[M-GI28] 地球掘削科学

[MGI28-P02] 堆積物コアからの海洋古生物生産の復元：分解・保存効果に対しての留意点

*沢田 健^1,2、星 恒太郎² (1.北海道大学大学院理学研究院地球惑星科学部門、2.北海道大学大学院理学院 自然史科学専攻)

キーワード：海洋生物生産、堆積物コア、続成作用、沈積流量

For understanding long time-scale biogeochemical cycles and climatic changes, especially related to the greenhouse effect, evaluation of marine primary production (quantitative parameter) and productivity (qualitative parameter) is essential and can promote the reconstruction of atmospheric CO2 concentrations and related analysis for paleothermometry. Basically, marine primary production/productivity at long time-scale have been evaluated by the fossils and chemical materials in marine sediments. The authors have used biogenic organic matter, biomarkers, for the analysis. In paleoclimatic and paleoceanographic studies, paleoproduction data were provided on the basis of export fluxes, through the mass accumulation rates (MARs) in sediments, and paleoproductivity were interpreted by the proxy of biogenic fossils, elements, isotopes, and compounds. In such evaluations, separating degradation /preservation of fossils and chemical materials during diagenesis from productivity is a key question. The proxies for production / productivity must experience microbial degradation, geochemical diagenetic alteration, and modification. Such investigation has been often neglected, resulting in misleading interpretations. Here we suggest the consideration for the degradation and preservation effects in the investigations of marine primary productivity / production as follows.
1) Reconstruction of variation in redox conditions in the same sediments
2) Evaluation of the degree of selective degradation / preservation
3) Development of new proxies for analysis of marine primary productivity / production.