Department of Earth and Atmospheric Sciences

Determination, assessment, and interpretation of molecular and isotopic characteristics of organic matter to identify biogeochemical signatures of life of Earth and processes associated with how organisms shape the fate and cycling of carbon in modern and ancient natural systems.

Planetary Geoscience

Brassell’s work on the organics of desiccated lake systems are relevant to the interpretation of organic compounds as evidence for past life on other planets.

Research Activities

Activities are focused on the exploration and application of geochemical biomarkers and their isotopic signatures as environmental, paleoclimatic, and stratigraphic tools to better understand:

• Environmental and climatic signals recorded in the temporal and spatial variations of the molecular and isotopic characteristics of sedimentary organic matter.
• The capacity of molecular and isotopic signals to reflect controls on primary production and factors that affect the survival and transformation of organic matter in sediments, particularly microbial processes.
• The evolutionary progression of life through time, especially biosynthetic responses preserved in the biogeochemical carbon cycle related to global perturbations of the ocean and atmosphere.
• Controls on preservation of sedimentary organic matter, the formation of source rocks and influences on the generation, composition, and biodegradation of petroleum, plus the fate of hydrocarbons in the environment.

Undergraduate classes

E131: Oceans and Our Global Environment. An introductory online course for non-science majors incorporating exercises utilizing web-based resources of oceanic data in an interdisciplinary exploration of controls on physical, chemical, and biological oceanographic processes with an emphasis on the climatic and environmental importance of Earth’s oceans.

C105: Records of Global Climate Change. An introductory science course that examines evidence for climate change in Earth’s past, explores present-day climate trends, and assesses predictions of future change and its consequences for society and the environment.

E488: Paleoclimatology: The Geological Record of Earth’s Climate History. An examination of Earth’s climate over geological time that explores approaches to reconstructing past climates from the evidence of sediment records and fossil occurrences, complemented by geochemical data, and building connections between life on Earth, extinction events, and drivers for climate change.

Graduate classes in aspects of biogeochemistry, supplemented by training in analytical techniques and seminars in topical areas of interdisciplinary research

G587 Organic Geochemistry: A comprehensive exploration of measurement and applications of molecular and isotopic characteristics of organic matter focused on principles and processes, coupled with topical readings from recent literature.

G588: Paleoclimatology: The Geological Record of Earth’s Climate History. A graduate-level exploration of Earth’s climate over geological time co-taught with E488.

Graduate seminars in aspects of biogeochemistry

Recent topics for G690 Graduate seminars in aspects of biogeochemistry have included: Organic Geochemical Stratigraphy, Petroleum Geochemistry, Paleoclimatology, and Organic Chemistry for Earth Scientists.

Projects representative of opportunities for research, including collaborative activities, which are, or have been, supported by the National Science Foundation (NSF), the US Science Support Program (USSSP) for the International Ocean Drilling Program (IODP), the Department of Energy (DOE), and other funding agencies:

• Evolution of temperature controls on alkenone biosynthesis and the relationship between the alkenone paleotemperature proxy and biological response of calcareous nannoplankton to global cooling events during the Paleogene.
• Cretaceous biogeochemistry examining stratigraphic variations in molecular and isotopic characteristics of organic matter to explore depositional conditions and biotic responses during oceanic anoxic events.
• Temporal changes in molecular and isotopic compositions of sediments from Olduvai Gorge that reflect its Pleistocene paleoclimate and responses of terrestrial vegetation and aquatic organisms to alternating wet/dry cycles during a pivotal interval of hominin evolutionary history.
• Evaluation of geocatalytic generation of hydrocarbons at comparatively low temperatures by evaluation of biomarkers in shales and heating experiments with natural and synthetic clays to elucidate how biomarker transformation pathways play a role in CH₄ generation.
• Elucidation of the pre- and post-glacial paleoclimate history of Southeast Asia from examination of molecular and isotopic records in Vietnamese lake sediments.
• Molecular diversity in the sedimentary record exploring assessment of compositional variations in biomarkers as a measure of biocomplexity through geological time.

• Fellow of the American Geophysical Union
• Fellow of the Geochemical Society
• Fellow of the European Association of Geochemistry
• Royal Society University Research Fellowship
• David and Lucile Packard Fellowship for Science and Engineering
• Kavli Fellow, National Academy of Sciences
• Fellow, Hanse-Wissenschaftskolleg, Delmenhorst, Germany
• Best Paper Award for 2006 from the Organic Geochemistry Division, Geochemical Society
• Teaching Excellence Recognition Awards and Trustees Teaching Awards

Roles on major committees within the Department and University, and aspects of professional service:

Department:

• Current Standing Committee: Diversity and Inclusion Committee
• Policy Committee; Former Chair (2007-11)
• Director of Graduate Studies (1996-2003, 2015-16, 2018-19)

College:

• Member, College Policy Committee (2006-7)
• Chair, College Octagon Committee on Faculty Hiring and Retention (2016-17)

University:

• Chair, BFC Educational Policies Committee (2016-19)
• Member, Bloomington Faculty Council (BFC; 2003-5, 2015-19)
• BFC Executive Committee (2016-2019)
• University Faculty Council (2016-19)
• General Education Committee (2006-8)
• Advisory Council and Steering Committee for SOTL (Scholarship of Teaching and Learning (2003-10)

Professional:

• Former Review panelist for NSF, NASA, GoMRI programs
• Prior Associate Editor for Geochimica et Cosmochimica Acta and Organic Geochemistry
• Former member, Council of the European Association of Organic Geochemists