Arctic and Antarctic submarine gullies—A comparison of high latitude continental margins

Abstract

Submarine gullies are common features of high latitude continental slopes and, over the last decade, have been shown to play a key role in continental margin evolution, submarine erosion, downslope sediment transport, slope deposits, and the architecture of petroleum reservoirs. However, the processes that form these gullies, the timescales over which they develop, and the environmental controls influencing their morphology remain poorly constrained. We present the first systematic and comparative analysis between Arctic and Antarctic gullies with the aim of identifying differences in slope character, from which we infer differences in processes operating in these environments.Quantitative analysis of multibeam echosounder data along 2469 km of the continental shelf and upper slope and morphometric signatures of over 1450 gullies show that six geomorphically distinct gully types exist on high latitude continental margins. We identify distinct differences between Arctic and Antarctic gully morphologies. In the Arctic data sets, deep relief (> 30 m gully incision depth at 50 m below the shelf edge) and shelfincising gullies are lacking. These differences have implications for the timescales over which the gullies were formed and for the magnitude of the flows that formed them. We consider two hypotheses for these differences: (1) some Antarctic gullies developed through several glacial cycles; and (2) larger Antarctic gullies were formed since the Last Glacial Maximum as a result of erosive flows (i.e., sediment-laden subglacial meltwater) being more abundant on parts of the Antarctic margin over longer timescales.A second difference is that unique gully signatures are observed on Arctic and on Antarctic margins. Environmental controls, such as the oceanographic regime and geotechnical differences, may lead to particular styles of gully erosion observed on Arctic and Antarctic margins.

Large-scale submarine landslides, channel and gully systems on the southern Weddell Sea margin, Antarctica

“…The mass wasting features incise the gullies, suggesting that they formed later. The features are similar to 'type IV' gullies observed on other high-latitude margins (Gales et al, 2013a;2013b), which are characteristic of smallscale mass wasting. The fact that all the small-scale mass wasting features initiate along a common boundary at ~1300 m water depth, suggests their formation is due to a change in substrate strength within the shallow subsurface, for example due to failure within weak interglacial substrate sediments.…”

“…At ~1300 m water depth, a boundary occurs where small-scale mass wasting features are observed, similar to 'type IV' gullies observed on other high-latitude continental margins (Gales et al, 2013a;2013b). The small-scale mass wasting features cross-cut the submarine gullies ( …”

Submarine sediment and landform record of a palaeo‐ice stream within the British−Irish Ice Sheet

“…; Gales et al . ). These glacially fed debris lobes and gullies represent important pathways for sediment transfer beyond the continental shelf edge.…”

Gulf of Alaska continental slope morphology: Evidence for recent trough mouth fan formation

“…We find two distinct statistical groupings, based on gully relief, that correspond to the regions of slope progradation and erosion previously observed through the large‐scale morphologic characterization (Figures , and ). Gully morphology is controlled by numerous processes including erosion by sediment gravity flows, such as turbidity currents, as well as small‐scale slumping and mass wasting [ Harris and Whiteway , ; Gales et al ., ]. The majority of these gullies are V‐shaped, commonly attributed to dense fluid flow such as sediment laden meltwater while the remainder are U‐shaped and are likely due to small‐scale mass wasting [ Noormets et al ., ; Gales et al ., ].…”