10:45 〜 12:15
[MIS20-P03] Insights from a geomorphological comparison between terrestrial and martian eskers
キーワード：地球、火星、エスカー
Eskers are glaciofluvial subglacial landforms, positive relief depositional ridges of glaciofluvial sand and gravel (e.g., Brennand, 2000), and locate primarily in previous areas of the late Pleistocene glaciations (Canada, Fennoscandia, and Britain-Ireland, e.g., Storrar et al., 2014; Stroeven et al., 2016; Clark et al., 2018) on Earth, and in the south circumpolar Dorsa Argentea Formation, possibly representing an extensive ancient ice sheet in the south polar region, on Mars (~3.8–3.5 Ga, Kress and Head, 2015; Butcher et al., 2016). Their planform is straight-to-sinuous and anastomosing ridges with sharp- to round-crested cross-sectional crest morphology. The length is up to hundreds of kilometers with gaps; the width is hundreds of meters; the height is tens of meters (e.g., Storrar et al., 2014). Eskers are interpreted to have been deposited through discharges of meltwater beneath ice sheets and in subglacial channels which are incised into the ice (R-channels, e.g., Storrar et al., 2020); thus, eskers indicate the presence of former ice sheets, its subglacial drainage conduits of meltwater, trajectories of ice sheet retreat patterns, and subglacial groundwater systems (e.g., Boulton et al., 2009; Storrar et al., 2014; Dewald et al., 2021).
The length and planform of eskers could reflect meltwater drainage extent (Brennand, 2000). Long and dendritic eskers can be deposited in extensive and synchronous drainage systems where sufficient supplies of meltwater and sediment are maintained. On the other hand, short and subparallel can be deposited in limited drainage systems. As for sinuosity, longer eskers tend to be straight may indicate pressurized conditions under thicker ice and vice versa (Storrar et al., 2014). Esker spacing is partly controlled by the transmissivity of the substrate (Boulton et al., 2007, 2009). Additionally, as for cross-sectional crest morphology, the sharpness of the ridge crest may indicate meltwater flow magnitude because a balance between ice creep closure and opening by viscous heating of meltwater flow governs subglacial channels in which esker deposited (Shreve, 1985; Perkins et al., 2016). To date, however, no comprehensive and large-scale classification which combines planform and crest morphology for terrestrial and martian eskers has been constructed.
In the present study, we undertake morphometric mappings and analyses of aspects of planform morphology and cross-sectional crest morphology along Laurentide eskers in comparison with martian eskers in the south circumpolar Dorsa Argentea Formation. We carry out the mapping from ArcticDEM (Porter et al., 2018), a digital surface model of the Arctic, in a geographic information system software.
The length and planform of eskers could reflect meltwater drainage extent (Brennand, 2000). Long and dendritic eskers can be deposited in extensive and synchronous drainage systems where sufficient supplies of meltwater and sediment are maintained. On the other hand, short and subparallel can be deposited in limited drainage systems. As for sinuosity, longer eskers tend to be straight may indicate pressurized conditions under thicker ice and vice versa (Storrar et al., 2014). Esker spacing is partly controlled by the transmissivity of the substrate (Boulton et al., 2007, 2009). Additionally, as for cross-sectional crest morphology, the sharpness of the ridge crest may indicate meltwater flow magnitude because a balance between ice creep closure and opening by viscous heating of meltwater flow governs subglacial channels in which esker deposited (Shreve, 1985; Perkins et al., 2016). To date, however, no comprehensive and large-scale classification which combines planform and crest morphology for terrestrial and martian eskers has been constructed.
In the present study, we undertake morphometric mappings and analyses of aspects of planform morphology and cross-sectional crest morphology along Laurentide eskers in comparison with martian eskers in the south circumpolar Dorsa Argentea Formation. We carry out the mapping from ArcticDEM (Porter et al., 2018), a digital surface model of the Arctic, in a geographic information system software.