Jurassic-Early Cretaceous stratigraphy of North Atlantic sedimentary basins: a review

Integrated stratigraphies of the Jurassic and Early Cretaceous successions of more than 20 sedimentary basins situated at the Atlantic margins of North America, west and southwest Europe and northwest Africa are presented. Several of these basins currently produce hydrocarbons or are thought to have hydrocarbon potential. The presented syntheses are based on extensive review of the literature (>1,300 publications screened), compiling information on lithostratigraphy, unit thicknesses, palaeoenvironments, major stratigraphic boundaries, sea-level trends, source and reservoir rocks, tectonics, magmatism and biostratigraphy. Schematic lithostratigraphic columns are displayed, which enable comparison of sedimentary successions at regional scale and identification of regional events. Two major phases of source rock deposition, during the Sinemurian to Toarcian and Oxfordian to Kimmeridgian are identified. Important reservoir rocks, in contrast, are more dispersed in time. Widespread unconformities occur in the Hettangian, Callovian, Berriasian and Late Aptian, and, taking the current low precision of dating in several basins into account, may have regional significance.

A fresh look at old data also helps to highlight the degrees of uncertainty of what we do actually know. Overall, the current state of knowledge decreases from north to south along both the western and eastern Atlantic margins. This is on one hand a result of limited access, with part or all of the sedimentary succession being situated offshore or in the subsurface and much of the respective data being confidential. On the other hand, this also clearly reflects the depth of study of the respective basins. The Wessex Basin, for example, has been analysed in great detail, and a major portion of these data is in the public domain. The Aquitaine Basin is equally well studied, but a large part of the results is not public. For other areas, like the Essaouira and Tarfaya basins, published stratigraphy is not state of the art. For several basins, finally, no biostratigraphic or chronostratigraphic constraints are available from the literature. Concluding, careful literature review highlights that even a seemingly well studied region like the North Atlantic still offers lots of unknowns for future petroleum systems research.