Geometries and kinematics of fault systems in the Flemish Pass Basin: Insights from the Bay du Nord 3D seismic survey, offshore Newfoundland, Eastern Canada

The Flemish Pass Basin is a Mesozoic basin offshore Newfoundland in Eastern Canada. This basin has proven petroleum systems, and formed via multiple rifting episodes as a part of the wider North Atlantic rift system during Pangaea’s disintegration. We utilise the Bay du Nord 3D seismic survey to derive 3D fault models, which include throws profile. The aim of this was to investigate fault nucleation and growth history, and how this may relate to previous interpretations of multi-stage rifting, plus the possible role of structural inheritance in controlling basin evolution.

Through our interpretation of the 3D volume, we identified three fault systems (1: NE-SW, 2: NW-SE & 3: NNE-SSW), plus one distinctive basin-bounding fault (trending E-W). The NE-SW basement-involved system typically comprises 12 – 17 km long faults dipping 10–25^o, with throws of 250–1250 m. This fault system exhibits throws of 600–1250 m between the hanging wall and footwall of the interpreted Pre–Mesozoic cut–off horizon. We interpret this observation of large throw values to relate to the initiation of extension following the Pre-Mesozoic horizon, which likely coincides with the previously interpreted regional Late Triassic–Early Jurassic rift phase. Moreover, although lower throws (≤200 m) were recorded between the Base Upper Tithonian and Late Jurassic horizons, evidence of reactivation of this fault system is interpreted from the throw values, which range from 300–750 m between the Base Upper Tithonian and the Aptian horizons. We interpret this to result from further reactivation due to the previously interpreted 2nd regional rift phase in the Late Jurassic – Early Cretaceous. The NW-SE fault system constitutes 3 – 10 km long planar normal faults, with throws ranging from 50–300 m scattered between the Base Upper Tithonian and Late Cretaceous cut-off lines. We interpret that this fault set propagated downward and linked with pre-existing basement-involved faults, and that the nucleation of this fault set occurred during the 2nd rift phase. The NNE-SSW planar normal fault system is interpreted to be younger based on stratigraphic relationships and comprises 2–8 km long faults. This fault system was interpreted to correspond with the 3rd rift phase during the Cretaceous, and has throw values between the Base Upper Tithonian and the Base Cretaceous horizons ranging from 100–350 m. Finally, the distinct E-W striking basin-bounding normal fault revealed throws of 250–4000 m. This fault acts as a sub-basin confinement on the southern part of the 3D survey area, with throw variation distributed in the Pre-Mesozoic horizon from 1000–4000 m and between Base Upper Tithonian–Aptian Cretaceous horizons with values of 250-800 m.

Overall, our results demonstrate that: 1) in the Flemish Pass basin, there are three fault systems, and one distinctive basin-bounding fault, all of which display variable throw values corresponding to three rift phases (Late Triassic-Early Jurassic, Late Jurassic–Early Cretaceous, and Cretaceous) and 2) pre-existing structures influenced basin development by providing an initial seed for subsequent faulting and may have possibly formed a mechanical link aiding propagation.