Organic geochemical proxies of paleoceanographic, paleolimnologic, and paleoclimatic processes1.pdf

Org. Geochem. Vol. 27, No. 5/6, pp. 213±250, 1997
# 1997 Elsevier Science Ltd. All rights reserved
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Organic geochemical proxies of paleoceanographic, paleolimnologic,
and paleoclimatic processes
PHILIP A. MEYERS*
Program in Marine Geology and Geochemistry, Department of Geological Sciences, and Center for
Great Lakes and Aquatic Science, The University of Michigan, Ann Arbor, MI 48109-1063, .
anic matter constitutes a minor fraction of marine and freshwater sediments, yet its im-
portant contribution to the sedimentary record can be used to reconstruct marine and continental
paleoenvironments. anic matter content of sediments is the residue of past biota. The amounts
and types anic matter present in sediments consequently re¯ect environmental conditions that
impacted ecosystems at di€erent past times. General sources of anic matter are inferred from
bulk properties such as positions, carbon and nitrogen stable isotope ratios, Rock-Eval
pyrolysis data, anic petrography. Details anic matter origins are re®ned by analyses of
biomarker positions. Source changes are proxies for ¯uctuations in sea-level, oceanic sur-
face currents, and continental climates. Algal paleoproductivity rates are indicated anic-carbon
mass accumulation rates and carbon and nitrogen stable positions. These parameters
record past availability of nutrients and, therefore, are proxies of surface mixing in the oceans and
amount of land runo€ to lakes. Sea-surface paleotemperatures are recorded by the number of carbon±
carbon double bonds in lipid biomarkers produced by marine algae. Larger proportions of the double
bonds are proxies for the cooler surface waters that panied periods of global glaciation and inter-
vals of enhanced upwelling. The d13C and dD values of anic matter record past concentrations
of carbon dioxide in the atmosphere and changes in delivery of atmo