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Integration of regional seismic interpretation, sonic velocity, vitrinite reflectance and apatite fission-track analysis (AFTA ® ) studies has demonstrated that the western region of the Moray Firth rift arm (UK North Sea) experienced pronounced exhumation during the Cenozoic. Although this basin is usually considered to have experienced regionally uniform exhumation, interpretation of new seismic data has revealed the presence of a major system of post-Jurassic normal faults, with throws commonly in the range of 10–300 m and locally exceeding 1 km. New, high-quality seismic data are used in combination with AFTA and vitrinite reflectance data to investigate the role of extensional faulting during exhumation of this basin. Results of this interpretation not only confirm the offsets across major faults, but also show that greater exhumation and erosion occurred on their footwalls than on their hanging walls. We conclude that the localized, differential exhumation is the result of superposition of local or short-spatial-wavelength extensional tectonics upon regional, long-spatial-wavelength exhumation. These results suggest that differential exhumation might be characteristic of unroofed rift basins where normal faults subcrop the exhumation-related unconformity and that, in such cases, thermal histories from footwall locations may yield inaccurate predictions of the burial history of hanging-wall depocentres. Inaccurate burial histories will lead to a misrepresentation of the thermal history, with an impact on the estimation of hydrocarbon source rock maturity for petroleum basins.

Passive margins have been the reliable, accessible mainstay of exploration success worldwide for the last 25 years, and have hosted the spectacularly fast exploitation of deepwater resources (Angola, Nigeria, Brazil, Trinidad, USA Gulf of Mexico, Egypt, Australia and India). Despite, or perhaps because of this, there is still much to learn about the variety of hydrocarbon habitats they present.For example: (1) deep seismic observations and deep sea drilling have revealed more of the diversity of passive margins geodynamics. This liberates explorationists from simple geodynamic models, with consequences not only for new views of thermal history but also for the whole tectonic and stratigraphic evolution. For example, the time significance assigned to the geometries traditionally labelled 'pre-rift, syn-rift and sag' may be misleading. This has implications for correlations, the significance assigned to unconformities and sequence boundaries, heat flow and structural history. (2) New deep imaging of the sedimentary sections has revealed mistaken assumptions about the importance of 'mobile substrate' in major deltas and allowed the detailed unravelling of salt and shale movement and its implications for reservoir and trap. (3) Depositional models for deepwater reservoirs have increased in predictive capability and modern seismic imaging supports new models for shallow water sequences. (4) Discoveries of very large amounts of dry bacterial methane in stratigraphic traps have challenged old assumptions about prospectivity based on thermally matured source rocks. (5) New engineering and development technologies are opening up the commercialization of remote frontiers. As a consequence there is legitimate scope to re-visit old 'dogmas' and to propose that each passive margin segment is best regarded as unique, with analysis and interpretation rooted in observation rather than models (at least while the newly proposed models evolve to stability). Many of these themes were visited in the Passive Margins session of the Seventh Petroleum Geology Conference, held in London in 2009. This paper outlines some of these ideas, and considers how exploration along passive margins in the next decade can use new geoscience thinking.

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Interpretation of high-quality seismic data, constrained by exploration wells, provides insights into controls on the stratigraphic architecture and deep-water sedimentary processes that governed deposition of the Lower Cretaceous Punt Sandstone Member in the Inner Moray Firth Basin. We suggest a model of deposition in which sediment provenance from the north and west progressively filled depositional accommodation in proximal depocentres before spilling into more distal areas via linear, confined and incised channel complexes. As well as giving important clues into post-rift depositional processes in the basin, and a well-imaged ancient analogue for the deposition of massive deep-water sands, the seismic and stratigraphic data may also provide important insights into factors governing the poorly imaged Lower Cretaceous sands in neighbouring basins of the North Sea.