Recurrent mass-wasting in the Sørvestsnaget Basin Southwestern Barents Sea: A test of multiple hypotheses

Abstract

Mass-wasting on the NE Atlantic margin is generally attributed to Cenozoic glaciations. Using high-quality 2D seismic datasets and two exploration wells, this study investigates the types and driving mechanisms of mass-wasting in the Sørvestsnaget Basin, Southwestern Barents Sea. The methods include seismic interpretation of shelf margin clinoforms, mass-transport deposits (MTDs), submarine channels and v-shaped canyons. The shelf-edge trajectory provided information about sea-level conditions, paleo-sediment routes, and dispersal patterns during the evolution of the basin. In terms of the internal geometry of reflectors, the major depositional units in this work are five sedimentary packages (P1 to P5) characterised by distinct southwest dipping shelf margin clinoforms. The seven MTDs here discussed have Late Miocene to Pleistocene ages. Miocene and Early Pliocene MTDs in the basin demonstrate a tendency for initial translation through canyons and channels. The youngest MTDs are composed of glaciogenic sediments remobilized by ice streams during large-scale Neogene and Quaternary glaciations. This work shows that mass-wasting has been a recurrent and inherent process in the Sørvestsnaget Basin from the Miocene until recent times. The main triggering 1 mechanisms for slope failure in the basin are increased pore pressure from sea-level fall and high sedimentation rate. Mass-wasting in the study area occurred through progressive, retrogressive and coherent downslope failures.

A flexural isostasy model for the Pleistocene evolution of the Barents Sea bathymetry

“…There seems to be some disparity in the ages assigned to the horizons above the Miocene. Authors such as Ryseth et al (2003) and Omosanya et al (2016) relied only on biostratigraphic data to define the ages of the units above the Miocene reflector whereas Butt et al (2000), Hjelstuen et al (2007) and Knies et al (2009) used a combination of palaeomagnetic and biostratigraphic data. Hence, this study has relied on the most common ages used for the Pliocene to Pleistocene reflectors (Table 2).…”

“…Hence, this study has relied on the most common ages used for the Pliocene to Pleistocene reflectors (Table 2). In addition, the shelf-edge position defined by Omosanya et al (2016) was used to compare some of the results from the present study to see how the model fits with their seismic interpretation. …”

“…Horizon R4 corresponds to the base of the Pliocene or Pliocene 1 of Omosanya et al (2016) while horizon R5 represents Pliocene 2 . In addition, R7 corresponds to top Pliocene 3 of Omosanya et al (2016) and the base of the Pleistocene of Ryseth et al (2003).…”

“…Horizon R4 corresponds to the base of the Pliocene or Pliocene 1 of Omosanya et al (2016) while horizon R5 represents Pliocene 2 . In addition, R7 corresponds to top Pliocene 3 of Omosanya et al (2016) and the base of the Pleistocene of Ryseth et al (2003). On seismic sections, the packages underlying all these three horizons are characterised by shelf-margin clinoforms that are more than 1 km in height and about 40 km in length (Fig.…”

“…4). Omosanya et al (2016) considered the packages to have flat to descending clinoforms from R4 to R5, which changes to high-angle ascending clinoforms from R5 to R6 and to low-angle ascending clinoforms at the top i.e., R6 to R7. All previous data agree that the package above R7 is Pleistocene in age (Myhre et al, 1995;Butt et al, 2000;Ryseth et al, 2003;Geissler & Jokat, 2004;Hjelstuen et al, 2007;Knies et al, 2009;Mattingsdal et al, 2014;Omosanya et al, 2016).…”