Geology and Chronology of the Lunar Taruntius Crater: Implications for the Retention Age of Lunar Ray Patterns and Lifetime of Lunar Explosive Volcanism

Abstract

The Taruntius crater, situated between Maria Fecunditatis, Crisium, and Tranquillitatis, is characterized by a prominent bright ray system and a floor‐fractured morphology and has long been interpreted as a relatively young Eratosthenian or Copernican crater. Here, we combine high‐resolution imagery, topography, and multispectral data to characterize its morphology, composition, and chronology. Taruntius exhibits a complex internal structure, including central peaks, fractures, and ridges, and its regolith has reached full optical maturity. Elemental abundances of FeO (6.9–19.1 wt.%), TiO ₂ (0–8.7 wt.%), and Th (3.0–3.4 ppm) indicate low‐Ti and moderately Th‐enriched compositions. Plagioclase dominates the crater rim and walls (>60 wt.%), whereas the central peaks and ejecta are characterized by reduced plagioclase (<45 wt.%) and enhanced pyroxene (>40 wt.%) with minor olivine (<10 wt.%). Basaltic materials identified within floor fractures record localized volcanic activity predating the impact event. Crater size‐frequency distribution analysis yields a model age of 3.7 ± 0.03 Ga, placing the formation of Taruntius in the late Imbrian period. These results revise previous age estimates, demonstrate that prominent ray systems do not necessarily indicate young lunar craters, and highlight the importance of integrating compositional and chronological analyses in reconstructing lunar surface evolution.