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

Benjamin Bellwald,Sverre Planke,Reidun Myklebust,Lukas W M Becker

doi:10.1038/s41467-020-18337-4

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.

Highlights

Trough mouth fans comprise the largest sediment deposits along glaciated margins, and record Pleistocene climate changes on a multi-decadal time scale
The large sediment volumes building these fans are dominated by two sediment types accumulated during very short time periods: The first type are fans characterized by rapidly deposited glacigenic debris flows (GDFs), which indicate Pleistocene periods when eroding ice-streams reached the shelf edge and released the eroded sediment to the upper slopes (Fig. 1a)[1,5,6,7,8,9,10,11]
Additional to the turbidite flows, deglacial plumites are released as the increased meltwater generated during the icesheet decay generates sediment plumes that deposit with high sedimentation rates on the upper slopes[2,9,14,24,25,26,27,28,29,30]

Summary

Introduction

Trough mouth fans comprise the largest sediment deposits along glaciated margins, and record Pleistocene climate changes on a multi-decadal time scale. The large sediment volumes building these fans are dominated by two sediment types accumulated during very short time periods: The first type are fans characterized by rapidly deposited glacigenic debris flows (GDFs), which indicate Pleistocene periods when eroding ice-streams reached the shelf edge and released the eroded sediment to the upper slopes (Fig. 1a)[1,5,6,7,8,9,10,11]. During shelf-edge glaciations, rapidly deposited glacial sediments are thought to be temporarily stored on the upper slopes, and eventually become unstable and generate GDFs with maximum runouts of >250 km[5,6,12,13]. Additional to the turbidite flows, deglacial plumites are released as the increased meltwater generated during the icesheet decay generates sediment plumes that deposit with high sedimentation rates on the upper slopes[2,9,14,24,25,26,27,28,29,30]

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Results