Biological Markers Molecular Fossils

Rohmer M., Bisseret P., and Neunlist S. (1992) The hopanoids, prokaryotic triterpenoids and precursors of ubiquitous molecular fossils. In Biological Markers in Sediments and Petroleum (eds. J. M. Moldowan, P. Albrecht, and R. P. Philp). Prentice Hall, Englewood Cliffs, NJ, pp. I-17. 

Iron is concentrated most by cyanobacteria followed closely by phytoplankton (Jones et al., 1978) 7S). Copper is concentrated most by phytoplankton and next by cyanobacteria. Primitive photosynthesizers such as the cyanobacteria are especially rich in non-heme iron, which is involved in the reduction of C02, molecular nitrogen and many other substances. It has been speculated that during the evolution of the plant kingdom, the ratio of iron to other polyvalent metals decreased because the latter became more and more involved in metabolism, chiefly in oxidation reactions in the cells (Ochiai, 1983)76). Therefore, cyanobacteria contain much more iron than other plants. It has been also concluded from analyses of individual fossils that the evolution of different algal groupings in the Precambrian was accompanied by a decrease in the iron content and simultaneous enrichment in copper and others (Udel nova et al., 1981)77). Copper has been interpreted to be a marker element of the younger Proterozoic as far as its biological association is concerned. Thus, the two elements iron and copper cover the important period of the Earth s history, between 3.8 — 1.5 and 1.5 — 0.6 Ga resp. (Ochiai, 1983)76>. 

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