Multi‐proxy sequence stratigraphy of a mixed carbonate–siliciclastic shelf across the Jurassic–Cretaceous transition

Abstract Relative sea‐level change, climate variability and sediment supply exert a first‐order control on the architecture of mixed carbonate–siliciclastic shelves, yet their combined expression in fine‐grained successions with low facies diversity remains difficult to resolve. The Tithonian–Berriasian succession of central Tunisia provides a natural laboratory to address three questions: how many third‐order sequences can be distinguished in a clay‐rich mixed system; how reliably sequence boundaries and maximum flooding surfaces can be located using an integrated proxy set; and how these surfaces relate to regional tectonics and long‐term eustatic trends. Five sections along a ~93 km shelf‐to‐basin transect were logged at decimetre scale and analysed using facies and facies‐association analysis, systematic documentation of discontinuity surfaces, magnetic susceptibility measured selectively in marl–clay intervals, bulk CaCO 3 content and XRF‐derived elemental ratios that track detrital input and carbonate productivity. These new data are combined with published palynofacies, clay mineralogy and macrofaunal information. The resulting framework resolves five Tithonian and eight Berriasian third‐order sequences, each constrained by consistent shifts in facies stacking, the distribution and character of condensed surfaces, firmgrounds and hardgrounds, systematic changes in susceptibility and Ti‐, Zr‐ and Ca‐based geochemical ratios and associated changes in biotic assemblages. Correlation across the transect reveals an overall regressive trend overprinted by higher‐frequency transgressive–regressive cycles, with local departures linked to differential subsidence along the North–South structural axis. The results show that integrated sedimentological, geophysical and geochemical methods can recover high‐resolution sequence architecture from monotonous mixed successions, provide a reference shelf model for the southern Tethyan margin during the Tithonian–Berriasian and offer a transferable template for inter‐basinal correlation of sea‐level and climate signals in comparable carbonate–siliciclastic systems.