People on the Earth History team
Anne-Sofie Ahm, Assistant Professor (CV)
As an Earth Historian, I am interested in how we can use the chemistry of rocks to gain insight into the surface conditions of Earth in the past. The chemistry of marine carbonate sediments has been used to reconstruct the evolution of global biogeochemical cycles for a wide range of elements throughout the entirety of Earth history. However, one of the main limitations in using this geochemical archive is the susceptibility of carbonate sediments to diagenesis, as unlithified sediments are transformed into the rocks we can study in the geological record. Using multiple isotope systems and numerical models of diagenesis, my research seeks to extract the primary chemical information from ancient carbonate sediments by better understanding the diagenetic processes. I am particularly interested in the co-evolution of climate and life during fundamental transitional periods in Earth history such as the Great Oxidation Event, Neoproterozoic Snowball Earth events, the Cambrian explosion of animal life, and the end-Ordovician mass extinction.
Keyi Cheng, Postdoctoral Researcher
Understanding biogeochemical cycles in ancient oceans not only satisfies our curiosity, but also contributes to humanity’s future—by improving our ability to predict the ocean’s response to climate change, and guiding the search of potential habitable worlds in exoplanets. However, this endeavor is meanwhile a challenging task due to sparsity of preserved rock records and limitations in our understanding of these biogeochemical cycles in both seawater and sediments. My research aims to reveal a comprehensive picture of oceans in the past, with emphasis on—but not limited to—redox structure, nutrient dynamics, and weathering flux through integrating isotopic and elemental proxies, sedimentological analysis, and earth system models. Particularly, I am interested in exploring the co-evolution between ocean chemistry and life evolution during the Mesoproterozoic—the dawn of diversification of eukaryotic species which laid the foundation for today’s ecosystems.
Daniel Garduño Ruiz, PhD candidate
I am interested in investigating the interactions of climate, atmospheric chemistry, and geologic processes through Earth History. Specifically, my research focuses on the effects of the Great Oxidation Event on climate and atmospheric chemistry. The Great Oxidation Event fundamentally changed the Earth's surface redox conditions, increasing the atmosphere's oxygen content and affecting the Earth's biochemical cycles. Multiple lines of evidence suggest that the Earth suffered a period of climatic upheaval after the Great Oxidation Event, going from periods of global glaciations to periods of stability. My research tries to understand why climate behaved like this after the Great Oxidation Event and how these changes in climate could have affected the atmospheric chemistry of the Earth and vice versa. I am using a combination of photochemical, climate and simple mass balance models to try to understand these problems.
Jinfeng (Henry) Hong, MSc student
I am interested in exploring the co-evolution of climate, geochemistry, element cycling, and life throughout Earth history. My research interests also lies on understanding the interactions between geochemical processes and environmental changes, particularly during periods such as the Great Oxidation Event and the Boring Billion. Thus it is essential to try to reconstruct past biogeochemical cycles and unravel the complexities of diagenetic processes that influence the preservation of primary geochemical signals during the Boring Billion. In general, my goal is to gain a better understanding of why Earth's biosphere and climate have behaved in the ways they did, and how these interactions have impacted the evolving chemistry of our planet over time.