Tracking Dinosaurs across Equatorial Gondwana: Sedimentology and Ichnology of the Lower Cretaceous Koum Basin (Northern Cameroon).

Résumé fourni par la source

The Koum Basin (also known as Mayo Rey Basin) in northern Cameroon, dated to the Early Cretaceous (likely Berriasian–Hauterivian), preserves a dense and diverse ichnological record offering critical insights into paleoenvironmental dynamics, faunal behavior, and Gondwanan biogeography. We present new sedimentological data, ichnofabric analysis, and morphometric characterization of 283 footprints from the KB-17 tracksite, which preserves 34 trackways attributed to tridactyl theropods and large circular sauropod imprints across four stratigraphic surfaces. Notably, a large tridactyl footprint (TK-034; pes length ∼69 cm) is consistent with large-bodied theropods, indicating their presence in equatorial Africa during this period. Track-bearing horizons consist of fine-grained mudstones and siltstones bearing ripple marks, desiccation cracks, wrinkle structures, and bioturbation, indicating deposition in shallow fluvio-lacustrine environments under alternating wet and dry conditions and semi-arid climate regimes. These features promoted high-fidelity preservation, with microbial mat-induced sedimentary structures (MISS) playing a key role in surface stabilization and footprint fidelity. This study provides the first integrated ichnofabric and microfacies analysis of the KB-17 site, based on detailed thin-section characterization and a comprehensive distribution map of the trackways. Comparisons with ichnosites from the Sousa Basin (Brazil) reveal convergent preservation dynamics and support a trans-Gondwanan faunal corridor along the Borborema-Cameroon dispersal route prior to the complete opening of the South Atlantic. Our results demonstrate that the KB-17 tracksite constitutes one of the most ichnodiverse sites in equatorial Africa, refining paleogeographic models of Gondwanan dispersal and underscoring the urgent need for its geoconservation.

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