Two unresolved issues in the history of the Delaware Basin of western Texas and southeastern New Mexico are (1) whether basin-elevated thermal maturities of organic matter resulted from elevated paleogeothermal gradients or deeper burial and (2) the timing of pore fluid overpressure development in the Wolfcamp formation. These unresolved issues are explored through the application of U-Pb geochronology and clumped isotope thermometry of beef calcite veins taken from the Wolfcamp formation of the Delaware Basin. The age of the beef calcite is constrained by one successful U-Pb discordia of 152.9 ± 53.1 Ma (mean squared weighted deviation = 1.2), with attempted ages in samples resulting in prohibitively large errors due to high common lead and low uranium. The temperature of Wolfcamp beef calcites by clumped isotope (Δ47) thermometry ranges from ∼142°C to 162°C. Consistency between beef calcite temperature and interpreted organic maturity of fluid inclusions in beef calcite veins precludes solid-state reordering of the Δ47 thermometer. Consistency between beef calcite temperature and organic thermal maturity by pyrolysis indicates vein precipitation at basin thermal maximum. A one-dimensional burial history constrained by beef calcite age, temperature, and apatite fission-track analysis data is proposed that indicates a higher-than-present-day geothermal gradient (30°C/km) and deeper burial (∼1.8 km) during the Mesozoic. Because beef calcite samples were taken from presently overpressured intervals of the Wolfcamp formation and are thought to form in the presence of high overpressure, overpressure likely preceded beef calcite precipitation and persisted through to the present day.