Lithofacies variations within sandur deposits: the role of runoff regime, flow dynamics and sediment supply characteristics

Sedimentary and structural evolution of a relict subglacial to subaerial drainage system and its hydrogeological implications: an example from Anglesey, north Wales, UK

“…Beds of massive to crudely-imbricated open-framework gravel (Figure 4j, k) are common within the lower horizons with bedding distinguished by subtle changes in clast size. Open framework gravels are thought to reflect rapid deposition from bedload under a high but variable (lower) flow regime with the continued entrainment or winnowing of fines (Maizels, 1993). Localised normal and inverse grading (cobbles-medium sand) is common and records successive stages of waning and rising flow (Miall, 1978(Miall, , 1985.…”

“…The largely erosional base of Lithofacies C, coupled with beds of imbricated and massive gravel, the channelised sands and gravels with fining-upwards (waning-flow) sequences, record largely unconstrained flow which is more indicative of a subaerial (proglacial) braided channel system (Figure 9c) (McDonald & Banerjee, 1971;Rust, 1972a;1972b;Miall, 1977;Gustavson & Boothroyd, 1987). Sediment facies record phases of sheet-flow meltwater discharge punctuated by anastomosing channel development typically associated with diurnal, ablation-related, seasonal discharge (Gustavson & Boothroyd, 1987;Maizels, 1993). Sedimentation rates and discharge were variable, with evidence for multiple phases of scouring and sheet flow punctuated by episodes of lateral channel migration within both large and small channels (McDonald & Banerjee, 1971;Miall, 1977).…”

“…Proglacial glacial outburst flood deposits comprise an extensive range of sediments driven by source proximity and the shape of the flood hydrograph (Clarke, 2003;Benn & Evans, 2010). However, at a meso-to smallscale, deposits are frequently characterised by complex facies associations and bounding surface geometries which reflect marked and rapid shifts in energy regime, sediment supply and turbulence (Maizels, 1992(Maizels, , 1993(Maizels, , 1997Marren, 2005;Russell et al, 2005;Duller et al, 2008;Marren et al, 2009). This meso-to small-scale architectural and sedimentological complexity is not apparent in the sequences at Lleiniog.…”

Chasma Boreale, Mars: Topographic characterization from Mars Orbiter Laser Altimeter data and implications for mechanisms of formation

“…Jö kulhlaups drain onto gently sloping outwash plains, commonly called sandurs, which have been built-up by deposition of suspended load and bed load from proglacial drainage rivers. The catastrophic floods can sculpt [Kor and Cowell, 1998] and scour bedrock, add sediment to the sandur [Maizels, 1989a[Maizels, , 1989b[Maizels, , 1993, deposit icebergs that later melt and form kettles [Tómasson, 1996], create drumlins [e.g., Kor and Cowell, 1998;Shaw et al, 1996] carve new channels, and create various flood morphologies [e.g., Rains et al, 1993]. As with any stream, the effect of the jökulhlaups on the surrounding plains depends on the severity of the flood itself, on the sediment load, etc.…”

“…As with any stream, the effect of the jökulhlaups on the surrounding plains depends on the severity of the flood itself, on the sediment load, etc. The details of the stratigraphy and sedimentary deposits resulting from a jökulhlaup [Maizels, 1989a[Maizels, , 1989b[Maizels, , 1993 would not be possible to observe on Mars owing to limits in image resolution.…”