Significance of fine-grained sediment lofting from melt-water generated turbidity currents for the timing of glaciomarine sediment transport into the deep sea

Timing of massive ‘Fleuve Manche’ discharges over the last 350kyr: insights into the European ice-sheet oscillations and the European drainage network from MIS 10 to 2

“…This confirms the IRD origin of the outsized grains and strongly suggests that the mud deposition lasted at least as long as the ice-drift season (e.g. Hesse and Khodabakhsh, 2006). Intense activity of the 'Fleuve Manche' palaeoriver occurred during the deposition of the laminated facies at sites MD95-2002 andMD03-2692, in response to the substantial retreat of the European ice sheets and glaciers (Zaragosi et al, 2001;Eynaud et al, 2007;Toucanne et al, 2008).…”

A meltwater origin for Antarctic shelf bedforms with special attention to megalineations

“…Hesse et al (2001) made the surprising discovery of a 700-km-long braid plain on the floor of the Labrador Sea. It was constructed by powerful, hyperpycnal flows generated by meltwater outburst floods (Hesse et al, 2004;Hesse and Khodabakhsh, 2006). Curved megalineations, some in excess of 20 km long, are found on the braid plain (Hesse et al, 2001;Shaw and Lesemann, 2003).…”

Effects of topography on lofting gravity flows: Implications for the deposition of deep-water massive sands

“…The lofting point is associated with rapid sediment fallout and the removal of fine material in the rising plume (Klaucke et al, 2000;Gladstone and Pritchard, 2010). In natural submarine systems lofting gravity flows are predominantly hyperpycnal flows, generated from rivers discharging sedimentladen fresh water into the oceans (Mulder et al, 2003;Piper and Normark, 2009) or occasional catastrophic glacial outbursts of fresh water into the ocean (Russell and Knudsen, 1999;Hesse and Khodabakhsh, 2006). Such flows have been measured or estimated to be sustained from between several days to 3e4 weeks (Wheatcroft and Borgeld, 2000;Khan et al, 2005;Hesse and Khodabakhsh, 2006;Nakajima, 2006).…”

“…If the lofting point is stationary or largely stationary then material settling from the rising plume will settle in the absence of traction structures. Furthermore, if the rising plume carries with it the fines from the flow and disperses them over a wide area (Hesse and Khodabakhsh, 2006) or ocean currents transport the fines away from the area (Klaucke et al, 2000), then local accumulations of clean massive sands might be expected to form. Numerical modelling of sedimentation during lofting flows suggests that these lofting processes can indeed form massive beds, dependent on flow character and the behaviour of the rising plume (Gladstone and Pritchard, 2010).…”

“…These calculated grain sizes show that even small, slow moving hyperpycnal flows have enough competence to transport and deposit sands as products of lofting. Assuming faster velocities, representing more powerful lofting flows, such as larger flooding rivers or glacial melting (e.g., Hesse and Khodabakhsh, 2006), U ¼ 1 m s À1 , maximum calculated grain sizes are 237e291 mm; for U ¼ 1.5 m s À1 , maximum calculated grain sizes are 291e356 mm and for U ¼ 2 m s À1 , maximum calculated grain sizes are 335e410 mm. The higher assumed velocities show the potential for hyperpycnal flows and larger glacial meltwater events to be able to deposit medium sands within a lofting zone.…”