introduced primar�lyto encompass variations in
modern soils related to their position on hill.Slopes,
whereas most paleosols of interest to sedimentologists occur within the floodplain, and differences
within and between individual soils depend on
maturation time and the amount of dilution of the
soil with clastic sediment. They found that these
factors depend primarily on proximity to active fluvial channels, and they suggested that a different
terminology is required to accommodate such observational and interpretive differences. They introduced the term <'pedofacies", which they defined to
encompass the «laterally contiguous bodies of sedimentary rock that differ in their contained laterally
contiguous paleosols as a result of theii distance
(during formation) from areas of high sediment accumulation." These ideas are discussed further in
Sect. 7.4.2.
The dependency of soil type on substrate and
groundwater chemistry, on water saturation, and on
the rate of groundwater flow through the soil intra�
duces climatic factors into soil genesis, although care
must be taken to distinguish depositional from
diagenetic conditions. Thus ferric nodules and concretions typically indicate well-drained, oxidized
soils; siderite nodules indicate neutral to alkaline,
waterlogged soils; calcareous nodules indicate welldrained alkaline soils (Retallack 1988). Retallack
(1986) reached several generalized conclusions
based on his studies of the Upper Eocene and Oligocene succession of Badlands National Park, South
Dakota. Several features reflect rainfall and watertable factors. For example, calcic soils characterize
dry subtropical climates, where evapotranspiration
exceeds precipitation for most of the year, and the
depth to the top of the calcic horizon is related to
. mean annual rainfall) becoming deeper in wetter
climates. Clay production in soils increases with
humidity. The type of clay also varies with climate,