Research

My research largely focuses on reconstructing greenhouse climate conditions in Earth's geologic past from carbonate and siliciclastic sedimentary rock records. I am interested in questions such as: what were the warmest temperatures on the planet during the Phanerozoic? Were there ever geologic time intervals, like the Cretaceous, when the planet was free of ice? How did oceans and climates respond to mass volcanic activity and CO₂ emission at critical transitions in geologic time like during the Mesozoic Ocean Anoxic Events ("OAEs")? And what novel geochemical techniques and stratigraphic approaches can be further developed and utilized to reconstruct the natural history of Earth?

To answer these questions, I combine fieldwork to collect targeted samples with laboratory analyses. My fieldwork has spanned a variety of settings from drilling sediment cores from deep sea settings with the International Ocean Discovery Program, to continental coring projects in Utah and China, to accessing fossil specimens from museum collections. The common goal among the sites has been to obtain geologic specimens that preserve proxy evidence for paleoenvironmental conditions from the Cretaceous in the form of cores samples, macrofossils, and outcrops samples.

In the laboratory, I develop chemostratigraphic reconstructions of Earth history with both high-throughput standard measurements of sedimentary total organic carbon (TOC) and carbonate content, as well as with targeted, sophisticated isotope geochemical analyses. I use measurements of stable carbon isotope ratios (δ¹³C ∝ ¹³C/¹²C) in carbonate and organic carbon to detect changes in the geologic carbon cycle and use globally preserved δ¹³C excursions to correlate stratigraphic sections from different regions. To reconstruct global volcanic and continental weathering activity during OAEs, I have analyzed shale samples for initial osmium isotope ratios (¹⁸⁷Os/¹⁸⁸Os) in the platinum group element lab of collaborator Dave Selby at Durham University in the U.K. Most recently as a postdoctoral fellow working with Sierra Petersen at the University of Michigan, I have been measuring the temperature of biomineral precipitation for Cretaceous invertebrate fossils using the carbonate clumped isotope ("Δ₄₇") technique.

Broadly, my current areas of research can be divided into several themes:

1. studying the causes and paleoenvironmental effects of ocean anoxic events ("OAEs") in the Mesozoic along with their relevance to modern CO₂ emission and changes in marine chemistry.

2. quantifying paleotemperatures in deep geologic time, using carbonate clumped isotope analyses of invertebrate macrofossils.

3. understanding the causes of geologically-rapid relative sea level fluctuations during greenhouse climate intervals when large ice sheets are considered unlikely.

4. identifying Milankovitch cycles (periodic changes in Earth's orbit that affect solar insolation and climate) in marine sedimentary strata and using the known periods of these cycles to develop high-precision age models for events deep in Earth history.

5. resolving the depositional processes and biogeochemical conditions associated with the deposition of black shale energy resources.

If you are interested in a bit more detail, read the latest journal publications from my collaborators and me.