Plio‐Pleistocene fault reactivation within the Crag Basin, eastern UK: implications for structural controls of landscape development within an intraplate setting

Abstract

This study examines the long‐term neotectonic evolution of the Crag Basin of eastern England during the Plio‐Pleistocene (c. 4.0–0.48 Ma) and the influence of neotectonics on coastal and drainage development. The Crag Basin was situated within the western margins of the southern North Sea with palaeogeography influenced by changes in global sea‐level and longer‐term regional‐scale neotectonic uplift and subsidence. This study identifies an additional local‐scale neotectonic control on basin development with localized crustal displacement occurring along normal faults. Plio‐Pleistocene movement along these faults was accommodated by partial dip‐slip (normal) reactivation of an Oligocene‐age (Pyrenean) dextral strike‐slip shear zone, which in turn was inherited from much older Caledonian orogenic crustal structure. Fault displacement was driven by sediment‐loading reflecting enhanced landscape denudation under progressively deteriorating climates and increased rates of erosion/sedimentation. Faulting acted to regulate accommodation space, controlling sedimentation patterns and the courses of major preglacial drainage systems including the Kesgrave Thames and Bytham rivers. The lower reaches of both river systems are considered to have been confluent in the Crag Basin during much of the Early Pleistocene with their lower reaches structurally controlled. Divergence occurred at c. 0.9 Ma with the lower reaches of the Bytham utilizing the former Bytham‐Thames valley and the Kesgrave Thames adopting progressively more southern routes, aligned to the axis of subsidence within the London Basin. The study highlights the significance of tectonic inheritance in driving recent neotectonic crustal deformation and its influence on sedimentation patterns and drainage development within an intraplate setting.