Neil J. Tabor Isabel P. Montañez Julia A. McIntosh 2025 <p><span>To understand the effects of burial diagenesis on the stable isotope geochemistry of soil-formed clay and carbonate minerals in paleosols, samples were collected from seven cores, spanning middle- to upper-Pennsylvanian strata of the Illinois Basin, with varied maximum burial depths of 1–3&nbsp;km. Mixed-layer illite-smectite and kaolinite mixtures give δ</span>²<span>H and δ</span>¹⁸<span>O values of −83&nbsp;‰ to −36&nbsp;‰ and 11.9&nbsp;‰ to 21.1&nbsp;‰ (VSMOW), respectively. After carbonates were screened petrographically for diagenetic textures using transmitted light and cathodoluminescence, measured clumped isotope Δ</span>₄₇<span>&nbsp;values range from 0.504 to 0.563&nbsp;‰ (I-CDES). Resulting mineral formation temperatures for phyllosilicate mineral mixtures are 28 to 66&nbsp;°C (mean&nbsp;=&nbsp;47&nbsp;°C), whereas T(Δ</span>₄₇<span>) estimates for calcites are 36 to 61&nbsp;°C (mean&nbsp;=&nbsp;45&nbsp;°C). Calculated δ</span>¹⁸<span>O</span>_water<span>&nbsp;values from which phyllosilicate minerals and calcites precipitated under isotopic equilibrium ranges from −7.1 to −1.2 ‰ and&nbsp;−&nbsp;1.4 to +4.9 ‰, respectively. Closed and open-system phyllosilicate-fluid exchange modeling indicates that phyllosilicate alteration occurred in the presence of a low temperature brine or meteoric water and is interpreted to occur in a layer-by-layer illitization transformation. Due to the lack of diagenetic textures and positively correlated T(Δ</span>₄₇<span>) and δ</span>¹⁸<span>O</span>_water<span>, calcites are interpreted to have undergone solid-state bond reordering. Despite low to moderate temperatures (&lt;125&nbsp;°C) and varying depths of shallow burial (1–3&nbsp;km), solid-state transformation of phyllosilicates and calcites indicates paleosols had prolonged exposure to burial conditions which has implications for the use of paleosol minerals for paleoenvironmental reconstructions.</span></p> application/pdf 10.1016/j.chemgeo.2025.122941 en Elsevier The impact of burial diagenesis on soil-formed minerals in paleosols using stable isotopes of phyllosilicates and carbonate clumped isotopes article