Pollen and Spores in Marine Sediments from the East Atlantic
S39
(GIK 16776) indicates a time shift in the representation of Podocarpus being high in the western
Guinean area and low in the eastern area of
Nigeria and Cameroon (Dupont et al. 1996).
A box core ofthe same site provides a surface
sample and a modem pollen spectrum of Site
GIK16867. In the surface sample Podocarpus is
hardly represented, although a peak of pollen from
that tree occurs in the early Holocene. The disappearance of Podocarpus pollen from terrestrial
lowland sites in the east of Cameroon is dated between 2000 and 3000 years ago (Reynauld-F arrera
et al. 1996; Maley and Brenac 1998).
GeoB1008 (6°36'S 10°19'£)
Site GeoB 1 008 is offthe estuary of the Congo river
and the majority of pollen and spores found here is
of fluvial origin. Sediments are rich in pollen having their source areas in the huge Congo drainage
basin. Rain forest grows east and north ofthe site,
and the dry forest of the Zambezian vegetation zone
is located east and south of it. The small amounts
of pollen from Artemisia and other composites
probably had their source area in the Namib and
Kalahari deserts. Pollen from Poaceae and
Cyperaceae may have derived from open swamps,
but also from open vegetation types within the
forested area.
To illustrate the mirrored sense of direction between south and north ofthe equator, I have drawn
the diagram for this site and the next one, which
both are located on the Southern Hemisphere, as
in mirror images ofthose ofthe other sites, which
are located on the Northern Hemisphere (Fig. 9).
Representation ofthe forest is high during Stages
Sand 1 and lowest during Stages 6 and 2 (Jahns
1996). The division of Stage S into five periods is
prominent, with the Afromontane forest expanding during the cooler intervals. This record, together
with the previous and the next one, registers an expansion of the Afromontane Podocarpus forest
that must have been considerable. Podocarpus
pollen grains are also found in all other periods
indicating that the tree has been growing in many
places in highlands and mountains around the Congo
basin. However, the surface sediment sample north
of Site GeoB 1 008 is not rich in pollen and poor in
Podocarpus grains indicating that, although the
tree did not completely disappear, its occurrence
has been strongly reduced in the later part of the
Holocene (see above).
GeoB1016 (1]o46'S 11°41 'E)
The southernmost core in the transect is located
offthe coast of Angola in the trajectory ofthe SWtrade winds. The site is located at a distance of ca.
200 km from the nearest coast and about 2S0 km
from the nearest river mouth. This core is rich in
pollen, most of which is probably wind-dispersed.
A surface sediment sample SE of the site (12°S
12°E) was very poor in pollen and percentages can
only be regarded as a rough estimate.
Most forest types of West Africa cannot be
readily differentiated in the marine pollen diagrams,
but the Miombo woodland forms an exception.
Miom bo woodland is a type of dry forest from the
Zambezian vegetation zone on more elevated areas (White 1983). One ofthe main representatives
of the Miombo woodland (Brachystegia) is well
represented by its pollen, although not in large
amounts. Pollen of accompanying trees in the
Miombo forest are also found. In the Huambe
mountains, Podocarpus trees are part of the
Afromontane forest up to the present time.
Poaceae pollen have their main source area in the
Namib desert and the Kalahari Highveld area although grasses also grow in the open forest of the
Zambezian vegetation zone.
Representation of the forest in the pollen diagram indicates that the rain forest extended farther
southward during Substages Se and Sa than in the
Holocene. The Miombo woodland area increased
during Substages Se and Sc and other dry forest
types expanded during Substages Se, Sa, and Sc.
The area of the Afromontane forest was probably
quite small during Stage Se, but expanded during
the rest of Stage S. Increased Podocarpus pollen
percentages start at the beginning of Substage Sd,
around lIS kaBP, in this and other sites ofthe tropical eastern Atlantic. A maximum of Podocarpus
pollen percentages is found around the transition
between Substages Sd and Sc. However, the representation of Podocarpus declines during that
period at Sites GIK16856 and GeoB1008.
S39
(GIK 16776) indicates a time shift in the representation of Podocarpus being high in the western
Guinean area and low in the eastern area of
Nigeria and Cameroon (Dupont et al. 1996).
A box core ofthe same site provides a surface
sample and a modem pollen spectrum of Site
GIK16867. In the surface sample Podocarpus is
hardly represented, although a peak of pollen from
that tree occurs in the early Holocene. The disappearance of Podocarpus pollen from terrestrial
lowland sites in the east of Cameroon is dated between 2000 and 3000 years ago (Reynauld-F arrera
et al. 1996; Maley and Brenac 1998).
GeoB1008 (6°36'S 10°19'£)
Site GeoB 1 008 is offthe estuary of the Congo river
and the majority of pollen and spores found here is
of fluvial origin. Sediments are rich in pollen having their source areas in the huge Congo drainage
basin. Rain forest grows east and north ofthe site,
and the dry forest of the Zambezian vegetation zone
is located east and south of it. The small amounts
of pollen from Artemisia and other composites
probably had their source area in the Namib and
Kalahari deserts. Pollen from Poaceae and
Cyperaceae may have derived from open swamps,
but also from open vegetation types within the
forested area.
To illustrate the mirrored sense of direction between south and north ofthe equator, I have drawn
the diagram for this site and the next one, which
both are located on the Southern Hemisphere, as
in mirror images ofthose ofthe other sites, which
are located on the Northern Hemisphere (Fig. 9).
Representation ofthe forest is high during Stages
Sand 1 and lowest during Stages 6 and 2 (Jahns
1996). The division of Stage S into five periods is
prominent, with the Afromontane forest expanding during the cooler intervals. This record, together
with the previous and the next one, registers an expansion of the Afromontane Podocarpus forest
that must have been considerable. Podocarpus
pollen grains are also found in all other periods
indicating that the tree has been growing in many
places in highlands and mountains around the Congo
basin. However, the surface sediment sample north
of Site GeoB 1 008 is not rich in pollen and poor in
Podocarpus grains indicating that, although the
tree did not completely disappear, its occurrence
has been strongly reduced in the later part of the
Holocene (see above).
GeoB1016 (1]o46'S 11°41 'E)
The southernmost core in the transect is located
offthe coast of Angola in the trajectory ofthe SWtrade winds. The site is located at a distance of ca.
200 km from the nearest coast and about 2S0 km
from the nearest river mouth. This core is rich in
pollen, most of which is probably wind-dispersed.
A surface sediment sample SE of the site (12°S
12°E) was very poor in pollen and percentages can
only be regarded as a rough estimate.
Most forest types of West Africa cannot be
readily differentiated in the marine pollen diagrams,
but the Miombo woodland forms an exception.
Miom bo woodland is a type of dry forest from the
Zambezian vegetation zone on more elevated areas (White 1983). One ofthe main representatives
of the Miombo woodland (Brachystegia) is well
represented by its pollen, although not in large
amounts. Pollen of accompanying trees in the
Miombo forest are also found. In the Huambe
mountains, Podocarpus trees are part of the
Afromontane forest up to the present time.
Poaceae pollen have their main source area in the
Namib desert and the Kalahari Highveld area although grasses also grow in the open forest of the
Zambezian vegetation zone.
Representation of the forest in the pollen diagram indicates that the rain forest extended farther
southward during Substages Se and Sa than in the
Holocene. The Miombo woodland area increased
during Substages Se and Sc and other dry forest
types expanded during Substages Se, Sa, and Sc.
The area of the Afromontane forest was probably
quite small during Stage Se, but expanded during
the rest of Stage S. Increased Podocarpus pollen
percentages start at the beginning of Substage Sd,
around lIS kaBP, in this and other sites ofthe tropical eastern Atlantic. A maximum of Podocarpus
pollen percentages is found around the transition
between Substages Sd and Sc. However, the representation of Podocarpus declines during that
period at Sites GIK16856 and GeoB1008.