2
Weferetal.
oxygen isotope composition of planktic foraminifera, the ratio of magnesium or strontium to calcium
in calcareous shells or the ratio of certain organic molecules (e.g. alkenones produced by
coccolithophorids). Surface water salinity, which is important in modelJing of ocean circulation, is
much more difficult to reconstruct. At present there is no established method for a direct determination
ofthis parameter. Measurements associated with the paleochemistry of bottom waters to reconstruct
bottom water age and flow are made on benthic foraminifera, ostracodes, and deep-sea corals.
Important geochemical tracers are Ol3C and CdlCaratios. When using benthic foraminifera, knowledge
of the sediment depth habitat of species is crucial. Reconstructions of productivity patterns are of
great interest because of important links to current patterns, mixing of water masses, wind, the global
carbon cycle, and biogeography. Productivity is reflected in the flux of carbon into the sediment.
There are a number of fluxes other than those of organic carbon that can be useful in assessing
productivity fluctuations. Among others, carbonate and opal flux have been used, as well as
particulate barite. Furthermore, microfossil assemblages contain clues to the intensity of production
as some species occur preferentialJy in high-productivity regions while others avoid these. One
marker for the fertility of sub-surface waters (that is, nutrient availability) is the carbon isotope ratio
within that water (I3C/ l2 C, expressed as OI3C). Carbon isotope ratios in today's ocean are negatively
correlated with nitrate and phosphate contents. Another tracer of phosphate content in ocean
waters is the CdlCa ratio. The correlation between this ratio and phosphate concentrations is quite
well documented. A rather new development to obtain clues on ocean fertility (nitrate utilization) is
the analysis of the I5N/ 14 N ratio in organic matter. The fractionation dynamics are analogous to those
of carbon isotopes. These various ratios are captured within the organisms growing within the
tagged water. A number of reconstructions ofthe partial pressure of CO, have been attempted using
ODC differences between planktic and benthic foraminifera and Ol3C values of bulk organic material
or individual organic components. To defIne the carbon system in sea water, two elements of the
system have to be known in addition to temperature. These can be any combination of total CO"
alkalinity, or pH. To reconstruct pH, the boron isotope composition of carbonates has been used. Ba
patterns have been used to infer the distribution of alkalinity in past oceans. Information relating to
atmospheric circulation and climate is transported to the ocean by wind or rivers, in the form of
minerals or as plant and animal remains. The most useful tracers in this respect are silt-sized particles
and pollen.
Introduction
Recent decades have witnessed the rapid development of a new discipline in the earth sciences, that
is, paleoceanography. Paleoceanography deals with
the history of the ocean including the development
of the shape of ocean basins, of shallow and deep
currents, and of biological productivity. A central
goal is to elucidate the role that oceanic processes
play in climatic change and in the global environment in general. The main subject of study is the
stratigraphy of marine sediments, especially deepsea sediments. Paleoceanography employs a large
variety of methods with origins in the biological,
chemical, and physical sciences, and uses modern
statistical techniques for the interpretation of extensive and complex data sets. Perhaps the most important result of paleoceanographic work is the reconstruction of past climatc and environmental
conditions for various time intervals and at various
levels of precision.
Useful information for reconstructing ocean history is preserved in the sediments in the form of
microfossil assemblages, organic matter, and the
elemental and isotopic composition of shells and
other sediment components (see MESH Report
(Pisias et al. 1995) and Appendix 1). Those clues
that have a close relationship to anyone environmental parameter are called "proxies" for that particular parameter. Thus, a sediment-derived datum
useful in the reconstruction oftemperature is a "temporary proxy". Perhaps the best known synoptic
temperature reconstructions are those of the
CLIMAP group (1976), regarding the surface-
Weferetal.
oxygen isotope composition of planktic foraminifera, the ratio of magnesium or strontium to calcium
in calcareous shells or the ratio of certain organic molecules (e.g. alkenones produced by
coccolithophorids). Surface water salinity, which is important in modelJing of ocean circulation, is
much more difficult to reconstruct. At present there is no established method for a direct determination
ofthis parameter. Measurements associated with the paleochemistry of bottom waters to reconstruct
bottom water age and flow are made on benthic foraminifera, ostracodes, and deep-sea corals.
Important geochemical tracers are Ol3C and CdlCaratios. When using benthic foraminifera, knowledge
of the sediment depth habitat of species is crucial. Reconstructions of productivity patterns are of
great interest because of important links to current patterns, mixing of water masses, wind, the global
carbon cycle, and biogeography. Productivity is reflected in the flux of carbon into the sediment.
There are a number of fluxes other than those of organic carbon that can be useful in assessing
productivity fluctuations. Among others, carbonate and opal flux have been used, as well as
particulate barite. Furthermore, microfossil assemblages contain clues to the intensity of production
as some species occur preferentialJy in high-productivity regions while others avoid these. One
marker for the fertility of sub-surface waters (that is, nutrient availability) is the carbon isotope ratio
within that water (I3C/ l2 C, expressed as OI3C). Carbon isotope ratios in today's ocean are negatively
correlated with nitrate and phosphate contents. Another tracer of phosphate content in ocean
waters is the CdlCa ratio. The correlation between this ratio and phosphate concentrations is quite
well documented. A rather new development to obtain clues on ocean fertility (nitrate utilization) is
the analysis of the I5N/ 14 N ratio in organic matter. The fractionation dynamics are analogous to those
of carbon isotopes. These various ratios are captured within the organisms growing within the
tagged water. A number of reconstructions ofthe partial pressure of CO, have been attempted using
ODC differences between planktic and benthic foraminifera and Ol3C values of bulk organic material
or individual organic components. To defIne the carbon system in sea water, two elements of the
system have to be known in addition to temperature. These can be any combination of total CO"
alkalinity, or pH. To reconstruct pH, the boron isotope composition of carbonates has been used. Ba
patterns have been used to infer the distribution of alkalinity in past oceans. Information relating to
atmospheric circulation and climate is transported to the ocean by wind or rivers, in the form of
minerals or as plant and animal remains. The most useful tracers in this respect are silt-sized particles
and pollen.
Introduction
Recent decades have witnessed the rapid development of a new discipline in the earth sciences, that
is, paleoceanography. Paleoceanography deals with
the history of the ocean including the development
of the shape of ocean basins, of shallow and deep
currents, and of biological productivity. A central
goal is to elucidate the role that oceanic processes
play in climatic change and in the global environment in general. The main subject of study is the
stratigraphy of marine sediments, especially deepsea sediments. Paleoceanography employs a large
variety of methods with origins in the biological,
chemical, and physical sciences, and uses modern
statistical techniques for the interpretation of extensive and complex data sets. Perhaps the most important result of paleoceanographic work is the reconstruction of past climatc and environmental
conditions for various time intervals and at various
levels of precision.
Useful information for reconstructing ocean history is preserved in the sediments in the form of
microfossil assemblages, organic matter, and the
elemental and isotopic composition of shells and
other sediment components (see MESH Report
(Pisias et al. 1995) and Appendix 1). Those clues
that have a close relationship to anyone environmental parameter are called "proxies" for that particular parameter. Thus, a sediment-derived datum
useful in the reconstruction oftemperature is a "temporary proxy". Perhaps the best known synoptic
temperature reconstructions are those of the
CLIMAP group (1976), regarding the surface-