538
Dupont
winds (January trades) blow off the continent
when the ITCZ is at its southernmost position. The
sparcity of pollen during Stages 5 and I probably
reflects a reduction of the January trade-wind vigour. The core records a continuous presence of
lowland rain forest southwest of the Guinean
mountains even in Stages 6 and 2. Again, the under-representation of forest trees compared to
Poaceae and Cyperaceae in the pollen diagram has
to be taken into account.
Very interesting is the record of the
Afromontane forest mosty represented by
Podocarpus pollen grains. This conifer tree ofthe
Afromontane forest no longer grows in West Africa (compare the surface sediment sample that
was taken not far northeast of Site GTKI6776). The
modern westernmost occurrence of Podocarpus
is in Cameroon and on the island of Sao Tome.
Large relative values of Podocarpus pollen grains
were found at the end of Stage 6 and in the middle
and end of Stage 5. Low pollen percentage values
were found in Stages 4 to 2. Whilst low amounts
of Podocarpus pollen grains may have been longdistance transported from the east or the south,
the high percentages (up to 20%) testify that
Podocarpus trees must have been growing in the
Guinean mountains. It can be concluded that the
latest occurrence of Podocarpus in the Guinean
mountains was during Stage 5 and the tree disappeared at the beginning of Stage 4 (Dupont et al.
1996).
GIK16856 (4°48 'N 3°24E)
Site GIKI6856 is located in the outer regions of the
Niger fan south of Lagos. In contrast to the previously discussed cores, sediments of GIK16856 are
rich in river-borne pollen (see discussion above).
Preservation of the pollen was good indicating that
little redeposited pollen reached the site. The source
areas of the pollen at Site GIK16856 will be mainly
forest and savannas from Nigeria; but the Sahara,
the Sahelian savanna, the vegetation ofthe Jos Plateau and the mountains of Cameroon probably also
contributed to the pollen assemblages in the
Niger fan sediments. These include pollen from
Podocarpus, Poaceae, and Cyperaceae, and
small amounts of pollen from the desert and semidesert (Chenopodiaceae-Amaranthaceae, Artemisia, Ephedra). The record is good for the last 120
ka and that of the latest part of Stage 6 including
Termination II (Dupont and Weinelt 1996).
During Stages 5 and 1, the lowland rain forest
is represented by high pollen percentages exceeding 60%. A considarable proportion of the arboreal
pollen is from Alchornea, a tree that is widespread
and can be regarded as a pioneer (ReynauldFarrera et al. 1996). Its large pollen production
ensures good representation in the marine pollen
diagram, much better than that of the numerous
trees from the mature rain forest. Stage 3 shows
low percentages offorest pollen as do Stages 6, 4,
and 2. Pollen diagrams ofthe equatorial and south
tropical eastern Atlantic show little differentiation
between Stages 4 to 2 (Bengo and Maley 1991;
Marret 1994; Jahns 1996; Shi and Dupont 1997).
The low representation of forest trees and the
high pollen percentages of Poaceae and
Cyperaceae during Stages 6, 4, 3, and 2 indicate
that open forest and savanna vegetation types
occupied much of the the area along the northern
coast of the Gulf of Guinea. Nowadays, the wooded
savanna vegetation reaches the Gulf of Guinea in
Togo and Benin, and westernmost Nigeria. During the last few centuries, the lowland rain forest
in West Africa has been strongly reduced for agricultural purposes. A comparison of the pollen spectrum of the surface sample, which is from the same
site as the core, with samples from glacial stages,
however, indicates that the reduction of forest was
much larger in glacial times.
Fluctuations in the percentages of Po do carpus
are strong in Stage 5 and contemporaneous with
those of core GeoB 1 008 at 7 0 S, which is described
next. The large representation of Podocarpus
indicates a spread of the Afromontane forest to
lower altitudes during the cooler phases of Stage
5. Possible expansion areas are Cameroon and
Congo (and south of it) and, perhaps, the los Plateau. The latter can only be verified by terrestrial
pollen diagrams from that region. The extent of
Podocarpus was limited during glacial Stages 6
and 2, probably as a result of aridity. The spread
of Podocarpus probably indicates a cooler climate
and relative humid conditions. Tn the later part
of Stage 5, the previously described record
Dupont
winds (January trades) blow off the continent
when the ITCZ is at its southernmost position. The
sparcity of pollen during Stages 5 and I probably
reflects a reduction of the January trade-wind vigour. The core records a continuous presence of
lowland rain forest southwest of the Guinean
mountains even in Stages 6 and 2. Again, the under-representation of forest trees compared to
Poaceae and Cyperaceae in the pollen diagram has
to be taken into account.
Very interesting is the record of the
Afromontane forest mosty represented by
Podocarpus pollen grains. This conifer tree ofthe
Afromontane forest no longer grows in West Africa (compare the surface sediment sample that
was taken not far northeast of Site GTKI6776). The
modern westernmost occurrence of Podocarpus
is in Cameroon and on the island of Sao Tome.
Large relative values of Podocarpus pollen grains
were found at the end of Stage 6 and in the middle
and end of Stage 5. Low pollen percentage values
were found in Stages 4 to 2. Whilst low amounts
of Podocarpus pollen grains may have been longdistance transported from the east or the south,
the high percentages (up to 20%) testify that
Podocarpus trees must have been growing in the
Guinean mountains. It can be concluded that the
latest occurrence of Podocarpus in the Guinean
mountains was during Stage 5 and the tree disappeared at the beginning of Stage 4 (Dupont et al.
1996).
GIK16856 (4°48 'N 3°24E)
Site GIKI6856 is located in the outer regions of the
Niger fan south of Lagos. In contrast to the previously discussed cores, sediments of GIK16856 are
rich in river-borne pollen (see discussion above).
Preservation of the pollen was good indicating that
little redeposited pollen reached the site. The source
areas of the pollen at Site GIK16856 will be mainly
forest and savannas from Nigeria; but the Sahara,
the Sahelian savanna, the vegetation ofthe Jos Plateau and the mountains of Cameroon probably also
contributed to the pollen assemblages in the
Niger fan sediments. These include pollen from
Podocarpus, Poaceae, and Cyperaceae, and
small amounts of pollen from the desert and semidesert (Chenopodiaceae-Amaranthaceae, Artemisia, Ephedra). The record is good for the last 120
ka and that of the latest part of Stage 6 including
Termination II (Dupont and Weinelt 1996).
During Stages 5 and 1, the lowland rain forest
is represented by high pollen percentages exceeding 60%. A considarable proportion of the arboreal
pollen is from Alchornea, a tree that is widespread
and can be regarded as a pioneer (ReynauldFarrera et al. 1996). Its large pollen production
ensures good representation in the marine pollen
diagram, much better than that of the numerous
trees from the mature rain forest. Stage 3 shows
low percentages offorest pollen as do Stages 6, 4,
and 2. Pollen diagrams ofthe equatorial and south
tropical eastern Atlantic show little differentiation
between Stages 4 to 2 (Bengo and Maley 1991;
Marret 1994; Jahns 1996; Shi and Dupont 1997).
The low representation of forest trees and the
high pollen percentages of Poaceae and
Cyperaceae during Stages 6, 4, 3, and 2 indicate
that open forest and savanna vegetation types
occupied much of the the area along the northern
coast of the Gulf of Guinea. Nowadays, the wooded
savanna vegetation reaches the Gulf of Guinea in
Togo and Benin, and westernmost Nigeria. During the last few centuries, the lowland rain forest
in West Africa has been strongly reduced for agricultural purposes. A comparison of the pollen spectrum of the surface sample, which is from the same
site as the core, with samples from glacial stages,
however, indicates that the reduction of forest was
much larger in glacial times.
Fluctuations in the percentages of Po do carpus
are strong in Stage 5 and contemporaneous with
those of core GeoB 1 008 at 7 0 S, which is described
next. The large representation of Podocarpus
indicates a spread of the Afromontane forest to
lower altitudes during the cooler phases of Stage
5. Possible expansion areas are Cameroon and
Congo (and south of it) and, perhaps, the los Plateau. The latter can only be verified by terrestrial
pollen diagrams from that region. The extent of
Podocarpus was limited during glacial Stages 6
and 2, probably as a result of aridity. The spread
of Podocarpus probably indicates a cooler climate
and relative humid conditions. Tn the later part
of Stage 5, the previously described record