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Wagner and Dupont
resistant to biological degradation, such as lignine
and sporopollenine (wood and terrestrial
palynomorphs), retain their chemical structure and
isotopic composition. This study intends to briefly
describe transport mechanisms controlling supply
and dispersion of terrigenous OM in the marine
environment and introduce the most popular analytical approaches applied for its identification. With
regard of the scope of this work aspects of
diagenetic alteration of sedimentary OM are not
specifically addressed. Emphasis is placed on a
comparison and critical evaluation of analytical approaches (C/N, Rock-Eval Pyrolysis, stable carbon
isotopes, palynology, organic petrology, and selected
biomarkers) which are currently used for the qualitative and quantitative assessment of the terrigenous
proportion of the bulk organic carbon especially in
young, unconsolidated sediments. We finally present
new evidence for terrestrial OM in modern and late
Quaternary sediments ofthe open pelagic Equatorial Atlantic. Its paleoenvironmental implications are
discussed as a proxy linking continental and marine
records.
Knowledge of quantitative proportions and flux
rates of terrestrial OM in marine sediments is also
necessary with regard to one of the main targets
of paleoceanographic studies, the quantitative reconstruction of paleoproductivity based on marine
TOC records (see Sarnthein et al. 1992 for review).
The use ofTOC as a paleoproductivity proxy, however, strictly requires a dominant marine source of
the OM. This assumption is of relevance since late
Quaternary fluctuations in marine upwelling intensity offer an important mechanism to explain
changes in atmospheric CO 2 during past glacial
periods (e.g. Mix 1989; Berger and Herguera 1992).
With regard to this paleoceanographic application new evidence from a recently published study
on late Quaternary fluxes of terrestrial OM to the
central Equatorial Atlantic appears to be of general
relevance (Verardo and Ruddiman 1996). Despite
the fact that the position investigated by Verardo
and Ruddiman is located below the center of the
productive Equatorial Divergence (Site RC2407 in
Fig. 1) they conclude that variations in content and
flux rate ofTOC are dominantly related to changes
in wind-blown charcoal (burned terrestrial plant
matter, i.e. "fusinite" following Stach et al. 1982;
Taylor et al. 1998) from African dry areas. According to their estimates charcoal comprises on average 50% of the bulk TOC throughout the past 200
ky with a total glaciallinterglacial range from 90%
in glacial stage 2 to zero % in the Holocene. It has
to be pointed out that these estimates are based on
a chemical procedure (removal of CaC0 3 and refractory forms of carbon by acidification with hot
concentrated nitric acid) which is considered questionable. These results would imply that major areas of the modern and past ocean are influenced
by a similar charcoal-type OM. Nevertheless,
whatever the accuracy ofthese high numbers are,
they contradict the established model for high-productive oceanic upwelling areas where glacial!
interglacial cycles in TOC and CaC0 3 are commonly interpreted to document climate-driven fluctuations in surface water productivity, rather than
changes in supply of land-derived OM (e.g.
DeMenocal et al. 1993; Littke and Sachsenhofer,
1994; MUller et al. 1994; Verardo and McIntyre
1994; Schneider et al. 1994; Bickert and Wefer
1996).
Global Budgets and Transport Mechanism
of Terrigenous and Reworked Fossil OM
Terrigenous as well as reworked, fossil OM is supplied to the ocean by river discharge, eolian fall- or
wash-out, and, in high latitudes, by glaciomarine
deposition. Dominant factors controlling the composition, supply and distribution of terrigenous or
reworked, fossil OM are (I) distance from rivers
and continents, (II) surface and deep water
hydrography, (III) gravitative downslope movement
of sediment (i.e. via turbidity currents), (IV) atmospheric dust flux and vegetation cover of continental source areas, (V) position and extension ofterrestrial or submarine outcrops of TOC-rich fossil
strata, and (VI) sea-ice cover and iceberg transport in polar regions.
Rivers playa major role in the transfer of fresh
and, to a minor extent, reworked fossil organic carbon from land to the coastal sea (Michaelis et al.
1986; Emerson and Hedges 1988). The annual
riverine discharge of terrigenous particulate and
dissolved organic carbon (POC and DOC) is in the
order of 0.23 to 0.4* 10 '5 gC yr' (Ittekkot 1988)
Wagner and Dupont
resistant to biological degradation, such as lignine
and sporopollenine (wood and terrestrial
palynomorphs), retain their chemical structure and
isotopic composition. This study intends to briefly
describe transport mechanisms controlling supply
and dispersion of terrigenous OM in the marine
environment and introduce the most popular analytical approaches applied for its identification. With
regard of the scope of this work aspects of
diagenetic alteration of sedimentary OM are not
specifically addressed. Emphasis is placed on a
comparison and critical evaluation of analytical approaches (C/N, Rock-Eval Pyrolysis, stable carbon
isotopes, palynology, organic petrology, and selected
biomarkers) which are currently used for the qualitative and quantitative assessment of the terrigenous
proportion of the bulk organic carbon especially in
young, unconsolidated sediments. We finally present
new evidence for terrestrial OM in modern and late
Quaternary sediments ofthe open pelagic Equatorial Atlantic. Its paleoenvironmental implications are
discussed as a proxy linking continental and marine
records.
Knowledge of quantitative proportions and flux
rates of terrestrial OM in marine sediments is also
necessary with regard to one of the main targets
of paleoceanographic studies, the quantitative reconstruction of paleoproductivity based on marine
TOC records (see Sarnthein et al. 1992 for review).
The use ofTOC as a paleoproductivity proxy, however, strictly requires a dominant marine source of
the OM. This assumption is of relevance since late
Quaternary fluctuations in marine upwelling intensity offer an important mechanism to explain
changes in atmospheric CO 2 during past glacial
periods (e.g. Mix 1989; Berger and Herguera 1992).
With regard to this paleoceanographic application new evidence from a recently published study
on late Quaternary fluxes of terrestrial OM to the
central Equatorial Atlantic appears to be of general
relevance (Verardo and Ruddiman 1996). Despite
the fact that the position investigated by Verardo
and Ruddiman is located below the center of the
productive Equatorial Divergence (Site RC2407 in
Fig. 1) they conclude that variations in content and
flux rate ofTOC are dominantly related to changes
in wind-blown charcoal (burned terrestrial plant
matter, i.e. "fusinite" following Stach et al. 1982;
Taylor et al. 1998) from African dry areas. According to their estimates charcoal comprises on average 50% of the bulk TOC throughout the past 200
ky with a total glaciallinterglacial range from 90%
in glacial stage 2 to zero % in the Holocene. It has
to be pointed out that these estimates are based on
a chemical procedure (removal of CaC0 3 and refractory forms of carbon by acidification with hot
concentrated nitric acid) which is considered questionable. These results would imply that major areas of the modern and past ocean are influenced
by a similar charcoal-type OM. Nevertheless,
whatever the accuracy ofthese high numbers are,
they contradict the established model for high-productive oceanic upwelling areas where glacial!
interglacial cycles in TOC and CaC0 3 are commonly interpreted to document climate-driven fluctuations in surface water productivity, rather than
changes in supply of land-derived OM (e.g.
DeMenocal et al. 1993; Littke and Sachsenhofer,
1994; MUller et al. 1994; Verardo and McIntyre
1994; Schneider et al. 1994; Bickert and Wefer
1996).
Global Budgets and Transport Mechanism
of Terrigenous and Reworked Fossil OM
Terrigenous as well as reworked, fossil OM is supplied to the ocean by river discharge, eolian fall- or
wash-out, and, in high latitudes, by glaciomarine
deposition. Dominant factors controlling the composition, supply and distribution of terrigenous or
reworked, fossil OM are (I) distance from rivers
and continents, (II) surface and deep water
hydrography, (III) gravitative downslope movement
of sediment (i.e. via turbidity currents), (IV) atmospheric dust flux and vegetation cover of continental source areas, (V) position and extension ofterrestrial or submarine outcrops of TOC-rich fossil
strata, and (VI) sea-ice cover and iceberg transport in polar regions.
Rivers playa major role in the transfer of fresh
and, to a minor extent, reworked fossil organic carbon from land to the coastal sea (Michaelis et al.
1986; Emerson and Hedges 1988). The annual
riverine discharge of terrigenous particulate and
dissolved organic carbon (POC and DOC) is in the
order of 0.23 to 0.4* 10 '5 gC yr' (Ittekkot 1988)