Mass transport deposits in the Donegal Barra Fan and their association with British–Irish Ice Sheet dynamics

Abstract

This study analyses seismic data to investigate the kinematic indicators within the mass transport deposits (MTDs) of the Donegal Barra Fan complex in the Rockall Trough, along the NW European continental margin. Five episodes of mega-scale MTDs (DBF-01, -02, -03, -04 and -05) are identified. DBF-01 is the largest MTD in the NW British continental margin, comprising 1907 km3 of sediments. Fold-and-thrusts were identified within the MTDs where they attain maximum thickness of c. 300–380 ms TWT, but not at the toe region. This indicates that local erosion and deceleration caused bulking up of the MTD volume, but the MTD was not fully arrested due to the high mobility of the mass flow. MTD thickness distribution and thrust fault orientations indicate source areas and flow direction of MTD. The MTDs show a compensational stacking pattern with earlier deposits influencing the position and flow direction of succeeding slides, suggesting that glaciogenic debris flows are sensitive to topographic variability. We propose that increased sediment input associated with at least five expansions of the British–Irish Ice Sheet to the shelf edge led to the development of these MTDs and that the youngest of them, DBF-05, corresponds to the Last Glacial Maximum.

Channel and inter-channel morphology resulting from the long-term interplay of alongslope and downslope processes, NE Rockall Trough, NE Atlantic

“…They are separated by high-amplitude, sub-horizontal to steeply-dipping reflectors that are generally continuous for tens of kilometres but are abruptly truncated by overlying or adjacent packages (Figs 3,6,9,10). Unit C is described and discussed in detail by Roy et al (2020).…”

“…10). The Pleistocene MTD succession is not the focus of this paper, but is analysed in detail in Roy et al (2020).…”

Channel and inter-channel morphology resulting from the long-term interplay of alongslope and downslope processes, NE Rockall Trough, NE Atlantic

“…They are separated by high-amplitude, sub-horizontal to steeply-dipping reflectors that are generally continuous for tens of kilometres but are abruptly truncated by overlying or adjacent packages (Figs 3,6,9,10). Unit C is described and discussed in detail by Roy et al (2020).…”

“…10). The Pleistocene MTD succession is not the focus of this paper, but is analysed in detail in Roy et al (2020).…”

Channel and inter-channel morphology resulting from the long-term interplay of alongslope and downslope processes, NE Rockall Trough, NE Atlantic

“…They are separated by high-amplitude, sub-horizontal to steeply-dipping reflectors that are generally continuous for tens of kilometres but are abruptly truncated by overlying or adjacent packages (Figs 3,6,9,10). Unit C is described and discussed in detail by Roy et al (2020).…”

“…10). The Pleistocene MTD succession is not the focus of this paper, but is analysed in detail in Roy et al (2020).…”

Channel and inter-channel morphology resulting from the long-term interplay of alongslope and downslope processes, NE Rockall Trough, NE Atlantic

“…They are separated by high-amplitude, sub-horizontal to steeply-dipping reflectors that are generally continuous for tens of kilometres but are abruptly truncated by overlying or adjacent packages (Figs 3,6,9,10). Unit C is described and discussed in detail by Roy et al (2020).…”

“…10). The Pleistocene MTD succession is not the focus of this paper, but is analysed in detail in Roy et al (2020).…”