Subaqueous landsystems

Subaqueous depositional environments were recognized as extensions of the primary landsystems presented by Eyles (1983c; e.g. Eyles & Menzies, 1983). Models of the wide spectrum of glacima-rine processes and depositional features have appeared in reviews of offshore environments (e.g. Powell, 1984; Eyles et al., 1985), but subaqueous landform-sediment assemblages have only recently been given separate treatment in a landsystem context (e.g. Benn & Evans, 1998; Powell, 2003; Teller, 2003; Vorren, 2003). This is exemplified by Vorren's (2003) compilation of the landforms and sediments on glaciated passive continental margins (Fig. 18.5). Glaciation of the shelf is recorded by huge erosional troughs containing glacially streamlined forms and recessional ice marginal depocentres. Grounding-zone wedges and trough-mouth fans mark former glacier margins at the shelf edge. Although the glacial bedforms are draped by extensive glacimarine sediments and forms associated with glacier-margin, ice-shelf and iceberg processes, the imprint of former glacier flow is often impressive and can be readily used in palaeoglaciological reconstruction (e.g. glacier surges (Solheim, 1991), palaeo-ice streams (Canals et al., 2000; O Cofaigh et al., 2002a; Ottesen et al., 2002; Sejrup et al., 2003), glacitectonic thrusting (Ssttem, 1990), trough-mouth fan construction (Vorren & Laberg, 1997; O Cofaigh et al., 2003)). Sedimentary sequences and depositional architecture in former subaqueous environments (e.g. Powell, 1981, 2003; L0nne, 1995, 2001) also provide valuable information for reconstructions of glacier marginal stability and oscillations, and feedback into reconstructions of palaeoglaciation style along glaciated coasts.

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