Stratigraphic Plug Alignment for Integrating Plug-Based and XRF Data R package spaAlign version 0.0.6 Implements the Stratigraphic Plug Alignment (SPA) procedure for integrating sparsely sampled plug-based measurements (e.g., total organic carbon, porosity, mineralogy) with high-resolution X-ray fluorescence (XRF) geochemical data. SPA uses linear interpolation via the base approx() function with constrained extrapolation (rule = 1) to preserve stratigraphic order and avoid estimation beyond observed depths. The method aligns all datasets to a common depth grid, enabling high-resolution multivariate analysis and stratigraphic interpretation of core-based datasets such as those from the Utica and Point Pleasant formations. See R Core Team (2025) <https://stat.ethz.ch/R-manual/R-devel/library/stats/html/stats-package.html> and Omodolor (2025) <http://rave.ohiolink.edu/etdc/view?acc_num=case175262671767524> for methodological background and geological context. Software Depends: R (>= 4.0) Imports: stats Suggests: testthat (>= 3.0.0), knitr, rmarkdown Hope E. Omodolor <hopeomodolor@gmail.com> Comprehensive R Archive Network (CRAN) Hope E. Omodolor [aut, cre] (ORCID: <https://orcid.org/0009-0005-7842-406X>), Jeffrey M. Yarus [aut] MIT + file LICENSE (https://CRAN.R-project.org/package=spaAlign/LICENSE) 2026-01-08 application/tgz https://CRAN.R-project.org/package=spaAlign doi:10.32614/CRAN.package.spaAlign