Abstract On 18 November 1929, an M w 7.2 earthquake occurred south of Newfoundland, displacing >100 km 3 of sediment volume that evolved into a turbidity current. The resulting tsunami was recorded across the Atlantic and caused fatalities in Newfoundland. This tsunami is attributed to sediment mass failure because no seafloor displacement due to the earthquake has been observed. No major headscarp, single evacuation area nor large mass transport deposit has been observed and it is still unclear how the tsunami was generated. There have been few previous attempts to model the tsunami and none of these match the observations. Recently acquired seismic reflection data suggest that rotational slumping of a thick sediment mass may have occurred, causing seafloor displacements up to 100 m in height. We used this new information to construct a tsunamigenic slump source and also carried out simulations assuming a translational landslide. The slump source produced sufficiently large waves to explain the high tsunami run-ups observed in Newfoundland and the translational landslide was needed to explain the long waves observed in the far field. However, more analysis is needed to derive a coherent model that more closely combines geological and geophysical observations with landslide and tsunami modelling.

Abstract The Triassic Fundy rift basin in Nova Scotia is a large (>70 km wide) half-graben filled with alluvial, lacustrine and aeolian deposits. A major lithospheric lineament, the Cobequid–Chedabucto Fault Zone (CCFZ), which forms the tip of the Newfoundland–Gibraltar Fault Zone, occurs within the Fundy Basin. The timing of early movement on this important fault zone is poorly constrained. We present data from the alluvial and aeolian units that crop out adjacent to the CCFZ in the Minas sub-basin to determine the initiation of fault movement. We use the onset of alluvial fan deposition to infer when the fault became sufficiently active to create the intrabasinal topography and document the influence of fault activity on the intrabasinal drainage. The occurrence and preservation of aeolian deposits immediately adjacent to the CCFZ and concomitant with alluvial fan development suggests a wind shadow effect associated with the fault-generated topography. The onset of alluvial fan deposition associated directly with the fault occurred during Norian times, following an earlier phase of sedimentation in the Fundy Basin, and records a potentially important phase of plate reorganization during early Atlantic rifting.

Abstract Over the past decade, discoveries of super-giant, multibillion barrel presalt oil fields in Brazil’s offshore basins and related discoveries in its African conjugates highlighted the great importance of synrift/prebreakup fluvial-lacustrine successions to the success and efficiency of their petroleum systems. Improvements in seismic acquisition and processing technologies were keys in imaging the architecture of the underlying rift basins, and interpreting the basin fill and internal depositional facies later confirmed by drilling. Middle Triassic to Early Jurassic synrift basins are exposed onshore eastern North America and extend into adjacent offshore areas, including equivalent basins in Northwest Africa. Organic-rich lacustrine successions occur in a number of the U.S. basins and although no commercial discoveries have been made, hydrocarbon shows in outcrops and wells confirm that a working petroleum system exists in virtually every basin. The basin-fill model for these extensional basins’ sedimentary successions defines four tectonostratigraphic (TS) units. In the Fundy-Chignecto rift basin complex, TS I is an unconformity-bounded, early synrift fluvial-eolian sequence of Late Permian age. TS II is a dominantly fluvial (with some lacustrine) sequence believed representative of an underfilled, hydrologically open basin (subsidence < sedimentation). This is followed by either a closed basin or one in hydrological equilibrium (subsidence ≥ sedimentation) dominated by lacustrine (TS III), and later playa/lacustrine (and basal CAMP volcanics) successions (TS IV). The climate sensitive lacustrine facies—especially in TS III—are exquisite recorders of paleoclimate, and with paleomagnetic data refine the determination of the basins’ age and paleolatitudinal positions. Seismic profiles in the Fundy-Chignecto (Canada) and Newark (USA) basin reveal high-amplitude, laterally continuous reflections adjacent to the respective border faults. In the Newark basin, these are calibrated against academic and industry wells revealing a correlation with large scale climatic cycles and lacustrine facies in TS III. In both basins, similar reflections are observed in the undrilled distal portion of TS II fluvial successions and are interpreted as indicating similar lacustrine successions. This architecture departs from the original TS II model (subsidence < sedimentation) by inferring high levels of tectonically driven extension resulting in the basins being closed from their inception (subsidence ≥ sedimentation) thus facilitating lake formation. During TS II deposition (approximately Late Anisian to Early Carnian), paleomagnetic data positions these basins within the north equatorial humid belt. This is a favorable setting for the evolution of lakes; i.e. , elevated precipitation coupled with tectonic extension, and most importantly, under conditions for organic matter creation and preservation. If correct, this interpretation would have a significant impact on the potential for hydrocarbons sourced from Late Triassic lacustrine successions in presalt synrift basins offshore Nova Scotia and Morocco. Importantly, a potential new oil-rich resource play may exist beneath the shallow waters of Chignecto Bay. In the deep water portion of the offshore Scotian basin, presalt synrift basins having similar lacustrine source rock potential may also exist.

The eastern Laurentian margin in northeastern North America is marked by promontories and embayments that are defined by northeast-striking rift zones offset by northwest-striking transform faults. The complete history of the northeastern margin, from the initiation of continental rifting to the onset of passive-margin thermal subsidence, is preserved in a dynamic stratigraphic succession and in anorogenic magmatic suites. Late Neoproterozoic–Early Cambrian clastic and volcanic deposits overlie ca. 1.0 Ga and older Laurentian basement and define multiphase continental extension that rifted Laurentia out of Rodinia, opening the Iapetus Ocean as well as the more marginal Humber Seaway. Continental extension is also expressed in a set of basement fault systems that extend into the craton perpendicular to the northeastern Laurentian margin. Lower Cambrian sandstones at the base of a transgressive passive-margin succession overlie synrift rocks and basement, defining the time of transition for the eastern Laurentian margin from an active rift to a passive-margin environment. The passive margin is expressed as a broad late Early Cambrian through early Middle Ordovician carbonate bank and associated offshelf facies. Synthesis of the available data reveals significant along-strike variations in the thickness, composition, age, and facies of important synrift and postrift stratigraphic successions between the northern Appalachian rift zones. These variations are consistent with models for low-angle detachment rift systems and allow for the resolution of the underlying basement architecture of the eastern Laurentian margin specific to low-angle detachments, including upper-plate margins, lower-plate margins, and transform faults that bound zones of oppositely dipping low-angle detachments.