I study the connections between the evolution of Earth-system processes, biological innovation, and ecosystem change—foremost in Earth’s early history. My research integrates field, petrographic, and geochemical work. The protracted rise of oxygen over several billion years dramatically changed Earth’s surface environments. However, our current picture of Earth’s redox evolution is still painted with only broad strokes. A central theme of my research has been trying to piece together the history and effects of Earth’s oxygenation. With that end goal in mind, I am currently working on coupling paleoredox proxies in Precambrian sedimentary rocks, calibrating novel metal isotopes systems in modern aqueous systems, and untangling the distribution and diagenetic history of traces metals in sedimentary rocks.
Associate Research Scientist
I have operated the MC-ICP-MS machine under various projects and measuring a large variety of isotopic systems (e.g., Si, Fe, Ni, Cu, Mo, Nd, Sm and Pb). The work has included collaboration with scientists from IFREMER and from other research institutes and universities. Development and calibration of isotopic measurements by laser ablation MC-ICP-MS methods. Guiding students in all aspects of clean lab work and isotopic measurements.
Studying Mo isotopes (and possibly other metallic isotope systems) of Mesoproterozoic - Neoproterozoic sediments from the Mbuji-Mayi Supergroup of Congo. The ca. 1300 – 800 Ma Mbuji-Mayi Supergroup is associated with great climatic and biological changes also linked to the assembly (~ 1000 Ma) and break-up (~ 850 Ma) of Rodinia. In this project I attempt to reconstruct the paleo-redox conditions of the ocean and atmosphere during this time window using isotopic compositions of metallic elements. Other aspects of this project include the study of microfossils, carbon and oxygen isotopes and TOC.
Non-traditinoal stable isotopes of redox sensitive metals (Cr, U, Mo, Fe, etc.) are emerging new geochemical tools for studying biogeochemical cycling in Earth’s surface environments. My current research focuses on U and Cr, whose valence state depends on the reduction-oxidation (redox) state of the environment. Large isotope fractionation (238U/235U and 53Cr/52Cr) occurs during reduction of U(VI) and Cr(VI) to U(IV) and Cr(III), respectively. Based on this framework, U and Cr isotopes are emerging powerful tools to constrain the redox state of environments ranging from Earth’s surface to its interior. Specifically, U and Cr isotopes have been used to indicate and quantify the reductive attenuation of groundwater contamination by Cr(VI) and U(VI). In addition, U and Cr isotope record in sedimentary rocks provide very important information regarding the redox state of Earth’s early history, which is tied to the earliest evolution of oxygenic photosynthesis in the Archean and macroscopic animal life in the Neoproterozoic.
My research concerns improving our understanding of Precambrian marine environments. To do this I integrate sedimentology, stratigraphy and geochemistry in both field and lab work. I am a strong advocate for having a thorough understanding of the geology prior to any geochemical analysis, and to aid this I aim to develop our knowledge of Precambrian carbonate formation and sedimentology. I am particularly interested in reef development, marine cementation and syn-sedimentary dolomitisation in Precambrian sequences. Much of my research centers around the “Precambrian dolomite problem”, as it now appears that marine dolomitisation was widespread in the unusual oceans of the Precambrian.
Carbonate sediments play a key role in unlocking the secrets of the early Earth. Precambrian carbonates of North America, Australia and Africa contain newly discovered, primary marine carbonate precipitates that can reveal the redox chemistry of seawater over time. The development of these marine cements as a reliable proxy for ocean oxygenation forms part of my research at Yale. I hope to better constrain the redox state and associated chemical depth gradients of Precambrian seawater by geochemical and sedimentological examination of these dolomite marine cements. Geochemical analysis includes Laser Ablation- ICPMS of these components, and the application of several different isotope systems. Additionally, when analyzed in a stratigraphic framework, basic variations in carbonate mineralogy provides a record of ocean Mg/Ca during the Neoproterozoic.
Analysis of these carbonates is beginning to reveal just how unusual the oceans were during the Precambrian, and how complex the evolution of the ocean-atmosphere was in the early Earth.
Postdoctoral Fellow - Joint Hull-Planavsky Labs
I specialisein the development and application of geochemical proxies to the geological record, in particular the boron isotope-pH proxy (a tool for reconstructing past atmospheric CO2 concentrations). Primarily my focus is on the application of these proxies in planktic foraminifera during past periods of climate change. Intrinsically linked to this is a requirement to understand the biology and life processes of planktic foraminifera, both living and extinct, to quantify potential ‘vital effects’ that may interfere with recorded environmental proxy signals.
this period could provide valuable insights into the sensitivity of the earth system to pulses in greenhouse gas concentrations.
Postdoctoral Fellow - Joint Hull-Planavsky Labs
My research focuses on the interplay between Earth’s climate and the fluxes of carbon from the lithosphere into the atmosphere, ocean, and finally into sediments. As the oceans represent the largest surficial reservoir of carbon, characterizing the marine carbon cycle is crucial to understanding the long-term regulation of atmospheric and climate.2
I am interested in the redox evolution of the Earth’s atmosphere - ocean system in the Precambrian, and the impact of these environmental changes on early life. I combine field geology, sedimentology, and geochemistry to investigate this vast and poorly understood interval in Earth history. In particular, I am using Chromium isotopes as a tracer for atmospheric oxidative cycling (or lack thereof) in the Mesoproterozoic, leading up to the diversification and radiation of complex animal life.
My research aims to form and test hypothesis of global change in deep time, particularly concerning the early evolution of microbial life and its environment. Specifically, I integrate field, petrographic and geochemical work to try and reconstruct marine ecosystem dynamics, and the availability of micronutrients such as Mo, Cu, Fe, Zn, Cd and Ni which may have had a limiting/co-limiting effect on primary production and hence the distribution of specific microorganisms.
I study the co-evolution of tectonics and ocean chemistry, in particular I am interested in how these may have influenced the oxygenation of earth and early evolution of life on early Earth. I conduct my research by combining field research, petrography and geochemistry on sedimentary rocks. These rocks are located throughout the world and contain both physical and chemical signatures which reflect the environment and the conditions they formed in millions to billions of years ago.
Over the course of the Proterozoic (2.5 - 0.54 Billions years ago) we see the evolution of life from simple, single celled algae and cyanobacteria to a plethora of complex multicellular organisms by the Cambrian explosion (542 Millions years ago). Likewise, the early Proterozoic was nearly devoid of oxygen, but progressively by leaps and bounds, oxygen levels reached near modern levels by the Cambrian. Unfortunately, we only broadly understand these changes and how they happened. Central to this problem is our poor grasp on many of the most basic geochemical cycles. Erosion of continental rocks is a fundamental processes in modern geochemical cycles where continental material is broken down and transported to the oceans by wind and water. Among other important cycles, it controls phosphate output to the oceans, the major limiting nutrient for life over earth history, and calcium output, a major component of carbonate rocks which help govern carbon dioxide levels in the atmosphere. The primary goal of my research is to determine how erosion of the continents has changed over time and how it has been influenced by continental breakup and major orogenic events. With this goal in mind, I am using both well established and novel global weathering proxies to understand erosion over time while establishing new geochemical methods to limit the effect of alteration on determining primary signals.
I am broadly interested in CO2 and the role it plays in climate change. My research focuses on testing and applying the boron isotope-pH proxy to reconstruct the carbonate system in past oceans and decipher past atmospheric pCO2. Shallow modern marine carbonates and planktonic foraminifera from the Eocene (e.g. during the MECO) are my primary focus. My other research interests include organic carbon degassing during metamorphism and mineral carbonation in ultramafic/mafic rocks.
I am interested in how climate change alters the ecology and the marine environment. My research in this lab focuses on the use of both organically and inorganically precipitated carbonates in climate reconstruction and proxy development. My senior thesis is about how lithium isotopes may be used in climate reconstruction outside of the context of weathering. I am also working on a computer model to examine how Snowball Earth theory corresponds to the carbonate record.