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ATLAS OF SUBMARINE GLACIAL LANDFORMS To be published in 2015 by the Geological Society of London as a Memoir within the Lyell Collection

Multibeam imagery of and in the Gulf of Bothnia, . The data are from a bathymetric survey contracted by the Swedish Maritime Administration. This imagery is shown in the Atlas contribution: Edited by J.A. Dowdeswell, M. , M. Jakobsson, B.J.Todd, E.K. DowdeswelL. K.A. Hogan “Drumlins in the Gulf of Bothnia”, M. JAKOBSSON1, S. L. GREENWOOD1, B. HELL2 & H. ÖIÅS

Example of a 4-page contribution describing an assemblage of glacial landforms

The J. A. DOWDESWELL ET AL. J. A. DOWDESWELL ET AL. J. A. DOWDESWELL ET AL. Assemblage of glacial and related landforms in the of southern Chile ice-sheet retreat after the LGM occasionally protruding through a fine- many Chilean fjords is mainly smooth, although bedrock break J. A. DOWDESWELL1*, E. K. DOWDESWELL1, C. RODRIGO2, & J. DIAZ3 grained basin-fill (Dowdeswell & Vásquez 2013). This interpretation through occasionally. Landforms that are not sustained by is confirmed by the presence of draping and ponded acoustically contemporary processes are likely to be buried by relatively rapid Geological 1Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER, UK laminated reported from a numbers of Chilean fjords (Fig. fine-grained sedimentation from meltwater plumes (Fig. 2c), and, in 2 2c). DaSilva et al. (1997) noted that the inner fiords of central Chilean progressively more ice-distal settings, by Holocene marine or pelagic Department of Geology, Andrés Bello University, Quillota 980, Viña del Mar, Chile contained 200-400 ms-thick acoustically laminated ice- sediments (Fig. 2d) (Fernández et al. 2013). 3School of Ocean Sciences, Catholic University of Valparaiso, Altamirano 1480, Valparaiso, Chile proximal sediments that relate, in part, to from the LGM, Subglacial and ice-contact landforms, similar to those imaged in augmented by continuing fine-grained sedimentation from turbid and Antarctic fjords and shelves, are likely to have developed *Corresponding author (e-mail: [email protected]) meltwater where Holocene tidewater and -fed at the base and margins of Chilean glaciers under full-glacial and are present at heads. Similar processes can be inferred from a deglacial conditions (Dowdeswell & Vásquez 2013); they can be Society sub-bottom profile of Ainsworth Fjord in Tierra del Fuego (Boyd et al. identified in fjord acoustic stratigraphy (Fig. 3). High rates of snow- The fjords of southern Chile (Fig. 1a) are one of the lowest-latitude Smaller fluvial catchments also have deltas at their marine margins 2008). Holocene basin fill is of mainly weakly-laminated acoustic accumulation and ice-surface melting on Chilean glaciers led, and mildest regions in which glaciers reach the sea today that have built out into relatively deep fjord waters (Fig. 1g). character with scattered chaotic facies inside a recessional however, to rapid meltwater and fine-grained delivery to the (Dowdeswell & Vasquez 2013). The Andean ice caps and the glaciers Swath bathymetry of the large glacifluvial delta fronts images (Fig. 2c). Radiocarbon dates suggest accumulation rates of up to a few fjords from tidewater glaciers and glacifluvial sources subsequent to of the Darwin Cordillera are of high mass throughput, with small submarine channels and narrow chutes which appear to organise tens of millimetres per year (Boyd et al 2008). Crater-like features that deglaciation. Most pre-existing glacial landforms on the fjord floor, precipitation often metres per year and, to balance this, very high rates into single major submarine channels on the fjord floors (Fi. 1e, f). break the smooth fjord floor in some areas are interpreted as with the exception of major retreat (Fig. 1b, d) and of surface melting. These ice masses either reach the sea at fjord The submarine channels continue for a number of kilometres along the pockmarks, probably produced from the escape of shallow gas from protruding streamlined bedrock, are largely buried and obscured by heads, or feed braided systems that flow into the fjord systems. flat floors of Iceberg and Bernardo fjords and into Messier Fjord (Fig. the underlying sediments. In addition, very few iceberg ploughmarks this subsequent glacimarine and glacifluvial sediment delivery (Figs. Large volumes of meltwater and glacial sediment are therefore 2a, b). The submarine in outer Iceberg Fjord is at least 15 km are observed on the relatively smooth floors of Chilean fjords. This is 2c, 3); it is predominantly submarine landforms that remain in an delivered to Chilean fjords either directly from subglacial long, up to about 50 m deep, and with an average width of 275 m and a result of relatively deep water combined with the calving of only active process-environment today, such as turbidity- channels beneath tidewater glaciers, or indirectly by glacifluvial processes. At that in Bernardo Fjord extends about 10 km, with a width and depth of small, irregular-shaped icebergs from tidewater glacier termini. and those relating to neoglacial ice advance, which are observed on the (LGM), the Patagonian expanded about 100 m and 50 m, respectively. Large transverse ridges, found along and at the mouths of a number our swath-bathymetric imagery (Fig. 2a, b). to fill these fjords, which were reoccupied by ocean waters as Much of the Chilean fjord system, especially with increasing of Chilean fjords, are of similar dimensions to the in The fjords of Chile represent an environmental setting similar to the deglaciation proceeded. distance from tidewater-glacier margins, is devoid of major inner Iceberg Fjord (Fig. 1b). They are interpreted as recessional high mass-throughput glacial system of SE Alaska in the northern sedimentary landforms, with the exception of occasional streamlined moraines formed as grounded tidewater glaciers retreated through the hemisphere, where sedimentation rates in fjords are also very high Description features and pockmarks. Streamlined sea-floor lineations, orientated Chilean fjords after the LGM. The ridges indicate former still-stand (Powell 1990). In progressively colder polar settings, ice-surface along-fjord, are observed in several areas (Dowdeswell & Vásquez positions, probably on the order of decades. This interpretation is melting is reduced, slowing the rate of sediment delivery to fjords. Some Chilean fjords have experienced tidewater-glacier advance 2013); some appear as streamlined bedrock protruding above the flat, supported by the location of several moraine ridges at the mouths of Here, subglacial landforms produced during the LGM and subsequent during the cool Little , followed by retreat over the past sedimentary fjord floors. Sets of crater-like structures, numbering tens fjords; likely pinning-points points where water deepens by tens to deglaciation can still be observed in swath-bathymetric imagery century or so (Masiokas et al. 2009). In inner Iceberg Fjord the sea- of individual features, are also observed on the floor of several hundreds of metres immediately distal of the ridges. because they remain at or just below the modern sea floor. floor contains several sets of features (Dowdeswell & Vásquez 2013): Chilean fjords; median crater depth is between 3 and 5 m and median Submarine channel systems (Fig. 2a, b), formed beyond major a series of transverse ridges of varying height distributed across the diameter is 40 to 60 m (Dowdeswell & Vásquez 2013). glacifluvial deltas in Iceberg and Bernardo fjords (Fig. 1e, f), are We thank the Servicio Hidrografico y Oceanografico de la Armada de fjord; a number of sub-parallel ridges orientated in the likely direction interpreted to be turbidity-current channels eroded by dense Chile (SHOA) for allowing use of their swath-bathymetric data. of past ice flow; and areas of flat, smooth sea floor (Fig. 1b). The Interpretation underflows (Syvitski et al. 1987). These dense submarine currents outermost transverse is about 100 m high and is asymmetrical, probably formed when: (i) strongly seasonal meltwater flow delivered References with a steeper ice-distal face (Fig. 1b); a second large ridge is about 50 The cross-fjord ridges observed in many Chilean fjords are Accepted papers (25 November 2014) interpreted as moraines produced at the former margins of tidewater large quantities of coarse-grained sediment from the braid plain: An Atlas of Submarine Glacial Landforms: m in height. A further ten or so transverse ridges are smaller, at about and/or (ii) slope failures on glacifluvial delta fronts, areas of high and BOYD, B. L., ANDERSON, J. B., WELLNER, J. S. & 10 m high. Closer to the modern ice front, a series of sedimentary glaciers. The largest ridge in inner Iceberg Fjord is a terminal moraine FERNANDEZ, R.A. 2008. The sedimentary record of glacial marking the outer limit of a advance of Tempano very variable rates of sediment delivery, translated downslope into lineations up to about 0.5 km long trend first just north of west and turbidity currents. The delta-fronts appear from swath bathymetry to retreat, Marinelli Fjord, Patagonia: regional correlations and then northward (labelled s in Fig. 1b). The rest of the floor of inner Glacier (Fig. 1b). Its steeper distal face is typical of moraines formed ties. Marine Geology, 255, 165-178. ANDERSON, J.B. & JAKOBSSON, M. Grounding-zone wedges on Antarctic continental shelves (820) at the maximum neoglacial positions of many northern hemisphere be dominated by down-slope sediment-transfer processes that produce Modern, Quaternary and Ancient Iceberg Fjord is predominantly flat and smooth (Fig. 1b). channels and chutes (Fig. 1e, f). At some other delta-fronts, with more DaSILVA, J. L., ANDERSON, J. B. & STRAVERS, J. 1997. Seismic In inner Eyre Fjord, Pio XI Glacier, which is of -type, has tidewater glaciers (e.g. Ottesen & Dowdeswell 2009). The sets of facies changes along a nearly continuous 24° latitudinal transect: th smaller transverse ridges closer to the modern are lobate relief (Dowdeswell & Vásquez 2013), mass-wasting processes AMBLAS, D. & CANALS, M. Contourite drifts and -channel systems on the Northern Antarctic Peninsula undergone advances of up to 5 km during the 20 Century (Masiokas in the form of sediment slumps and slides probably predominate. the fjords of Chile and the northern Antarctic Peninsula. Marine et al. 2009). The sea floor beyond about a kilometre from the modern very similar to those deposited during still-stands, or minor Geology, 143, 1-3-123. Pacific margin (844) readvances, superimposed on more general glacier retreat in Svalbard glacier terminus is largely flat, with a number of hummocks up to 14 Discussion: landform assemblage for Chilean fjords DOWDESWELL, J. A. & VÁSQUEZ, M. 2013. Submarine In the past two decades there have been several advances that make the production of an atlas of submarine glacial m high together with short ridge segments, but otherwise shows few fjords (e.g. Ottesen & Dowdeswell 2006). The lineations trending first landforms in the fjords of southern Chile: implications for west and then north in the innermost part of Iceberg Fjord (Fig. 1b) BARNES, P., PICKRILL, R. & BOSTOCK, H. Thompson and Bradshaw Sounds, Fiordland, New Zealand: a relict, signs of an organised set of submarine landforms (Fig. 1c). These The assemblage of glacial, glacifluvial and glacimarine landforms glacimarine processes and sedimentation in a mild glacier- landforms timely. First is the development of high-resolution imaging technologies: multibeam echo-sounding or swath rather chaotic positive-relief features give way to a smooth sea-floor are interpreted as streamlined sedimentary landforms produced found in the fjords of Chile is summarised in the schematic model in influenced environment. Quaternary Science Reviews, 64, 1-19. mid-latitude, temperate glacier system (880) down-fjord (Fig. 1c). beneath active glacier ice (Ottesen & Dowdeswell 2009). They Figure 3. The three principal components of the landform-assemblage FERNANDEZ, R., GULICK, S., RODRIGO, C., DOMACK, E., In several Chilean fjords, large sedimentary ridges are present indicate that the tidewater glacier was grounded in the deepest parts of model for these relatively mild, meltwater-dominated fjords are LEVENTER, A. & SAUSTRUP, S. 2013. The seismic record of bathymetry that allows the detailed mapping of the seafloor at water depths of tens to thousands of metres across con- across fjord axes (Dowdeswell & Vásquez 2013). In the 50 km-long the inner fjord. They also suggest that ice flow included a northward (Dowdeswell & Vásquez 2013): late glacial variations in the Strait of Magellan: new clues for the BARNES, P. M., PICKRILL, R. A., BOSTOCK, H. C., DLABOLA, E. K., GORMAN, A. R. & WILSON, G. S. Relict Europa Fjord, a prominent ridge is located at the fjord mouth where it component, perhaps occurring when ice had retreated from the area of (a) Moraine ridges, indicating still-stands during ice retreat down interpretation of the glacial history of Magallanes. Bollettino di proglacial deltas in Bradshaw and George Sounds, Fiordland, New Zealand (903) joins the 250 m-deeper Wide Fjord. Three other sedimentary ridges transverse ridges to fill only the innermost fjord. The smooth and flat fjords (Figs. 1d, 3), including the limit of recent Little Ice Age Geofisica Teorica ed Applicata, Supp. 2 - Geosur, 54, 257-259. tinental margins, and 3-D seismic methods that enable the visualisation of palaeo-continental shelves in Quaternary are spaced about 8 km apart in the inner half of the fjord (Fig. 1d). areas of the sea-floor, for example between the transverse moraine advance (Fig. 1b). The ridges are orientated transverse to past ice- MASIOKAS, M., RIVERA, A., ESPIZUA, L. E. VILLALBA, R. Prominent sedimentary ridges of similar geometry are located where ridges (Fig. 1b), are interpreted as sedimentary infill from the rainout flow, are asymmetrical with steeper ice-distal sides, and sometimes DELGADO, S. & ARAVENA, J. C. 2009. Glacier fluctuations in BELLEC, V., PLASSEN, L., RISE, L. & DOWDESWELL, J. A. Malangsdjupet: a cross-shelf trough on the North relatively shallow fjords enter the 40-km long Farquahar- of fine-grained debris transported away from the tidewater glacier as a have debris-flow lobes on their ice-distal flanks. Smaller transverse- extratropical South America during the past 1000 years. sediments and ancient palaeo-glacial rocks (e.g. Late Ordovician of Northern Africa). A second technological develop- Norwegian margin (860) Bernardo Fjord system and in Ringdove Fjord (49q42’S), usually turbid plume of suspended sediment (Powell 1990). moraines ridge, found inside Little Ice Age moraines, mark ice Palaeogeog., Palaeoclim., Palaeoecol., 281, 242-268. extending the full width of the fjord. On their steeper, outer-fjord Beyond Pio XI Glacier, in the 35 km-long Eyre Fjord (Fig. 1c), the recession over approximately the last century (Fig. 1b). OTTESEN, D. & DOWDESWELL, J. A. 2006. Assemblages of ment is that of ice-breaking or ice-strengthened ships that can penetrate deep into the ice-infested waters of the Arctic slopes, small channels or chutes (up to a few hundred metres long and overall rather flat sea-floor observed proximal to the present ice front (b) Glacifluvial and fluvial deltas, formed through sedimentation submarine landforms produced by tidewater glaciers in Svalbard. BELLEC, V., RISE, L., BØE, R. & DOWDESWELL, J. A. Glacially related on the upper continental slope, a few metres wide) are sometimes imaged, along with lobate features is most likely also a result of of fine-grained material from from braided rivers from glaciated or fluvial catchments (Fig. 1e-g). Journal of Geophysical Res., 111, doi:10.1029/2005JF000330. SW Barents Sea margin (861) that appear to override fjord-floor sediments (Fig. 1d). turbid meltwater plumes. Isolated hummocks and ridges were The deltas have small channels and chutes, and sometimes debris-flow OTTESEN, D. & DOWDESWELL, J. A. 2009. An inter-ice and Antarctic to deploy the multibeam systems. A third component is that of relevance – through both the recognition Where glaciers from the Patagonian Ice Caps do not reach the sea probably formed during a previous surge of the glacier, given that lobes, on their submarine faces. glaciated margin: submarine landforms and a geomorphic model today, braided rivers or sandurs link the glacial and marine deformed medial moraines on the glacier surface imply recent surge (c) Relatively deep, sinuous turbidity-current channels, often found based on marine-geophysical data from Svalbard. Geological BØE, R., BELLEC, V. K., DOLAN, M. F. J., RISE, L., BUHL-MORTENSEN, P. & BUHL-MORTENSEN, L. Cold-water sedimentary systems. For example, Occidental Glacier reaches outer activity (Masiokas et al. 2009). within predominantly smooth fjord floors (Fig. 2a, b). Society of America Bulletin, 121, 1647-1665. that the polar regions, and especially the Arctic, are particularly sensitive parts of the global environmental system and The floor of Eyre Fjord, in common with many Chilean fjords (e.g. coral reefs in the Hola glacial trough off Vesterålen, North (821) Iceberg Fjord via an 11 km-long braided channel (Fig. 1e), and a 2 Both glacifluvial and fluvial deltas, together with turbidity-current POWELL, R. D. 1990. Glacimarine processes at grounding-line fans km-long braid plain links Bernardo Glacier with the adjacent fjord DaSilva et al. 1997; Boyd et al. 2008), is largely smooth, with channels, are active sites of debris transfer today in the Chilean fjords. and their growth to ice-contact deltas. In Dowdeswell, J. A. & that these high-latitude margins (both modern and ancient) are likely to contain significant hydrocarbon resources. An (Fig. 1f). Sediment delivery from these braided channels has built streamlined bedrock lineations and recessional-moraine ridges from The glacial imprint in the landform-assemblage model, however, is Scourse, J. D., (eds.), Glacimarine Environments: Processes and BROTHERS, L. L., LEGERE, C., HUGHES CLARKE, J. E., KELLEY, J. T, BARNHARDT, W. A., ANDREWS, B. D. & glacifluvial deltas 1.5 to 2 km wide into the fjords beyond (Fig. 1e, f). often limited and related to recession from the LGM, except where Sediments. Geological Society Special Publications, 53, 53-73. tidewater glacier termini have advanced within the past few centuries SYVITSKI, J. P. M., BURRELL, D. C. & SKEI, J. M. 1987. Fjords: BELKNAP, D. F. Pockmarks in Passamaquoddy Bay, New Brunswick, (904) Fig. 1. Sun-illuminated multibeam bathymetric images of submarine landforms in fjords of Chilean Patagonia. Acquisition system Atlas Fansweep. Frequency 200 kHz. Grid-cell enhanced understanding of the sediments and landforms of these fjord-shelf-slope-rise systems is, therefore, of in- size 20 m. (a) Location of study area (red box; map from GEBCO_08). (b) Terminal moraine ridge and other transverse ridges produced by Tempano Glacier. S is streamlined (Figs. 1b-c). Apart from these three landform-components, the floor of Processes and Products. Springer, Berlin. lineations. (c) Hummocky but otherwise largely flat sea-floor beyond Pio XI Glacier in Eyre Fjord. H is hummocky glacial debris. (d) Swath image of 100 m-high recessional BURTON, D. J., DOWDESWELL, J. A., HOGAN, K. A. & NOORMETS, R. Little Ice Age terminal and retreat mo- From: DOWDESWELL, J. A., CANALS, M., JAKOBSSON, M., TODD, B. J., DOWDESWELL, E. K. & HOGAN, K. A. (eds) Atlas of Submarine Glacial moraine in Europa Fjord. (e) Glacifluvial delta in Iceberg Fjord and associated . (f) Glacifluvial delta in Bernardo Fjord, showing braided river and adjacent Bernardo creasing importance to both academics and industry. We are editing an Atlas of Submarine Glacial Landforms that Landforms: Modern, Quaternary and Ancient. Geological Society, London, Memoirs, xx, 1-4. © The Geological Society of London, 2014. DOI: xx.xxxx/xxx.x. Glacier. (g) Small fluvial delta in Eyre Fjord. Images modified after Dowdeswell & Vásquez (2013). presents a series of individual contributions that describe, discuss and illustrate features on the high-latitude, glacier- raines in Kollerfjorden, northwest Spitsbergen (865) CHAND, S., THORSNES, T., RISE, L., BRUNSTAD, H. & STODDART, D. Pockmarks in the SW Barents Sea and influenced seafloor. Contributions are organised in two ways: first, by position on a continental margin – from fjords, their links with iceberg ploughmarks (852)

through continental shelves to the continental slope and rise; secondly, by scale – as individual landforms and assem- DECALF, C., DOWDESWELL, J. A. & FUGELLI, E. M. G. Seismic character of possible buried grounding-zone blages of landforms. A final section provides discussion of integrated fjord-shelf-slope-rise systems. Over 100 contri- wedges in the Late Ordovician glacial rocks of Algeria (915) DOWDESWELL, J. A. & OTTESEN, D. 3D seismic imagery of deeply buried iceberg ploughmarks in butions by scientists from many countries contain descriptions and interpretation of swath-bathymetric data from both sediments (893) Examples of 2-page contributions describing glacial landforms

Arctic and Antarctic margins and use 3D seismic data to investigate ancient glacial landforms. The Atlas will be pub- DOWDESWELL, J. A. & OTTESEN, D. Current-modified recessional-moraine ridges on the northwest Spitsber- lished in late 2015 in the Memoir Series of the Geological Society of London. gen shelf (916) DOWDESWELL, J. A. & OTTESEN, D. Eskers formed at the beds of modern surge-type tidewater glaciers in Spitsbergen (918) M. JAKOBSSON & J. B. ANDERSON B.J. TODD DOWDESWELL, J. A., BATCHELOR, C. L., HOGAN, K. A. & SCHENKE, H.-W. Nordvestfjord: a major East Green- Corrugation ridges in the Pine Island Bay glacier trough, West Antarctica De Geer moraines on German , southern Scotian Shelf of Atlantic Canada land fjord system (870) DOWDESWELL, J. A., OTTESEN, D. & NOORMETS, R. Submarine slides from the walls of Smeerenburgfjorden, M. JAKOBSSON1* & J. B. ANDERSON2 B.J. TODD1* NW Svalbard (850) 1Department of Geological Sciences, Stockholm University, Svante Arrhenius väg 8, 106 91 Stockholm, Sweden 1Geological Survey of Canada, Natural Resources Canada, P.O. Box 1006, Dartmouth, Nova Scotia, Canada B2Y 4A2 2Department of Earth Sciences, Rice University, 6100 Main Street, Houston, Texas 77005, USA *Corresponding author (e-mail:[email protected]) DOWDESWELL, J. A., OTTESEN, D. & RISE, L. Skjoldryggen terminal moraine on the mid-Norwegian Shelf (917) *Corresponding author (e-mail: [email protected]) Numerous, regularly-spaced, parallel, linear to curvilinear ridges of DOWDESWELL, J. A., SOLHEIM, A. & OTTESEN, D. Rhombohedral -fill ridges at the marine margin of sediment are recognized as forming at or close to the position of the The distribution and pattern of De Geer moraines provides insight into Glacial landforms with dimensions smaller than the imaging capability of The corrugation ridges in PIB are interpreted to have been generated at grounding lines of water-terminating glaciers (Lindén & Möller 2005). the subtleties of deglaciation of German Bank. After the Last Glacial a surging Svalbard ice cap (908) the first generation multibeam sonars will become a more frequent topic as the trailing edge of mega-icebergs that broke off at the grounding line of These ice-flow transverse ridges, sometimes known as De Geer moraines Maximum, the margin of the Laurentide retreated to the high-resolution seafloor mapping technology advances. In Pine Island Bay the former PIB and drifted seaward (Jakobsson et al. 2011). (De Geer 1889), have modest heights and widths and variable lengths. De northwest, punctuated by many small readvances that formed De Geer (PIB) glacial trough, West Antarctica, small regular ridges, only a few Each ridge is formed when an iceberg, or an armada of icebergs in the ELVENES, S. & DOWDESWELL, J. A. Possible 'lift-off moraines' at grounded ice-sheet margins, North Norwe- Geer’s original description of Swedish moraines with these characteristics moraines. The pattern of segmented, southeast-convex moraines suggests metres high from trough to crest, were mapped in water depths around 700 case of PIB, rhythmically settles to the sea floor under the influence of invoked an annual cycle. Present use of ‘De Geer moraine’ refers to that the ice sheet margin was gently scalloped in nature. De Geer moraines gian shelf edge (856) m. The small size of these ridges is on the limit for what modern deep- tidal motion and squeezes sediments into ridges that are preserved in the closely spaced subaqueous moraine ridges which may or may not be are absent on exposed bedrock but are numerous on thin deposits of water multibeam sonars are capable of mapping. They are interpreted to wake of the drifting icebergs (Fig. 1d). In PIB, where the corrugation annual. The distribution and pattern of ubiquitous De Geer moraines on streamlined lineations of (Fig. 1a); in swales between the lineations the have been formed at the trailing end of mega-icebergs moving up and ridges exist in large parallel furrows, the formation model calls for a rather German Bank provides insight into the direction and timing of regional moraines are partly to completely buried by sediment. ELVENES, S., BØE, R. & RISE, L. Post-glacial sand drifts burying De Geer moraines on the continental shelf off down in response to tides while ploughing the seafloor (Jakobsson et al. uniformly thick iceberg armada just thick enough to keep the icebergs deglaciation of the southern Scotian Shelf (Todd et al. 2007). North Norway (855) 2011). The mega-icebergs in PIB were produced by an break-up grounded on the gently upward-sloping glacial trough. This mélange of ice The observations on German Bank are consistent with De Geer moraine and associated grounding-line retreat. would eventually disintegrate into individual icebergs that drifted away on EVANS, J. & DOWDESWELL, J. A. Submarine gullies and an axial channel in glacier-influenced Courtauld formation at the grounding line of a tidewater glacier as a result of their own; most of them were probably unstable and thus soon to rotate Description deposition and (or) pushing during minor readvances and stillstands. The Fjord, East (851) (Fig. 1d). In PIB, iceberg plough ridges were formed at the end of each generally regular horizontal spacing of De Geer moraines suggests that the Description large megaberg-induced furrow before the icebergs rotated (Fig. 1a). Across a bathymetric range of over 100 m, southern German Bank is mantled by swarms of ridges; each ridge displays a quasi-linear or curved rate of ice-front retreat was consistent from one cycle of formation to the The glacial trough in central PIB contains a suite of landforms indicative While corrugation ridges may form in slightly different glacial next. Ottesen & Dowdeswell (2006), in a study based on the interpretation FLINK, A. E., NOORMETS, R. & KIRCHNER, N. Annual moraine ridges in Tempelfjorden, Spitsbergen (911) environments, i.e. behind icebergs or underneath a fractured ice stream, line in planform. In topographic depressions, the ridges are subdued in of fast-flowing ice streams and episodic ice-sheet retreat following the relief or are absent (Fig. 1a). The strike of the ridge crests is generally of multibeam sonar imagery and historical aerial photographs of a FORWICK, M., KEMPF, P. & LABERG, J. S. Eskers in deglacial sediments of three Spitsbergen fjords (881) Last Glacial Maximum (Anderson et al. 2002; Graham et al. 2010; the vertical and rhythmic tidal motion is the common denominator for the tidewater glacier in a Svalbard fjord setting, provide compelling evidence formation process. west-southwest–east-northeast. Individual ridges can be traced Jakobsson et al. 2011). The relatively flat 690 to 710 m deep central horizontally from short segments of a few hundred metres up to almost 10 that De Geer moraines formed there when the glacier underwent a minor Overview maps showing the geographic distribution of some contributions to the Atlas of the Submarine Glacial Landforms section of the PIB trough is dominated by linear to curvilinear sets of large km. Most ridge crests are simple lines in planform, but in some areas the readvance each winter during its general retreat. However, GALES, J. A., LARTER, R. D. & LEAT, P. T. Iceberg ploughmarks and associated sediment ridges on the south- furrows aligned parallel to the trough axis with a spacing of 150 m to crests are complex with bifurcating crest lines and (or) short, en echelon sedimentological studies from suggest that several annual ern Weddell Sea margin, Antarctica (831) >500 m (Fig. 1). These large furrows resemble mega-scale glacial References crest segments. The longer ridge crests are formed of multiple curved cycles may in some cases contribute to the formation of a single De Geer lineations, although their more irregular alignment suggests formation sections 2 to 4 km in length with the crests slightly convex toward the moraine (Lindén & Möller 2005); thus, such moraines do not always from an armada of clustered icebergs rather than from a more intact fast- ANDREASSEN, K., KARIN ANDREASSEN, WINSBORROW, M.C., represent annual formation. The larger De Geer moraines on German Bank BJARNADÓTTIR, L.R., RÜTHER, D.C. Accepted. Landform assemblage southeast. In places on German Bank, individual ridges traverse GALES, J. A., LARTER, R. D. & LEAT, P. T. Submarine gullies on the southern Weddell Sea slope, Antarctica flowing ice stream (Jakobsson et al. 2011). bathymetric ranges of up to 25 m. (Fig. 1a) may be the product of several years of ice-front stability or major Within the large furrows, remarkably regular sets of smaller ridges from the collapse of the Bjørnøyrenna Palaeo-ice stream, northern Barents Sea. readvances. (832) occur oriented at close-to-right-angles to them (Fig. 1a, b). These ridges Quaternary Science Reviews. ANDERSON, J.B. 1999. Antarctic Marine Geology, Cambridge University Press, The horizontal distance between ridges, normal to strike, is variable. In are separated by ~60–200 m, with spacing generally decreasing Cambridge. some areas, well-defined parallel ridges have a roughly regular spacing of Additional contributions are welcome. Deadline is January 30, 2015. GREENWOOD, S. L., JAKOBSSON, M., HELL, B. & ÖIÅS, H. systems in the Gulf of Bothnia (858) progressively in a seaward direction; ridge heights range from 1 to 2 m ANDERSON, J.B., SHIPP, S.S., LOWE, A.L., WELLNER, J.S., MOSOLA, A.B. approximately 150 to 200 m. In other areas, sub-parallel ridges are as References from trough to crest. The extremely regular appearance of these ridges 2002. The Antarctic Ice Sheet during the Last Glacial Maximum and its closely spaced as 30 to 50 m. The ridges vary in height and width. Ridges BLAKE, K.P. 2000. Common origin for De Geer moraines of variable composition makes the furrows look corrugated; hence the smaller ridges were named subsequent retreat history: a review. Quaternary Science Reviews, 21, 49-70. displaying a subtle appearance on the large-scale multibeam-bathymetric in Raudvassdalen, northern Norway. Journal of Quaternary Science, 15, 633– Please contact Julian Dowdeswell, [email protected] BARNES, P.W., LIEN, R. 1988. Iceberg rework shelf sediments to 500 m off , J. C. Iceberg ploughmarks on the upper continental slope, South Carolina (891) “corrugation ridges” by Jakobsson et al. (2011). 644. Antarctic. Geology, 16, 1130-1133. image (Fig. 1b) are approximately 1.5 m high and 40 m wide. The more Similar landforms have been mapped in the eastern Weddell Sea in BRADWELL, T., STOKER, M.S., et al. 2008. The northern sector of the last JAKOBSSON, M. & ANDERSON, J. B. Corrugation ridges in the Pine Island Bay glacier trough, West Antarctica GRAHAM, A.G.C., LARTER, R.D., GOHL, K., DOWDESWELL, J.A., prominent ridges are approximately 5 to 8 m high and 100 to 130 m wide individual iceberg plough marks using side-scan sonar (Lien 1981; Barnes British Ice Sheet: Maximum extent and demise. Earth-Science Reviews, 88, HILLENBRAND, C.-D., SMITH, J.A., EVANS, J., KUHN, G., DEEN, T. (Fig. 1 c, d). The ridges are generally symmetrical in cross section with (817) and Lien, 1988). Furthermore, features identical to the corrugation ridges 207–226. 2010. Flow and retreat of the Late Quaternary Pine Island-Thwaites palaeo-ice some of the larger ridges displaying asymmetry with a gentle slope to the DE GEER, G.F. 1889. Ändmoräner I trakten mellan Spånga och Sundbyberg. of PIB have been mapped in large iceberg furrows in the northern part of stream, West Antarctica. Journal of Geophysical Research. 115, F03025. north and a steeper slope to the south (Fig. 1d). Cobbles and boulders were Geologiska Föreningens i Stockholm Förhandlingar, 11, 395–397. Bjørnøyrenna, Barents Sea (Andreassen et al. 2013), and within mega- GRAHAM, A. G. C., DUTRIEUX, P., VAUGHAN, D. G., NITSCHE, F. O., JAKOBSSON, M., GREENWOOD, S. L., HELL, B. & ÖISÅS, H. Drumlins in the Gulf of Bothnia (873) observed and recovered from ridges and gravel was recovered from LARSEN, E., LONGVA, O. & FOLLESTAD, B.A. 1991. Formation of De Geer scale glacial lineations in the central (Jakobsson et al. 2011) and western GYLLENCREUTZ, R., GREENWOOD, S. L., LARTER, R. D., AND smooth seafloor in troughs (Fig. 1b). moraines and implications for deglaciation dynamics. Journal of Quaternary Ross Sea (Anderson, 1999). JENKINS, A., 2013, Seabed corrugations beneath an Antarctic ice shelf Science, 6, 263–277. revealed by autonomous underwater vehicle survey: Origin and implications LINDÉN, M. & MÖLLER, P. 2005. Marginal formation of De Geer moraines and JAKOBSSON, M. & O'REGAN, M. Arctic Ocean iceberg ploughmarks (838) for the history of Pine Island Glacier. Journal of Geophysical Research: Earth Interpretation their implication on the dynamics of grounding-line recession. Journal of Surface, 115, F03025. Interpretation Quaternary Science, 20, 113–133. HOPPE, G., 1959. Glacial morphology and inland ice recession in northern Sweden. The ridge swarms on German Bank are interpreted to be subaqueous, ice- OTTESEN, D. & DOWDESWELL, J.A. 2006. Assemblages of submarine JAKOBSSON, M., O'REGAN, M., GREENWOOD, S. L., FLODEN, T., SWÄRD, H., BJÖRCK, S. & SKELTON, A. Several formation mechanisms for corrugation ridges have been explored Geografiska Annaler, 41, 193-212. flow transverse De Geer moraines formed at or close to the grounding line landforms produced by tidewater glaciers in Svalbard. Journal of Geophysical by Jakobsson et al. (2011) and Graham et al. (2013). Their extreme JAKOBSSON, M., ANDERSON, J.B., NITSCHE, F.O., DOWDESWELL, J.A., Post-glacial tectonic structures and mass wasting in Lake Vättern, southern Sweden (901) of the southeastern margin of the marine-terminating . Research, 111, F01016. regularity excludes formation as recessional moraines formed near a GYLLENCREUTZ, R., KIRCHNER, N., O’REGAN, M.A., ALLEY, R.B., Subaerially exposed De Geer moraines have been interpreted as marking SOLHEIM, A., RUSSWURM, L., ELVERHØI, A. & NYLAND BERG, M. 1990. ANANDAKRISHNAN, S., MOHAMMAD, R., ERIKSSON, B., Editors retreating ice margin. This also eliminates the interpretation that the Glacial geomorphic features in the northern Barents Sea: direct evidence for FERNANDEZ, R., KIRSHNER, A., MINZONI, R., STOLLDORF, T., former ice-margin positions where sediment is deposited or pushed up LASTRAS, G. & DOWDESWELL, J. A. Terminal and recessional moraines in the fjords of southern Chile (859) corrugation ridges are De Geer moraines (Hoppe, 1959; Lindén and grounded ice and implications for the pattern of deglaciation and late glacial MAJEWSKI, W. 2011. Geological record of Ice Shelf Breakup and Grounding during brief stillstands or minor readvances (De Geer 1889; Blake 2000). Möller, 2005) or corrugation moraines (Shipp et al. 1999). Sediment cores sedimentation. In Dowdeswell, J.A. & Scourse, J.D. (eds.): Glacimarine Line Retreat, Pine Island Bay, West Antarctica. Geology, 39, 691-694. 1 2 3 4 1 5 from the ridges contained poorly sorted glacial diamict and glacimarine environments: processes and sediments. Geological Society of London, LIEN, R. 1981. Seabed features in the Blaaenga area, Weddell Sea, Antarctica, Port Using the traditional marine geophysical survey tools of seismic Special Publication, 53, 253–268. J.A. Dowdeswell , M. Canals , M. Jakobsson , B.J. Todd , E.K. Dowdeswell , K.A. Hogan . LASTRAS, G., AMBLAS, D. & CANALS, M. Fjord flank collapse and associated deformation in Aysén fjord, sandy clays, suggesting that a current-influenced formation process could and Ocean Engineering under Arctic Conditions, Quebec, Canada, pp. 706- reflection profiling and side-scan sonar, De Geer moraines have been TODD, B.J., VALENTINE, P.C., LONGVA, O. & SHAW, J. 2007. Glacial be dismissed. The discovery of corrugation ridges within individual 716. Chile (842) recognized in the Barents Sea (Solheim et al. 1990) and western Norway landforms on German Bank, Scotian Shelf: evidence for Late Wisconsinan ice- iceberg ploughmarks points towards a formation mechanism that occurs at LINDÉN, M., MÖLLER, P., 2005. Marginal formation of De Geer moraines and (Larsen et al. 1991). In the marine environment, technological constraints sheet dynamics and implications for the formation of De Geer moraines. the trailing end of a ploughing iceberg, because otherwise the iceberg their implications to the dynamics of grounding-line recession. Journal of precluded small-scale (i.e. regional) mapping of glacial landforms like De Boreas, 36, 148–169. Quaternary Science, 20, 113-133. Fig.1. Multibeam swath bathymetry and geophysical profiles of De Geer moraines on German Bank, Scotian Shelf. (a) Sun-illuminated multibeam-bathymetric image NITSCHE, F. O., LARTER, R. D., GOHL, K., GRAHAM, A. G. C. & KUHN, G. Bedrock channels in Pine Island Bay, would itself remove the seafloor imprints from its own impact with the VAN LANDEGHEM, K.J.J., WHEELER, A.J. & MITCHELL, N.C. 2009. Seafloor 1 SHIPP, S., ANDERSON, J.B., DOMACK, E.W. 1999. Late -Holocene Geer moraines until the advent of multibeam sonar in the early 1990s. showing De Geer moraines. Acquisition system Kongsberg EM1000. Frequency 95 kHz. Grid-cell size 5 m. Single-headed arrow denotes younger, larger moraine seafloor.  evidence for palaeo-ice streaming and calving of the grounded Irish Sea Ice University of Cambridge, UK West Antarctica (771) retreat of the West Antarctic ice-sheet system in the Ross Sea; Part 1. Fig.1. Multibeam bathymetry from Pine Island Bay (PIB), West Antarctica, colllected during the Oden-Southerrn Ocean 2010 expedition (OSSO0910) with Swedish Applying this technology, De Geer moraines have also been mapped in the overriding and cross-cutting older, smaller moraines. Trend of streamlined lineations of till indicated by double-headed arrow. (b) Detailed multibeam image of De Irish Sea (Van Landeghem et al. 2009) and in the North Sea (Bradwell et Stream: Implications for the interpretation of its final deglaciation phase. Geophysical results Geological Society of America Bulletin, 111, 1468-1516. icebreaker Oden. Acquisition system Kongsberg EM122. Frequency 12 kHz. Grid-ccell size 30 m. (a) Examples of ccorrugation ridgees in the centrall part of PIB located in Geer moraines indicating location of geophysical profiles. Yellow dots denote samples; white dashed line denotes video transect (Todd et al. 2007). (c) Side-scan sonar 2 al. 2008). Boreas, 38, 119–131. University of Barcelona, Spain O'BRIEN, P., SMITH, J. & RIDDLE, M. Bouldery debris mantle deposited by cold-based ice offshore of the Vest- large furrows with wiidths from about 150 m to >500 m. (b) Detail of corrugation ridges, white box in (a) shows the llocation. (c) Loccation of study area (red box; map from image of De Geer moraines. Acquisition system Simrad MS992. Frequency 120 kHz. (d) Seismic reflection profile of De Geer moraines. VE x 23. Acquisition system Huntec Deep-Tow Seismic. Frequency 0.5–8 kHz. (e) Location of study area (red box; map from GEBCO_08). 3University of Stockholm, Sweden fold , East Antarctica (887) IBCSOIBSCO v. 1.0) (d) Schematic model of stages of corrugation ridge formation. From: DOWDESWELL, J.A., CANALS, M., JAKOBSSON, M., TODD, B.J., DOWDESWELL, E.K. & HOGAN, K.A. (eds) Atlas of Submarine Glacial Landforms: From: DOWDESWELL, J.A., CANALS, M., JAKOBSSON, M., TODD, B.J., DOWDESWELL, E.K. & HOGAN, K.A. (eds) Atlas of Submarine Glacial Landforms: 4Geological Survey of Canada, Dartmouth, Nova Scotia, Canada REBESCO, M., CAMERLENGHI, A. & LLOPART, J. Glacigenic deposits, Storfjorden Fan (864) Modern, Quaternary and Ancient. Geological Society, London, Memoirs, xx, 1-2. © The Geological Society of London, 2014. DOI: xx.xxxx/xxx.x. Modern, Quaternary and Ancient. Geological Society, London, Memoirs, xx, 1-2. © The Geological Society of London, 2014. DOI: xx.xxxx/xxx.x. 5 RISE, L., BELLEC, V., OTTESEN, D., BØE, R. & THORSNES, T. Hill-hole pairs on the Norwegian Continental British Antarctic Survey, Cambridge, UK Shelf (872)

RISE, L., OTTESEN, D., OLESEN, O. & DOWDESWELL, J.A. Buried mid-Quaternary mega-scale glacial linea- The Atlas is sponsored by the following companies: tions in the Norwegian Channel from 3D seismic imagery (867)

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SHAW, J. & POTTER, D. P. Anthropogenic modification of a fjord: Bay of Islands, Newfoundland (914)

TODD, B. J. De Geer moraines on German Bank, southern Scotian Shelf of Atlantic Canada (818)