Fossil indicators of nutrient levels. 2: Evolution and extinction in relation to oligotrophy

Abstract

Abstract An overview of hypotheses on the impact of nutrients on biosphere history reveals the need for quantitative fossil indices for oligotrophy. Emphasis is given to indicators for endosymbiosis in relation to oligotrophic regimes, and a middle Eocene case history is selected for closer examination. Quantitative data, relating to changes in cellular integration in foraminifera are consistent with a catastrophic shift from highly oligotrophic towards eutrophic conditions, associated with global cooling near the end of the middle Eocene.