John A. Higgins
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View article: Magnesium (Mg∕Ca, <i>δ</i> <sup>26</sup> Mg), boron (B∕Ca, <i>δ</i> <sup>11</sup> B), and calcium (Ca <sup>2+</sup> ) geochemistry of <i>Arctica islandica</i> and <i>Crassostrea virginica</i> extrapallial fluid and shell under ocean acidification
Magnesium (Mg∕Ca, <i>δ</i> <sup>26</sup> Mg), boron (B∕Ca, <i>δ</i> <sup>11</sup> B), and calcium (Ca <sup>2+</sup> ) geochemistry of <i>Arctica islandica</i> and <i>Crassostrea virginica</i> extrapallial fluid and shell under ocean acidification Open
The geochemistry of biogenic carbonates has long been used as proxies to record changing seawater parameters. However, the effect of ocean acidification (OA) on seawater chemistry and organism physiology could impact isotopic signatures an…
View article: 81Kr dating of 1 kg Antarctic ice
81Kr dating of 1 kg Antarctic ice Open
Recovering earth's climate history from ice cores requires reliable dating of the ice. 81Kr is ideal for radiometric dating up to more than one million years, but the isotope is so rare that it has long been a challenge to apply…
View article: Calcium isotope constraints on Mesoarchean seawater
Calcium isotope constraints on Mesoarchean seawater Open
The cause of the Great Oxidation Event ~2.4 billion-years-ago (Ga) is hotly debated. Recent models favor the emergence of continents as driving the event. However, we suggest that extensive shallow-marine carbonate platforms existed in the…
View article: Global ocean heat content over the past 3 million years
Global ocean heat content over the past 3 million years Open
The Pleistocene Epoch is characterized by global cooling and an increase in the intensity and duration of glacial cycles. Regional surface and subsurface ocean temperature records follow distinct trends over this interval, suggesting dynam…
View article: Ice cores from the Allan Hills, Antarctica show relatively stable atmospheric CO2 and CH4 levels over the last 3 million years
Ice cores from the Allan Hills, Antarctica show relatively stable atmospheric CO2 and CH4 levels over the last 3 million years Open
The role greenhouse gases play in the evolution of Earth's climate over the last 3 million years is uncertain beyond the continuous ice core record (800,000 years). Here, we present new snapshots of carbon dioxide (CO2) and meth…
View article: Kinetic Modeling of In Vivo K+ Distribution and Fluxes with Stable K+ Isotopes: Effects of Dietary K+ Restriction
Kinetic Modeling of In Vivo K+ Distribution and Fluxes with Stable K+ Isotopes: Effects of Dietary K+ Restriction Open
Maintaining extracellular potassium (K+) within narrow limits, critical for membrane potential and excitability, is accomplished through the internal redistribution of K+ between extracellular fluid (ECF) and intracellular fluid (ICF) in c…
View article: Magnesium (Mg/Ca, δ <sup>26</sup> Mg), boron (B/Ca, δ <sup>11</sup> B), and calcium ([Ca <sup>2+</sup> ]) geochemistry of Arctica islandica and Crassostrea virginica extrapallial fluid and shell under ocean acidification
Magnesium (Mg/Ca, δ <sup>26</sup> Mg), boron (B/Ca, δ <sup>11</sup> B), and calcium ([Ca <sup>2+</sup> ]) geochemistry of Arctica islandica and Crassostrea virginica extrapallial fluid and shell under ocean acidification Open
The geochemistry of biogenic carbonates has long been used as proxies to record changing seawater parameters. However, the effect of ocean acidification on seawater chemistry and organism physiology could impact isotopic signatures and how…
View article: Variability in strontium and lithium composition of ancient seawater from fluid inclusions in halite&#8212;implications for reconstructing drivers of seawater secular variability
Variability in strontium and lithium composition of ancient seawater from fluid inclusions in halite—implications for reconstructing drivers of seawater secular variability Open
Secular variations in the major ion chemistry and isotopic composition of seawater on multimillion-year time scales over the Phanerozoic are well documented, but the causes of these changes are debated. δ7Li and 87Sr/86Sr are widely u…
View article: Late Pliocene and Early Pleistocene CO2 and CH4 from ice cores from the Allan Hills, Antarctica
Late Pliocene and Early Pleistocene CO2 and CH4 from ice cores from the Allan Hills, Antarctica Open
Currently, chronologically discontinuous ice cores from the Allan Hills Blue Ice Area (BIA), Antarctica, are our only direct insight into the atmospheric composition of periods beyond the continuous ice core record (800 ka BP). An accurate…
View article: Chloroplast magnesium transporters play essential but differential roles in maintaining magnesium homeostasis
Chloroplast magnesium transporters play essential but differential roles in maintaining magnesium homeostasis Open
Magnesium (Mg 2+ ) is essential for photosynthesis in the chloroplasts of land plants and algae. Being the central ion of chlorophyll, cofactor and activator of many photosynthetic enzymes including RuBisCO, magnesium-deficient plants may …
View article: Mapping UV radiation in the East Antarctic sea ice zone
Mapping UV radiation in the East Antarctic sea ice zone Open
Ozone depletion has been a well-researched phenomenon since its discovery in the early 1980s. It is now scientifically accepted that if all other factors (cloudiness, turbidity, surface albedo, etc.) remain the same, decreases in stratosph…
View article: Primary evidence for redox cycling in 2.8-billion-year-old microbialites
Primary evidence for redox cycling in 2.8-billion-year-old microbialites Open
View article: Formation and diagenetic alteration of Bahamian carbonate mud found in deep-water settings using clumped isotope analyses
Formation and diagenetic alteration of Bahamian carbonate mud found in deep-water settings using clumped isotope analyses Open
View article: Reconstructing the secular evolution of lithium isotope composition of seawater from marine halite
Reconstructing the secular evolution of lithium isotope composition of seawater from marine halite Open
The lithium isotopic composition of seawater (δ 7 Li SW ) has emerged as a promising tracer for reconstructing global terrestrial silicate weathering and marine reverse weathering.While chemical weathering plays an important role acting as…
View article: Stable potassium isotopes (41K/39K) track transcellular and paracellular potassium transport in biological systems
Stable potassium isotopes (41K/39K) track transcellular and paracellular potassium transport in biological systems Open
As the most abundant cation in archaeal, bacterial, and eukaryotic cells, potassium (K + ) is an essential element for life. While much is known about the machinery of transcellular and paracellular K transport–channels, pumps, co-transpor…
View article: The origin of carbonate mud and implications for global climate
The origin of carbonate mud and implications for global climate Open
Carbonate mud represents one of the most important geochemical archives for reconstructing ancient climatic, environmental, and evolutionary change from the rock record. Mud also represents a major sink in the global carbon cycle. Yet, the…
View article: Estimating in vivo potassium distribution and fluxes with stable potassium isotopes
Estimating in vivo potassium distribution and fluxes with stable potassium isotopes Open
Extracellular potassium (K + ) homeostasis is achieved by a concerted effort of multiple organs and tissues. A limitation in studies of K + homeostasis is inadequate techniques to quantify K + fluxes into and out of organs and tissues in v…
View article: Ice core evidence for atmospheric oxygen decline since the Mid-Pleistocene transition
Ice core evidence for atmospheric oxygen decline since the Mid-Pleistocene transition Open
The 1.5-million-year-old Antarctic ice indicates a balanced atmospheric oxygen budget before the Mid-Pleistocene Transition.
View article: Enhanced moisture delivery into Victoria Land, East Antarctica, during the early Last Interglacial: implications for West Antarctic Ice Sheet stability
Enhanced moisture delivery into Victoria Land, East Antarctica, during the early Last Interglacial: implications for West Antarctic Ice Sheet stability Open
The S27 ice core, drilled in the Allan Hills Blue Ice Area of East Antarctica, is located in southern Victoria Land, ∼80 km away from the present-day northern edge of the Ross Ice Shelf. Here, we utilize the reconstructed accumulation rate…
View article: The Ca and Mg isotope record of the Cryogenian Trezona carbon isotope excursion
The Ca and Mg isotope record of the Cryogenian Trezona carbon isotope excursion Open
View article: Small calcium isotope fractionation at slow precipitation rates in methane seep authigenic carbonates
Small calcium isotope fractionation at slow precipitation rates in methane seep authigenic carbonates Open
View article: Groundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba
Groundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba Open
Groundwater-derived solute fluxes to the ocean have long been assumed static and subordinate to riverine fluxes, if not neglected entirely, in marine isotope budgets. Here we present concentration and isotope data for Li, Mg, Ca, Sr, and B…
View article: Cenozoic Biomarker (TEX86) Temperature Estimates from ODP Hole 198-1209A
Cenozoic Biomarker (TEX86) Temperature Estimates from ODP Hole 198-1209A Open
This table includes temperatures calculated from organic biomarker (TEX86) measurements performed on Paleocene, Eocene and Oligocene sediment material from Ocean Drilling Program (ODP) Hole 198-1209A, Shatsky Rise.
View article: A modern scleractinian coral with a two-component calcite–aragonite skeleton
A modern scleractinian coral with a two-component calcite–aragonite skeleton Open
Significance Until now, all of the ca. 1,800 known modern scleractinian coral species were thought to produce skeletons exclusively of aragonite. Asymbiotic Paraconotrochus antarcticus living in the Southern Ocean is the first example of a…
View article: A Mg Isotopic Perspective on the Mobility of Magnesium During Serpentinization and Carbonation of the Oman Ophiolite
A Mg Isotopic Perspective on the Mobility of Magnesium During Serpentinization and Carbonation of the Oman Ophiolite Open
Alteration of mantle peridotite in the Samail ophiolite forms secondary minerals, mainly serpentine and Mg‐rich carbonates. Magnesium accounts for ∼25 – 30% of peridotite mass and its mobility can be used to trace this alteration. We repor…
View article: Oxygen-to-nitrogen ratios in 1.5-million-year-old ice cores from Allan Hills Blue Ice Areas: implications for the long-term atmospheric oxygen concentrations
Oxygen-to-nitrogen ratios in 1.5-million-year-old ice cores from Allan Hills Blue Ice Areas: implications for the long-term atmospheric oxygen concentrations Open
<p>Gases preserved in ice cores provide a potential direct archive for atmospheric oxygen. Yet, oxygen-to-nitrogen ratios in ice cores (expressed as δO<sub>2</sub>/N<sub>2</sub>) are modified by a num…
View article: Sea level, carbonate mineralogy, and early diagenesis controlled δ13C records in Upper Ordovician carbonates
Sea level, carbonate mineralogy, and early diagenesis controlled δ13C records in Upper Ordovician carbonates Open
Stratigraphic variability in the geochemistry of sedimentary rocks provides critical data for interpreting paleoenvironmental change throughout Earth history. However, the vast majority of pre-Jurassic geochemical records derive from shall…
View article: Two-million-year-old snapshots of atmospheric gases from Antarctic ice
Two-million-year-old snapshots of atmospheric gases from Antarctic ice Open
Over the past eight hundred thousand years, glacial-interglacial cycles oscillated with a period of one hundred thousand years ('100k world'1). Ice core and ocean sediment data have shown that atmospheric carbon dioxide, Antarct…
View article: Nitrogen isotope evidence for expanded ocean suboxia in the early Cenozoic
Nitrogen isotope evidence for expanded ocean suboxia in the early Cenozoic Open
Circulation more than temperature Changes in continental configuration and sea level affected the ocean's oxygen levels and the rate of denitrification between 70 and 30 million years ago. That finding by Kast et al. shows a fundamental di…
View article: An early diagenetic deglacial origin for basal Ediacaran “cap dolostones”
An early diagenetic deglacial origin for basal Ediacaran “cap dolostones” Open