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The investigation of trough mouth fans (TMFs), important paleoclimatic archives on mid- and high-latitude continental margins, has so far mainly been based on the integration of various types of acoustic data supplemented with short sediments cores. In consequence, sedimentological and chronological data about parts of TMFs deposited prior to the Last Glacial Maximum remains sparse. Here, we re-evaluate the upper part of ODP Site 987 drilled on the distal part of the Scoresby Sund TMF on the east Greenland continental margin, which records the former dynamics of the Scoresby Sund sector of the Greenland Ice Sheet. Based on a more detailed sedimentological description than previously available we find that lithological unit I, deposited over the last ~ 2.14 Ma, can be divided into two parts, a lower part dominated by glacimarine and marine deposits including some scattered, sandy turbidites and an upper part of debris flow deposits interbedded with sandy turbidites. The transition between these parts occurred at about 0.99 Ma, i.e. at the same time when the mode of ice-sheet variation changed globally, the average ice sheet size increased significantly and the periodicity of ice-volume variation increased from around 41 ka to approximately 100 ka (the “Mid-Pleistocene Transition”). On the distal Scoresby Sund TMF, this change appears to be reflected through a marked increase in the abundance of sandy turbidity flows accompanied by a longer run-out of some of the debris flows due to the delivery of larger sediment volumes during longer-lasting glacial maxima. This suggests that long sediment cores from TMFs have the potential to record the major climatic trends occurring during the Pleistocene. [ABSTRACT FROM AUTHOR]

The Neogene–Quaternary development of the ∼700 km long mid-Norwegian and Lofoten–Vesterålen continental margin is reconstructed using a dense grid of 2D seismic data and exploration wellbores. Overall, widespread ocean current-controlled contourite drifts built up along the whole margin segment from the mid-Miocene onwards (c. 11 Ma, Kai Formation). The onset (c. 8.8 Ma) of a large inner shelf progradation (Molo Formation) was, however, restricted to the southern part of the study area, the inner mid-Norwegian shelf. In the Quaternary (c. 2.7 Ma), grounded ice sheets repeatedly brought large sediment volumes (Naust Formation) to the shelf beyond the Molo Formation. A similar build-out is less pronounced further north, where contourite drift growth instead continued and resulted in build-up of the Lofoten and Vesterålen drifts. In contrast, the drifts of the southern part of the study area occur for the most part stratigraphically below, interbedded with and distal to the progradational Molo and Naust deposits. The study area exemplifies pronounced variability in Neogene–Quaternary continental margin growth. The wide and gently dipping mid-Norwegian margin facilitated coastal and shelf progradation related to fluvial and glacial processes, while the narrow and steep Lofoten–Vesterålen margin received little input from these sources although exposed to the same paleoclimate. Instead, erosion of canyons promoted downslope reworking across the slope and into the deep basins. This low sediment input is interpreted to be controlled by the alpine relief in the north resulting in a small source area and thus low fluvial and glacial sediment input. To the south, hinterland relief allowed for a much larger fluvial and later, glacial source area. Both margin segments were also influenced by contour currents throughout the studied period. We emphasize their importance for understanding the role of erosion and deposition in source-to-sink systems, and thus the need for these processes to be integrated within source-to-sink models. • Regional seismic study of along- and downslope processes on the Norwegian margin. • New contourites are defined that evolved from ∼11 Ma due to inflowing Atlantic Water. • Miocene fluvial (∼8.8 Ma) and Quaternary glacial sources formed progradational wedges. • Hinterland/basin topography, sediment supply and climate, controlled margin growth. • Erosion-sedimentation from ocean currents influence source-to-sink systems. [ABSTRACT FROM AUTHOR]

Trough mouth fans contain information about the evolution of high-latitude continental margins, including rates of glacial sedimentation and hinterland erosion. Here, the late Cenozoic evolution of high-gradient trough mouth fans and canyons on the Troms margin, northern Norway, is reconstructed. Paleocanyons were active prior to the Quaternary glaciations. Glaciomarine and glaciofluvial conditions prevailed between ca. 2.7 Ma and ca. 1.5 Ma, and ice sheets possibly reached the paleo-shelf break at least once. The minimum average sedimentation rate of this period was 0.22 m/k.y. From ca. 1.5 Ma to ca. 0.7 Ma, the glaciations intensified, and fast-flowing ice streams reaching the shelf break were established in the cross-shelf troughs. Subglacial deformation till was deposited at the outer shelf and later reworked by debris flows and turbidity currents. The Fennoscandian Ice Sheet started to route much of its ice mass to the north and south of the study area, and so the Troms margin possibly was a low-ice-flow sector from this time, with a minimum average sedimentation rate of 0.15 m/k.y. During the last ca. 0.7 m.y., ice streams continued to traverse the troughs, while sluggish-flowing ice prevailed on the banks. A minimum average sedimentation rate of 0.14 m/k.y. is estimated for this period. The minimum total erosion and erosion rate for the Quaternary are 50-140 m and 0.02-0.05 m/k.y., respectively. Compared with previous studies from other areas, this implies up to one order of magnitude variation in average glacial erosion rates along the western sector of the Fennoscandian-Barents Sea ice sheets. This is interpreted to be due to the size and bedrock composition of the catchment areas and the timing of ice growth and ice-sheet dynamics. In addition, the steep preglacial continental slope promoted high sediment flow velocity for the glacigenic sediments, causing much of the debris flows to transform into turbidity currents, which efficiently transported sediments across the slope and thereby maintained its steep gradient. [ABSTRACT FROM AUTHOR]