One of the few detailed records of Mesozoic deep-water sedimentation and volcanism preserved along the tectonically emplaced Arabian continental margin is from the Baer–Bassit region of northern Syria. South-Tethyan units there occur as blocks, broken formation and disrupted thrust sheets within the Bear–Bassit Melange. Two overall composite successions are identified. The first comprises mainly sedimentary successions ranging from Late Triassic to Late Cretaceous (Cenomanian) in age. The second is dominated by Middle Jurassic–Lower Cretaceous alkaline/per-alkaline volcanic and minor intrusive igneous rocks. The extrusives are intercalated with radiolarian sediments and capped by Cenomanian ferromanganese-rich pelagic limestone. Facies comparisons and the regional setting suggest that the Triassic to Cenomanian, mainly sedimentary units, formed in deep water near the base of the slope of the Arabian continental margin. The contrasting volcanogenic successions developed in a more distal off-margin setting. Regional comparisons (e.g. with southwestern Cyprus and southwestern Turkey) suggest that continental break-up to form a South-Tethyan oceanic basin took place in Late Triassic time, associated with alkaline volcanism. Similar alkaline volcanism of Middle Jurassic to Early Cretaceous age could reflect the activity of a mantle plume beneath the Arabian plate. Overall, sedimentation was mainly controlled by an interplay of post-rift thermal subsidence, plume-related uplift, siliceous oceanic productivity, climatic change and eustatic sea-level change. The South-Tethyan marginal to oceanic units in northern Syria were detached from an inferred oceanic basement in latest Cretaceous time, emplaced onto the Arabian continental margin, then transgressed by Maastrichian and younger autochthonous successions.