John M McArthur | University College London (original) (raw)
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Papers by John M McArthur
Encyclopedia of Mathematical Geosciences, 2020
Environmental Science & Technology, 2018
Newsletters on Stratigraphy
At Peniche, Portugal, the GSSP for the base of the Toarcian and in a Submediterranean province, a... more At Peniche, Portugal, the GSSP for the base of the Toarcian and in a Submediterranean province, a value of 0.707 073 ± 0.000 002 (2s.e., n = 13) is determined for 87Sr/86Sr at the base of the Toarcian. In Yorkshire, UK, a Subboreal province, the base of the Toarcian has an 87Sr/86Sr value of0.707 072 ± 0.000 002 (2s.e., n = 23). The similarity of the values shows that, within analytical uncertainty, these levels are exactly equivalent in time. At Peniche, the base of the Serpentinum (Falciferum/Levisoni) Chronozone has an 87Sr/86Sr value of 0.707 096 ± 0.000 003 (2.s.e). The value for this boundary in Yorkshire is 0.707 094 ± 0.000 002 (2s.e., n = 27). The similarity of the values shows that, within analytical uncertainty, these levels are exactly equivalent in time. The same ammonite successions occur through the lowermost Toarcian successions at Peniche and in Yorkshire. Between Peniche and Yorkshire, there is therefore an exact coincidence, within measurement uncertainty, between the Lower Toarcian, Tethyan Realm, Tenuicostatum (Polymorphum) [ammonite] Chronozone of Peniche and the Lower Toarcian, Boreal Realm, Tenuicostatum [ammonite] Chronozone of Yorkshire. The 87Sr/86Sr profile through the Tenuicostatum Subchronozone at Peniche reveals large variations in sedimentation rate, with lowest rates in a condensed basal 3 m of the zone, highest rates in mid-zone, with rates decreasing upward through the upper half of the zone. Apportioning time in proportion to 87Sr/86Sr shows that around half of Tenuicostatum time is condensed into the basal 3 m of the section.
The Journal of Geology, 2016
Water Resources Research, 2001
Quaternary Science Reviews, 2009
... 23 ka and its shoreline was relatively stable in spite of rapid early Holocene ... Yet the i... more ... 23 ka and its shoreline was relatively stable in spite of rapid early Holocene ... Yet the increased accommodation space, created by rising sea level, was rapidly filled up by enormous ... Using the available and new radiocarbon dates, published sea-level data along the Indian east ...
Hydrogeology Journal, 2014
Hydrogeology Journal, 2014
Environmental Science & Technology, 2008
Earth and Planetary Science Letters, 1998
Applied Geochemistry, 2000
Arsenic exposure and …, 2001
... 12. Model of how arsenic pollution occurs in the Bengal Basin, and in any sedimentary sequenc... more ... 12. Model of how arsenic pollution occurs in the Bengal Basin, and in any sedimentary sequence host-ing buried swampland and marsh. In shallow Bangladesh sequences, hydraulic gradients cause down-ward movement of water. ...
Environmental Science & Technology, 2015
Case Studies in Isotope Stratigraphy, 2019
The ages of carbonate rocks can be determined by comparing their 87Sr/86Sr ratios with the well-e... more The ages of carbonate rocks can be determined by comparing their 87Sr/86Sr ratios with the well-established seawater 87Sr/86Sr curve. Current models and databases provide no explicit solution to the problem of accurately assigning uncertainties to derived ages when the 87Sr/86Sr ratios of carbonate rocks contain analytical uncertainties. This is particularly concerning as significant amount of 87Sr/86Sr ratios are being measured by multi-collector inductively-coupled-plasma mass-spectrometry (MC-ICP-MS) which typically has a lower precision (1σ is typically several tens of ppm) compared with thermo-ionization mass-spectrometry (TIMs, 1σ can be as low as several ppm) used for calibrating the seawater 87Sr/86Sr curve. Deriving ages from carbonate 87Sr/86Sr ratios with large analytical uncertainties could introduce significant, sometimes asymmetric uncertainties in age estimates following a non-Gaussian distribution. More importantly, uncertainties in age estimates around the local max...
In Bangladesh, concentrations of boron in groundwater reach 2.1 mgL and are high regionally in al... more In Bangladesh, concentrations of boron in groundwater reach 2.1 mgL and are high regionally in alluvial aquifers of Late Pleistocene/Holocene age. Concentrations exceed 0.5 mgL 1 across approximately 6700 km of the deep aquifer (>150 m depth) and 3000 km of the shallow aquifer (<150 m depth). In the Carboniferous sandstone and shale aquifers in Ingham County, Michigan, concentrations reach 6.1 mgL 1 and high values are widespread in the NE of the county. These concentrations exceed the regulatory guideline values for human consumption of 0.5 mgL 1 (WHO) or 0.9 mgL 1 (USA). The boron has desorbed from mineral surfaces as freshwater flushing displaces saline waters from the aquifers. In Bangladesh, desorption is driven by decreasing ionic strength, the equilibrium re-adjustment of mineral sorption sites to the low boron concentration in freshwater, and competitive exchange with HCO3/CO3. In deep Bangladesh aquifers in Barisal District (>250 m deep), boron enrichment delineate...
Encyclopedia of Mathematical Geosciences, 2020
Environmental Science & Technology, 2018
Newsletters on Stratigraphy
At Peniche, Portugal, the GSSP for the base of the Toarcian and in a Submediterranean province, a... more At Peniche, Portugal, the GSSP for the base of the Toarcian and in a Submediterranean province, a value of 0.707 073 ± 0.000 002 (2s.e., n = 13) is determined for 87Sr/86Sr at the base of the Toarcian. In Yorkshire, UK, a Subboreal province, the base of the Toarcian has an 87Sr/86Sr value of0.707 072 ± 0.000 002 (2s.e., n = 23). The similarity of the values shows that, within analytical uncertainty, these levels are exactly equivalent in time. At Peniche, the base of the Serpentinum (Falciferum/Levisoni) Chronozone has an 87Sr/86Sr value of 0.707 096 ± 0.000 003 (2.s.e). The value for this boundary in Yorkshire is 0.707 094 ± 0.000 002 (2s.e., n = 27). The similarity of the values shows that, within analytical uncertainty, these levels are exactly equivalent in time. The same ammonite successions occur through the lowermost Toarcian successions at Peniche and in Yorkshire. Between Peniche and Yorkshire, there is therefore an exact coincidence, within measurement uncertainty, between the Lower Toarcian, Tethyan Realm, Tenuicostatum (Polymorphum) [ammonite] Chronozone of Peniche and the Lower Toarcian, Boreal Realm, Tenuicostatum [ammonite] Chronozone of Yorkshire. The 87Sr/86Sr profile through the Tenuicostatum Subchronozone at Peniche reveals large variations in sedimentation rate, with lowest rates in a condensed basal 3 m of the zone, highest rates in mid-zone, with rates decreasing upward through the upper half of the zone. Apportioning time in proportion to 87Sr/86Sr shows that around half of Tenuicostatum time is condensed into the basal 3 m of the section.
The Journal of Geology, 2016
Water Resources Research, 2001
Quaternary Science Reviews, 2009
... 23 ka and its shoreline was relatively stable in spite of rapid early Holocene ... Yet the i... more ... 23 ka and its shoreline was relatively stable in spite of rapid early Holocene ... Yet the increased accommodation space, created by rising sea level, was rapidly filled up by enormous ... Using the available and new radiocarbon dates, published sea-level data along the Indian east ...
Hydrogeology Journal, 2014
Hydrogeology Journal, 2014
Environmental Science & Technology, 2008
Earth and Planetary Science Letters, 1998
Applied Geochemistry, 2000
Arsenic exposure and …, 2001
... 12. Model of how arsenic pollution occurs in the Bengal Basin, and in any sedimentary sequenc... more ... 12. Model of how arsenic pollution occurs in the Bengal Basin, and in any sedimentary sequence host-ing buried swampland and marsh. In shallow Bangladesh sequences, hydraulic gradients cause down-ward movement of water. ...
Environmental Science & Technology, 2015
Case Studies in Isotope Stratigraphy, 2019
The ages of carbonate rocks can be determined by comparing their 87Sr/86Sr ratios with the well-e... more The ages of carbonate rocks can be determined by comparing their 87Sr/86Sr ratios with the well-established seawater 87Sr/86Sr curve. Current models and databases provide no explicit solution to the problem of accurately assigning uncertainties to derived ages when the 87Sr/86Sr ratios of carbonate rocks contain analytical uncertainties. This is particularly concerning as significant amount of 87Sr/86Sr ratios are being measured by multi-collector inductively-coupled-plasma mass-spectrometry (MC-ICP-MS) which typically has a lower precision (1σ is typically several tens of ppm) compared with thermo-ionization mass-spectrometry (TIMs, 1σ can be as low as several ppm) used for calibrating the seawater 87Sr/86Sr curve. Deriving ages from carbonate 87Sr/86Sr ratios with large analytical uncertainties could introduce significant, sometimes asymmetric uncertainties in age estimates following a non-Gaussian distribution. More importantly, uncertainties in age estimates around the local max...
In Bangladesh, concentrations of boron in groundwater reach 2.1 mgL and are high regionally in al... more In Bangladesh, concentrations of boron in groundwater reach 2.1 mgL and are high regionally in alluvial aquifers of Late Pleistocene/Holocene age. Concentrations exceed 0.5 mgL 1 across approximately 6700 km of the deep aquifer (>150 m depth) and 3000 km of the shallow aquifer (<150 m depth). In the Carboniferous sandstone and shale aquifers in Ingham County, Michigan, concentrations reach 6.1 mgL 1 and high values are widespread in the NE of the county. These concentrations exceed the regulatory guideline values for human consumption of 0.5 mgL 1 (WHO) or 0.9 mgL 1 (USA). The boron has desorbed from mineral surfaces as freshwater flushing displaces saline waters from the aquifers. In Bangladesh, desorption is driven by decreasing ionic strength, the equilibrium re-adjustment of mineral sorption sites to the low boron concentration in freshwater, and competitive exchange with HCO3/CO3. In deep Bangladesh aquifers in Barisal District (>250 m deep), boron enrichment delineate...