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.
I am interested in understanding the interactions between tectonics, climatic processes and geochemical cycles on a range of time scales. I use radiogenic isotope geochemistry, in particular the rhenium-osmium (Re-Os) geochronometer, Sr and Nd isotopes combined with field-based mapping, sedimentology, stratigraphy and mineralogy to interrogate the rock record of critical transitions in Earth history. My near term research interests are centered on four main areas: 1) refining Earth history records, especially Proterozoic tectonic reorganizations and eukaryotic diversification, 2) combining geochemical proxies with microfossil and sedimentological analyzes to provide better constraints on ice sheet dynamics over the last 5 million years, 3) understanding hydrocarbon systems and ore genesis through the use of geochronology and geochemistry, and 4) integrating the Re-Os geochronometer into the EARTHTIME organization and leading an international effort for inter-laboratory standardization.
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.
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 was trained as an Economic Geologist with extensive expertise in Isotope Geology. In addition to understanding the timescales and fluid evolutiuon of magmatic-hydrothermal systems through intergrating field geology, high-precision geochronology and in-situ analysis, I am also devoting my enthusiasm in sharpening the Re-Os chronometer. My further research interests include error propogation and visualization of geochronology data.
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.
Flint Postdoctoral Fellow
Experimental geochemistry utilizing isotopic techniques to better understand water-rock interactions associated with atmosphere-ocean CO2 buffering mechanisms.
My near-term research interests are centered on four main areas: 1) the investigation of the crustal evolution history of Archean terranes; 2) the refinement of the redox proxy record and temporal history of the rise of atmospheric oxygen; 3) analytical technique development, and 4) environmental and geoforensic analysis. With a particular focus on chronology, I specialize in using and integrating multiple isotope systems via high-precision mass spectrometry measurements. Much of the work I have done has required the development of analytical techniques for small, complex samples and this will continue to be a theme of my research moving forward. A significant goal of mine is to integrate the themes of crustal and atmospheric evolution in my research and to establish a better understanding of the relationships between them.
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.