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The Mesozoic and Cenozoic history of the Porcupine Basin may be broadly summarized as a Jurassic synrift phase, followed by Cretaceous and Cenozoic post-rift subsidence. Two periods, Early Cretaceous and Early Eocene times, do not fit the simple pattern of post-rift subsidence and are characterized by increased sedimentation. We recognize distinctive sedimentological responses to the basin flanks being either exposed or submerged, and infer that transient regional uplift caused the Early Eocene event. Modelling subsidence histories of wells and of the Porcupine Bank allows quantification of the magnitude and timing of anomalous uplift and subsidence. Transient uplift of 300-600 m occurred at the Paleocene-Eocene boundary, followed by subsidence of 500-800 m after Early Eocene time, over a period with a minimum length of 25 Ma and a maximum of 55 Ma. Renewed rifting is unlikely to be responsible for the Paleogene subsidence because it cannot account for the preceding uplift, and significant normal faults of Paleogene age are absent. A Paleogene uplift-subsidence cycle has also been noted in the basins surrounding Scotland and along Hatton continental margin. One way to explain regional subsidence between Eocene time and the present is that the European plate moved off the topographic swell above the Iceland plume following continental separation between Greenland and Europe in Early Eocene time. Another possibility is that an anomalously hot layer c. 50 km thick was emplaced beneath the entire region just before the onset of sea-floor spreading in Early Eocene time and was then dissipated by convection following continental separation. A Cretaceous transient uplift-subsidence cycle that shares many similarities with the Paleogene cycle is also recognized. Immediately following Late Jurassic rifting, 200-700m transient uplift occurred in Early Cretaceous time, followed by 0-500m subsidence coeval with the onset of sea-floor spreading at the Goban Spur margin. The Cretaceous uplift-subsidence cycle might also be caused by anomalously hot mantle.

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An explanation for high-frequency cycles of sea level in non-glacial times has remained elusive, despite more than two centuries of research since Lavoisier's seminal observations were published in 1789. In the development of seismic stratigraphy in the 1970s, putatively global high-frequency changes in relative sea level (Vail third-order cycles) were attributed to an unknown eustatic mechanism, prompting a search for Mesozoic ice ages. Over the last decade, a regional mechanism of sea-level control has been developed from studies of the sedimentary record in high-quality oil-industry data. These geological studies have supported the geophysical prediction that significant regional control of sea level is exercised by mantle-induced vertical motions of the Earth's surface. These vertical motions can occur over time intervals from several tens of million years to less than a million years, with amplitudes of tens of metres or more even at the shorter intervals. The vertical motions are not confined to regions with major hotspots. There are two related controls of surface vertical motion: evolution of mantle-convection cells, and pulsing flow within each cell. The effects are evident in the sedimentary record of North Atlantic basins. Mantle convection provides an alternative, regional, mechanism to eustatic control for explaining medium-frequency to high-frequency sea-level cycles.