Meltwater sediment transport as the dominating process in mid-latitude trough mouth fan formation

Abstract

Trough mouth fans comprise the largest sediment deposits along glaciated margins, and record Pleistocene climate changes on a multi-decadal time scale. Here we present a model for the formation of the North Sea Fan derived from detailed horizon and attribute interpretations of high-resolution processed 3D seismic reflection data. The interpretation shows that stacked channel-levee systems form up to 400 m thick sedimentary sequences. The channels are elongated and can be traced from the shelf edge towards the deep basin for distances of >150 km, and document long-distance sediment transport in completely disintegrated water-rich turbidite flows. Downslope sediment transport was a continuous process during shelf-edge glaciations, reaching accumulation rates of 100 m/kyr. Our data highlight that exceptionally large volumes of meltwater may discharge to the slopes of trough mouth fans and trigger erosive turbidite flows. We conclude that freshwater supply is likely an underestimated factor for sedimentary processes during glacial cycles.

Pliocene–Pleistocene glacimarine shelf to slope processes in the south‐western Barents Sea

“…The dominance of channels seaward of palaeo‐shelves incised by MSGLs, and the relative absence of glacigenic‐debris flows of characteristic lobate form, is in agreement with recent work from the North Sea trough‐mouth fan (Bellwald et al., 2020). It has been suggested that when features that have been described previously as lobate, positive‐relief, glacigenic debris‐flows are imaged at higher seismic resolution, they appear as erosional channels with overflowing levees and associated sediment lobes (Bellwald et al., 2020). This may also be the case for the features that we identify within the Bear Island Fan stratigraphy.…”

Does Retrogression Always Account for the Large Volume of Submarine Megaslides? Evidence to the Contrary From the Tampen Slide, Offshore Norway

“…However, the Tampen Slide is thought to have occurred during MIS 6, ca. 130 ka (Nygård et al., 2005), and the subsequent retreat and growth of the Fennoscandian ice sheet, as evidenced by iceberg plow marks within the sedimentary layers (e.g., Bellwald et al., 2020; Montelli et al., 2018), may have led to erosion of any tsunami deposits related to the Tampen Slide. Furthermore, lower sea level at that time may also contribute to a lack of tsunami deposits related to the Tampen Slide.…”

“…The Tampen Slide occurred within the deposits of the North Sea Fan offshore Norway (Figure 1) ‐‐a trough mouth fan that comprises downslope‐related sediments (flow deposits that accumulated very rapidly at the termination of an ice stream), and along‐slope‐related sediments (contourites) that accumulated between ice sheet advances (Bellwald et al., 2020; Nygård et al., 2005). In addition, multiple submarine landslides are found within the North Sea Fan, several of which have total volumes exceeding 1,000 km 3 (Hjelstuen & Grinde, 2016; King et al., 1996; Nygård et al., 2005).…”

“…The Tampen Slide is located within the proximal deposits of the North Sea Fan, a region with highly variable sedimentation rates. In glacial periods, the presence of ice on the shelf can result in as much as a 10-fold increase in hemipelagic sedimentation (Lekens et al, 2009), with extreme sedimentation rates exceeding 20 m/Kyr (or even 100 m/Kyr during the last glaciation; Bellwald et al, 2020) on the upper slope directly affected by ice-stream sediment delivery (Hjelstuen et al, 2004). Nygård et al (2007) found that the Norwegian Channel ice stream loaded the North Sea Fan with as much as 1.1 Gt of sediment per year during the last glacial stage.…”

“…Consequently, the hazard associated with the failure of a similar megaslide is poorly constrained. This is largely due to its subsequent burial under up to 450 m of glacigenic sediment (Figure 2; Bellwald et al., 2020), and partial remobilization by the Storegga Slide. Several previous studies have analyzed the character of the Tampen Slide (Evans et al., 1996; Gafeira et al., 2010; Hjelstuen & Grinde, 2016; Nygård et al., 2005).…”