Tracking the rise and fall of oceanic O2 levels on the Precambrian Earth using the redox-sensitive trace metal geochemistry of sedimentary rocks

Pls join us for the following special lecture next week:

Tues Oct 22 at 3:30 pm in Biol 106

Dr. Brian Kendall – GAC Hutchison Lecture tour

Tracking the rise and fall of oceanic O2 levels on the Precambrian Earth using the redox-sensitive trace metal geochemistry of sedimentary rocks

Accurate estimates of atmosphere-ocean redox conditions through time are necessary to address grand challenges such as explaining the time lag of several hundred million years between the evolution of oxygenic photosynthesis and the early Paleoproterozoic Great Oxidation Event, as well as constraining the relative importance of environmental versus genetic barriers as controlling factors behind the late initial animal diversifications in the Ediacaran and Cambrian. Traditionally, efforts to infer Precambrian ocean redox conditions at ocean-basin to global scales have been hampered by the need to make such inferences from marine sedimentary rocks preserved in continental margin environments because open-ocean abyssal seafloor has been lost to subduction. Recently, new insights on Precambrian ocean redox conditions at these larger spatial scales have been provided using the concentration and isotopic composition of non-traditional redox-sensitive trace metals (e.g., molybdenum, uranium, rhenium, osmium, thallium) in black shales, carbonates, and iron formations. Despite the fragmentary nature of the Precambrian rock record, the redox-sensitive metal geochemical data from sedimentary rocks point to a complex history of rising and falling environmental O2 levels, including transient oxygenation events in the Archean and middle Proterozoic. The redox instability on the Proterozoic Earth likely contributed, at least partially, to the nearly ~2 billion-year delay in initial animal diversification after the Great Oxidation Event.