Giant paleo-seafloor craters and mass wasting associated with magma-induced uplift of the upper crust

Abstract

Giant seafloor craters are known along many a continental margin with recurrent mass-wasting deposits. However, the impact of breakup-related magmatism on the evolution of such craters is barely understood. Using high-quality geophysical datasets, this work examines the genetic relationship among the location of magmatic sills, forced folds and the formation of giant paleo-seafloor craters underneath an ancient mass-transport complex in the Møre and Vøring basins, offshore Norway. The data reveal that forced folding of near-seafloor strata occurred because of the intrusion of several interconnected magmatic sills. Estimates of 1-dimensional uplift based on well data show that uplift occurred due to the intrusion of magma in Upper Cretaceous to Lower Eocene strata. Our findings also prove that subsurface fluid plumbing associated with the magmatic sills was prolonged in time and led to the development of several vertical fluid flow conduits, some of which triggered mass wasting in Neogene to Recent times. The repeated vertical expulsion of subsurface fluids weakened the strata on the continental slope, thereby promoting mass wasting, the selective cannibalization of the paleo-seafloor, and the formation of elongated craters at the basal shear zone of the mass-transport complex. Significantly, the model presented here proves a close link between subsurface magmatic plumbing systems and mass wasting on continental margins.

Long-term slope instability induced by the reactivation of mass transport complexes: An underestimated geohazard on the Norwegian continental margin

“…In this study area, MTC 1 is recognized in the lower continental slope to fills ooze evacuation structures (craters) below, perhaps as a result of focused fluid flow and sediment density reversal during Slide W (Riis et al, 2005;Lawrence and Cartwright, 2010;Omosanya et al, 2022). Above MTC 1, MTC 2 can be distinguished by its glide plane (Horizon H2) that eroded the top of MTC 1, where a group of NW-striking furrows is recorded in Terrace 2 with a sinuosity approaching 1.01 (Horizon H2;Figs.…”

“…The relief map of its basal glide plane reveals local depressions, previously interpreted as craters or ooze evacuation structures (Riis et al, 2005;Lawrence and Cartwright, 2010). Above the basal glide plane, MTCs with basal striations, inner imbrications and ooze mounds suggest recurrent slope failure during ooze evacuation (Riis et al, 2005;Jing et al, 2022;Omosanya et al, 2022). Except for slide blocks along their sidewalls, these MTCs comprise transparent to chaotic seismic facies (Riis et al, 2005;Lawrence and Cartwright, 2010;Omosanya et al, 2022).…”

“…Except for slide blocks along their sidewalls, these MTCs comprise transparent to chaotic seismic facies (Riis et al, 2005;Lawrence and Cartwright, 2010;Omosanya et al, 2022). On the northwest flank of the Storegga Slide, three craters are observed cutting into the Brygge Formation (C1 to C3 in Omosanya et al, 2022). In study area, these Slide W MTCs have been eroded and removed by subsequent slope failure events, leaving an 'L'shaped ramp on the modern seafloor (Jing et al, 2020, 2022) (Figs.…”

“…Above the basal glide plane, MTCs with basal striations, inner imbrications and ooze mounds suggest recurrent slope failure during ooze evacuation (Riis et al, 2005;Jing et al, 2022;Omosanya et al, 2022). Except for slide blocks along their sidewalls, these MTCs comprise transparent to chaotic seismic facies (Riis et al, 2005;Lawrence and Cartwright, 2010;Omosanya et al, 2022). On the northwest flank of the Storegga Slide, three craters are observed cutting into the Brygge Formation (C1 to C3 in Omosanya et al, 2022).…”

“…1b and 2b-2d. MTC 1 was deposited in association with Slide W, before the Storegga Slide proper (Bryn et al, 2003;Omosanya et al, 2022). b) TWT map of the seafloor (Horizon H1).…”