Pollen and Spores in Marine Sediments from the East Atlantic
-A View from the Ocean into the African Continent
L.M. Dupont*
Universitat Bremen, Fachbereich Geowissenschaften, Postfach 330440,
D-28334 Bremen, Germany
*corresponding author (e-mail):dupont@uni-bremen.de
Abstract: Selected results of marine palynological studies for the West African region are presented.
Emphasis is laid on the aeolian and fluvial transport of pollen grains from the continent to the ocean.
The relative importance of transport processes from the continent to the ocean varies from region to
region. Aeolian pollen transport to the Atlantic accounts for a major proportion of the pollen found
in marine sediments off Northwest Africa. On the shelves along the Gulf of Guinea and the Angolan
Basin, particularly in the vicinty of river mouths, pollen transport is predominantly fluvial. NE-trade
winds drift pollen from the southern Mediterranean and the northern Sahara southwest- and
southwards. The African Easterly Jet transports pollen from the southern Sahara and the Sahel to
the eastern Atlantic. As the southward trade-wind transport strongly increased during glacial stages,
the westward African Easterly Jet transport stayed latitudinally stable. A transect of cores from 30 0 N
to 12°S covering the last 150 ka provides infonnation of the vegetation history of the adjacent
African continent. During glacial Stages 6 and I, the Mediterranean forest strongly declined or
disappeared completely from the southwest Mediterranean area and was replaced by an open
steppe-like vegetation. The Saharan-Sahelian boundary migrated between 15"N (during Stages 6, 2
and Substage 5d) and 23°N (during Substage 5e). The rain forest was widespread during Stages I
and 5, but strongly reduced during Stages 3 and 4 and especially during Stages 2 and 6 when open,
grass-rich vegetation prevailed. Glacial rain forest refuges are found in the southwest of the Guinean
mountains and along the eastern coast of the Gulf of Guinea. Miombo woodland expanded during
Stage 5. Afromontane Podocarpus forests had their largest expansion during Substages 5d and 5b.
Podocarpus did no longer occur in the Guinean mountains after Stage 5.
Introduction
Palynology investigates microfossils that resist drastic maceral treatment. Starting with the study of
pollen and spores, the scope broadened when other
entities, generally called palynomorphs, gained
more and more attention. Palynomorphs can be
fungal spores and small fructifications, polychaete
jaws, extinct chitinozoans, animal and vegetable
tissue fragments, as well as the more familiar
algal cysts, spores, and pollen grains. The content
of palynology is circumscribed by its techniques
more than by the unity of the material studied
(Jansonius and McGregor 1996).
It is thus not suprising that palynology has
branched into various disciplines, of which the more
important are briefly mentioned here. Knowledge
of the morphology of pollen, spores, and algal cysts
is essential. Several textbooks dedicate considerable
sections to pollen and spore morphology (Moore et
al. 1991; Nilsson andPraglowski 1992). While pollen morphologists often pursue taxonomic problems,
paleoclimatic and paleoenvironmental studies are at
the forefront of Quaternary palynology. Pollen
analysis reconstructing former vegetation by means
of the pollen grains it produced is a tool in paleoecology as well as in plant geography (Faegri et al.
1989; Lang 1994). Pre-Quatarnary palynology is
strongly geologically orientated and covers biostratigraphic topics, palynofloras, and paleo-environments (Traverse 1988). Important contributions
From FISCHER G, WEFER G (eds), 1999, Use 0/ Proxies in Paleoceanography: Examples/rom the South Atlantic. Springer-Verlag
Berlin Heidelberg, pp 523-546
-A View from the Ocean into the African Continent
L.M. Dupont*
Universitat Bremen, Fachbereich Geowissenschaften, Postfach 330440,
D-28334 Bremen, Germany
*corresponding author (e-mail):dupont@uni-bremen.de
Abstract: Selected results of marine palynological studies for the West African region are presented.
Emphasis is laid on the aeolian and fluvial transport of pollen grains from the continent to the ocean.
The relative importance of transport processes from the continent to the ocean varies from region to
region. Aeolian pollen transport to the Atlantic accounts for a major proportion of the pollen found
in marine sediments off Northwest Africa. On the shelves along the Gulf of Guinea and the Angolan
Basin, particularly in the vicinty of river mouths, pollen transport is predominantly fluvial. NE-trade
winds drift pollen from the southern Mediterranean and the northern Sahara southwest- and
southwards. The African Easterly Jet transports pollen from the southern Sahara and the Sahel to
the eastern Atlantic. As the southward trade-wind transport strongly increased during glacial stages,
the westward African Easterly Jet transport stayed latitudinally stable. A transect of cores from 30 0 N
to 12°S covering the last 150 ka provides infonnation of the vegetation history of the adjacent
African continent. During glacial Stages 6 and I, the Mediterranean forest strongly declined or
disappeared completely from the southwest Mediterranean area and was replaced by an open
steppe-like vegetation. The Saharan-Sahelian boundary migrated between 15"N (during Stages 6, 2
and Substage 5d) and 23°N (during Substage 5e). The rain forest was widespread during Stages I
and 5, but strongly reduced during Stages 3 and 4 and especially during Stages 2 and 6 when open,
grass-rich vegetation prevailed. Glacial rain forest refuges are found in the southwest of the Guinean
mountains and along the eastern coast of the Gulf of Guinea. Miombo woodland expanded during
Stage 5. Afromontane Podocarpus forests had their largest expansion during Substages 5d and 5b.
Podocarpus did no longer occur in the Guinean mountains after Stage 5.
Introduction
Palynology investigates microfossils that resist drastic maceral treatment. Starting with the study of
pollen and spores, the scope broadened when other
entities, generally called palynomorphs, gained
more and more attention. Palynomorphs can be
fungal spores and small fructifications, polychaete
jaws, extinct chitinozoans, animal and vegetable
tissue fragments, as well as the more familiar
algal cysts, spores, and pollen grains. The content
of palynology is circumscribed by its techniques
more than by the unity of the material studied
(Jansonius and McGregor 1996).
It is thus not suprising that palynology has
branched into various disciplines, of which the more
important are briefly mentioned here. Knowledge
of the morphology of pollen, spores, and algal cysts
is essential. Several textbooks dedicate considerable
sections to pollen and spore morphology (Moore et
al. 1991; Nilsson andPraglowski 1992). While pollen morphologists often pursue taxonomic problems,
paleoclimatic and paleoenvironmental studies are at
the forefront of Quaternary palynology. Pollen
analysis reconstructing former vegetation by means
of the pollen grains it produced is a tool in paleoecology as well as in plant geography (Faegri et al.
1989; Lang 1994). Pre-Quatarnary palynology is
strongly geologically orientated and covers biostratigraphic topics, palynofloras, and paleo-environments (Traverse 1988). Important contributions
From FISCHER G, WEFER G (eds), 1999, Use 0/ Proxies in Paleoceanography: Examples/rom the South Atlantic. Springer-Verlag
Berlin Heidelberg, pp 523-546