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   https://doi.org/10.1016/j.epsl.2021.117002  

   Ahm, Anne-Sofie C.; Bjerrum, Christian J.; Hoffman, Paul F.; Macdonald, Francis A.; Maloof, Adam C.; Rose, Catherine V.; Strauss, Justin V.; Higgins, John A. (August 2021, Earth and Planetary Science Letters)
2. Uranium Isotope Fractionation in Non‐sulfidic Anoxic Settings and the Global Uranium Isotope Mass Balance

   https://doi.org/10.1029/2020GB006649  

   Cole, Devon B.; Planavsky, Noah J.; Longley, Martha; Böning, Philipp; Wilkes, Daniel; Wang, Xiangli; Swanner, Elizabeth D.; Wittkop, Chad; Loydell, David K.; Busigny, Vincent; et al (August 2020, Global Biogeochemical Cycles)

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3. Carboniferous isotope stratigraphy

   https://doi.org/10.1144/SP512-2020-72  

   Chen, Jitao; Chen, Bo; Montañez, Isabel P. (April 2022, Geological Society, London, Special Publications)

   Abstract We present an updated set of Carboniferous Sr, C and O isotope stratigraphies based on the existing literature, given the importance of chemostratigraphy for stratigraphic correlation in the Carboniferous. The Carboniferous⁸⁷Sr/⁸⁶Sr record, constructed using brachiopods and conodonts, exhibits five first-order phases beginning with a rapid decline from a peak value ofc.0.70840 at the Devonian–Carboniferous boundary to a trough (0.70776–0.70771) in the Visean followed by a rise to a plateau (c.0.70827) in the upper Bashkirian. A decline toc.0.70804 follows from the lowermost Gzhelian to the close of the Carboniferous. Contemporaneous carbonate δ¹³C records exhibit considerable variability between materials analysed and by region, although pronounced excursions (e.g. the mid-Tournaisian positive excursion and the end-Kasimovian negative excursion) are present in most records. Bulk carbonate δ¹³C records from South China and Europe, however, are generally consistent with those of brachiopod calcite from North America in terms of both absolute values and trends. Both brachiopod calcite and conodont phosphate δ¹⁸O document large regional variability, confirming that Carboniferous δ¹⁸O records are invalid for precise stratigraphic correlation. Nevertheless, significant positive δ¹⁸O shifts in certain intervals (e.g. mid-Tournaisian and the Mississippian–Pennsylvanian transition) can be used for global correlation. 

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4. Calcium isotope cosmochemistry

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   Valdes, Maria C.; Bermingham, Katherine R.; Huang, Shichun; Simon, Justin I. (June 2021, Chemical Geology)

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5. Respiration, isotope composition, and carbon source partitioning from incubations of soil amended with litter and isotope-labeled lignin

   https://doi.org/10.6073/pasta/ca93711d9b792e424a74457345db1c24  

   Hall, Steven J; Huang, Wenjuan; Hammel, Kenneth E (January 2020, Environmental Data Initiative)

   We incubated 10 forest soils (collected from sites across North America, including the Luquillo LTER/CZO) in the laboratory for over two years to quantify the decomposition of carbon derived from added litter and lignin, as well as from extant soil organic matter. Each soil was subjected to two substrate addition treatments: a) litter derived from a C4 grass precipitated with 13C-enriched lignin, or the same C4 grass litter was precipitated with natural-abundance lignin. The concentrations and delta13C composition of carbon dioxide produced from each soil were measured periodically over time and partitioned into sources (soil organic matter, litter, and added lignin) using isotope mixing models. The methods and results are described in detail by a manuscript in Ecology (Hall et al., 2020). 

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