GeoScienceWorld

Abstract

The volume highlights developments in our understanding of the palaeogeographical, palaeobiological, palaeoclimatic and cryospheric evolution of Antarctica. It focuses on the sedimentary record from the Devonian to the Quaternary Period. It features tectonic evolution and stratigraphy, as well as processes taking place adjacent to, beneath and beyond the ice-sheet margin, including the continental shelf.

The contributions in this volume include several invited review papers, as well as original research papers arising from the International Symposium on Antarctic Earth Sciences in Edinburgh, in July 2011. These papers demonstrate a remarkable diversity of Earth science interests in the Antarctic. Following international trends, there is particular emphasis on the Cenozoic Era, reflecting the increasing emphasis on the documentation and understanding of the past record of ice-sheet fluctuations. Furthermore, Antarctic Earth history is providing us with important information about potential future trends, as the impact of global warming is increasingly felt on the continent and its ocean.

    1. Page 1
      Abstract
      Corresponding author (e-mail: mjh@aber.ac.uk)

      The 26 papers in this volume comprise those presented at the International Symposium on Antarctic Earth Sciences in Edinburgh in July 2011, as well as several invited review papers, on Antarctic geology and geomorphology. These papers demonstrate a remarkable diversity of Earth science interests in the Antarctic. It is evident that during recent decades there has been a marked change in emphasis from pre-Cenozoic geology to topics related to the 34 million years of directly documented Antarctic glacial history. Increasing emphasis is being placed on the documentation and understanding of the palaeorecord of ice-sheet growth and decay. Furthermore, Antarctic Earth history is providing us with important information about potential future trends, as the impact of global warming is increasingly felt on the continent and its ocean.

    1. Page 7
      Abstract

      The development of the Transantarctic Mountains was initiated with the rifting of Rodinia and the formation of a late Neoproterozoic passive continental margin. In Cambrian time this rift setting evolved into an active margin with batholith emplacement into deformed and lightly metamorphosed upper Neoproterozoic–Cambrian strata, creating the Ross Orogen. Denudation and erosion of the Ross Orogen led to the formation of the pre-Devonian Kukri Erosion Surface on which Devonian quartzose sandstones accumulated in a continental setting. Palaeozoic magmatic arcs were intermittently active along the distal Panthalassan margin. Intra-cratonic basins developed in Permian time, one of which evolved into a foreland basin clearly related to a Permo-Triassic magmatic arc. The Palaeozoic–early Mesozoic arcs can be traced into both Australasia and South America. In Early Jurassic time the margin migrated outboard simultaneously with the advent of proximal silicic volcanism, emplacement of the Ferrar Large Igneous Province and Gondwana break-up. These events marked the onset of plate margin reorganization, and with it the early uplift of the Transantarctic Mountains. During Cretaceous and later time episodic uplift of the Transantarctic Mountains was accompanied by formation of a major crustal and lithospheric boundary marking the edge of the East Antarctic craton and the regions of crustal attenuation in the Ross (West Antarctic Rift System) and Weddell embayments.

    2. Page 37
      Abstract
      Corresponding author (e-mail: ed.stump@asu.edu)

      The objectives of this study were to assess possible differential movement across an inferred fault beneath Byrd Glacier, and to measure the timing of unroofing in this portion of the Transantarctic Mountains. Apatites separated from rock samples collected from known elevations at various locations north and south of Byrd Glacier were dated using single crystal (U–Th)/He analysis. Results indicate a denudation rate of c. 0.04 mm a−1 in the time range c. 140–40 Ma. Distinct age v. elevation plots from north and south of Byrd Glacier indicate an offset of c. 1 km across the glacier with south side up. A Landsat image of the Byrd Glacier area was overlain on an Aster Global Digital Elevation Model and spot elevations of the Kukri erosion surface to the north and south of Byrd Glacier were mapped. The difference in elevation of the erosion surface across Byrd Glacier also shows an offset of c. 1 km with south side up. Results support a model of relatively uniform cooling and unroofing of the region with later, post-40 Ma fault displacement that uplifted the south side of Byrd Glacier relative to the north.

      Supplementary material: Sample and apatite (U–Th)/He data are listed at http://www.geolsoc.org.uk/SUP18671

    3. Page 45
      Abstract
      Corresponding author (e-mail: a.maestro@igme.es)

      Palaeostresses inferred from approximately 3200 brittle mesostructures measured at 43 sites in Signy Island show a stress field characterized by compressional, strike-slip and extensional stress states. There is a dominant NW–SE horizontal compression direction as well as three (NNW–SSE, WNW–ESE and ENE–WSW) secondary σ1 horizontal stress directions. Orientation of σ3 shows a main mode trending NW–SE together with secondary north–south and NE–SW extensional stress directions. The NNW–SSE horizontal compression is consistent with the stretching–shearing direction defined from the fold-axis trend. This is owing to a subduction-related tectonic regime during early to middle Jurassic times. In middle Jurassic/early Cretaceous times, the tectonic regime changes to extensional with north–south extensional stress directions. The early processes of subduction of the northern sector of the Weddell Sea oceanic crust below the South Orkney Microcontinent, from the Paleocene until the middle Miocene, is related to the σ1 direction WNW–ESE to NW–SE. The spreading of Powell Basin took place from the late Eocene to the early Miocene and is the cause of east–west and NE–SW extensional processes in the southern South Orkney Microcontinent. Finally, the NW–SE σ3 direction is related to the current left-lateral strike-slip movement between the Scotia and Antarctic plates.

    4. Page 67
      Abstract

      The Taylor Group, the lower division of the Beacon Supergroup, comprises mainly quartzose sandstones of Devonian age deposited after the development of the Kukri Erosion Surface across the Cambrian Ross orogen. Devonian sediments accumulated in a McMurdo Basin that now incorporates most of the Transantarctic Mountains, and a larger Ellsworth Basin that extends from West Antarctica into southern Africa. In southern Victoria Land (McMurdo Basin) the seven formations total around 1200 m in thickness. Sequence stratigraphy suggests five sedimentary cycles, the lower four of which may show shallow marine influence. Provenance studies indicate derivation solely from Ross Orogen sources. The Taylor Group in the central Transantarctic Mountains consists of two thin formations, only one of which is extensive. In the Ellsworth Basin, Taylor Group equivalents rest concordantly on thick piles of post-Ross Palaeozoic sediment. Shallow-water Devonian sediments in the Ohio Range contain a marine fauna linked with those of the Ellsworth Mountains, southern Africa, South America, New Zealand and Australia. A seaway probably existed along the Pacific edge of the East Antarctic craton, allowing these faunal links, and may also have communicated with the McMurdo Basin to drive the five sedimentary sequences.

    5. Page 99
      Abstract
      Corresponding author (e-mail: regui@fcnym.unlp.edu.ar)

      The fossil record of terrestrial vertebrates from the Late Cretaceous of Antarctica is currently composed of non-avian and avian dinosaurs from the marine sediments of the James Ross Basin, Antarctic Peninsula (West Antarctica). Although two dinosaurian formational assemblages (Late Campanian/Early Maastrichtian and Late Maastrichtian) are known, the record is still scattered, and evolutionary scenarios are tentative. Ten non-avian dinosaurs have been reported from Coniacian to Maastrichtian deposits, along with possible sauropod footprints of Early Maastrichtian age from Snow Hill Island. Five avian dinosaurs have been recorded or described exclusively from the Maastrichtian. The presence of an advanced titanosaur with characteristic procoelous mid-caudal vertebrae in Snow Hill Island Formation at Santa Marta Cove implies that the group achieved a global distribution by the Late Campanian. The Late Campanian/Early Maastrichtian non-avian dinosaur (ankylosaurs, ornithopods and dromaeosaurid theropods) clades probably attained a near-cosmopolitan distribution before the Late Cretaceous, and some aspects of this hallmark ‘Gondwanan’ fauna may therefore reflect climate-driven provinciality, not vicariant evolution driven by continental fragmentation. Antarctic Late Cretaceous avian dinosaurs are rare. They are restricted to the Maastrichtian and consist of a cariamid?, gaviids, a charadriiform and the basal Anseriformes Vegavis, and provide the first strong evidence for a basal radiation of birds known to exist in the Cretaceous.

    6. Page 117
      Abstract
      Corresponding author (e-mail: thomas.saucede@u-bourgogne.fr)

      Few studies have been devoted to the palaeobiogeography of Antarctic echinoids, all of them analysing and discussing distribution patterns in a qualitative way. The present work aims at exploring the evolution of palaeobiogeographic relationships of Austral echinoid faunas through four time intervals, from the Maastrichtian to the present day, using a quantitative approach: the Bootstrapped Spanning Network procedure. Analyses were successfully performed and improve our knowledge of biogeographic relationships between the different Austral regions. Biogeographic maps were produced that can be easily and intuitively discussed. Our results mostly agree with palaeobiogeographic studies performed on other benthic invertebrates and are congruent with the palaeogeographic evolution of Antarctica. However, two main points markedly contrast with other works: there is no evidence of an Austral provincialism at the end of the Cretaceous and early Cenozoic, and echinoid data suggest isolation of southern Argentina from other Austral regions, including Antarctica, in the Early Miocene.

    1. Page 129
      Abstract

      Eocene Antarctic penguins, at least 10 species in six genera, are known only from the La Meseta Formation, Seymour Island, Antarctic Peninsula. They are most numerous (in terms of individuals, body sizes and taxa) in Late Eocene strata. Specimens from three species and phylogenetic analysis presented in this work shed new light on the systematics and evolution of Antarctic Sphenisciformes. The earliest reported bones of giant penguins from the genus Anthropornis set the conservative estimate of its divergence time at c. 53 Ma (Early Eocene). They also document the oldest known appearance of quite a high diversity of Sphenisciformes; altogether, three morphotypes (differing in size) have been found within the same sampling locality. A newly described, relatively small and intriguingly elongated, tarsometatarsus from the Late Eocene of the La Meseta Formation, belonging to another genus of large-sized Antarctic penguins (Palaeeudyptes), suggests the possible existence of an unnamed species within this long-established genus. The phylogenetic analysis based on tarsometatarsal features shows that the relationship between ‘Archaeospheniscuswimani and three species of Delphinornis (all of them co-existed during the Late Eocene time period) does not appear to be close enough to justify merging them into a single genus (as was recently postulated).

      Supplementary material: An annotated data matrix used for the phylogenetic analysis is available at www.geolsoc.org.uk/SUP18599

    2. Page 139
      Abstract
      Corresponding author (e-mail: rdla@bas.ac.uk)

      Results are reported from seven heat flow stations in small basins of the southern part of the central Scotia Sea (CSS), undertaken in order to determine basement ages. The basins are small, which makes magnetic anomaly-based ages ambiguous and preserves basin subsidence that may have been anomalous as a result of local factors. The fact that these small basins formed in a back-arc setting adds additional uncertainty to depth-based age estimates. The results confirm that basin extension commenced in the Eocene, and indirectly support a relatively young, back-arc origin for the northern CSS, but do not affect previously published suggestions of the age of onset of the Antarctic Circumpolar Current.

    3. Page 151
      Abstract

      Landforms and sediments in the Prince Charles Mountains record the timing and magnitude of Cenozoic palaeotopographic changes in the Lambert Glacier–Amery Ice Shelf system. A review of geomorphic and sedimentological evidence indicates that considerable (>1–2 km) glacial incision into a pre-glacial palaeosurface occurred along the major outlet glaciers during the Cenozoic. This erosion was in turn the likely driver for uplift that averaged c. 50 m/Ma along the flank of the Amery Ice Shelf since at least the mid-Miocene Epoch. The volume of eroded material is an order of magnitude greater than the quantity of sediment presently preserved in Prydz Bay, suggesting considerable export of Cenozoic sediment off the continental shelf. The magnitude of erosion recorded in the Prince Charles Mountains is sufficient to have focussed Cenozoic ice-drainage patterns, but was too slow to have driven Quaternary changes in ice volume.

    4. Page 167
      Abstract
      Corresponding author (e-mail: BrendaH@maine.edu)

      Knowledge of variations in the extent and thickness of the Antarctic Ice Sheet is key for understanding the behaviour of Southern Hemisphere glaciers during the last ice age and for addressing issues involving global sea level, ocean circulation and climate change. Insight into past ice-sheet behaviour also will aid predictions of future ice-sheet stability. Here, we review terrestrial evidence for changes in ice geometry that occurred in the Ross Sea sector of Antarctica at the Last Glacial Maximum (LGM) and during subsequent deglaciation. During the LGM, a thick grounded ice sheet extended close to the continental shelf edge in the Ross Embayment. This ice reached surface elevations of more than 1000 m along the coast of the central and southern Transantarctic Mountains and Marie Byrd Land. The local LGM occurred by 18 ka on the coast, but as late as 7–10 ka inland. The first significant thinning took place at roughly 13 ka, with most ice loss happening in the Holocene. This history makes it unlikely that the Ross Sea sector was a major contributor to meltwater pulse 1A (MWP 1A). Resolution of a possible Antarctic origin for MWP 1A awaits detailed reconstructions from all sectors of the ice sheet.

    5. Page 183
      Abstract
      Corresponding author (e-mail: kari.strand@oulu.fi)

      The transition from a glaciofluvial to a glacial sedimentary environment contains critical information for evaluating the onset of glaciation and early glacial dynamics in Antarctica. This study presents investigations of a sediment core from Ocean Drilling Program Leg 188, Site 1166, on the continental shelf in Prydz Bay, in order to provide evidence for the first occurrence of late Eocene glaciers in the Lambert Graben, East Antarctica. The Lambert Graben is a large fault-bounded structure, at least 700 km long and 100 km wide, and presently hosts the Lambert Glacier–Amery Ice Shelf system. The core consists of middle Eocene glacially influenced alluvial plain sediments, c. 110 m in total thickness that are overlain by a c. 20 m-thick early Oligocene glaciomarine succession. The upper contact is a major unconformity. Grain-surface microtextures, such as fractured plates and a relatively high content of ilmenite in alluvial outwash-plain sediments, indicate mixed northern and southern Prince Charles Mountains provenance and initiation of glaciers as early as middle Eocene time. Distribution of the major heavy minerals indicates a change to garnet-rich granulite terrain in sediment-supply during later ice-sheet evolution, when a lack of detritus from the southern Prince Charles Mountains becomes apparent. Glacier advance was no longer restricted to the Lambert Graben and the drainage area became wider. Good preservation of these low-stand glaciofluvial outwash-plain deposits was related to regional subsidence that progressed to a marine transgression and glaciomarine deposition when ice was able to advance to the continental shelf edge.

    6. Page 199
      Abstract
      Corresponding author (e-mail: stephen.pekar@qc.cuny.edu)

      In the Austral spring of 2008, over 48 km of multi-channel seismic data were collected offshore of New Harbour, which is located in the western most Ross Sea, Antarctica. This project is part of the ANDRILL (Antarctic Geological Drilling) Programme's Offshore New Harbour Project, with its aim to investigate the stratigraphic and tectonic history of the inner shelf of southern McMurdo Sound. Correlating the seismic data to CIROS-1 and ANDRILL AND-2A drillholes provided age dates ranging from Late Miocene to at least Late Eocene for the reflectors and lithological descriptions for the seismic units. This permitted development of a glacial history of this area, resulting in dividing the seismic data into three units: an Upper Eocene–Lower Oligocene unit; an Upper Oligocene–Lower Miocene unit; and a Middle Miocene and younger unit. The seismic section below 700 mbsf has two possible interpretations: (1) substantial Eocene strata are present downdip of CIROS-1, which would represent a potential future-drilling objective for the ANDRILL Programme; or (2) these reflectors may be equivalent to Devonian strata recovered at the Cape Roberts 3 as the two-way traveltime of Eocene and Devonian strata are nearly identical, making it difficult to discriminate between them in seismic data.

    7. Page 215
      Abstract
      Corresponding author (e-mail: johna@rice.edu)

      Marine geological studies provide a record of diachronous expansion and retreat of the Antarctic Peninsula Ice Sheet, West Antarctic Ice Sheet and East Antarctic Ice Sheet during the past c. 30 000 cal yr BP. Retreat of these ice sheets and Antarctica’s contribution to sea-level rise was largely complete by the early Holocene. Estimates of ice sheet thickness, based on maximum grounding depths, range from 640 to 1640 m on the inner continental shelf. Grounding depths on the outer continental shelf equate to minimum thicknesses of 410–950 m. Geomorphic features indicate that retreat from the continental shelf was mostly step-wise around the continent, a result of the different factors that control ice sheet behaviour and the degree to which these factors vary regionally. Thus, the nature of post-LGM (Last Glacial Maximum) sea-level rise was episodic and believed to have been punctuated by rapid pulses triggered by individual ice stream collapse. Most of these pulses would have been of sub-metre magnitudes and below the resolution of existing sea-level curves, but they would have had significant impact on coastal evolution, especially along low-gradient coasts.

    8. Page 233
      Abstract
      Corresponding author (e-mail: Katharina.Hochmuth@awi.de)

      Sedimentary sequences of the continental shelf of the eastern Amundsen Sea Embayment in West Antarctica represent records of past outlet glaciers and ice streams. The former flow of ice streams was channelled through glacial troughs, which now form large bathymetric depressions. We therefore selected one of the largest troughs, the Abbot glacial trough in the outer shelf, to analyse its glacial depositional and erosional history, based on horizon-stratigraphy derived from seismic data. Several basement highs channellized the delivery of sediment and controlled the grounded ice sheet in early glacial periods. Both pre-glacial and full glacial seismic facies were identified. Glacially transported and deposited sediments extended the shelf break by 75 km from the pre-glacial shelf-edge. The main Abbot glacial trough contains sediment from confluent ice flows of the Pine Island/Thwaites, Cosgrove and Abbot Glacier systems, as well as smaller contributions from local ice streams emanating from Thurston Island. Sherman Island of Peacock Sound played an important role in the dynamics of the Abbot Glacier by dividing the ice flow into two ice streams, which interfered with the main glacial sediment transport paths from the south. This study contributes to an understanding of the formation of the Amundsen Sea shelf and the extent of past ice sheet advances.

    9. Page 245
      Abstract
      Corresponding author (e-mail: dsprenk@uni-koeln.de)

      We present biogenic opal flux records from two deep-sea sites in the Scotia Sea (MD07-3133 and MD07-3134) at decadal-scale resolution, covering the last glacial cycle. In addition to conventional and time-consuming biogenic opal measuring methods, we introduce new biogenic opal estimation methods derived from sediment colour b*, wet bulk density, Si/Ti-count ratio and Fourier transform infrared spectroscopy (FTIRS). All methods capture the biogenic opal amplitude; however, FTIRS–a novel method for marine sediment – yields the most reliable results. 230Th normalization data show strong differences in sediment focusing with intensified sediment focusing during glacial times. At MD07-3134 230Th normalized biogenic opal fluxes vary between 0.2 and 2.5 g cm−2 kyr−1. Our biogenic opal flux records indicate bioproductivity changes in the Southern Ocean, strongly influenced by sea ice distribution and also summer sea surface temperature changes. South of the Antarctic Polar Front, lowest bioproductivity occurred during the Last Glacial Maximum when upwelling of mid-depth water was reduced and sea ice cover intensified. Around 17 ka, bioproductivity increased abruptly, corresponding to rising atmospheric CO2 and decreasing seasonal sea ice coverage.

    10. Page 263
      Abstract
      Corresponding author (e-mail: mv217@cam.ac.uk)

      We present results of a multi-proxy study on marine sediment core JR179-PC466 recovered from the crest of a sediment drift off the West Antarctic Peninsula at approximately 2300 m water depth. The 10.45 m-long core consists dominantly of glaciomarine terrigenous sediments, with only traces of calcium carbonate (<1 wt%). Despite the very low abundance of calcareous foraminifera, planktonic shell numbers are sufficient for stable isotope analyses in two-thirds of the samples studied. The core chronology is based on oxygen isotope stratigraphy and correlation of its relative palaeomagnetic intensity (RPI) with a stacked reference curve. According to the age model, core PC466 spans the last 75 ka, with average sedimentation rates of between about 4 and 25 cm ka−1. Planktonic foraminifera abundances fluctuate between 0 and 30 individuals per gram throughout the core, with minima observed during Marine Isotope Stage (MIS) 2 (14–29 ka before present, BP) and MIS4 (57–71 ka BP). Planktonic foraminifera are present in the Holocene but more abundant in sediments deposited during MIS3 (29–57 ka BP), owing to less dilution by terrigenous detritus and/or better carbonate preservation. During MIS3, foraminifera maxima correlate with Antarctic warming events as recorded in the δ18O signal of the EPICA Dronning Maud Land (EDML) ice core. They indicate higher planktonic foraminifera production and better carbonate preservation west of the Antarctic Peninsula during that time. The abundance of ice-rafted detritus (IRD) in core PC466 increased during the last deglaciation between about 19 and 11 ka BP, when numerous icebergs drifted across the core site, thereby releasing IRD. During this time, sea-level rise destabilized the Antarctic Peninsula (APIS) and West Antarctic (WAIS) ice sheets that had advanced onto the shelf during the sea-level low-stand of the Last Glacial Maximum (LGM; c. 19–23 ka BP). Overall, our results demonstrate that it is possible to establish an age model and reconstruct palaeoceanographical and climatic changes at high temporal resolution from sedimentary sequences recovered at 2300 m water depth from a West Antarctic drift.

    11. Page 277
      Abstract
      Corresponding author (e-mail: pantnc@rediffmail.com)

      Site U1359 is located on the eastern levée of the Jussieau submarine channel on the Wilkes Land margin, East Antarctica. The upper approximately 60 m of the sediment core records more than 2.5 Ma of the depositional history. Present work focuses on inferring provenance from the heavy mineral fraction from the Pleistocene sediments. Clay and non-clay fractions were characterized using X-ray diffraction and micro-beam techniques. Metamorphic minerals including orthopyroxene, high-Ca garnet and high-Ti biotite indicate a source in a high-grade metamorphic terrain. Mixing from a low- to medium-grade metamorphic component is also indicated. Several basaltic rock fragments, showing mineralogical affinities to the Ferrar volcanic province in the Ross Sea sector, are present. The metamorphic component is correlatable with the Proterozoic East Antarctic cratonic shield component. Ordovician–Silurian ages for the euhedral xenotime and monazite, coupled with the Ferrar equivalent basalts, indicate an additional sediment source from the Ross Orogen along with that from the craton.

    1. Page 299
      Abstract

      Cold-based glaciers have long been recognized as capable of covering and protecting landscapes. However, recent studies of modern cold-based glaciers in Antarctica show that, in some situations, erosion, deformation and deposition can occur. Recognizing the dual ability of cold-based glaciers to protect and preserve surfaces on the one hand and erode and modify on the other is important for correctly interpreting the often-subtle imprint of cold-based glaciers on landscapes. A range of geomorphological features related to cold-based glacier activity has now been documented along with an improved understanding of cold-based glacier structure, processes and interaction with various substrates. Collectively, this provides an enhanced ability to understand the impact of cold-based glaciers on landscapes and reappraise the geomorphological record. Such insight allows recognition of previously unknown glacial events and better interpretations of the landscape exposure record. This is particularly important at the margins of the Antarctic Ice Sheets, where past fluctuations in ice sheet volume and its contributions to post glacial sea-level rise are poorly constrained. This paper reviews the known geomorphological evidence associated with cold-based glaciers in the South Victoria Land region of the Transantarctic Mountains. It aims to provide progress towards a set of criteria for recognizing cold-based glacier activity in other regions and to highlight the implications of cold-based glacial activity for surface exposure studies and interpreting glacial history.

    2. Page 319
      Abstract
      Corresponding author (e-mail: marchant@bu.edu)

      The Dry Valleys are subdivided into three microclimate zones on the basis of summertime measurements of atmospheric temperature, soil moisture, relative humidity and wind-speed/ direction. Subtle variations in these climate parameters result in considerable differences in process geomorphology and in the development of unique landforms within each zone. The mapped zones include a coastal thaw zone, an inland mixed zone and a stable upland zone. Landforms within each zone are subdivided into macroscale features (e.g. valleys, slopes and gullies), mesoscale features (e.g. polygons and viscous-flow features) and microscale features (e.g. rock and near-surface soil features, including the effects of salt weathering, wind erosion and pitting). We present a review of landscape development in the Dry Valleys with implications for long-term climate change and ice-sheet stability. Chronological control is afforded by 40Ar/39Ar dating of volcanic ash-fall deposits and cosmogenic nuclide analyses of surface boulders. Collectively, the data call for persistent cold and dry conditions in the stable upland zone for approximately the last 14 Ma, although some level of climatic amelioration and landform modification may have occurred within low-lying regions and in the inland mixed zone.

    3. Page 353
      Abstract
      Corresponding author (e-mail: bdd@aber.ac.uk)

      This study of landscape evolution presents both new modern and palaeo process-landform data, and analyses the behaviour of the Antarctic Peninsula Ice Sheet through the Last Glacial Maximum (LGM), the Holocene and to the present day. Six sediment-landform assemblages are described and interpreted for Ulu Peninsula, James Ross Island, NE Antarctic Peninsula: (1) the Glacier Ice and Snow Assemblage; (2) the Glacigenic Assemblage, which relates to LGM sediments and comprises both erratic-poor and erratic-rich drift, deposited by cold-based and wet-based ice and ice streams respectively; (3) the Boulder Train Assemblage, deposited during a Mid-Holocene glacier readvance; (4) the Ice-cored Moraine Assemblage, found in front of small cirque glaciers; (5) the Paraglacial Assemblage including scree, pebble-boulder lags, and littoral and fluvial processes; and (6) the Periglacial Assemblage including rock glaciers, protalus ramparts, blockfields, solifluction lobes and extensive patterned ground. The interplay between glacial, paraglacial and periglacial processes in this semi-arid polar environment is important in understanding polygenetic landforms. Crucially, cold-based ice was capable of sediment and landform genesis and modification. This landsystem model can aid the interpretation of past environments, but also provides new data to aid the reconstruction of the last ice sheet to overrun James Ross Island.

    4. Page 397
      Abstract
      Corresponding author (e-mail: m.balks@waikato.ac.nz)

      This paper brings together topographic cross-section ‘windows’ from across Antarctica to illustrate soil–landscapes from the margins of the polar plateau in the Transantarctic Mountains and McMurdo Dry Valleys, through East Antarctic coastal areas, to the northern Antarctic Peninsula Region. Soils identified range from Gelisols in the Ross Sea Region, through Gelisols and Entisols in coastal East Antarctica, to a mixture of Gelisols, Entisols, Spodosols and Inceptisols in the northern Antarctic Peninsula Region where permafrost is not ubiquitous. The relative impacts of the soil-forming factors are considered. At a continental scale climate is the main driver of the differences observed between soils in different areas. At local scales strong soil–topographic relationships are observed. Organisms, time and parent material are dominant influences on soil properties only in relatively localized situations. Organisms dominate in areas of organic matter or guano accumulation and time is a dominant influence on exceptionally old upland surfaces in the McMurdo Dry Valleys. The US Department of Agriculture’s Soil Taxonomy gives a useful overall appraisal of Antarctic soils; however, for detailed work, there is a need to introduce some new categories at subgroup level to better capture the range of soils described.

    5. Page 411
      Abstract
      Corresponding author (e-mail: rajeshasthana.antarctica@gmail.com)

      Schirmacher Oasis and Bharati Promontory in Larsemann Hills of East Antarctica are currently ice-free coastal areas exposed in physiographically different polar periglacial environments. Schirmacher Oasis is bound by the presence of a vast stretch of ice shelf in the north and the polar ice sheet in the south. It exhibits well-developed patterned ground, abundant till deposition, block-fields, episodic development of curvilinear morainic ridges, extensive outwash plains and erratics. In contrast, the occurrence of such depositional features is sparse on Bharati Promontory, where landmass is directly in contact with the ocean. The sedimentary processes vary in their magnitude owing to different physiographic settings in these two geographically separated locations. Scanning electron microscopy of quartz grains shows subsequent reworking under glaciofluvial environment and final deposition of material in glacially scoured basins. The fluvial action is more pronounced in the Schirmacher Oasis than on Bharati Promontory. The transport of sediment by polar ice is mainly through englacial pathways with a minor contribution from the supraglacial component. Discharge of all sizes of sediments ranging from large boulders to glacially abraded rock-flour in varying proportions takes place at the ice–bedrock interface. Granulometric analysis also shows turbulence of transporting media and reworking of sediments before final deposition.

    6. Page 429
      Abstract

      The wide range of periglacial environments of the Antarctic, from the wet, mild oceanic sub-Antarctic through to the cold, dry continent, provides not only an extensive modern laboratory, but also one that offers insights into conditions in the Northern Hemisphere at the height of the last glacial, is an analogue for periglacial conditions on other planets, and can be used for monitoring climatic change. Almost the whole known suite of periglacial landforms is present. Recent research directions show strong linkages between the biotic components and the abiotic responses, offering new insights into periglacial synergies and hence landform development. Other new directions are those of using the Antarctic as an analogue for periglacial conditions on Mars, and multinational undertakings monitoring permafrost and active layer changes. During the past three decades there have been a number of reviews of periglacial landforms and processes for both the area as a whole as well as for specific locations or regions. Here information regarding material post-dating the most recent reviews is provided and an attempt is made to highlight new directions and findings. This broad-based review provides a foundation for more detailed accounts on some of the periglacial attributes provided in other papers within these volumes.

    7. Page 455
      Abstract
      Corresponding author (e-mail: skonfal@hotmail.com)

      We present a new record of crustal deformation for the Dry Valleys and surrounding region of Antarctica. Values of crustal tilt resulting from the differential uplift of lacustrine strandlines are derived and linked with age data to provide a history of solid earth deformation since deglaciation. We present tilt directions and gradients for 13 strandlines formed c. 18 100–2100 cal yr BP. Derived gradient magnitudes increase exponentially with age and indicate an ongoing response to deglaciation since the Last Glacial Maximum. Azimuths of crustal tilting are consistently down to the SE towards West Antarctica. This tilt pattern is opposite to that predicted by models of glacial isostatic adjustment for Antarctica. Tilt magnitudes are significantly larger than tilted strandlines documented elsewhere in the world, suggesting an influence from thin crust and weak mantle underlying the region. This study presents the first use of lacustrine strandline tilts to document crustal deformation due to glacial unloading in Antarctica and provides an important new datum for constraining glacial isostatic adjustment models.

    8. Page 469
      Abstract
      Corresponding author (e-mail: kanao@nipr.ac.jp)

      Several characteristic waves detected by seismographs in Antarctic stations have been recognized as originating from the physical interaction between the solid earth and the atmosphere–ocean–cryosphere system surrounding the Antarctic and may be used as a proxy for characterizing ocean wave climate. A Chaparral-type infrasound sensor was installed at Syowa Station (SYO; 39.6E, 69.0S), East Antarctica, in April 2008 during the International Polar Year (IPY2007–2008). Matching data are also available for this time period from the existing broadband seismic recorder located close by. Continuous infrasound data for 2008–2009 include background signals (microbaroms) with a broad peak in the wave period between the values of 4 and 10 s. Signals with the same period are recorded by the broadband seismograph at SYO (microseisms). This period band is identified as double-frequency microseisms/baroms (DFM). The DFM have relatively lower amplitudes during winter. We suggest that this is due to the sea-ice extent around the coast causing a decreased ocean loading effect. In contrast, the single frequency microseisms/baroms with a peak in period between 12 and 30 s are observed under storm conditions, particularly in winter. On the infrasound data, stationary signals are identified with harmonic overtones at a few Hertz to lowermost human audible band, which we suggest is due to local effects such as sea-ice cracking and vibration. Microseism measurements are a useful proxy for characterizing ocean wave climate, complementing other oceanographic and geophysical data. At SYO, continuous monitoring by both broadband seismograph and infrasound contributes to the Federation of Digital Seismographic Networks, the Comprehensive Nuclear-Test-Ban Treaty in the high southern latitudes and the Pan-Antarctic Observations System under the Scientific Committee on Antarctic Research.

    9. Page 481
      Abstract
      Corresponding author (e-mail: carlamora@campus.ul.pt)

      Advanced synthetic aperture radar image mode precision (ASAR IMP) scenes of Deception Island from December 2008 to September 2010 have been analysed to assess its potential for snow cover classification. Backscattering was checked against ground truth. Despite the good spatial resolution of the ASAR, its applicability for detecting snow cover, and especially wet snow, was only possible at much lower resolutions, since noise was found to be very high. Scenes with bare ground or with dry snow cover showed highest backscattering, with averages from −10 to −12 dB. Wet snow showed a shift towards lower values, peaking at −15 dB. A threshold of −13 to −14 dB was identified between dry/bare ground and wet snow scenes at Crater Lake. The backscatter difference to a reference snow-free scene usually provided better classification results, and a threshold ranging from −2 to −3 dB was found. Results show that, despite the relative ease of use of C-band ASAR, special care is necessary since the results show significant noise, and it should only be applied to large areas. Large seasonal patterns of snow melt were identified on Deception Island.

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