Stefan Lalonde, CNRS / Institut Universitaire Européen de la Mer, France
2019 Houtermans Award medallist
Stefan Lalonde is a CNRS researcher at the Laboratoire Géosciences Océan, Institut Universitaire Européen de la Mer and Université de Bretagne Occidentale, in Brest, France. A Canadian raised in Nova Scotia and Montana, Stefan completed BSc studies at McGill University and obtained an MSc degree in Geomicrobiology (2006) and PhD degree in Geochemistry (2011) at the University of Alberta. Stefan’s research is focused on the evolution of the Precambrian surface environment and biosphere.
Stefan’s work has combined laboratory experiments and sedimentary geochemical data to understand the chemical composition of seawater in the Archean and Paleoproterozoic, with a particular focus on iron-rich chemical sedimentary rocks such as banded iron formations (BIF). During PhD work in Edmonton with Kurt Konhauser, and continuing during postdoctoral work in Brest with Olivier Rouxel, Stefan constructed large BIF geochemical datasets that helped constrain the evolution of marine nutrients and redox status in deep geological time, including the histories of phosphorus, nickel, chromium, uranium, cobalt, copper, and zinc.
Stefan joined the CNRS as a researcher at the Laboratoire Géosciences Océan in Brest in 2013. His focus turned to incipient oxidative weathering on the Archean to Paleoproterozoic Earth, including kinetics of mineral oxidation and microbial oxygen production. He elaborated novel models for early oxidative weathering by benthic microbial mat communities. He guided studies of fossilized microbial mats in the Barberton Greenstone Belt (S. Africa) that revealed colonization of the land surface ca. 3.2 billion years ago and indicated differences in carbon and nitrogen cycling between terrestrial and marine settings at that time. Stefan has also published on trace element uptake onto iron oxides and bacterial surfaces in natural and laboratory settings, on microbial silicification, and on paleoenvironmental applications of iron, molybdenum, and germanium stable isotopes.
Work in progress, funded by the European Commission and in close collaboration with Philip Fralick (Lakehead University), is aimed at understanding links between carbonate production, seawater composition, and photosynthesis in Archean shallow waters via field and drill core study of some of Earth’s oldest (Mesoarchean) carbonate platforms preserved in Northern Ontario, Canada.
Additional information and a list of publications can be found here.