Current Research Interests: |
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Our group works extensively in the Laboratory for Isotopes and Metals in the Environment (LIME). We also conduct research at Penn State's Materials Characterization Lab and at numerous synchrotron facilities, including SSRL, APS, and ESRF.
Please check out this page if you are interested in joining our group.
Please check out this page if you are interested in joining our group.
the geochemistry of marine sediments
Marine sediments are commonly the largest sink in global biogeochemical cycles. For example, most of the carbon that is buried from the oceans and atmosphere is removed as either organic carbon or carbonate minerals.
My research seeks to understand how, and in what forms, key elements are removed in marine sediments. In addition to carbon, my group works on critical minerals such as uranium and rare earth elements and major nutrients such as phosphorus. We use geochemical (e.g., whole-rock and spatially resolved analyses), characterization (e.g., synchrotron-based u-XRF and u-XAFS), and numerical modeling (e.g., reactive transport) methods.
I work on the geochemistry of carbonate and siliciclastic sedimentary rocks, include phosphorites. I am also on the leadership of the Sedimentary Geochemistry and Paleoenvironments Project, which seeks to provide a high quality sedimentary geochemical database.
Relevant papers:
Uranium isotopes are an exciting new proxy that is showing a lot of promise and yet requires additional development. You can check out reviews of the uranium isotope proxy and its use for paleoceanographic reconstructions in Lau et al., 2019 and Zhang et al., 2020.
My work on uranium in siliciclastic rocks: Lau et al. (2020, 2021); Bazarkina et al. (2025)
My research seeks to understand how, and in what forms, key elements are removed in marine sediments. In addition to carbon, my group works on critical minerals such as uranium and rare earth elements and major nutrients such as phosphorus. We use geochemical (e.g., whole-rock and spatially resolved analyses), characterization (e.g., synchrotron-based u-XRF and u-XAFS), and numerical modeling (e.g., reactive transport) methods.
I work on the geochemistry of carbonate and siliciclastic sedimentary rocks, include phosphorites. I am also on the leadership of the Sedimentary Geochemistry and Paleoenvironments Project, which seeks to provide a high quality sedimentary geochemical database.
Relevant papers:
Uranium isotopes are an exciting new proxy that is showing a lot of promise and yet requires additional development. You can check out reviews of the uranium isotope proxy and its use for paleoceanographic reconstructions in Lau et al., 2019 and Zhang et al., 2020.
My work on uranium in siliciclastic rocks: Lau et al. (2020, 2021); Bazarkina et al. (2025)
linking ocean oxygenation and deoxygenation to animal evolution and extinction events
My research is focused on investigating the causes of environmental change in Earth's history. I am interested in the links between the biogeochemical cycles of oxygen, carbon, and redox-sensitive elements. I reconstruct past environmental conditions using geochemical clues in the marine sedimentary record. Much of my research interests lies in paleo-redox proxies and quantitative interpretations of these records.
Relevant papers: Lau et al. (2016), Lau et al. (2017), Hardisty and Lau (2024)
Relevant papers: Lau et al. (2016), Lau et al. (2017), Hardisty and Lau (2024)
anoxia, climate change, and mass extinction recovery
The end-Permian mass extinction (ca. 252 Ma) was the most catastrophic event in the Phanerozoic (at least, from the perspective of animals), with ~80% of marine genera going extinct. The extinction is attributed to the eruption of Siberian Traps, a large volcanic province that resulted in disastrous conditions on land (wild fires, denudation of the continents, ozone hole, acid rain) to the oceans (acidification, extremely hot temperatures, toxic conditions and low oxygen). The recovery of biodiversity, ecological complexity, animal body size, metazoan reefs, and other measures of a healthy ecosystem did not appear to be fully complete until the Middle Triassic, about 5 million years after the extinction. This event represents a severe perturbation to the carbon cycle, and may be instructive for understanding how the Earth system responds to climate change on long time scales.
We show that anoxia expanded dramatically, concurrently with the extinction, and likely played a role in delaying the recovery [Lau et al., 2016 PNAS; figure below]. To infer this record of de-oxygenation, we measured uranium isotopes in multiple carbonate stratigraphic sections. Uranium isotopes are emerging as a promising proxy for redox conditions of past oceans. The basis of this proxy relies on the fact that the solubility and 238U/235U ratio of aqueous uranium varies depending on its redox state. In the ocean, uranium is reduced primarily within anoxic sediments; thus, the uranium isotopic composition of seawater tracks the areal extent of anoxia. Because of its long residence time, uranium is representative of global redox conditions. Limestones are useful archives of seawater uranium because primary CaCO3 precipitates are not fractionated from seawater, although bulk carbonates may be affected. Our records show good agreement despite being situated on opposite sides of the Paleo-Tethys, indicating that this non-traditional isotopic proxy may be used to infer global changes. We construct a box model to provide first-order quantitative constraints on seafloor anoxia during the Early Triassic recovery.
We show that anoxia expanded dramatically, concurrently with the extinction, and likely played a role in delaying the recovery [Lau et al., 2016 PNAS; figure below]. To infer this record of de-oxygenation, we measured uranium isotopes in multiple carbonate stratigraphic sections. Uranium isotopes are emerging as a promising proxy for redox conditions of past oceans. The basis of this proxy relies on the fact that the solubility and 238U/235U ratio of aqueous uranium varies depending on its redox state. In the ocean, uranium is reduced primarily within anoxic sediments; thus, the uranium isotopic composition of seawater tracks the areal extent of anoxia. Because of its long residence time, uranium is representative of global redox conditions. Limestones are useful archives of seawater uranium because primary CaCO3 precipitates are not fractionated from seawater, although bulk carbonates may be affected. Our records show good agreement despite being situated on opposite sides of the Paleo-Tethys, indicating that this non-traditional isotopic proxy may be used to infer global changes. We construct a box model to provide first-order quantitative constraints on seafloor anoxia during the Early Triassic recovery.
Lau et al., 2016 PNAS
Relevant papers: Lau et al. (2016), Jost et al. (2017), Silva-Tamayo et al. (2018), Zhang et al. (2018), Hulse et al. (2021), Pimentel-Galvan et al. (2021), Singh et al. (2021), Isson et al. (2022), Taylor et al. (2026)
neoproterozoic-cambrian rise in oxygen
Lau et al., 2017 EPSL
Uranium isotopes and other redox proxies can also reveal new insights into ocean oxygenation, its relationship to carbon cycling, and the rise of animals in the Neoproterozoic. My uranium isotope record in two well-preserved limestone stratigraphic sections from Mongolia suggest that the oceans became widely oxygenated following the Sturtian Snowball Earth glaciation [Lau et al., 2017; figure to left]. This may possibly be attributed to post-glacial weathering. However, oxygenation was temporary, and more anoxic conditions returned prior to the Marinoan Snowball Earth. This return to reducing conditions occurs at the same time as a large negative carbon isotope excursion, providing a new clue to the enigmatic carbon isotope record of the Neoproterozoic.
Relevant papers: Lau et al. (2017), Chanchai et al. (2026)
Relevant papers: Lau et al. (2017), Chanchai et al. (2026)
diagenesis and carbonate geochemistry
Lau et al., 2017 Chemical Geology
Carbonates are an important archive of seawater geochemistry, but are also susceptible to diagenetic alteration. Calcium isotopes have shown promise as tracers of seawater calcium [Silva-Tamayo et al., 2018], and thus may track changes to the ancient calcium cycle. Because the carbon and calcium cycles are linked through CaCO3 weathering, acidification, and burial, mass flux imbalances may be tracked using calcium isotopes. My study of calcium isotopes in the Lower and Middle Triassic carbonates illustrates that local processes can easily overprint any original record of seawater calcium chemistry. I use the relationship with strontium concentration to help identify early diagenetic recrystallization [Lau et al., 2017; figure to right]. A model of water-rock exchange suggests that this process is likely to have occurred in many calcium isotope records measured in bulk carbonates, but the first-order trend may still be captured.
Relevant papers: Lau et al. (2017), Silva-Tamayo et al. (2018), Fantle et al. (2020), Gussone et al. (2020), Lau and Hardisty (2022), McCormick et al. (2026)
Relevant papers: Lau et al. (2017), Silva-Tamayo et al. (2018), Fantle et al. (2020), Gussone et al. (2020), Lau and Hardisty (2022), McCormick et al. (2026)
the geologic carbon cycle
Changes in pCO2 reflect carbon cycling at the Earth's surface (involving the atmosphere, oceans, and terrestrial biosphere) and exchange between these surficial reservoirs and the crust and mantle. On geologic time scales, the second group of processes---which include weathering, mantle degassing and volcanism, and carbon burial---play a large role in determining atmospheric pCO2 and its stability.
The silicate weathering feedback drives the recovery of the carbon cycle following a perturbation---a natural "thermostat." To illustrate, an increase in volcanic CO2 emissions and the subsequent bump in pCO2 drives chemical weathering of the continents. The chemical reaction results in an increase in the flux of aqueous weathering solutes (such as bicarbonate) that ultimately reaches the oceans as alkalinity, bumping up the saturation state of CaCO3 minerals. Greater CaCO3 precipitation and burial follows, drawing down atmospheric pCO2 on time scales of 10,000 to 100,000 years. This can be represented very generally as:
CaSiO3 + CO2 --> CaCO3 + SiO2 .
The strength of this feedback has varied through time, and is dependent on a combination of processes, including climate, tectonics, lithology, continental area, the physiochemical response of plants, and so on [Caves et al., 2016 and Ibarra et al., 2019; see figure below illustrating changes in the feedback strength through the Cenozoic]. I am interested in how changes in the strength of this feedback may determine the stability of the carbon cycle to perturbations through Earth history.
The silicate weathering feedback drives the recovery of the carbon cycle following a perturbation---a natural "thermostat." To illustrate, an increase in volcanic CO2 emissions and the subsequent bump in pCO2 drives chemical weathering of the continents. The chemical reaction results in an increase in the flux of aqueous weathering solutes (such as bicarbonate) that ultimately reaches the oceans as alkalinity, bumping up the saturation state of CaCO3 minerals. Greater CaCO3 precipitation and burial follows, drawing down atmospheric pCO2 on time scales of 10,000 to 100,000 years. This can be represented very generally as:
CaSiO3 + CO2 --> CaCO3 + SiO2 .
The strength of this feedback has varied through time, and is dependent on a combination of processes, including climate, tectonics, lithology, continental area, the physiochemical response of plants, and so on [Caves et al., 2016 and Ibarra et al., 2019; see figure below illustrating changes in the feedback strength through the Cenozoic]. I am interested in how changes in the strength of this feedback may determine the stability of the carbon cycle to perturbations through Earth history.
Caves et al., 2017 EPSL
On >1 Myr time scales, the carbon isotope record is our best archive of past carbon cycle variability. Oscillations of the carbon isotope record decrease in amplitude through the Phanerozoic [Bachan et al., 2017.; figure below]. In an extension of a carbon cycle model that I constructed for the Early Triassic [Lau et al., 2016], co-authors and I show that fluctuations in the depth of the oxygen minimum zone through time may modulate organic carbon burial and thus the carbon cycle. We show that the carbon isotopic composition of seawater is particularly sensitive to variations in parameters relating to organic carbon burial and phosphate burial on 1 to 10 Myr time scales. Sea-level change may be a factor that acts on these time scales, but its functional relationship with the oxygen minimum zone and drivers on these time scales remain unknown. I am interested in continuing to explore how sea-level change can influence the oxygen minimum zone.
Bachan et al., 2017 AJS
Relevant papers: Caves et al. (2016), Bachan et al. (2017), Ibarra et al. (2019), Nana Yobo et al. (2021), Isson et al. (2022), Kukla et al. (2023), Coogan et al. (2026), Hantsoo and Lau (2026)
astrobiology and nutrients on waterworld exoplanets
My research investigates the potential for seafloor weathering on water-covered rocky planets to produce sufficient levels of phosphorus to support a biosphere. Modeling work has discovered that the lithology of an exoplanets' oceanic crust is a crucial driver of P availability [Stone et al. (2025)].
Relevant paper: Stone et al. (2025)
Relevant paper: Stone et al. (2025)