W.W. Hutchison Medal
The W.W. Hutchison Medal is named after Dr. William W. Hutchison in recognition of his many contributions to Canadian and international geoscience. The medal is awarded to a young individual for recent exceptional advances in Canadian earth science research.
2019 W.W. Hutchison Medalist
Dr. Brian Kendall (University of Waterloo)
Dr. Brian Kendall uses the concentration and isotopic composition of redox-sensitive metals in sedimentary rocks to reconstruct changes in atmosphere-ocean redox conditions and seawater chemistry through time, and infer their impacts on biological evolution and mass extinction. This effort initially focused on the rhenium-osmium geochronology of Precambrian black shales, leading to MSc and PhD degrees from the University of Alberta in 2003 and 2008, respectively. Subsequently, Dr. Kendall held a two-year Agouron Institute Geobiology Postdoctoral Fellowship at Arizona State University where he expanded his research program to include non-traditional metal isotope systems, particularly molybdenum and uranium. After four years at Arizona State University, Dr. Kendall moved to the Department of Earth and Environmental Sciences at the University of Waterloo in 2012 to begin a faculty position and establish a new metal isotope geochemistry laboratory. Dr. Kendall teaches undergraduate courses in introductory geochemistry, petrography and igneous petrology, as well as graduate courses in radioactive/radiogenic isotope geochemistry and metal stable isotope geochemistry. A Tier II Canada Research Chair in redox-sensitive metal isotope geochemistry was awarded to Dr. Kendall and will begin in September 2019.
Upcoming lecture tour dates:
Tuesday, Oct 22, 3:30 pm – University of Saskatchewan, Saskatoon – W.P. Thompson Building, Biology Room 106
Wednesday, Oct 23, 11:30 am – Canadian Institute of Mining – Park Town Hotel, 924 Spadina Crescent East, Saskatoon. Talk will begin at 12:00 pm.
Thursday, Oct 24, 12:00 pm – University of Alberta, Edmonton – Henry Marshall Tory Building, Room 3-36
Friday, Oct 25, 11:30 am – Mount Royal University, Calgary – Room B206
Friday, Oct 25, 4:00 pm University of Calgary – Earth Science Building, Room 162
Friday Nov 29, 2:30 pm, University of Western Ontario – Biological and Geological Sciences Building, Room 0153
Past lecture tour dates:
Tuesday Oct 8, 1:00 pm – Saint Mary’s University, Halifax – Science Building, Room 408
Wednesday Oct 9, 12:30 pm – Acadia University, Wolfville – Huggins Science Hall, Room 336
Thursday Oct 10, 12:15 pm – St. Francis Xavier University, Antigonish – Physical Sciences Center, Room 2045
Friday Oct 11, 4:00 pm – Dalhousie University, Halifax – Life Sciences Center, Milligan Room
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.
Non-traditional redox-sensitive metals in sedimentary rocks as tracers of global ocean redox conditions: Lessons from Phanerozoic anoxic events
Global ocean redox conditions can be inferred from the concentration and isotopic composition of redox-sensitive metals in sedimentary rocks (particularly black shales and carbonates) when these metals have oceanic residence times significantly longer than typical ocean mixing times. Mass-balance models can use the sedimentary data to infer the global extent of seafloor covered by oxygenated, anoxic/non-sulfidic, and euxinic waters. These models take advantage of distinctive metal burial rates and isotope fractionations in different oceanic redox settings and are becoming more sophisticated. Molybdenum and uranium isotope data from sedimentary rocks can constrain the extent of ocean euxinia but are more ambiguous regarding the extent of oxygenated versus anoxic/non-sulfidic marine environments. Rhenium enrichments in black shales are a potential tracer for the extent of total global ocean anoxia (euxinic and non-euxinic) whereas thallium isotope compositions from black shales may constrain the extent of well-oxygenated seafloor where manganese oxides are buried. Using these redox proxies, studies of Phanerozoic sedimentary rocks deposited during large igneous province events (and their associated mass extinctions) suggest that ocean anoxia expanded by ~1-2 orders of magnitude relative to the modern ocean. A multi-proxy approach applied to the same samples, coupled with improved mass-balance models, has potential to yield more precise estimates of global ocean redox changes.