Fluid flow and pore pressure development throughout the evolution of a trough mouth fan, western Barents Sea

Abstract

Using a combination of geophysical and geotechnical data from Storfjorden Trough Mouth Fan off southern Svalbard, we investigate the hydrogeology of the continental margin and how this is affected by Quaternary glacial advances and retreats over the continental shelf. The geotechnical results show that plumites, deposited during the deglaciation, have high porosities, permeabilities and compressibilities with respect to glacigenic debris flows and tills. These results together with margin stratigraphic models obtained from seismic reflection data were used as input for numerical finite element models to understand focusing of interstitial fluids on glaciated continental margins. The modelled evolution of the Storfjorden TMF shows that tills formed on the shelf following the onset of glacial sedimentation (ca. 1.5 Ma) acted as aquitards and therefore played a significant role in decreasing the vertical fluid flow towards the sea floor and diverting it towards the slope. The model shows that high overpressure ratios (up to λ ca. 0.6) developed below the shelf edge and on the middle slope. A more detailed model for the last 220 kyrs accounting for ice loading during glacial maxima shows that the formation of these aquitards on the shelf focused fluid flow towards the most permeable plumite sediments on the slope. The less permeable glacigenic debris flows that were deposited during glacial maxima on the slope hinder fluid evacuation from plumites allowing high overpressure ratios (up to λ ca. 0.7) to develop in the shallowest plumite layers. These high overpressures likely persist to the Present and are a critical precondition for submarine slope failure.

Deep Structure, Tectonics and Petroleum Potential of the Western Sector of the Russian Arctic

“…There are serious concerns that the official resource assessment [40,41,63] may be biased due to over-reliance on the official point of view about the huge potential of the Arctic [40]. This conclusion is based on the fact that estimates of the petroleum potential of the least explored parts of the Arctic shelf in the last 20 years show a steady increase, regardless of the increase in the knowledge database, the number of new important discoveries, or the development of fundamentally new ways of increasing the hydrocarbon resource base.…”

A mixed turbidite – contourite system related to a major submarine canyon: The Marquês de Pombal Drift (south‐west Iberian margin)

“…6D), large lateral variations in thickness (Figs 3B and 5D) and fine particle size, usually associated with low permeability, that constitute the Marquês de Pombal Drift (Fig. 7) may have had a significant influence in overpressure build‐up of the underlying units (Urgeles et␣al ., 2010; Dugan & Sheahan, 2012; Urlaub et␣al ., 2015; Llopart et␣al ., 2019; Sammartini et␣al ., 2019; Mencaroni et␣al ., 2020). Hydrogeological models that consider the mechanical/hydrodynamic properties of the mixed turbidite – contourite system and its architecture as described in this work would enable the quantification of excess pore pressure build‐up.…”

“…6) refer to the normalized decompacted thickness of a sedimentary unit or, in other words, the depositional thickness prior to compaction, divided by the time needed for the unit to deposit. This approach allows a more accurate comparison between older units, which have undergone more compaction relative to younger (less compacted) sediments (Llopart et␣al ., 2019). Decompacted thickness of the units has been calculated using Van Hinte’s equation␣(Van Hinte, 1978):where is the initial porosity at deposition, is the present day porosity and is the present day sediment thickness.…”

Long‐term and long‐distance deformation in submarine volcanoclastic sediments: Coupling of hydrogeology and debris avalanche emplacement off W Martinique Island

“…Parameter uncertainties are related to the models architecture and variability in mechanical and hydraulic properties. The first incorporates seismic data resolution issues, choice of relationship for time to depth conversion, accuracy of sound speed determination and uncertainties in facies attribution (together with heterogeneity) along the modelled transect (Llopart et al., 2019; Nadim, 2015). Another source of uncertainty is related to the timing of occurrence of the flank collapses since accurate ages could not be constrained for DAD1 and DAD2, but also proper to the dating techniques used.…”