ORCID Profile
0000-0003-2324-1619
Current Organisations
University of St Andrews
,
Blue Marble Space Institute of Science
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Publisher: Proceedings of the National Academy of Sciences
Date: 06-2020
Abstract: The inability to resolve the exact temporal relationship between two pivotal events in Earth history, the Paleoproterozoic Great Oxidation Event (GOE) and the first “snowball Earth” global glaciation, has precluded assessing causality between changing atmospheric composition and ancient climate change. Here we present temporally resolved quadruple sulfur isotope measurements (δ 34 S, ∆ 33 S, and ∆ 36 S) from the Paleoproterozoic Seidorechka and Polisarka Sedimentary Formations on the Fennoscandian Shield, northwest Russia, that address this issue. Sulfides in the former preserve evidence of mass-independent fractionation of sulfur isotopes (S-MIF) falling within uncertainty of the Archean reference array with a ∆ 36 S/∆ 33 S slope of −1.8 and have small negative ∆ 33 S values, whereas in the latter mass-dependent fractionation of sulfur isotopes (S-MDF) is evident, with a ∆ 36 S/∆ 33 S slope of −8.8. These trends, combined with geochronological constraints, place the S-MIF/S-MDF transition, the key indicator of the GOE, between 2,501.5 ± 1.7 Ma and 2,434 ± 6.6 Ma. These are the tightest temporal and stratigraphic constraints yet for the S-MIF/S-MDF transition and show that its timing in Fennoscandia is consistent with the S-MIF/S-MDF transition in North America and South Africa. Further, the glacigenic part of the Polisarka Formation occurs 60 m above the sedimentary succession containing S-MDF signals. Hence, our findings confirm unambiguously that the S-MIF/S-MDF transition preceded the Paleoproterozoic snowball Earth. Resolution of this temporal relationship constrains cause-and-effect drivers of Earth’s oxygenation, specifically ruling out conceptual models in which global glaciation precedes or causes the evolution of oxygenic photosynthesis.
Publisher: Springer Science and Business Media LLC
Date: 17-05-2021
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-05-2023
Abstract: The release of phosphorus (P) from crustal rocks during weathering plays a key role in determining the size of Earth’s biosphere, yet the concentration of P in crustal rocks over time remains controversial. Here, we combine spatial, temporal, and chemical measurements of preserved rocks to reconstruct the lithological and chemical evolution of Earth’s continental crust. We identify a threefold increase in average crustal P concentrations across the Neoproterozoic-Phanerozoic boundary (600 to 400 million years), showing that preferential biomass burial on shelves acted to progressively concentrate P within continental crust. Rapid compositional change was made possible by massive removal of ancient P-poor rock and deposition of young P-rich sediment during an episode of enhanced global erosion. Subsequent weathering of newly P-rich crust led to increased riverine P fluxes to the ocean. Our results suggest that global erosion coupled to sedimentary P-enrichment forged a markedly nutrient-rich crust at the dawn of the Phanerozoic.
Publisher: Wiley
Date: 18-06-2021
DOI: 10.1111/GBI.12459
Abstract: Due to their potential to support chemolithotrophic life, relic hydrothermal systems on Mars are a key target for astrobiological exploration. We analysed water and sediments at six geothermal pools from the rhyolitic Kerlingarfjöll and basaltic Kverkfjöll volcanoes in Iceland, to investigate the localised controls on the habitability of these systems in terms of microbial community function. Our results show that host lithology plays a minor role in pool geochemistry and authigenic mineralogy, with the system geochemistry primarily controlled by deep volcanic processes. We find that by dictating pool water pH and redox conditions, deep volcanic processes are the primary control on microbial community structure and function, with water input from the proximal glacier acting as a secondary control by regulating pool temperatures. Kerlingarfjöll pools have reduced, circum‐neutral CO 2 ‐rich waters with authigenic calcite‐, pyrite‐ and kaolinite‐bearing sediments. The dominant metabolisms inferred from community profiles obtained by 16S rRNA gene sequencing are methanogenesis, respiration of sulphate and sulphur (S 0 ) oxidation. In contrast, Kverkfjöll pools have oxidised, acidic (pH 3) waters with high concentrations of SO 4 2‐ and high argillic alteration, resulting in Al‐phyllosilicate‐rich sediments. The prevailing metabolisms here are iron oxidation, sulphur oxidation and nitrification. Where analogous ice‐fed hydrothermal systems existed on early Mars, similar volcanic processes would likely have controlled localised metabolic potential and thus habitability. Moreover, such systems offer several habitability advantages, including a localised source of metabolic redox pairs for chemolithotrophic microorganisms and accessible trace metals. Similar pools could have provided transient environments for life on Mars when paired with surface or near‐surface ice, these habitability niches could have persisted into the Amazonian. Additionally, they offer a confined site for biosignature formation and deposition that lends itself well to in situ robotic exploration.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United States of America
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Aubrey Zerkle.