Quantitative and Nuanced Approaches Elucidate Carbon Isotope Records

Earth scientists have leveraged carbon isotope records to interpret Earth history and establish chronostratigraphic frameworks for decades (e.g., Halverson et al., 2005, https://doi.org/10.1130/b25630.1; Kaufman & Knoll, 1995, https://doi.org/10.1016/0301‐9268(94)00070‐8; Knoll et al., 1986, https://doi.org/10.1038/321832a0; Saltzman & Thomas, 2012, https://doi.org/10.1016/b978‐0‐444‐59425‐9.00011‐1; Scholle & Arthur, 1980, https://doi.org/10.1306/2f91892d‐16ce‐11d7‐8645000102c1865d). Increasingly detailed and nuanced approaches have been applied to understanding carbon isotope records in light of local‐ and regional‐scale processes that complicate interpretations. The recent work of Gazdewich et al. (2024, https://doi.org/10.1029/2023gc011376) is a prescient example, in which they conduct a series of analyses to constrain the influence of authigenic carbonate burial on the global carbon isotope mass balance during the Late Devonian. Here, I briefly review some recent developments in quantitative approaches to understanding carbon isotope values measured from carbonate rocks (δ13Ccarb), with a focus on comparisons of measured δ13Ccarb values, models for understanding what controls δ13Ccarb values, and correlation tools for aligning δ13Ccarb stratigraphies. These new approaches are elucidating carbon isotope records across Earth history and may prove to be transformative for our understanding of the global carbon cycle. Plain Language Summary The ratio of stable carbon isotopes measured in carbonate rocks (δ13Ccarb) has long been used as a tool for geologists to estimate the relative ages of ancient rocks by matching trends in δ13Ccarb between localities. Recent work has demonstrated that biological and geological processes at local and regional scales can influence δ13Ccarb, making the matching between localities more complicated. Because of this, increasingly detailed and nuanced approaches have been developed to understand trends in δ13Ccarb. Gazdewich et al. (2024, https://doi.org/10.1029/2023gc011376) recently provided a new protocol for constraining the degree to which one of these geological processes–the burial of in situ‐forming carbonate minerals (authigenic carbonate)–impacted δ13Ccarb values during the Late Devonian (382.7–358.9 million years ago). In this commentary, I provide context for this advancement, highlighting other recent developments in quantitative approaches for understanding δ13Ccarb values. These new approaches have the potential