Cyclo‐Sequence Stratigraphy of the Turonian–Santonian Succession in Hamza Basin, Jordan

ABSTRACT

This study presents the first integrated framework combining lithostratigraphy, spectral gamma‐ray (SGR), cyclostratigraphy, and astronomical tuning for the Upper Cretaceous Wadi As Sir and Rajil Formations, based on data from wells WR5, HZ13, and HZ15 in the Azraq–Hamza Graben, Jordan. Unlike adjacent regions, this graben exhibits a distinct sedimentation pattern marked by more continuous deposition and a greater siliciclastic influx from surrounding uplifted areas, reflecting localized tectonic influence within a broader eustatic framework. Astronomical tuning of gamma‐ray (GR) records based on long‐eccentricity solution yields a refined age model spanning ∼92.3–84.1 Ma. The tuned ages constrain the Wadi As Sir Formation between ∼92.3 and ∼89.6–89.8 Ma and Rajil Formation (Lower Rajil sand unit between ∼89.4–89.1 and ∼87 Ma and the Upper Rajil unit between ∼86.9–86.6 and ∼84.1 Ma). A key finding are two regional hiatuses at the Wadi As Sir/Rajil Formational boundary (g1) and Lower/Upper Rajil boundary (g2), coinciding with the Turonian/Coniacian transition and Upper Coniacian, respectively. The two hiatuses’ duration varies across the wells where g1: ∼0.5 Myr and g2: ∼0.09–0.3 Myr. These boundaries are further expressed by abrupt shifts in lithofacies, SGR ratios, Th/K clay–mineral proxies, evolutionary correlation coefficient (eCOCO)‐derived sedimentation accumulation rates (SARs), and evolutionary fast Fourier transform (eFFT) spectral power, collectively indicating a major reorganization of depositional regimes. The dynamic noise after orbital tuning (DYNOT) analysis revealed 1 Myr obliquity modulation of the Turonian–Santonian sea level. Sequence‐stratigraphic analysis reveals seven third‐order sequence boundaries that correlate with global eustatic sea‐level fluctuations, subdividing the succession into six depositional sequences. These sequences record a three‐phase paleoenvironmental evolution: (1) restricted carbonate–evaporite platform deposition (Sequences 1 and 2, Wadi As Sir Formation); (2) post‐hiatus siliciclastic‐dominated sedimentation (Sequences 3 and 4, Lower Rajil Formation); and (3) a return to mixed carbonate–argillaceous marine conditions (Sequences 5 and 6, Upper Rajil Formation). This integrated approach demonstrates that the Wadi As Sir–Rajil succession constitutes a combined influence of global eustasy and regional tectonism.