Fluid flow and pore pressure development throughout the evolution of a trough mouth fan, western Barents Sea. (4th February 2019)

• Record Type: Journal Article
• Authors: Llopart, Jaume; Urgeles, Roger; Forsberg, Carl Fredrik; Camerlenghi, Angelo; Vanneste, Maarten; Rebesco, Michele; Lucchi, Renata Giulia; Rüther, Denise Christina; Lantzsch, Hendrik
• Is Part Of: Basin research. Volume 31:Number 3(2019)
• Page Start: 487
• Page End: 513
• Publication Date: 2019-02-04
• Subjects: Sedimentation and deposition -- Periodicals; Sedimentary basins -- Periodicals; 551
• DOI: 10.1111/bre.12331
• Languages: English
• ISSNs: 0950-091X

Abstract

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. Abstract : Conceptual model of TMF evolution during a full glacial/interglacial cycle. (a) Interglacial stage with hemipelagic sedimentation. During winter, dense shelf water flows due to sea ice formation and brine release maintain free of sediment some of the upper and middle slope gullies excavated during the deglaciation. (b) GM, the material transported by ice streams is dumped over the shelf edge as debris flows which can erode the underlying sediments. (c) Deglaciation: the turbid meltwater plumes leave a bed of plumite/turbidite sediments covering the shelf and TMF area, while the most energetic flows excavate gullies on the upper slope. The thickness of this unit increases towards the south. d: Submarine landslides triggered by earthquakes from isostatic rebound induced by ice sheet retreat. (1) hyperpycnal flow; (2) hemipelagic (interglacial) sediments; (3) gullies; (4) contour currents, (5) subglacial (diamicton) till; (6) debris flows; (7) meltwater plumes; (8) gully erosion and plumite/turbidite sedimentation; (9) iceberg rafting; (10) earthquake; (11) landslides; (12) glacial trough. In (b) to (d), sea‐ice is not shown for a better visualisation of the slope processes. Overpressure shading and fluid flow vectors are depicted.