Proxies for Paleoclimate Reconstruction
Organic matter preserved in ancient marine, lacustrine, and peat deposits are vast repositories of information on Earth’s climate through time. Biomarkers provide insight into the organisms living in the past, and the environmental conditions necessary for such organisms to thrive can then be elucidated. Further information is provided by the isotopic compositions of such biomarkers. Because δ13C and δD values of biomass are governed by environmental conditions, compound-specific isotope proxies can be used to reconstruct ancient pCO2 levels, rainfall, temperature, food web structure, and methane cycling. Our research focuses on the development and refinement of such proxies by using cultures and field samples to identify diagnostic compounds and the controls on their isotopic compositions. We are also engaged in research that applies those techniques to specific problems in Earth history, including mass extinctions, the transition into and out of greenhouse climates, and the evolution of life.
Bacteria and Archaea comprise two of the three Domains of life and are essentially ubiquitous on the Earth’s surface. Recent developments in genetic techniques have reinvigorated the field of geomicrobiology by prompting new discoveries and reaffirming the importance of microbes in biogeochemical processes. At the same time, new analytical chemistry techniques now allow direct contributions to microbiology from molecular biogeochemists, particularly when novel biomarkers are integrated with isotopic determinations. Our work in this area includes studies of the microbiology of CO2 and methane cycling in peat deposits and the role of archaea in anaerobic methane oxidation. We also study the archaea and bacteria present in extreme environments, such as hydrothermal vents and deep-sea brine lakes. Interest in extreme settings arises from the potential that extremophiles could generate medicinal compounds and the prevailing impression that such settings represent good models for life on the early Earth.
Preservation of Organic Matter
The preservation of organic matter is a topic of much interest to a range of scientists: it is critical to the formation of fossil fuel deposits, has important implications for the global carbon cycle and is an essential process in the preservation of organic materials in the fossil record. Our research focuses on both the types of environmental conditions in the past that would have favoured extensive organic matter burial and preservation (e.g. oceanic anoxic events) as well as the chemical transformation of biological organic matter into kerogen. This latter process is of much interest as it is still unclear from where the aliphatic signature of most sedimentary organic matter derives. However, recent work in our group suggests that organic materials previously thought to be relatively labile, including lipids, could be bound into resistant ‘geomacromolecules’, playing an important role in organic matter preservation and governing its chemical structure.