We present and make publicly available a dynamic programming algorithm to simultaneously align the inclination and declination vector directions of sedimentary paleomagnetic secular variation data.This algorithmgenerates a library of possible alignments through the systematic variation of assumptions about the relative accumulation rate and shared temporal overlap of two or more time-series. The paleomagnetist can then evaluate this library of reproducible and objective alignments using available geologic constraints, statistical methods, and expert knowledge.We apply the algorithm to align previously (visually) correlated medium to high accumulation rate northern North Atlantic Holocene deposits (10¹– 10² cm/ka) with strong radiocarbon control. The algorithm generates plausible alignments that largely conform with radiocarbon and magnetic acquisition process uncertainty. These alignments illustrate the strengths and limitations of this numerical approach.

For GSA Today article 575A: Align: A User-Friendly App for Numerical Stratigraphic Correlation by Cedric J. Hagen et al.

The measured carbon isotopic compositions of carbonate sediments (δ ¹³ C _carb ) on modern platforms are commonly ¹³ C‐enriched compared to predicted values for minerals forming in isotopic equilibrium with the dissolved inorganic carbon (DIC) of modern seawater. This offset undermines the assumption that δ ¹³ C _carb values of analogous facies in the rock record are an accurate archive of information about Earth's global carbon cycle. We present a new data set of the diurnal variation in carbonate chemistry and seawater δ ¹³ C _DIC values on a modern carbonate platform. These data demonstrate that δ ¹³ C _carb values on modern platforms are broadly representative of seawater, but only after accounting for the recent decrease in the δ ¹³ C value of atmospheric CO ₂ and shallow seawater DIC due to anthropogenic carbon release, a phenomenon commonly referred to as the ¹³ C Suess effect. These findings highlight an important, yet overlooked, aspect of some modern carbonate systems, which must inform their use as ancient analogs.

As warming intensifies across the Greenland ice sheet, an increasing number of shallow coring and radar studies are targeting the melt-impacted firn column to investigate meltwater processes. Highly inhomogeneous infiltration and refreezing, however, redistributes mass, distorting age–depth relationships and confounding comparisons between different cores. Here, we utilize a dynamic time warping algorithm for time series alignment to investigate and quantify the heterogeneous impact of melt processes on nine closely spaced (within 50 m) firn core-density profiles. The 10 m cores were collected relatively high in Greenland's percolation zone, where melt alteration is minimal compared to lower elevation. Our analysis demonstrates the effectiveness of dynamic time warping as a tool for assessing heterogeneity between ice core records. We find that the optimal alignment of density profiles in the nine cores requires vertical stretching and compression of individual profiles, ranging from, on average, <1 to ~16% of the core lengths. We identified four depth zones of mass redistribution that appear to coincide with observed ice layers. Further, ~75% of density measurements from each core do not align with an age model-derived density profile that assumes no mass redistribution of meltwater, indicating the pervasive impact of melt processes.

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 (δ¹³C_carb), with a focus on comparisons of measured δ¹³C_carb values, models for understanding what controls δ¹³C_carb values, and correlation tools for aligning δ¹³C_carb 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.