ORCID Profile
0000-0001-7621-189X
Current Organisation
University of Leeds
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Publisher: Research Square Platform LLC
Date: 23-09-2022
DOI: 10.21203/RS.3.RS-2084887/V1
Abstract: The Permian–Triassic Mass Extinction (PTME), life’s most severe crisis1, has been attributed to intense global warming triggered by CO2 emissions from Large Igneous Province volcanism2–8. It remains unclear, however, why super-greenhouse conditions persisted for around five million years after the volcanic episode, when Earth system feedbacks should have returned temperatures to pre-extinction levels within a few hundred thousand years8. Here we use fossil occurrences and lithological indicators of climate to reconstruct spatio-temporal maps of plant productivity and biomass changes through the Permian–Triassic and undertake climate-biogeochemical modelling to investigate the unusual longevity and intensity of warming. Our reconstructions show that terrestrial vegetation collapse during the PTME, especially in tropical regions, resulted in an Earth system with low levels of organic carbon sequestration and chemical weathering, leading to limited drawdown of greenhouse gases. This led to a protracted period of extremely high surface temperatures, during which biotic recovery was delayed for millions of years. Our results support the idea that thresholds exist in the climate-carbon system beyond which warming may be lified substantially.
Publisher: Elsevier BV
Date: 04-2017
Publisher: Informa UK Limited
Date: 09-02-2019
DOI: 10.1080/01635581.2018.1542011
Abstract: Combination gemcitabine and nab-paclitaxel (Gem-Nab-P) is a common regimen used to treat metastatic pancreatic ductal adenocarcinoma (PDAC). Toxicity from this regimen is associated with significant morbidity. Currently, Gem-Nab-P is dosed using estimated body surface area, derived from height and weight. This study investigates whether skeletal muscle assessment could be a useful tool in the dosing of Gem-Nab-P in metastatic PDAC. This study included 52 patients who had received first-line treatment with Gem-Nab-P for PDAC. Demographic and chemotherapy treatment information was gathered from medical records and body composition analysis was performed using single slice computed tomography methods, at spinal level L3. Patients who experienced first-cycle chemotherapy-associated toxicity did not have a different median skeletal muscle area (SkMA) to those who did not (128.6 cm
Publisher: Springer Science and Business Media LLC
Date: 31-05-2023
Publisher: Elsevier BV
Date: 10-2018
Publisher: American Association for the Advancement of Science (AAAS)
Date: 14-10-2022
Abstract: Mapping the history of atmospheric O 2 during the late Precambrian is vital for evaluating potential links to animal evolution. Ancient O 2 levels are often inferred from geochemical analyses of marine sediments, leading to the assumption that the Earth experienced a stepwise increase in atmospheric O 2 during the Neoproterozoic. However, the nature of this hypothesized oxygenation event remains unknown, with suggestions of a more dynamic O 2 history in the oceans and major uncertainty over any direct connection between the marine realm and atmospheric O 2 . Here, we present a continuous quantitative reconstruction of atmospheric O 2 over the past 1.5 billion years using an isotope mass balance approach that combines bulk geochemistry and tectonic recycling rate calculations. We predict that atmospheric O 2 levels during the Neoproterozoic oscillated between ~1 and ~50% of the present atmospheric level. We conclude that there was no simple unidirectional rise in atmospheric O 2 during the Neoproterozoic, and the first animals evolved against a backdrop of extreme O 2 variability.
Publisher: Copernicus GmbH
Date: 16-07-2012
Abstract: Abstract. In this study, we investigate phosphorus (P) and iron (Fe) cycling in sediments along a depth transect from within to well below the oxygen minimum zone (OMZ) in the northern Arabian Sea (Murray Ridge). Pore-water and solid-phase analyses show that authigenic formation of calcium phosphate minerals (Ca-P) is largely restricted to where the OMZ intersects the seafloor topography, likely due to higher depositional fluxes of reactive P. Nonetheless, increased ratios of organic carbon to organic P (Corg/Porg) and to total reactive P (Corg/Preactive) in surface sediments indicate that the overall burial efficiency of P relative to Corg decreases under the low bottom water oxygen concentrations (BWO) in the OMZ. The relatively constant Fe/Al ratio in surface sediments along the depth transect suggest that corresponding changes in Fe burial are limited. Sedimentary pyrite contents are low throughout the ~25 cm sediment cores at most stations, as commonly observed in the Arabian Sea OMZ. However, pyrite is an important sink for reactive Fe at one station in the OMZ. A reactive transport model (RTM) was applied to quantitatively investigate P and Fe diagenesis at an intermediate station at the lower boundary of the OMZ (bottom water O2: ~14 μmol L−1). The RTM results contrast with earlier findings in showing that Fe redox cycling can control authigenic apatite formation and P burial in Arabian Sea sediment. In addition, results suggest that a large fraction of the sedimentary Ca-P is not authigenic, but is instead deposited from the water column and buried. Dust is likely a major source of this Ca-P. Inclusion of the unreactive Ca-P pool in the Corg/P ratio leads to an overestimation of the burial efficiency of reactive P relative to Corg along the depth transect. Moreover, the unreactive Ca-P accounts for ~85% of total Ca-P burial. In general, our results reveal large differences in P and Fe chemistry between stations in the OMZ, indicating dynamic sedimentary conditions under these oxygen-depleted waters.
Publisher: Elsevier BV
Date: 09-2017
Publisher: American Journal of Science (AJS)
Date: 26-08-2016
DOI: 10.2475/07.2016.03
Publisher: Elsevier BV
Date: 09-2023
Publisher: Springer Science and Business Media LLC
Date: 20-10-2023
Publisher: Elsevier BV
Date: 2023
Publisher: Geological Society of London
Date: 07-07-2021
DOI: 10.1144/JGS2020-222
Publisher: Elsevier BV
Date: 08-2015
Publisher: European Association of Geochemistry
Date: 03-2018
Publisher: American Association for the Advancement of Science (AAAS)
Date: 25-08-2023
Abstract: The body fossil and biomarker records hint at an increase in biotic complexity between the two Cryogenian Snowball Earth episodes (ca. 661 million to ≤650 million years ago). Oxygen and nutrient availability can promote biotic complexity, but nutrient (particularly phosphorus) and redox dynamics across this interval remain poorly understood. Here, we present high-resolution paleoredox and phosphorus phase association data from multiple globally distributed drill core records through the non-glacial interval. These data are first correlated regionally by litho- and chemostratigraphy, and then calibrated within a series of global chronostratigraphic frameworks. The combined data show that regional differences in postglacial redox stabilization were partly controlled by the intensity of phosphorus recycling from marine sediments. The apparent increase in biotic complexity followed a global transition to more stable and less reducing conditions in shallow to mid-depth marine environments and occurred within a tolerable climatic window during progressive cooling after post-Snowball super-greenhouse conditions.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Simon Poulton.