Seismic Stratigraphic Interpretation and High Amplitude Anomalies of the Cretaceous Sequence, Porcupine Basin

This report presents a description of a set of high amplitude anomalies along a 3D seismic stratigraphic interpretation for the Cretaceous sequence in the north-west margin of Porcupine basin. Porcupine is a sedimentary basin, western offshore of Ireland, closely related to the Opening of the North Atlantic Ocean. This basin presents three tectono-sedimentary sequences: late Permian to Early Triassic pre-rift sequence, middle Triassic to Jurassic syn-rift sequence and Cretaceous to present post-rift sequence. The Cretaceous sequence is characterized by two main events: a Berriasian to Aptian thermal passive sag and an Albian-Maastrichtian tectono-eustatic relative sea level rise. During the former a series of relative sea level changes were masked by the thermal sag. Deposition was mainly related to submarine fan deposits. The latter was characterized by prograding events when the thermal sag slowed down. Deposition was dominated by siliciclastic deltaic deposits and carbonates that deposited a chalk unit on top of the Cretaceous sequence. The Cretaceous sequence was subdivided into four sequences, namely sequences I, II, III and IV respectively and further subdivided into systems tracts. Six high amplitude anomalies were reported. They are constrained in sequences II and III with no apparent connection to a particular systems tract. The anomalies are located basinward as deep water deposits that either follow the basin floor along contours or are merely spread out. They can be mudstone-prone and sandstone-prone. Despite a lack of proper control, they have been interpreted as contourite deposits that sequentially step out landward. This is only a hypothesis based on the seismic character of the anomaly and its geometry. However, contourites have been already reported in the Porcupine basin in younger deposits of Tertiary age. Future studies should bring a proper controlled data in order to define the precise origin of these high amplitude anomalies and to assess their hydrocarbon potential.Applied Geophysics and PetrophysicsGeoscience & EngineeringCivil Engineering and Geoscience