COG3 Seminar - Peter Crockford (Weizmann Institute/Harvard)
Most talks will take place on Fridays at 11 am, but some talks will be at 10 am to accommodate different time zones.
Title and abstract:
Exploring the geologic history of Earth's biosphere
Modern primary producers perform oxygenic photosynthesis that provides O2 to the atmosphere and fixes carbon to fuel initial heterotrophic consumption in the global biosphere. Although atmospheric O2 levels over the Proterozoic are vigorously debated, multiple lines of evidence point to lower levels compared to the modern. In such a low-oxygen world this photosynthetic oxygen flux (gross primary production (GPP)) is widely assumed to be much less than modern. This assumption is so deeply entrenched that mechanistic explanations for Proterozoic low-oxygen surface environments largely focus on how to limit the productivity of the biosphere, despite the lack of direct empirical evidence for lower productivity at this time. The Proterozoic biosphere may indeed have been significantly nutrient limited when compared to the modern biosphere, however proposals for sustaining the apparent environmental stasis that characterized this interval of Earth history would be strengthened if their key components could be validated from the geologic record. In this talk I will introduce the triple oxygen isotope (∆17O) system and argue that it can be used to quantify the size of the biosphere (GPP) across the past 2.4 billion years of Earth history. I will then present this new record and showcase some interesting highlights and then finally explore questions such as, what has the sum total of life on Earth accomplished since its origins?
Zoom Meeting link: