A5030649466- Paleontology and Stratigraphy of Fossils
- Geochemistry and Elemental Analysis
- Hydrocarbon exploration and reservoir analysis
- Geochemistry and Geologic Mapping
- Geology and Paleoclimatology Research
- Geological and Geochemical Analysis
- Methane Hydrates and Related Phenomena
- Hydraulic Fracturing and Reservoir Analysis
- Microbial Community Ecology and Physiology
- Marine and coastal ecosystems
- Marine Biology and Ecology Research
- Geological and Geophysical Studies
- Isotope Analysis in Ecology
- Mineralogy and Gemology Studies
- Groundwater and Isotope Geochemistry
- Wastewater Treatment and Nitrogen Removal
- Aquatic Ecosystems and Phytoplankton Dynamics
- Offshore Engineering and Technologies
- Geological Studies and Exploration
- Heavy metals in environment
- Problem and Project Based Learning
- Chemical Analysis and Environmental Impact
- Silicon Effects in Agriculture
- Outdoor and Experiential Education
- Mercury impact and mitigation studies
University of Cape Town
2019-2025
University of Oxford
2018-2023
Science Oxford
2018
University of Otago
2016-2018
University College London
2014-2017
Rare earth elements and yttrium (REY) have a distinct distribution pattern in seawater, this may be faithfully preserved carbonate sediments rocks. Anomalous concentrations of redox-sensitive cerium (Ce) compared with neighbouring REY originate oxic water column conditions, as such, Ce anomalies can provide potentially useful redox proxy carbonate-dominated marine settings. The methods used to extract from carbonates vary widely, suffer widespread leaching accessory non-carbonate minerals...
We present 28 multiple sulfur isotope measurements of seawater sulfate (δ34SSO4 and Δ33SSO4) from the modern ocean over a range water depths sites along eastern margin Pacific Ocean. The average measured δ34SSO4 is 21.24‰ (±0.88‰,2σ) with calculated Δ33SSO4 +0.050‰ (±0.014‰,2σ). With these values, we use box-model to place constraints on gross fraction pyrite burial in sediments. This model presents an improvement previous estimates global flux because it does not rely assumed value...
The oceans at the start of Neoproterozoic Era (1,000-541 million years ago, Ma) were dominantly anoxic, but may have become progressively oxygenated, coincident with rise animal life. However, control that oxygen exerted on development early ecosystems remains unclear, as previous research has focussed identification fully anoxic or oxic conditions, rather than intermediate redox levels. Here we report anomalous cerium enrichments preserved in carbonate rocks across bathymetric basin...
Reef-building in metazoans represents an important ecological innovation whereby individuals collectively enhance feeding efficiency and gain protection from competitors predation. The appearance of metazoan reefs the fossil record therefore indicates adaptive response to complex pressures. In Nama Group, Namibia, we found evidence reef-building by earliest known skeletal metazoan, globally distributed Cloudina, ~548 million years ago. These Cloudina formed open frameworks without a...
Abstract Prebiotic systems chemistry suggests that high phosphate concentrations were necessary to synthesise molecular building blocks and sustain primitive cellular systems. However, current understanding of mineral solubility predicts negligible for most natural waters, yet the role Fe 2+ , ubiquitous on early Earth, is poorly quantified. Here we determine Fe(II)-phosphate in synthetic seawater as a function pH ionic strength, integrate these observations into thermodynamic model across...
The geological timescale before 720 Ma uses rounded absolute ages rather than specific events recorded in rocks to subdivide time. This has led increasingly mismatches between subdivisions and the features for which they were named. Here we review formal processes that current timescale, outline rock-based concepts could be used pre-Cryogenian time propose revisions. An appraisal of Precambrian rock record confirms purely chronostratigraphic subdivision would require only modest deviation...
Abstract Chert is abundant in Archean and Paleoproterozoic rocks commonly densely packed with authigenic Fe(II)-silicate nanoparticles such as greenalite, indicating a close relationship between iron silica deposition. We investigate the minerals dissolved during precipitation, settling, diagenesis using anoxic synthesis, sorption, heating experiments. Excess associated solid resulting high molar Si/Fe ratios (<1.52) that exceed of stoichiometric greenalite (0.67). At pH 8–8.5, sorbs...
<title>Abstract</title> Metals are required by all life to build metalloproteins, but the metal preferences of dominant microbes have evolved over geological time. Consistent with this, experiments and models predict that availability in anoxic seawater during Archean Proterozoic eons (4.0–0.541 billion years ago) would been radically different today. Corroborating this record is challenging because bulk rock geochemistry reflects complex histories. Here we take a novel approach, determining...
Enhanced rock weathering is a promising carbon dioxide removal (CDR) technology that involves the dissolution of silicate minerals (e.g., wollastonite). This process releases elements such as calcium, which can remain in solution and be charge balanced by bicarbonate, or stored pedogenic carbonate on soil exchange sites. To verify credits, robust monitoring, reporting, verification (MRV) approaches are essential. In this study, we explore total cation accounting (TCA) novel method for MRV....
Enhanced weathering (EW) of silicate minerals on agricultural fields is a promising natural carbon dioxide removal (CDR) method that has potential co-benefits for soil health and crop safety. However, the scalability EW suffering from labor-intense requirements pore water extraction monitoring, reporting verification (MRV) credits. Furthermore, in-field MRV can be challenging as existing methods, such rhizon samplers or ceramic suction cups, may lose vacuum ineffective at low moisture...
Enhanced weathering (EW) is cited as a promising carbon dioxide removal (CDR) strategy, and being rapidly commercialized. Rigorous monitoring, reporting verification (MRV) are essential to ensure claims accurate credits not mis-sold. MRV protocols incorporate multiple approaches, including soil porewater sampling. This paper calculates potential CDR from porewater, via an alkalinity estimation calculated charge balance, samples, the accumulation of exchangeable cations on exchange sites....
Abstract Persistently low atmospheric oxygen requires that net organic carbon burial was muted through much of Earth’s middle age. In order to achieve global mass balance with respect O2, recent models have suggested redox-dependent mechanisms, such as Fe(II)-phosphate precipitation, limited phosphate availability in dominantly anoxic and ferruginous oceans, turn limiting primary production, therefore burial. Nevertheless, observational constraints on phosphorus cycling Proterozoic systems...
Abstract The spread of marine anoxia is believed to have played a key role in the development SPICE (Steptoean Positive Carbon Isotope Excursion) event and end-Marjuman extinction late Cambrian (~497.5 m.y. ago), but their cause-and-effect relationship poorly constrained. Here we present an integrated analysis carbonate δ13C, cerium anomalies (Ce/Ce*), genus-level diversity data trilobites from North China Platform. Our results show tightly coupled changes between SPICE, increase Ce/Ce*,...
Abstract Namacalathus hermanastes is one of the oldest known skeletal metazoans, found in carbonate settings terminal Ediacaran (~550–541 million years ago [Ma]). The palaeoecology this widespread, goblet‐shaped, benthic organism poorly constrained yet critical for understanding dynamics earliest metazoan communities. Analysis situ assemblages from Nama Group, Namibia (~548–541 Ma), shows that exhibited size variation response to differing water depths, hydrodynamic conditions and substrate...
Iron formations (IF) were widely deposited in the Archean Eon and Palaeoproterozoic Era hold potential as an archive of marine biogeochemistry. However, reconstructions are challenging due to their fine-grained nature complex mineralogy. Recent work has identified greenalite, Fe(II)-silicate mineral, abundant, primary phase IF. Several depositional mechanisms have been proposed for greenalite precipitation, spanning hydrothermal vent systems shelf environments. We report new situ rare earth...