Vol. 321, Issue 3, 2021

Science Paper
Carbon Cycle Evolution Before and After the Great Oxidation of the Atmosphere
Don E. Canfield
The rock record of organic carbon abundance and its isotopic composition is consistent with the evolution of life more than 3800 million years ago (Ma). Despite this, there are very...
Science Paper
Unmixing Multiple Metamorphic Muscovite Age Populations With Powder X-ray Diffraction and 40Ar/39Ar Analysis
Ryan J. McaleerDavid L. BishMichael J. KunkPeter M. ValleyGregory J. WalshRobert P. Wintsch
A combination of modal estimates from powder X-ray diffraction (XRD) experiments and argon isotopic data shows that muscovite 40Ar/39Ar total gas age correlates with muscovite composition near the retrograde Bald...
Science Paper
⁴⁰Ar³⁹Ar and LA-ICP-MS U–Pb Geochronology for the New England Portion of the Early Cretaceous New England-Quebec Igneous Province: Implications for the Postrift Evolution of the Eastern North American Margin
Jennifer R. Cooper BoemmelsJean M. CrespiLaura E. WebbJulie C. Fosdick
The Early Cretaceous New England-Quebec igneous province is a classic example of postrift magmatism along the eastern North American passive margin. Although a suite of <sup>40</sup>Ar/<sup>39<sup>Ar ages has been available...