The Cloud Paradigm: Geostable Molecules as Proxies for Surface Oxygenation

摘要

Over the past fifty years, geoscientists have struggled to understand how and when earth's surface became habitable to complex, intelligent life. One of the prevailing scenarios, comprehensively articulated by Cloud, Holland and others, proposes an initially anoxic or very low O2 atmosphere. Although photosystem Ⅱ appeared relatively early, there was an extended period of imbalance between sources and sinks of O2 through pervasive feedback between biosphere, atmosphere, hydrosphere and lithosphere. Ultimately, O2 accumulated in the atmosphere to near its present level at about 540 Ma. Life evolved concurrently. This talk examines new evidence for and against this idea based on the distributions and stable carbon isotopic values of molecular fossils that were extracted from well-preserved Late Archaean sediments. Samples were recovered as drill core from the Mount McRae Formation in the Mt.