| Popis: |
The Jeanne d’Arc Basin offshore Newfoundland and the Porcupine Basin to the west of Ireland, developed under similar tectono-sedimentary conditions in pre-Late Cretaceous times. Rifting events in Permo-Triassic, Late Jurassic–Early Cretaceous and mid Cretaceous times were each followed by a phase of thermal subsidence. While a broadly common lithofacies pattern occurs within and between the basins, the detailed response of the basins differs in terms of style of structuring, reservoir architecture and quality of source rock development. The Late Jurassic–Early Cretaceous (Tithonian to Berriasian) rift episode is the most significant, with good reservoir sandstones and rich source rocks forming part of this rift sequence. A Late Oxfordian to Kimmeridgian onset warp phase resulted in the development of shallow marine limestones and deeper water organic-rich shales and marls in the Jeanne d’Arc Basin, with non-marine, shoreface and restricted marine sandstones and shales in the Porcupine Basin. The Late Jurassic–Early Cretaceous syn-rift episode resulted in the development of sandstone-prone successions which interfinger with good oil-prone source rocks in both basins. Reservoir architecture in both basins was influenced by this episode. Within the Porcupine Basin a range of lithofacies developed, ranging from fluvial channels and bars, to submarine fan turbidites. Within the Jeanne d’Arc Basin, periodic rejuvenation of fault footwalls produced conglomeratic pulses resulting in transverse alluvial fans which interfinger with axially-flowing braid channels and bars within the incised valley fills. Periods of increased subsidence resulted in the development of lacustrine facies and flood plain mudstones. |
