Geological controls on syn- to post-rift alluvial stratigraphy and depositional architecture, Permian–Triassic of the Horda Platform, North Sea

Continental rift basins commonly exhibit strong lateral variability in subsidence rates during syn-rift deposition, but the extent to which this affects stratigraphic correlation and depositional architecture remains ill-constrained. We integrate wireline logs, core data and structural interpretations across the Horda Platform, northern North Sea, to examine the evolution of the Permian–Triassic syn- to post-rift alluvial systems. The syn-rift succession is characterised by weak continuity and correlation of stratigraphic units owing to localised fault-controlled accommodation. In contrast, post-rift successions display greater lateral continuity and more consistent proximal–distal trends as basin relief diminished and eustatic influence increased. Sediment flux and autogenic processes further modulated the stratigraphic expression of base-level change, locally obscuring tectonic and eustatic signals. Sedimentological analysis records a transition from dryland fluvial and aeolian systems to wetter fluvial and coastal-marine environments, while palaeosols and floodplain deposits record a corresponding transition from arid to humid climatic conditions during the Permian–Triassic time. Overall, stratigraphic and facies architecture observed in wells penetrating syn-rift successions is strongly dependent on well position relative to active faults and sediment-source areas. These results highlight the importance of detailed structural analysis for stratigraphic correlation in syn-rift basins, particularly where stratigraphic dating and well data are limited.