PRIMARY PRODUCTIVITY IN AN EARLY ARCHEAN MICROBIAL ECOSYSTEM

The total amount of carbon deposited in the sediments of the Sheba Formation of the Fig Tree Group (Swaziland Sequence, South Africa) has been calculated to be 0.42% of the rock column. These rocks of the Barberton Mountain land are approximately 3400 Ma old. From geochemical, sedimentological and micropaleontological considerations an estimate of the primary production preserved in these sediments has been made. The rate of organic carbon preservation in the shales of this Formation is estimated to be 0.32 gm-2yr-1. Thus the production rate of organic carbon preserved in sediments was apparently the same order of magnitude as that in comparable sedimentary basins today. Presumably due to microbial photosynthesis, primary productivity has been continuously high throughout the Precambrian since the early Archean. © 1979.