Isotopologues: isotope patterns within organic molecules
Funded by a generous NASA Astrobiology center award, we are investigating new ways to measure and to understand patterns of C, N, H, O, S, Cl isotopes within molecules. Isotopologues offer exciting potential insights to biotic and abiotic signatures as they capture and reflect both sources and history of individual atom sites. Research collaborations include studies of methane-cycling by microbes, origins of organic acids, biogeochemistry of environmental compounds and contaminants, and potential proxies for past life and environments, among others.

Carbon, water and climate

Biomarkers of ancient plants and algae carry signatures of CO2, temperature and water.  These signals are encoded in their carbon, hydrogen and nitrogen isotope abundances.  We are interested in how isotope ratios of plant waxes, terpenoids and pigments reflect the biota, growth conditions and climate of ancient environments.  We use these signals to study plants, water and climate during the Cretaceous, Paleocene, Eocene, Miocene and the Pleistocene.

Biomarkers of ancient landscapes

We are continuously developing our biomarker and proxy "toolbox" for reconstructing landscapes of the past.  This includes developing novel biomarkers, such as alkyl resorcinols (left) that are common in sedge.  We also study well-known biomarkers in new ways. For example, we are evaluating waxes in C3 and C4 plants to understand physiological, ecological and environmental controls on their abundance, distribution and carbon isotopic signatures.

Fire markers

We are studying polycyclic aromatic hydrocarbons (PAH) as indicators of fire in ancient terrestrial environments.  We are interested in the occurrence and nature of fire as a possible source of carbon released during the PETM.  We also are interested in relationships between fire and grassland expansion during the mid to late Miocene around the world, and as a response to Plio-Pleistocene climate variability in eastern Africa. These compounds have also been applied to studies of landscape changes following the rise of C4 grassland habitats, and to evaluate wildfires following the K/Pg bolide impact.

Habitats of early humans

We have been collaborating with Gail Ashley (Rutgers) to study the molecular fossils in lake sediments and paleosols surrounding Olduvai Gorge, Tanzania.  Our work has documented climate variability that is orbitally paced during the rise of early humans.  We have been working with archaeological samples to map spatial patterns in vegetation associated with vertebrate remains and human artifacts.

Microbial biogeochemistry and biosignatures

We collaborate with microbiologists to study the lipid and isotopic signatures of microbes in anoxic environments.  We are currently studying F430, a co-enzyme that is critical to methanogenesis, and possibly methane oxidation through reverse methanogenesis.  We also are investigating hopane polar lipids of cyanobacteria and sulfur-oxidizing bacteria.  These compounds are important in studies of petroleum, past oceans and early life on Earth.  Yet, we still know little of their biochemical functions and microbial sources.

Pico-CSIA and early life on Earth

Compound-specific carbon isotope analyses were introduced over 25 years ago. Today, they are widely used in biogeochemistry, environmental, petroleum, flavor, and forensics applications. We think it is time for a new generation of instrumentation, and we aim to reduce sample size to picomoles by innovations in the interface and signal processing.  Our goal is to analyze the world's oldest biomarkers.