Caleb Bishop - Academia.edu (original) (raw)
Papers by Caleb Bishop
The Tonian was a remarkable period in Earth's history, experiencing dramatic changes in the Earth... more The Tonian was a remarkable period in Earth's history, experiencing dramatic changes in the Earth system that resulted in a series of global climatic catastrophes, ultimately leading to marked changes in the biosphere. The break-up of the supercontinent Rodinia is thought to have had a profound impact on the Earth system during the Tonian, ultimately resulting in the ~58 million-year deep freeze of the Sturtian glaciation. Increased continental margins and the weathering of vast continental flood basalts, promoting high levels of primary productivity, were large players in the drawdown of atmospheric CO2, the chemical implications of which resonate through Tonian ocean chemistry. The laterally extensive Skillogalee and Myrtle Springs Formations, within the Burra Group sediments of South Australia, span a pre-Sturtian carbonate succession that offer further insights into late Tonian paleo-environments. High resolution geochemical trends throughout the Skillogalee and Myrtle Springs Formations display evidence of a shift from a restricted to a more open marine setting, that was met with a flux of hydrothermally influenced waters. A hydrothermal flux through underlying basalts likely accounts for the enigmatic widespread deposition of sedimentary magnesites throughout the Skillogalee Formation. The longevity and regional reproducibility of significant europium anomalies suggests that a mafic mantle flux endured throughout Burra Group sedimentation. Cerium anomalies, supported by Zn/Fe ratios, evince open marine seawaters were largely dysoxic throughout the late Tonian, constraining Neoproterozoic oxygenation to post-Sturtian. Neodymium isotopes in Burra Group marine waters display a rise towards primitive endmembers, reflecting a mafic weathering flux, induced, no doubt, by the break-up of Rodinia. High levels of organic carbon burial are coupled with pronounced mafic weathering, detailing a mass drawdown of CO2 throughout Burra Group sedimentation during the late Tonian, hereby also holding important ramifications for the instatement of the Cryogenian glaciations. iii
Computers & Geosciences, 2019
After the embargo period via non-commercial hosting platforms such as their institutional repos... more After the embargo period via non-commercial hosting platforms such as their institutional repository via commercial sites with which Elsevier has an agreement In all cases accepted manuscripts should: link to the formal publication via its DOI bear a CC-BY-NC-ND licensethis is easy to do if aggregated with other manuscripts, for example in a repository or other site, be shared in
Goldschmidt2022 abstracts, 2022
Fossilized lipids offer one of only few windows into ancient ecosystems. The utility of such biom... more Fossilized lipids offer one of only few windows into ancient ecosystems. The utility of such biomarkers is determined by the phylogenetic distribution of lipid biosynthetic capabilities in extant organisms and extrapolation of this information into the past. 2-Methylhopanes in sedimentary rocks were once used to infer the importance of Cyanobacteria as primary producers in the geological past. However, the discovery of the hopanoid C-2 methyltransferase (HpnP) in Alphaproteobacteria led to the downfall of this molecular proxy. In the present study, we re-examined the distribution of HpnP in a new phylogenetic framework including novel candidate phyla, and re-interpreted a revised geological record of 2-methylhopanes based on contamination-free samples. We show that HpnP was likely present in the last common ancestor of Cyanobacteria, while the gene appeared in Alphaproteobacteria only around 750 million years ago. A subsequent rise of sedimentary 2-methylhopanes around 600 Ma likely...
Global major element geochemical data for igneous and sedimentary rocks. This dataset is used to ... more Global major element geochemical data for igneous and sedimentary rocks. This dataset is used to train via machine learning a classifier for igneous and sedimentary protoliths. It contains the major element chemistry, ilr transformed chemistry, rock type, protolith class, and reference to the original data. Codes to train a protolith classifier and analyze the results are found in the GitHub repository github.com/dhasterok/global_geochemistry/
Goldschmidt Abstracts, 2020
The Tonian was a remarkable period in Earth's history, experiencing dramatic changes in the Earth... more The Tonian was a remarkable period in Earth's history, experiencing dramatic changes in the Earth system that resulted in a series of global climatic catastrophes, ultimately leading to marked changes in the biosphere. The break-up of the supercontinent Rodinia is thought to have had a profound impact on the Earth system during the Tonian, ultimately resulting in the ~58 million-year deep freeze of the Sturtian glaciation. Increased continental margins and the weathering of vast continental flood basalts, promoting high levels of primary productivity, were large players in the drawdown of atmospheric CO2, the chemical implications of which resonate through Tonian ocean chemistry. The laterally extensive Skillogalee and Myrtle Springs Formations, within the Burra Group sediments of South Australia, span a pre-Sturtian carbonate succession that offer further insights into late Tonian paleo-environments. High resolution geochemical trends throughout the Skillogalee and Myrtle Springs Formations display evidence of a shift from a restricted to a more open marine setting, that was met with a flux of hydrothermally influenced waters. A hydrothermal flux through underlying basalts likely accounts for the enigmatic widespread deposition of sedimentary magnesites throughout the Skillogalee Formation. The longevity and regional reproducibility of significant europium anomalies suggests that a mafic mantle flux endured throughout Burra Group sedimentation. Cerium anomalies, supported by Zn/Fe ratios, evince open marine seawaters were largely dysoxic throughout the late Tonian, constraining Neoproterozoic oxygenation to post-Sturtian. Neodymium isotopes in Burra Group marine waters display a rise towards primitive endmembers, reflecting a mafic weathering flux, induced, no doubt, by the break-up of Rodinia. High levels of organic carbon burial are coupled with pronounced mafic weathering, detailing a mass drawdown of CO2 throughout Burra Group sedimentation during the late Tonian, hereby also holding important ramifications for the instatement of the Cryogenian glaciations. iii
Computers & Geosciences, 2019
After the embargo period via non-commercial hosting platforms such as their institutional repos... more After the embargo period via non-commercial hosting platforms such as their institutional repository via commercial sites with which Elsevier has an agreement In all cases accepted manuscripts should: link to the formal publication via its DOI bear a CC-BY-NC-ND licensethis is easy to do if aggregated with other manuscripts, for example in a repository or other site, be shared in
Goldschmidt2022 abstracts, 2022
Fossilized lipids offer one of only few windows into ancient ecosystems. The utility of such biom... more Fossilized lipids offer one of only few windows into ancient ecosystems. The utility of such biomarkers is determined by the phylogenetic distribution of lipid biosynthetic capabilities in extant organisms and extrapolation of this information into the past. 2-Methylhopanes in sedimentary rocks were once used to infer the importance of Cyanobacteria as primary producers in the geological past. However, the discovery of the hopanoid C-2 methyltransferase (HpnP) in Alphaproteobacteria led to the downfall of this molecular proxy. In the present study, we re-examined the distribution of HpnP in a new phylogenetic framework including novel candidate phyla, and re-interpreted a revised geological record of 2-methylhopanes based on contamination-free samples. We show that HpnP was likely present in the last common ancestor of Cyanobacteria, while the gene appeared in Alphaproteobacteria only around 750 million years ago. A subsequent rise of sedimentary 2-methylhopanes around 600 Ma likely...
Global major element geochemical data for igneous and sedimentary rocks. This dataset is used to ... more Global major element geochemical data for igneous and sedimentary rocks. This dataset is used to train via machine learning a classifier for igneous and sedimentary protoliths. It contains the major element chemistry, ilr transformed chemistry, rock type, protolith class, and reference to the original data. Codes to train a protolith classifier and analyze the results are found in the GitHub repository github.com/dhasterok/global_geochemistry/
Goldschmidt Abstracts, 2020