Late Quaternary Organic Carbon and Biomarker Records from the
Laptev Sea Continental Margin (Arctic Ocean): Implications for
Organic Carbon Flux and Composition
R. Stein, K. Fahl, F. Niessen and M. Siebold
A/fred-Wegener-[nstitut!iir Polar- und Meere;!orschung, Postfach 120161, D 27515 Bremerhaven, Germany
Received to April 1997 and accepted in revised form I October 1997
Abstract - In order to understand the processes controlling organic carbon deposition (i.e.,
primary productivity vs. terrigenous supply) and their paleoceanographic significance, three
sediment cores (PS2471, PS2474, and PS2476) from the Laptev Sea continental margin
were investigated for their content and composition of organic carbon. The characterization
of organic matter includes the determination of bulk parameters (hydrogen index values and
C/N ratios) and the analysis of specific biomarkers (n-alkanes, fatty acids, aiken ones, and
pigments).
Total organic carbon (TOC) values vary between 0.3 and 2%. In general, the organic matter
from the Laptev Sea continental margin is dominated by terrigenous matter throughout.
However, significant amounts of marine organic carbon occur. The turhidites, according to
a still preliminary stratigraphy probably deposited during glacial Oxygen Isotope Stages 2
and 4, are characterized by maximum amounts of organic carbon of terrigenous origin.
Marine organic carbon appears to show enhanced relative abundances in the Termination I
en and early Holocene time intervals, as indicated by maximum amounts of short chain nalkanes, short-chain fatty acids, and alkenones. The increased amounts of fatty acids,
however, may also have a freshwater origin due to increased river discharge at that time.
The occurrence of alkenones is suggested to indicate an intensification of Atlantic water
int10w along the Eurasian continental margin starting at that time.
Oxygen Isotope Stage I accumulation rates of total organic carbon are 0.3, 0.17, and 0.02
g C/cm 2 /ky in cores PS2476, PS2474, and PS247 I , respectively.
Introduction
The Arctic Ocean and the surrounding continental margins (Figure I) are key areas for
understanding the global climate system and its change through time (for overviews see
ARCSS Workshop Steering Committee, 1990; NAD Science Committee, 1992; and further
references therein), The present state of the Arctic Ocean itself and its influence on the global
climate system strongly depend on the large river discharge. The fluvial freshwater supply
contributes significantly to the strong stratification of the near-surface water masses of the
Arctic Ocean and, thus, favors sea-ice formation. The melting and freezing of sea ice result in
distinct changes in the surface albedo, the energy balance, the temperature and salinity structure
of the upper water masses, and the biological processes. Furthermore, large amounts of
dissolved and particulate (organic and inorganic) material are transported by the major Arctic
rivers onto the shelves. The annual discharge of total suspended sediments by the Lena River
alone, for example, is 17.6* 10 6 tons, and the amount of dissolved organic carbon reaches
maximum values of 11 mg/l during summer floods (Martin et aI., 1993). Particulate organic
carbon supply by the Lena River is estimated to reach about 1.3 * 10 6 tons per year (Rachold et
aI., 1996). Although most of this material is deposited in the inner Laptev Sea (Kuptsov and
Lisitzin, 1996), significant amounts are further transported by different mechanisms onto the
outer continental margin and the open ocean (Figure 2), which may contribute significantly to
the entire Arctic Ocean sedimentary and chemical budgets. Riverine sediments are incorporated
into the sea ice in the shelf areas and then transported as ice-rafted debris (IRD) through the
In: Kassens, H., H.A. Bauch, I. Dmitrenko, H. Eicken, H.-W. Hubberten, M. Melles, J. Thiede and L. Timokhov (eds.)
Land-Ocean Systems in the Siberian Arctic: Dynamics and History. Springer-Verlag, Berlin. 1999,635-655.
Laptev Sea Continental Margin (Arctic Ocean): Implications for
Organic Carbon Flux and Composition
R. Stein, K. Fahl, F. Niessen and M. Siebold
A/fred-Wegener-[nstitut!iir Polar- und Meere;!orschung, Postfach 120161, D 27515 Bremerhaven, Germany
Received to April 1997 and accepted in revised form I October 1997
Abstract - In order to understand the processes controlling organic carbon deposition (i.e.,
primary productivity vs. terrigenous supply) and their paleoceanographic significance, three
sediment cores (PS2471, PS2474, and PS2476) from the Laptev Sea continental margin
were investigated for their content and composition of organic carbon. The characterization
of organic matter includes the determination of bulk parameters (hydrogen index values and
C/N ratios) and the analysis of specific biomarkers (n-alkanes, fatty acids, aiken ones, and
pigments).
Total organic carbon (TOC) values vary between 0.3 and 2%. In general, the organic matter
from the Laptev Sea continental margin is dominated by terrigenous matter throughout.
However, significant amounts of marine organic carbon occur. The turhidites, according to
a still preliminary stratigraphy probably deposited during glacial Oxygen Isotope Stages 2
and 4, are characterized by maximum amounts of organic carbon of terrigenous origin.
Marine organic carbon appears to show enhanced relative abundances in the Termination I
en and early Holocene time intervals, as indicated by maximum amounts of short chain nalkanes, short-chain fatty acids, and alkenones. The increased amounts of fatty acids,
however, may also have a freshwater origin due to increased river discharge at that time.
The occurrence of alkenones is suggested to indicate an intensification of Atlantic water
int10w along the Eurasian continental margin starting at that time.
Oxygen Isotope Stage I accumulation rates of total organic carbon are 0.3, 0.17, and 0.02
g C/cm 2 /ky in cores PS2476, PS2474, and PS247 I , respectively.
Introduction
The Arctic Ocean and the surrounding continental margins (Figure I) are key areas for
understanding the global climate system and its change through time (for overviews see
ARCSS Workshop Steering Committee, 1990; NAD Science Committee, 1992; and further
references therein), The present state of the Arctic Ocean itself and its influence on the global
climate system strongly depend on the large river discharge. The fluvial freshwater supply
contributes significantly to the strong stratification of the near-surface water masses of the
Arctic Ocean and, thus, favors sea-ice formation. The melting and freezing of sea ice result in
distinct changes in the surface albedo, the energy balance, the temperature and salinity structure
of the upper water masses, and the biological processes. Furthermore, large amounts of
dissolved and particulate (organic and inorganic) material are transported by the major Arctic
rivers onto the shelves. The annual discharge of total suspended sediments by the Lena River
alone, for example, is 17.6* 10 6 tons, and the amount of dissolved organic carbon reaches
maximum values of 11 mg/l during summer floods (Martin et aI., 1993). Particulate organic
carbon supply by the Lena River is estimated to reach about 1.3 * 10 6 tons per year (Rachold et
aI., 1996). Although most of this material is deposited in the inner Laptev Sea (Kuptsov and
Lisitzin, 1996), significant amounts are further transported by different mechanisms onto the
outer continental margin and the open ocean (Figure 2), which may contribute significantly to
the entire Arctic Ocean sedimentary and chemical budgets. Riverine sediments are incorporated
into the sea ice in the shelf areas and then transported as ice-rafted debris (IRD) through the
In: Kassens, H., H.A. Bauch, I. Dmitrenko, H. Eicken, H.-W. Hubberten, M. Melles, J. Thiede and L. Timokhov (eds.)
Land-Ocean Systems in the Siberian Arctic: Dynamics and History. Springer-Verlag, Berlin. 1999,635-655.