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Improvements in the resolution of sea-floor mapping techniques have revealed extremely regular, sub-metre-scale ridge landforms produced by the tidal flexure of ice-shelf grounding lines as they retreated very rapidly (i.e. at rates of several kilometres per year). Guided by such novel sea-floor observations from Thwaites Glacier, West Antarctica, we present three mathematical models for the formation of these corrugation ridges at a tidally migrating grounding line (that is retreating at a constant rate), where each ridge is formed by either constant till flux to the grounding line, till extrusion from the grounding line, or the resuspension and transport of grains from the grounding-zone bed. We find that both till extrusion (squeezing out till like toothpaste as the ice sheet re-settles on the sea floor) and resuspension and transport of material can qualitatively reproduce regular, delicate ridges at a retreating grounding line, as described by sea-floor observations. By considering the known properties of subglacial sediments, we agree with existing schematic models that the most likely mechanism for ridge formation is till extrusion at each low-tide position, essentially preserving an imprint of the ice-sheet grounding line as it retreated. However, when realistic (shallow) bed slopes are used in the simulations, ridges start to overprint one another, suggesting that, to preserve the regular ridges that have been observed, grounding line retreat rates (driven by dynamic thinning?) may be even higher than previously thought. [ABSTRACT FROM AUTHOR]

This paper reports geochemical characteristics of mafic gneisses and granulites collected from four localities in central Dronning Maud Land to evaluate the tectonic setting of their precursor rocks. Precursor rocks for the mafic gneisses and granulites in central Dronning Maud Land were formed in different geological backgrounds and tectonic settings. The mafic gneisses and granulites in the Schirmacher Hills were derived from basaltic rocks in a back-arc setting. Published U–Pb zircon ages and the geochemical variation of the basement rocks indicate their emplacement between 800 and 650 Ma, close to peak metamorphism. While similar protoliths were recognized in the inland nunataks of Hochlinfjellet, in Filchnerfjella the mafic gneisses/granulites were derived from basaltic rocks formed in marginal continental arcs or island arcs. Highly disturbed trace-element patterns indicate that the metamorphic process influenced the geochemical composition during the prograde metamorphic stage. Our results imply that the outcrops in central Dronning Maud Land with different metamorphic ages contain mafic gneisses/granulites from precursor rocks formed under different tectonic settings. [ABSTRACT FROM AUTHOR]

The detailed geomorphology of ice‐free landscapes of Antarctica is key to understanding how their highly fragile environments respond to climate change, at different temporal and spatial scales. Despite the recent advances in geomorphological studies of ice‐free areas, machine learning applications to produce landform maps are still scarce on the Antarctic continent. In this study, we evaluated the predictive performance of different supervised machine learning algorithms to produce digital geomorphological maps in Vega Island—Antarctic Peninsula region. We tested six different models: average artificial neural networks, C5.0 decision tree, random forest, support vector machine, supervised self‐organizing map and weighted k‐nearest neighbours. We used an initial set of 54 geomorphometric and spectral predictors, from which redundant variables with Pearson correlation coefficient >|0.95| were removed, and only the most important predictors for each model were selected using recursive feature elimination. For training, we ran each model 100 times and predictions were assessed by the kappa and global accuracy values. The best predictors were the Red Edge 6 and SWIR 11 bands, roughness concentration index, elevation and drainage density. The decision trees C5.0 and random forest had the best performance, with average validation kappa of 0.85 ± 0.03 and 0.84 ± 0.03, respectively, evidencing excellent prediction. Despite the similar performance, random forest showed greater uncertainty degree and accuracy when classifying complex landforms, attesting to its great robustness. From sensitivity and specificity values, we observed that the glaciers and talus showed higher accuracy, whereas cryoplanated platforms and scree slopes had the worst classification. The presented methodology optimized the classification by selecting the most important predictors, assessing accuracy and evaluating uncertainty. The results indicated that machine learning methods have great potential to produce geomorphological mappings in the Antarctic ice‐free areas, as a promising tool to provide detailed information on remote, harsh polar environments. [ABSTRACT FROM AUTHOR]

Basal properties beneath ice streams and glaciers are known to be a control for ice flow dynamics, hence knowledge of them is crucial for predicting sea level due to changes in glacial dynamics. Basal properties, processes and topography also drive the formation of subglacial landforms. Bed properties beneath Rutford Ice Stream (West Antarctica) have previously been described using seismic acoustic impedance measurements at a sparse spatial coverage. Here, we derive bed properties in a 15 × 17 km grid of surface radar data with coverage and sampling much higher than previous seismic studies. Bed reflection amplitudes in surface radar data were calibrated using sediment porosities (ranging from 0.4–0.5) derived from seismic acoustic impedance. We find the bed properties are spatially variable, consisting of low porosity material in some areas and soft sediment in other areas. Comparison of seismic and surface radar data imply the low porosity material to be a consolidated sediment or sedimentary rock. Mega‐scale glacial lineations (MSGLs) are ubiquitous on the bed and consist of soft, high porosity, probably deforming sediment, consistent with previous interpretations of MSGLs. We find some MSGLs have high reflectivity on their crest, interpreted as water bodies overlying high porosity sediment, whereas the trough around and the upstream end of some landforms consist of low porosity material. Integrating these different observations, we place constraints on possible explanations for the occurrence of water on the crest of landforms. Plain Language Summary: Physical properties of rocks and sediments as well as the presence of water beneath ice streams and glaciers control the flow of the ice. Understanding glacial flow is important to better constrain predictions of sea‐level changes. Within this study we present physical properties of material beneath Rutford Ice Stream in West Antarctica over a 15 × 17 km area. Our data show areas of high porosity interpreted as wet sediment and areas of low porosity beneath the ∼2 km thick ice stream. Ice movement above areas of soft sediment is assumed to be maintained by sediment deformation, whereas in areas overlain by low porosity material, sliding of the ice over this material is assumed to maintain flow. The topography beneath Rutford Ice Stream shows many elongated landforms, some over 14 km long. We show that these landforms partly consist of soft sediment. Some of these seem to have a water layer on their crest, but it is not well understood why. However, there might be variations in the sediment composition of the landforms enabling the creation of this water layer. The occurrence of materials with different properties and water show us how heterogenous the bed beneath ice streams can be, which is important for modeling ice stream motion. Key Points: Glacier bed properties (water content, porosity) are constrained using surface radar data calibrated with seismic acoustic impedanceResults show sequences of low porosity material (consolidated sediment or rock), soft sediment and free‐water beneath Rutford Ice StreamMega‐scale glacial lineations are pervasive beneath ice streams, some with a free water layer >10 km long and 100 m wide along their crest [ABSTRACT FROM AUTHOR]

We describe the glacial geomorphology and initial geochronology of two ice-free valley systems within the Neptune Range of the Pensacola Mountains, Antarctica. These valleys are characterized by landforms associated with formerly more expanded ice sheet(s) that were at least 200 m thicker than at present. The most conspicuous features are areas of supraglacial debris, discrete debris accumulations separated from modern-day ice and curvilinear ridges and mounds. The landsystem bears similarities to debris-rich cold-based glacial landsystems described elsewhere in Antarctica and the Arctic where buried ice is prevalent. Geochronological data demonstrate multiple phases of ice expansion. The oldest, occurring > 3 Ma, overtopped much of the landscape. Subsequent, less expansive advances into the valleys occurred > 2 Ma and > ~1 Ma. An expansion of some local glaciers occurred < 250 ka. This sequence of glacial stages is similar to that described from the northernmost massif of the Pensacola Mountains (Dufek Massif), suggesting that it represents a regional signal of ice-sheet evolution over the Plio-Pleistocene. The geomorphological record and its evolution over millions of years makes the Neptune Range valleys an area worthy of future research and we highlight potential avenues for this. [ABSTRACT FROM AUTHOR]

Cryoplanation terraces (CTs) are large (3000–800 000 m2) erosional landforms found in upland periglacial environments. Two hypotheses for the formation of CTs are supported in contemporary literature: (1) CT formation is controlled primarily by geologic structure; and (2) CTs are climatically controlled through nivation, a suite of erosional processes associated with late-lying snowbanks. A persistent question in periglacial geomorphology is whether nivation can produce CT-scale landforms. This paper examines the unusual deglaciation history of "Frost Ridge" on the Cathedral Massif, northwestern British Columbia, to estimate long-term denudation attributable to nivation processes active since the last glacial maximum. Frost Ridge forms one flank of an east–west-oriented glacial valley. During deglaciation, marginal drainage created V-shaped erosional notches on both valley walls. Minimization of solar radiation on the steep north-facing wall (Frost Ridge) allowed snowbanks to accumulate and persist in the marginal drainage features and nivation processes to erode the slope. Today, several large nivation hollows (incipient CTs) are present near the summit of Frost Ridge, while the V-shaped marginal drainage features are preserved at lower elevations and on the opposite, south-facing valley wall. A high-resolution survey using an unmanned aerial vehicle (UAV) allowed volumes of marginal drainage and incipient terrace features to be compared. Based on this volumetric comparison, denudation rates are estimated to range from 4.2 to 125.8 mm/kyr, which are comparable with relatively short-term nivation rates reported from Antarctica and mid-latitude alpine periglacial areas. [ABSTRACT FROM AUTHOR]

Here, a geomorphological map of Horseshoe Island, which is one of the most ice-free islands in Marguerite Bay of the Antarctic Peninsula, is provided. The landforms on the island were mapped by using Google Earth images. Field reconnaissance of the landforms was carried out in March 2018. The island is subdivided into three major geomorphologically different sectors. The northern sector is mostly covered by a remnant of a non-erosive ice cap and has limited glacial landforms and deposits. The central sector is rich in terms of glacial and periglacial landforms and deposits. Glaciers are still sculpting the southern sector and it has extensive features of glacial erosion and deposition. The most common landforms on the island are talus cones, moraines, patterned ground, and raised beaches. The geomorphological map of the island will be a useful base for further geomorphic and/or glaciologic research in this climate-sensitive region. [ABSTRACT FROM AUTHOR]

The Vestfold Hills sector on the coastal fringe of the Princess Elizabeth Land forms part of an Archean to Paleoproterozoic aged cratonic nucleus of the East Antarctic Shield. A charnockite-granite association from the Mossel Gneiss Group in the northern region of the Vestfold Hills is investigated in this work to characterise the metamorphic-magmatic evolution of the area. Conventional thermometry and phase equilibria modelling indicate that the charnockite formed as a result of ultra-high temperature metamorphism at low-intermediate pressure (∼4 kbar). Phase equilibria modelling, reveals that the melt-integrated charnockite composition is a restitic product of a protolith of quartz diorite composition which underwent isobaric heating (peak temperature up to 960 °C) at 4 kbar pressure followed by anatexis. The anatexis of the quartz diorite protolith also resulted in the formation of the associated granitic melt. U–Th-Pb Total ages obtained from monazites of the granite integrated with CHIME ages extracted using the isochron method indicate an emplacement age of ∼2200 Ma and two younger events are recorded at ∼2000 Ma and ∼1700 Ma. The younger ages are ascribed to the resetting during the emplacement of younger basalt dykes that cross cut the charnockite-granite sequence. Vestfold Hills' geological correlations with Indian and Australian cratons are discussed considering this new data. [ABSTRACT FROM AUTHOR]

As a general trend in the life history of marine organisms, species inhabiting cold waters have reduced growth rates and increased lifespans. Studies based on egg sizes and brooding times of deep-sea and polar octopods support this hypothesis, but empirical data on growth are still scarce. To test the hypothesis that octopods inhabiting cold waters (< 3°C) live longer than temperate and warm water species, this study investigated size-at-age, maturation and growth rates in incirrate Antarctic octopods. Octopod age was estimated via the interpretation and quantification of beak growth increments, which in shallow water octopods have been validated to be formed on a daily basis. Specimens from the families Megaleledonidae (Adelieledone spp., Pareledone spp. and Megaleledone setebos) and Enteroctopodidae (Muusoctopus rigbyae) were collected on the shelf and slope regions off the Antarctic Peninsula during a cruise in 2012. Examined specimens included early juveniles to animals in advanced maturity. The total number of growth increments ranged from 192–599 in Pareledone aequipapillae (body mass [BM] 2–109 g), 182–431 in Pareledone charcoti (BM 5–124 g), 98–906 in M. setebos (BM 10–6000 g) and 207–425 in M. rigbyae (BM 24–256 g). After the cruise, eleven specimens of P. charcoti were kept alive in captivity for more than 12 months and these animals had 219–364 growth increments, suggesting that increment formation in this species takes longer than one day. The complex population structure (size, age and maturity range) of the specimens that were captured during a relatively short time, the number of beak increments quantified, and the preliminary validation observations indicate that Antarctic octopods do not deposit increments daily, and may have lifespans exceeding 3 years. These findings corroborate the general trend that cold water molluscs have a longer lifespan than their warm water relatives. [ABSTRACT FROM AUTHOR]

Soils and landforms of Nelson Island remain one of the least studied in the South Shetlands Archipelago, despite that it is one of the oldest ice-free areas and is strongly vegetated. In this paper, we examine the main processes and factors of soil formation at Harmony Point and the relation of soils to landforms, vegetation and lithology. To achieve the goals, 26 pedons were collected and studied from a 4 km2 ice-free area at Harmony Point (S62°18′; W059°10′) on the southern area of Nelson Island (Maritime Antarctica). The soils were sampled on all representative local landforms, including three levels of uplifted marine terraces up to cryoplanated plateau, waterlogged depressions, rock felsenmeer, debris slopes and patterned ground, and a paraglacial border of the ice cap (270 m a.s.l). Sampling along the cryoplanated plateau was carried out along a gradient extending inland from the margins of the Ice Cap; and sampling of the marine terraces was performed along a chronosequence under varying bird-nesting influence and age. The main pedogenetic processes observed in this area are marked phosphatization, melanization from the accumulation of organic matter, and cryoturbation. Soil development varies from weakly developed, shallow, stony and cryoturbated to well-developed and organic-rich, phosphate soils with colors ranging from grayish to brown. The mineralogical composition of the clay fraction contains secondary minerals, indicating the active role of chemical weathering. Ornithogenic soils have mature phosphate minerals such as vivianite and taranakite, as well as poorly crystalline leucophosphite. Intensively cryoturbated soils are underlain by permafrost and are classified as Typic Haploturbels; polygonal soils are widespread on the cryoplanated plateau. Areas without permafrost were classified as Typic Gelorthents. Phosphatization is a dominant soil-forming process in this area and is associated with past and present-day guano accumulation by bird nesting and has led to the the development of deeper Ornithogenic Haplorthels. The ornithogenic soils occur at different topographic levels on the cryplanated platform and marine terraces. High P concentrations can be used as a proxy of the past nesting birds' activities, with far-reaching implications, especially with regards to vegetation growth and microbial activity and diversity. • In Harmony Point the soils and the landforms are related. • The main soil-forming processes are cryoturbation, humification and phosphatization. • Solifluction, cryoplanation, frost heave, and thermokarst occur in the landscape. • The landforms and vegetation are associated to the water and bird distribution. [ABSTRACT FROM AUTHOR]

Quaternary period has witnessed perceptible climatic change in Schirmacher region, central Dronning Maud Land (cDML), East Antarctica. There were buildup of ice sheet and its recession throughout the period. The Schirmacher Oasis, Baalsrudfjellet, Veteheia and Veten nunataks are the prominent northernmost exposures in cDML area and play a major role in controlling the ice flow in this region resulting in glacial erosional as well as depositional landforms. These developments reveal vital information about the evolution of the region in Quaternary period. Erosional features such as roche-moutonees, glacially polished and abraded rocky outcrops with excellent preservation of glacial striations indicates the paleo-movement of overriding glaciers. Striations are generally preserved on polished surfaces of bedrock exposed on the high lands, however, glacial striations are also preserved over some mafic and resistant hard rocks in low lying areas. In general, the glacial striations indicate north-northeast movement of paleo ice sheet. Majority of the boulders in east-central valley show their longer axis trending in NNE-WSW to NE-SW directions. The cross cutting relation of striations give the changing directions of paleo ice sheet movement. Further, back calculation of depth of indentation and corresponding ice load gives a value of 100 to 500 m thick paleo-ice sheet in different parts of this region, documenting vast deglaciation in this region. [ABSTRACT FROM AUTHOR]

We identify late Paleozoic ice age (LPIA) subglacial megalineations from field and geospatial imagery of the Twyfelfontein area of northern Namibia, and present the results of a geomorphometric analysis of those data. Asymmetric 0.1–1.5 km-long megawhalebacks indicate a paleo-ice flow to the northwest. We infer that an ice stream draining the LPIA Kaokoveld ice sheet existed within the proto-Huab River valley and that was comparable to ice streams in modern Antarctica. Recognition of a paleo-ice stream in northern Namibia supports interpretations of glaciogenic sedimentary successions (Itararé Group) in southern Brazil that suggest the presence of major, terrestrial glacial outlet systems in southern Africa during the LPIA. [ABSTRACT FROM AUTHOR]

Seabirds and pinnipeds play an important role in biogeochemical cycling by transferring nutrients from aquatic to terrestrial environments. Indeed, soils rich in animal depositions have generally high organic carbon, nitrogen and phosphorus contents. Several studies have assessed bacterial diversity in Antarctic soils influenced by marine animals; however most have been conducted in areas with significant human impact. Thus, we chose Cape Shirreff, Livingston Island, an Antarctic Specially Protected Area designated mainly to protect the diversity of marine vertebrate fauna, and selected sampling sites with different types of animals coexisting in a relatively small space, and where human presence and impact are negligible. Using 16S rRNA gene analyses through massive sequencing, we assessed the influence of animal concentrations, via their modification of edaphic characteristics, on soil bacterial diversity and composition. The nutrient composition of soils impacted by Antarctic fur seals and kelp gulls was more similar to that of control soils (i.e. soils without visible presence of plants or animals), which may be due to the more active behaviour of these marine animals compared to other species. Conversely, the soils from concentrations of southern elephant seals and penguins showed greater differences in soil nutrients compared to the control. In agreement with this, the bacterial communities of the soils associated with these animals were most different from those of the control soils, with the soils of penguin colonies also possessing the lowest bacterial diversity. However, all the soils influenced by the presence of marine animals were dominated by bacteria belonging to Gammaproteobacteria, particularly those of the genus Rhodanobacter. Therefore, we conclude that the modification of soil nutrient composition by marine vertebrates promotes specific groups of bacteria, which could play an important role in the recycling of nutrients in terrestrial Antarctic ecosystems. [ABSTRACT FROM AUTHOR]

Extended glacier retreat is among the main consequences of the rapid warming of the West Antarctic Peninsula. Particularly, in the inner part of Potter Cove (South Shetland Islands, Antarctica) large areas are now exposed to open sea conditions owing to the retreat of Fourcade glacier. During the 2010 austral summer, underwater photographic surveys were undertaken by SCUBA diving up to 30 m in these new ice-free areas 80 m from the glacier front. Our main aim was to investigate colonization and early succession of the benthic assemblages on soft-bottom areas. Here, we reported a total of 1,146 animals belonging to 13 taxa. Filter-feeders comprised the largest trophic group and sessile fauna showed much higher coverages and densities than mobile fauna at all depths. The most abundant groups were ascidians and bryozoans, which together comprised ~90% of all taxa documented. In a region where most of marine-terminating glaciers are in retreat, these results are an important contribution to improve our knowledge on colonization in the newly ice-free areas. [ABSTRACT FROM AUTHOR]

• The complexity of geomorphic features is explained by lithological diversity. • Paraglacial domain is more dynamic and presents soils considered as immature. • Periglacial domain has many rocky outcrops, interspersed with Holocene beaches. • The existence of vegetated marine terraces suggests a greater stability. • Soil-landforms relationships broaden the discussion about geomorphology processes. Despite progress in the last decade on periglacial geomorphology and permafrost research in Antarctica, many areas in Maritime Antarctica remain unsurveyed. This study aimed to identify and describe the main periglacial landforms of President Head Peninsula, at Snow Island, Maritime Antarctica, with emphasis on the relationships between soils, landforms and lithology. We identified and mapped landforms and their physiographic aspects at 1:15,000 scale using Sentinel-2 satellite image (10 m spatial resolution) and georeferenced using portable GPS. Morphological, physical, chemical, micromorphological and mineralogical properties of selected soils were also analyzed. Seventeen types of landforms were mapped (glacial, glaciofluvial, tectonics and structural, periglacial, and marine landforms), whose complexity of geomorphic features is explained by the diversity of morphogenetic processes and lithological diversity. Three distinct geomorphological domains were identified (proglacial, paraglacial, and periglacial). The paraglacial domain is more dynamic and presents immature or poorly developed soils. The periglacial domain has many rocky outcrops, interspersed with Holocene beaches and vegetated marine terraces. Landforms associated with gelifluction, patterned ground and permafrost were only observed on the upper plateaus of the periglacial domain. No soil formation were observed in the proglacial domain. [ABSTRACT FROM AUTHOR]

Fildes Peninsula (F.P.) and Ardley Island (A.I.) are among the first ice-free areas in Maritime Antarctica. Since the last glacial retreat in this part of Antarctica (8000 to 5000 years BP), the landscape in these areas evolved under paraglacial to periglacial conditions, with pedogenesis marked by cryogenic processes. We carried out a detailed soil and geomorphology survey, with full morphological and analytical description for both areas; forty-eight soil profiles representing different landforms were sampled, analyzed and classified according to the U.S. Soil Taxonomy and the World Reference Base for Soil Resources (WRB). Soils are mostly turbic, moderately developed, with podzolization and strong phosphatization (chemical weathering of rock minerals and formation of amorphous Al and Fe minerals) in former ornithogenic sites while in areas with poor vegetation show typical features of cryogenic weathering. Nivation, solifluction, cryoturbation, frost weathering, ablation and surface erosion are widespread. The most represented landform system by surface in Fildes Peninsula is the periglacial one, and 15 different periglacial landforms types have been identified and mapped. These features occupy about 30% of the land surface, in which patterned ground and stone fields are the most common landforms. Other significant landforms as protalus lobes, rock glaciers or debris lobes indicate the extensive presence of permafrost. Soil variability was high, in terms of morphological, physical and chemical properties, due to varying lithic contributions and mixing of different rocks, as well as to different degrees of faunal influence. Three soil taxonomy orders were identified, whereas thirty four individual pedons were differentiated. Fildes Peninsula experiences a south–north gradient from periglacial to paraglacial conditions, and apparently younger soils and landforms are located close to the Collins Glacier. Arenosols/Entisols and Cryosols/Gelisols (frequently cryoturbic) are the most important soil classes; Leptosols/Entisols, Gleysols/Aquents and Cambisols/Inceptisols also occur, all with gelic properties, and with varying faunal influences. Both soil classification systems are adequate to distinguish the local pedogenesis processes. The WRB system is broader, since it was designed to be applied in all Polar Regions; the family classes adopted by the ST were effective in separating soils with important differences with regard to texture and gravel content, all important attributes accounting for the ecological succession and periglacial processes. An altitudinal organization of landforms and processes can be recognized from geomorphological mapping. Periglacial features are dominant above 50 m a.s.l. although are present at lower altitude. [ABSTRACT FROM AUTHOR]

Molecular variation among Antarctic Collembola has been well appreciated over the last decade. The majority of studies have focussed on the Transantarctic Mountains and Antarctic Peninsula, and more recently Dronning Maud Land, which now accounts for all known continental species. Within most species, mean mitochondrial DNA (mtDNA) sequence divergence has not been more than around 2%, but in 2010 far greater levels of infraspecific sequence divergence (9.2–10.9%) were discovered in three species:Friesea grisea(10.2%),Gressittacantha terranova(10.4%) andCryptopygus antarcticus(9.2%). Here, we present the first phylogeographic study onCryptopygus sverdrupifrom Dronning Maud Land. We found that mtDNACOIand16Shaplotypes clustered into two lineages with a meanCOIsequence divergence of around 7.1%. The mixing of haplotypes between nearby nunataks separated by up to 15 km revealed support for ongoing (but rare) dispersal, although a single site, the most geographically isolated (by 40–58 km) was also the most genetically divergent. These levels of sequence divergence indicate persistence of biota throughout the Miocene and Pliocene isolated in glacial refugia. Expanding sampling ofC. sverdrupifrom additional ice-free refugia throughout Dronning Maud Land will be important to further our understanding of the evolutionary processes that have influenced the Antarctic continent, its landscape and biota. [ABSTRACT FROM PUBLISHER]

Investigations of openwork block deposits have the potential to improve understanding of the production of substrates for biological colonisation, the control of geological structure and the impacts of climate change on landforms. As part of research into the morphology and characterisation of a blockfield located on the Northern Buttress of the Vesleskarvet Nunataks, Western Dronning Maud Land, Antarctica (2° W, 71° S), this paper investigates the influence that aspect has on weathering for a blockfield using data collected during the 2009-2012 Austral summer seasons. Proxy data recorded for weathering included rock hardness rebound values as well as visual evidence of flaking, pitting, surface roughness and lichen presence. Aspect was found to affect weathering of blockfield samples across the study site, with the south-facing sides being the least weathered of the directional aspects. This paper argues that a higher radiation budget associated with slope aspect and angle could drive thermal regimes and subsequent weathering of clast faces. Furthermore, in the absence of abundant precipitation, ice and snow cover become the primary source of moisture in this high-latitude Antarctic environment. [ABSTRACT FROM AUTHOR]

Abstract: Inter-ice stream areas cover significant portions of Antarctica''s formerly glaciated shelves, but have been largely neglected in past geological studies because of overprinting by iceberg scours. Here, we present results of the first detailed survey of an inter-ice stream ridge from the West Antarctic continental shelf. Well-preserved sub- and proglacial bedforms on the seafloor of the ridge in the eastern Amundsen Sea Embayment (ASE) provide new insights into the flow dynamics of this sector of the West Antarctic Ice Sheet (WAIS) during the Last Glacial cycle. Multibeam swath bathymetry and PARASOUND acoustic sub-bottom profiler data acquired across a mid-shelf bank, between the troughs of the Pine Island-Thwaites (PITPIS) and Cosgrove palaeo-ice streams (COPIS), reveal large-scale ribbed moraines, hill-hole pairs, terminal moraines, and crevasse-squeeze ridges. Together, these features form an assemblage of landforms that is entirely different from that in the adjacent ice-stream troughs, and appears to be unique in the context of previous studies of Antarctic seafloor geomorphology. From this assemblage, the history of ice flow and retreat from the inter-ice stream ridge is reconstructed. The bedforms indicate that ice flow was significantly slower on the inter-ice stream ridge than in the neighbouring troughs. While terminal moraines record at least two re-advances or stillstands of the ice sheet during deglaciation, an extensive field of crevasse-squeeze ridges indicates ice stagnation subsequent to re-advancing ice, which deposited the field of terminal moraines in the NE. The presented data suggest that the ice flow behaviour on the inter-ice stream ridge was substantially different from that in the adjacent troughs. However, newly obtained radiocarbon ages on two sediment cores recovered from the inter-ice stream ridge suggest a similar timing in the deglaciation of both areas. This information closes an important gap in the understanding of past WAIS behaviour in the eastern ASE. Our newly-documented bedforms will also serve as an important diagnostic tool in future studies for interpreting ice-sheet histories in similar inter-ice stream areas. [Copyright &y& Elsevier]

During the last 50 years, the western coast of the Antarctic Peninsula and adjacent archipelagos, also known as the maritime Antarctic, has experienced notable climate warming. As a result, expansion of the local distributions of the two native species of vascular plants, Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth.) Bartl., over previously unoccupied ground has been noted. Birds have been suggested to be partially responsible for this spread. The focus of the present study was to document the use of vascular plants in nest building by the kelp gull ( Larus dominicanus) in the Argentine Islands region. During the 2009/2010 season, samples from kelp gull nests were collected and analyzed. Besides nests, material lost by birds during transfer was also studied. We demonstrate that, in the Argentine Islands region, Deschampsia antarctica and some bryophytes contribute the majority of nest building material for the kelp gull. Other materials, including lichens, gull feathers, and limpet shells, are used less frequently. The plants can reestablish upon transfer via vegetative or generative means. It thus seems that the kelp gull may potentially serve as a dispersal agent for Deschampsia antarctica. [ABSTRACT FROM AUTHOR]

During the nearly 40 years covered by the study, major height differences of over ± 25 m have been revealed in the volcanic landscape of the 1970 craters in Deception Island, an active volcano in the South Shetland Islands (West Antarctica). In the last 14 years, the mean volcanic filling rate has been 1 m yr-1 and the mean erosion rate has been -0.2 m yr-1. There has been considerable landform modification mainly associated with landslide-induced accumulation, and erosion may indicate the craters’ fill over the next 30–40 years. Deception Island's eruptions have been recorded since 1842. Special attention was paid to the zones affected by the most recent volcanic events and the geomorphological changes that have taken place in those zones since then (e.g. the 1970 volcanic craters area in the last episode occurring between 1967 and 1970). Historical maps (produced before and just after the 1970 eruption) were compared with maps plotted in 1992 and updated using a 2003 image from the Quickbird satellite and data obtained with Global Navigation Satellite System technology in 2006. Techniques used included both geodetic transformation and the geometric correcting of maps. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the spatial distribution of soils from the northern part of Byers Peninsula, Livingston Island, which is the largest ice-free area of the South Shetlands archipelago, Maritime Antarctica. Physical and chemical characteristics are presented for 23 soil profiles. Soil parent materials vary from marine sedimentary to volcanic and volcanoclastic rocks, intruded by igneous bodies. To assess soil–landscape relationships, twenty-three soil profiles were described and sampled. Soil samples of selected horizons were submitted to chemical, physical and mineralogical analyses. Soil mapping was based on the soil profiles, integrated with the existent topographic map (1:25.000 scale), a digital elevation model, the geological map and a satellite image. Twenty different soil units were identified and mapped. According to the World Reference Base for Soil Resources (WRB) system, soils were classified as Fluvisols, Regosols, Leptosols or Cryosols, which correspond mostly to Fluvents, Orthents/Psamments, Inceptsols and Gelisols, respectively, according to the Soil Taxonomy. Soils from northern Byers Peninsula are generally shallow and coarse textured, with low organic matter content. Three soils from the rocky platforms of the northern coastal region possess ornithogenic character, with lower pH, higher P, Al3+ and organic C values when compared to soils not influenced by sea birds. In non-ornithogenic soils, the presence of easily weatherable minerals in the clay fraction indicates that physical weathering occurs with limited chemical alteration of primary minerals. The influence of penguin and other birds on coastal soils alters clay mineralogy, with formation of poorly crystalline P-rich phases. A better understanding of the depth of the permafrost table and the spatial distribution of permafrost is necessary for a more conclusive classification of Cryosols or Gelisols. [Copyright &y& Elsevier]

Abstract: This work describes periglacial features identified at Patriot Hills, at the southernmost part of Ellsworth Mountains, Antarctica, during the 2008/2009 Brazilian Antarctic Expedition, and discusses their morphogenetic environment. Identified periglacial features were classified into: (a) rock glacier-like landform; (b) slightly creeping debris-mantled slopes; (c) steep debris-mantled slopes; and (d) rock falls. Results obtained from sediment sample analysis suggest activity and passive movement of a rock glacier-like landform, albeit minimal. Wind seems to play an important role in Patriot Hills local geomorphology. Periglacial features such as slightly creeping debris-mantled slope appear to have preferred slope orientation. They are commonly found onto slopes where the katabatic wind flows down. Slopewash and groundwater movement processes may be limited or non-existent since most snow disappears through sublimation [Copyright &y& Elsevier]

Abstract: Periglacial processes and landforms together with the presence of permafrost are among the most relevant geomorphological elements in the northern Antarctic Peninsula region. Their distribution affects the hydrology and has consequences for the ecosystems of the ice-free areas. In this paper a compilation of the different types of periglacial landforms and processes occurring in the South Shetland Islands is carried out and their spatial distribution is analysed. Furthermore, the relationships of the periglacial landforms with local conditions and permafrost distribution have been taken into account. A total of thirty three types of periglacial landforms were identified and considered in this work. Patterned ground and stone fields are the most common periglacial landforms, which are located within a wide altitudinal range and mainly on platforms. Field studies, aerial photograph and satellite imagery interpretation were implemented to produce detailed maps from ten areas with different geological, geomorphological and relief characteristics, including the largest and most relevant ice-free areas within the archipelago, showing the presence and spatial distribution of periglacial landforms. This work shows that the periglacial environment, primarily conditioned by the regional climatic conditions, has a great diversity in the studied region and that the distribution of the periglacial landforms is also related to local relief and geomorphological characteristics, lithology, hydrogeology, and presence of permafrost where altitude plays an important role. Periglacial phenomena are widespread above 10m a.s.l. and are especially active on slopes and platforms between 30 and 100m a.s.l. The spatial distribution of periglacial landforms helps to identify the presence of permafrost that is dominant above 25–30m a.s.l. and more than 70% of the surface is occupied by active layer-related landforms. [Copyright &y& Elsevier]

Abstract: Pine Island Glacier drains portions of the West Antarctic Ice Sheet into the Amundsen Sea. During the Last Glacial Maximum the glacier extended nearly 500 km from its present location onto the outer continental shelf. Unusually restricted sea-ice cover during the austral summer of 2010 allowed for a systematic multibeam swath-bathymetric and chirp sonar survey of the mid-shelf section of Pine Island Trough. The mapped glacial landforms reveal new information about the paleo-Pine Island Ice Stream''s dynamic retreat from the mid-shelf area and confirm previous suggestion of a retreat in distinct steps. The periods of grounding line stability during the overall retreat phase are marked by sediment accumulations, i.e. grounding zone wedges. These wedges are here mapped in sufficient detail to characterize spatial dimensions and estimate the volume of deposited sediment. Considering a range of sediment flux rates from the paleo-Pine Island Ice Stream we estimate that the largest and most clearly defined grounding zone wedge, located at about 73°S in the surveyed area, took between 600 and 2000 years to form. The ice stream retreated landward of this wedge before 12.3 cal ka BP. The swath-bathymetric imagery of landforms in Pine Island Trough includes glacial features that suggest that retreat between periods of grounding line stability may be associated with episodes of ice shelf break-up. The depths of grounding line wedges decrease in a landward direction, from 740 to 670 m, and record elevation of the grounding line as it stepped landward. In all, the grounding line elevation varied by only ∼80 m over a distance of just over 100 km, implying a low ice sheet profile during retreat. Finally, we revisited seismic reflection profile NB9902, acquired along Pine Island Trough in 1999, in combination with the newly acquired swath-bathymetric imagery from 2010. Together these data show that the ice stream paused during its retreat to form grounding zone wedges at an area in central Pine Island Trough where a high in dipping bedrock strata exists and the glacial trough is narrow, forming a bathymetric “bottle neck”. [Copyright &y& Elsevier]

Abstract: We review the geomorphological, sedimentological and chronological evidence for palaeo-ice streams on the continental shelf of Antarctica and use this information to investigate basal conditions and processes, and to identify factors controlling grounding-line retreat. A comprehensive circum-Antarctic inventory of known palaeo-ice streams, their basal characteristics and minimum ages for their retreat following the Last Glacial Maximum (LGM) is also provided. Antarctic palaeo-ice streams are identified by a set of diagnostic landforms that, nonetheless, display considerable spatial variability due to the influence of substrate, flow velocity and subglacial processes. During the LGM, palaeo-ice streams extended, via bathymetric troughs, to the shelf edge of the Antarctic Peninsula and West Antarctica, and typically, to the mid-outer shelf of East Antarctica. The retreat history of the Antarctic Ice Sheet since the LGM is characterised by considerable asynchroneity, with individual ice streams exhibiting different retreat histories. This variability allows Antarctic palaeo-ice streams to be classified into discrete retreat styles and the controls on grounding-line retreat to be investigated. Such analysis highlights the important impact of internal factors on ice stream dynamics, such as bed characteristics and slope, and drainage basin size. Whilst grounding-line retreat may be triggered, and to some extent paced, by external (atmospheric and oceanic) forcing, the individual characteristics of each ice stream will modulate the precise timing and rate of retreat through time. [Copyright &y& Elsevier]

Landforms with the appearance of cryoplanation terraces were studied on Alexander Island in an attempt to better understand their formation and growth. Developed on sub-horizontal sedimentary rocks, with 360° exposure around a nunatak, the terraces show a distinct equatorward orientational preference and an increase in terrace size with elevation. Available data fail to indicate any evidence of freeze-thaw weathering and information relating to present-day debris transport is singularly absent. Thermal data from the rock exposures showed variability that could cause thermal fatigue but no rates of change of temperature commensurate with thermal shock were recorded. Terrace development appears to be connected with lithological differences in the local sandstones, with growth along sedimentary junctions. Although presently in a permafrost environment, the available information on these landforms does not appear to be compatible with that generally accepted for cryoplanation terraces. [ABSTRACT FROM AUTHOR]

In desert ecosystems, microbial activity and associated nutrient cycles are driven primarily by water availability and secondarily by nutrient availability. This is especially apparent in the extremely low productivity cold deserts of the McMurdo Dry Valleys, Antarctica. In this region, sediments near streams and lakes provide the seasonally wet conditions necessary for microbial activity and nutrient cycling and thus transfer energy to higher organisms. However, aside from a few studies of soil respiration, rates of microbial activity throughout the region remain unexplored. We measured extracellular enzyme activity potentials (alkaline phosphatase, leucine-aminopeptidase, beta-glucosidase, phenol oxidase, and peroxidase) in soils adjacent to lakes and streams, expecting activity to be primarily related to soil water content, as well as time of season and organic matter supply. Phosphatase and beta-glucosidase activities were higher in shoreline than upland soils; however, potential rates were not correlated with soil water content. Instead, soil organic matter, salinity, and pH were the best predictors of microbial activity. Microbial nutrient limitation metrics estimated from extracellular enzyme activity were correlated with pH and salinity and exhibited similar patterns to previously published trends in soil P and N content. Compared to other terrestrial ecosystems, organic matter specific rates for leucine-aminopeptidase and oxidative enzyme activities were high, typical of alkaline desert soils. Phosphatase activity was close to the global mean whereas beta-glucosidase activity was extremely low, which may reflect the lack of vascular plant derived organic matter in the Dry Valleys. In this cold desert ecosystem, water availability promotes microbial activity, and microbial nutrient cycling potentials are related to soil geochemistry. [ABSTRACT FROM AUTHOR]

Glacial landforms on the Barton and Weaver peninsulas of King George Island in the South Shetland Islands, West Antarctica were mapped and dated using terrestrial cosmogenic 36Cl methods to provide the first quantitative terrestrial record for late Quaternary deglaciation in the South Shetland Islands. 36Cl ages on glacially eroded and striated bedrock surfaces range from 15.5±2.5 kyr to 1.0±0.7 kyr. The 36Cl ages are younger with decreasing altitude, indicating progressive downwasting of the southwestern part of the Collins Ice Cap at a rate of ∼12 mm yr−1 since 15.5±2.5 kyr ago, supporting the previously published marine records for the timing and estimate of the rate of deglaciation in this region. [ABSTRACT FROM AUTHOR]

Deception Island is the largest volcano in the actively extending Bransfield Basin, a marginal basin situated behind the extinct South Shetland Islands arc. Deception Island has been well studied but its submerged flanks have not. A multibeam bathymetry survey was conducted around the island in 2005. Data from the flooded caldera show no evidence for recent localized resurgence. The gently-sloped bottom of the caldera basin is consistent with either a broad zone of resurgence on its east side associated with trap door deformation or with higher rates of sediment supply from the east side of the island. Around the island, numerous tectonic and volcanic features on the volcano's east and west flanks are nearly all aligned with the regional strike (~060°) of the Bransfield rift and there is very little evidence for the other fault populations that have been identified on the island. We infer that models that link the ongoing tectonic development of Deception Island to complex regional tectonics are less likely than models in which the dominant regional extension in Bransfield Strait is modulated by the local effects of caldera collapse and possibly a small right-lateral transfer zone offsetting the primary extension axes in the Central and Western Bransfield Basins. [ABSTRACT FROM AUTHOR]

Well-preserved vertebrate microremains are abundant in the residues from a calcareous grey siltstone in the karawaka biozone (?late Givetian) of the Aztec Siltstone at Mount Crean, Lashly Mountains, Antarctica. Acanthodians are represented by scales of acritolepid Pechoralepis juozasi sp. nov., climatiid Nostolepis sp. cf. N. gaujensis Valiukevičius, diplacanthid Milesacanthus antarctica Young & Burrow, and an undetermined acanthodiform. The acanthodian assemblage resembles those from early Frasnian carbonates of central Iran. Chondrichthyan elements in the fauna include rare teeth of Aztecodus harmsenae Long & Young and Antarctilamna prisca Young, ctenacanthoid-type scales and branchial denticles which are possibly from Antarctilamna, and scales of an indeterminate chondrichthyan. An isolated set of acanthodid acanthodiform jaws from the uppermost 'phyllolepid' biozone of the Aztec Siltstone at Mount Ritchie, Warren Range, Antarctica is also described. [ABSTRACT FROM AUTHOR]

We report the discovery of large accumulations of micrometeorites on the Myr-old, glacially eroded granitic summits of several isolated nunataks in the Victoria Land Transantarctic Mountains. The number (>3,500) of large (>400 µm and up to 2mm in size) melted and unmelted particles is orders of magnitudes greater than other Antarctic collections. Flux estimates, bedrock exposure ages and the presence of ≈0.8-Myr-old microtektites suggest that extraterrestrial dust collection occurred over the last 1 Myr, taking up to 500 kyr to accumulate based on 2 investigated find sites. The size distribution and frequency by type of cosmic spherules in the >200-sm size fraction collected at Frontier Mountain (investigated in detail in this report) are similar to those of the most representative known micrometeorite populations (e.g.. South Pole Water Well). This and the identification of unusual types in terms of composition (i.e.. chondritic micrometeorites and spherulitic aggregates similar to the ≈480-kyr-old ones recently found in Antarctic ice cores) and size suggest that the Transantarctic Mountain micrometeorites constitute a unique and essentially unbiased collection that greatly extends the micrometeorite inventory and provides material for studies on micrometeorite fluxes over the recent (≈1 Myr) geological past. [ABSTRACT FROM AUTHOR]

The article reports on meteorological controls on sand transport and dune morphology in Victoria Valley, Antarctica. It states that the hyperarid polar desert of the McMurdo Dry Valleys contains an abundance of aeolian sedimentary deposits, providing a setting of evaluating cold climate aeolian processes and dune morphology. It was identified that sand transport in this location was influenced by interparticle cohesion, topographically modified foehn southwesterly winds, and diurnal variations in the speed of thermally driven easterly valley winds because of solar heating by 'night.'

Abstract: Englacial tephra provide chronostratigraphic markers in the Antarctic ice sheets. Structural, mineralogical, geochemical and geochronological data on selected samples allowed the reconstruction of a chronostratigraphic framework for the Frontier Mountain blue-ice field—an important meteorite trap on the southeastern flank of Talos Dome in northern Victoria Land. The stratigraphic thickness of the blue-ice succession is ∼1150m. The 40Ar–39Ar age of one layer close to the stratigraphic bottom of the ice succession is 100±5ka and constrains the maximum age of the bulk of Frontier Mountain blue ice. The 49±11ka age of a second layer at a depth of ∼950m in the stratigraphic succession indicates that >90% of the ice is younger than this value. These ages agree well with the terrestrial ages of meteorites found on the blue ice (up to 140±30ka), suggesting a mechanism of exhumation of meteorites by ablation after englacial transport. Particle size (up to several tens of microns) and the alkaline compositional character of 22 layers allow correlation with source volcanoes within the Cenozoic magmatism associated with the West Antarctic Rift System. The proximal Mount Melbourne, Mount Rittman and The Pleiades (within a radius of ∼250km) are the best candidate source volcanoes. The reconstructed chronostratigraphic framework thus lays the foundations for a detailed investigation of ∼100ka of explosive volcanism in northern Victoria Land. Furthermore, in light of the ongoing ice core drilling project at Talos Dome, the Frontier Mountain ice succession may become important for establishing regional correlations, for sampling and dating key tephra layers, and for selecting ice successions for high-resolution studies of past atmospheric chemistry and fallout. [Copyright &y& Elsevier]

Abstract: Estimates of regolith degradation in the McMurdo Dry Valleys of Antarctica are currently based on indirect evidence and ancient ashes at or near the soil surface that suggest excellent preservation of surfaces. On the other hand, the existing cosmogenic-nuclide surface exposure ages from many parts of the Dry Valleys are younger than the age of surface deposits inferred from stratigraphic relations. This suggests some combination of surface erosion or past ice cover, both of which would reduce the apparent exposure age. This paper quantifies the regolith degradation and/or past ice cover by measuring 10Be and 26Al from a landslide deposit that contains 11.3 Ma volcanic ash. The surface sample yields an apparent exposure age of only 0.4 Ma. However, measurements of the subsurface nuclide concentrations show that the deposit has not been shielded by ice, and that the age of the ash does not conflict with the apparent exposure age when slow degradation of the deposit (2 m Ma−1) is taken into account. Soil creep, which is a common degradational process in a wide variety of environments, is non-existent at this field site, which likely reflects the persistent lack of bio- and cryoturbation. [Copyright &y& Elsevier]

The formation of a pronival (protalus) rampart on sub-Antarctic Marion Island is investigated. Morphological attributes show debris at the angle of repose on the rampart's proximal slope and at a lower angle on the distal slope. Relative-age dating, based on the percentage moss cover and weathering rind thickness of the elastic component, indicates accumulation mainly on the proximal slope and rampart crest, implying upslope (retrogressive) accumulation. This contrasts with a previously published model for pronival ramparts, which proposes rampart growth by addition of material to the distal slope. Development of the Marion Island rampart is suggested to result from the control exerted by a relatively low-angled surface and a shrinking snowbed. A small debris step formed on the proximal slope appears to be a response to decreased snowfalls due to changing climate over the last c. 50 years. Growth rate of the rampart is considered to be variable during the Holocene in response to changes in climate and debris supply. [ABSTRACT FROM AUTHOR]

Abstract: Aerogeophysical data collected in transects between the South Pole and West Antarctica, crossing the Transantarctic Mountains at the 150°W meridian, are used to constrain the sub-ice topography, the sub-ice geology and the inland structure of the Transantarctic Mountains. Forward modeling of gravity data suggests slight crustal thickening of 5 km beneath the mountain front indicating partial isostatic compensation by thickened crust. New magnetic data help characterize the sub-ice geology inland of the Transantarctic Mountains with the observed magnetic anomaly field dominated by Granite Harbour Intrusives, similar to the magnetic field in Victoria Land. However, the typical pattern of anomalies caused by Jurassic tholeiitic magmatism elsewhere along the Transantarctic Mountains is not observed, nor is the mesa topography that is often associated with the Ferrar Dolerite. Together, these observations rule out the widespread presence of Ferrar Dolerite sills within the survey area. A pronounced magnetic lineament, herein named the South Pole Lineament, parallel to the 0°/180° longitudinal meridian, beneath the South Pole defines a previously unknown tectonic trend of the East Antarctic craton. The lineament suggests the presence of a lithospheric-scale structure beneath South Pole, projecting into a fault mapped from ice-penetrating radar data and extending to Shackleton Glacier, the site of a major geological boundary across the Transantarctic Mountains. Potentially, the lineament is the expression of the edge of the undeformed craton, an inherited structure created during assembly or breakup of Rodinia and Gondwana supercontinents; or an intracontinental transform. [Copyright &y& Elsevier]

Abstract: Raised marine beach deposits along the coast of the Ross Embayment are important for relative sea-level reconstructions and for determining the timing of deglaciation following the last glacial maximum (LGM). Flights of beaches from McMurdo Sound to Terra Nova Bay long have been thought to be of Holocene age. However, new data from Cape Ross indicate that pre-Holocene beach material is common and may be predominant at elevations greater than 23 m above mean sea level. This discovery leads to unanswered questions regarding the full spatial extent of pre-Holocene beaches in the Antarctic and other formerly glaciated areas. More important, it indicates that undated raised beaches cannot be assumed to result from isostatic uplift following the LGM and should not be used for relative sea-level reconstructions. [Copyright &y& Elsevier]

Measurement of light intensity transmission was carried out on an ice core S100 from coastal Dronning Maud Land (DML). Ice lenses were observed in digital pictures of the core and recorded as peaks in the light transmittance record. The frequency of ice layer occurrence was compared with climate proxy data (e.g. oxygen isotopes), annual accumulation rate derived from the same ice core, and available meteorological data from coastal stations in DML. The mean annual frequency of melting events remains constant for the last ~150 years. However, fewer melting features are visible at depths corresponding to approximately 1890-1930 AD and the number of ice lenses increases again after 1930 AD. Most years during this period have negative summer temperature anomalies and positive annual accumulation anomalies. The increase in melting frequency around ~1930 AD corresponds to the beginning of a decreasing trend in accumulation and an increasing trend in oxygen isotope record. On annual time scales, a relatively good match exists between ice layer frequencies and mean summer temperatures recorded at nearby meteorological stations (Novolazarevskaya, Sanae, Syowa and Halley) only for some years. There is a poor agreement between melt feature frequencies and oxygen isotope records on longer time scales. Melt layer frequency proved difficult to explain with standard climate data and ice core derived proxies. These results suggest a local character for the melt events and a strong influence of surface topography. [ABSTRACT FROM AUTHOR]

Abstract: For many decades molluscan data have been critical to the establishment of the concept of a global-scale increase in species richness from the poles to the equator. Low polar diversity is key to this latitudinal cline in diversity. Here we investigate richness patterns in the two largest classes of molluscs at both local and regional scales throughout the Southern Ocean. We show that biodiversity is very patchy in the Southern Ocean (at the 1000-km scale) and test the validity of historical biogeographic sub-regions and provinces. We used multivariate analysis of biodiversity patterns at species, genus and family levels to define richness hotspots within the Southern Ocean and transition areas. This process identified the following distinct sub-regions in the Southern Ocean: Antarctic Peninsula, Weddell Sea, East Antarctic—Dronning Maud Land, East Antarctic—Enderby Land, East Antarctic—Wilkes Land, Ross Sea, and the independent Scotia arc and sub Antarctic islands. Patterns of endemism were very different between the bivalves and gastropods. On the basis of distributional ranges and radiation centres of evolutionarily successful families and genera we define three biogeographic provinces in the Southern Ocean: (1) the continental high Antarctic province excluding the Antarctic Peninsula, (2) the Scotia Sea province including the Antarctic Peninsula, and (3) the sub Antarctic province comprising the islands in the vicinity of the Antarctic Circumpolar Current. [Copyright &y& Elsevier]

Abstract: During the last glacial maximum (LGM), lake-ice conveyors transported glacial debris across the surface of large proglacial lakes in the Dry Valleys region of Antarctica. The resulting sediments and landform assemblages are keys to interpreting the glacial history of the Dry Valleys and, potentially, other areas of Antarctica. Paleoconveyor deposits occur in Taylor, Miers, Wright, and Victoria Valleys, as well as in many other parts of the region. Sediments typically consist of stratified to massive sand and/or silt grading upward into poorly sorted gravel, cobbles, and boulders. These sediments make up a variety of landforms, including mounds and moat line, cross-valley, and longitudinal ridges. The classic landform assemblage also displays an associated moraine bank, as well as deltas and shorelines. [Copyright &y& Elsevier]

Abstract: Thirteen discrete air-fall tephra layers were identified in the last 200,000-yr section of the EPICA-Dome C ice record drilled in the East Antarctic plateau (75°06′S, 123°21′E). Quantitative grain size, glass particle morphology, and the grain-discrete major element composition of the glass fraction of these layers were investigated. Through comparison with literature data on the rock composition of Quaternary volcanic centres located within and around Antarctica, five tephra layers were attributed to South Sandwich volcanoes in the South Atlantic Ocean, two to South Shetland volcanoes (northern Antarctic Peninsula), two to Andean volcanoes, and four to Antarctic (Marie Byrd Land and Melbourne) provinces. The abundance of layers originating in the southern part of the Atlantic confirms that westerly atmospheric circulation spiralling towards East Antarctica prevailed over the last 200 ka. Moreover, the record of events from Antarctic centres suggests that atmospheric trajectories from West to East Antarctica can also be significant. A few ash layers are geochemically distinct and appear equivalent to levels from Vostok and Dome Fuji deep ice records, located ca. 600 km and ca. 2000 km, respectively, from Dome C on the Antarctic plateau. These layers provide unambiguous markers for future correlation with other Antarctic ice cores and circumpolar marine climatic records. They also provide reliable constraints to get a common timescale by glaciological modelling, and represent a first step towards absolute ice core dating. [Copyright &y& Elsevier]

A revised stratigraphy of Cenozoic volcanic outcrops in the Brandy Bay area on James Ross Island is obtained by combining palaeomagnetic and stratigraphical anlysis with 40Ar/39Ar dating. The fieldwork was carried out between January and March 2002. Oriented palaeomagnetic samples were obtained from 17 volcanic units, the majority of samples being from lava-fed deltas. Individually the deltas are a few to several hundred metres thick and were formed during voluminous basaltic eruptions within an ice sheet or in a marine setting. Out of the sampled units, 15 carry a stable primary magnetization; six were of normal polarity and nine were reversely magnetized. Our 40Ar/39Ar dating constrains the emplacement of most of the Brandy Bay basalts to the Gilbert chron, with the youngest dated unit having an age of 3.95 Ma and the oldest 6.16 Ma. The mean palaeomagnetic field direction from 14 units has an inclination I = -76° and declination D = 352°, α95 = 7°. The results further suggest that the lava caps on some of the deltas have high remanent intensity and should generate recognizable aeromagnetic anomalies. The combination of palaeomagnetic and isotopic analysis with field mapping methods in a single field area is unique in Antarctica so far and demonstrates that the combination can yield rigorous local stratigraphy in a geographically remote volcanic terrain having discontinuous outcrops. [ABSTRACT FROM AUTHOR]

To date, Cretaceous nautilids from the Antarctic Peninsula have received little attention and only a single species had been reported, Eutrephoceras simile Spath, from Seymour, Snow Hill, and James Ross islands. Currently, it is considered a synonym of Eutrephoceras subplicatum (Steinmann), which has also been described from the Upper Cretaceous of central Chile, southern Argentina and Angola. Here, we report and describe E. subplicatum in detail, based on specimens from the Lower Campanian-Maastrichtian of Vega, Seymour and James Ross islands, presenting, for the first time, embryonic conch features related to the palaeoecology of these organisms. The nauta of this species had a diameter of approximately 30 mm with 5-6 septa. In addition, we describe a new species, Eutrephoceras antarcticum, and one specimen assigned to the same genus in open nomenclature, both recovered from the Lower Campanian beds of James Ross Island. [ABSTRACT FROM AUTHOR]

During fieldwork of the 1998-99 and 1999-2000 Chinese National Antarctic Research Expedition (CHINARE), three different kinds of Cenozoic sedimentary record were found in the Grove Mountains, which are in East Antarctica about 450km inland of Prydz Bay. These consist of (1) glaciogenic sedimentary erratics found in the moraine banks in the central area of Grove Mountains, which can be subdivided into four types according to different degrees of lithification as well as differences in inner structure and include in-situ diamicts; (2) palaeosols found in several small depressions in the southern slope of the Mount Harding; and (3) different kinds of glacial moraine floating on the surface of blue ice or around the foot of some nunataks. Preliminary results suggest that the in situ glaciogenic sediments were formed in the ice-sheet frontal area by the interaction of glacial movement and ice sheet melt water under climatic conditions warmer than today. [ABSTRACT FROM AUTHOR]

Fabric analysis is commonly used to infer former movement directions of diamictons; however, analysis techniques are typically time consuming and partly subjective. Stereological analysis provides an alternative for objective determination of the preferred orientation of particles. The ability of manual and automated stereological procedures to determine the preferred orientation of particles (120–4000 µm) in tillite is assessed, using core samples from Mount Feather, McMurdo Dry Valleys, Antarctica. Orthogonal sets of vertical thin sections were subjected to directed secant analysis involving the determination of the number of intersections between particle outlines and a rotating series of parallel lines. The manual analysis reveals a weakly developed three-dimensional tilt angle (plunge) of 68°. This reflects the depth-averaged subglacial deformational structure of the deposit. Because the preferred orientation signal is weak, in the automated set-up this signal is obscured by the effect of digitization, hampering the reliable assessment of the orientation direction. The study shows microfabric variability within the studied cored section that is interpreted as a shear fabric. Reliable macrostructural information that might constrain ice flow directions requires a larger number of randomly or systematically drawn core samples from which averaged microstructural fabrics can be derived. [ABSTRACT FROM AUTHOR]

Abstract: Ice-sheet basal erosion is controlled by ice dynamics (including the basal thermal regime) and the lithology of the substrate. Spatial variation in subglacial roughness is therefore likely to be a function of these controls. In Antarctica, very little is known about former ice dynamics and sub-ice geology. Here, we calculate the spectral roughness of subglacial East Antarctica from an analysis of radio-echo sounding data. As the modern glaciological setting is understood reasonably well in East Antarctica from numerical ice-sheet modelling, we are able to compare the roughness calculations with contemporary ice-sheet dynamics. We show that ice divides at Ridge B and Dome A are underlain by rough terrain and a cold thermal regime. At the Dome C ice divide, however, the bed is noticeably smooth at the shorter wavelengths (∼5–10 km) but rougher at longer wavelengths. One interpretation is that subglacial morphology has been eroded, leaving a smoothed landscape that contains valleys and hills. Regardless of the origin of the valleys, their erosion is only possible if the ice sheet were more dynamic than at present. Hence, whereas Dome A and Ridge B have a bed morphology consistent with the present ice sheet, the morphology at Dome C is likely to predate the present ice-sheet configuration. [Copyright &y& Elsevier]

Abstract: Multichannel and high-resolution seismic profiles complemented with swath bathymetry show a variety of contourite deposits in the northern Weddell Sea resulting from the interaction between bottom currents and the seafloor physiography. Seven types of contourite drifts are identified based on the seismic signature, reflector configuration and geometry of the depositional bodies. Giant elongated–mounded drifts are widespread in the area and associated with major channelized contour currents that flow at the base of large ridges. Thick basement/tectonic drifts result from the seafloor disruptions of the currents caused by the irregularities of the near-surface basement morphology. Sheeted drifts occur under the main core of the Weddell Gyre and also in areas of the abyssal plain away from the main flows. Various types of drifts in-fill depressions or are plastered against steep bathymetric ridges that intersect contour currents. The regional distribution of the drifts is mainly controlled by the physiography of the basin and the confined or unconfined nature of the bottom-current flows. The northern Weddell Sea is a region dominated by contourite processes and thus provides an area to compare contourite drifts with turbidite systems. The giant elongated–mounded drifts have a net asymmetry of the body, in contrast to turbidite channel–levee complexes that develop levees on each side of an axial turbidite channel. The basement/tectonic drifts prograde parallel to the main flow and are plastered following the irregularities of the basement unlike turbidite deposits. Other drifts, in contrast, show internal reflector characteristics similar to turbidite systems, such as the sheeted drifts. In these cases, however, the associations of turbidite and drift deposits are different. The giant elongate-mounded drifts are stacked along the margins and elongate or transverse drift sequences are observed in the basin centre of confined basins. In the unconfined setting, the drifts are normally asymmetric in relation to the marginal channel moats and sheeted drifts develop laterally from the ridges. In turbidite systems of confined or unconfined settings, generally symmetrical proximal channel–levee complexes evolve downstream to sheetlike basin plain sequences. Five main seismic units separated by regional unconformities are recognized above the oceanic basement. The age of the deposits is based on the magnetic anomalies of the oceanic crust and the overlying seismic sequences. The external geometry and acoustic character of the seismic units indicate strong bottom-current processes, except for the basal deposits attributed to the Early Miocene. The development of extensive drifts in the deposits of Unit 4 (∼Middle Miocene) shows the initial influence of the Weddell Sea Bottom Water (WSBW). The opening of the connection of Jane Basin with the Scotia Sea also is marked by a regional unconformity that records a reorganization of bottom flows. The two uppermost Units 1 and 2 (Late Miocene to Recent) indicate intensified bottom currents, which may reflect the increased production of WSBW. The evolution through time of the contourite deposits and the distribution of regional unconformities reflect the ice sheet dynamics that controlled the production of Antarctic Bottom Water (AABW). [Copyright &y& Elsevier]

A network of sinuous valleys with typical dendritic pattern characterizes northern Victoria Land (NVL) in Antarctica. Subparallel to parallel and angular to rectangular patterns are also present. Quantitative geomorphic analysis of the valley network has been carried out utilizing GIS spatial analysis. While drainage densities and drainage frequencies show low values, segments of the NVL valley network are substantially well organized, as indicated by bifurcation ratio (Rb) and direct bifurcation ratio (Rbd) parameters. All basins faithfully adhere to Horton's laws of drainage network composition. Quantitative geomorphic analysis suggests that the valley system can be ascribed to fluvial origin and that consequently, a morphoclimatic system completely different from that of present day must have driven its carving. The resulting data provide indications about the origin of the valley network and this invaluable information can be used for the reconstruction of earlier phases of glacial history and climatic and tectonic evolution of this significant Antarctic region. Fluvial erosion enhanced the denudation of the Transantarctic Mountains from at least 55 Ma to at least the Focene-Oligocene boundary (ca 34 Ma). Fluvial basins adapted to the tectonic structure, following the main regional fault systems. A well-developed alpine topography postdates the fluvial morphology. Temperate glaciers were responsible for denudation until the Late Miocene. Parasitic glaciers presently mantle the previously sculpted topography. Present-day glacial erosion is negligible and denudation has been exceedingly slow since 7.5 Ma. [ABSTRACT FROM AUTHOR]

Male southern elephant seals (Mirounga leonina) are the largest of the pinnipeds and their foraging migrations take them from their breeding sites to Antarctica where some remain to moult. During February and March 2000, we stomach lavaged 23 male elephant seals that had migrated to a moult location in the Windmill Islands (66°30′S, 110°30′E) on the Antarctic coast. In the 8 stomachs that contained prey remains, we found beaks from 2 squid species (Alluroteuthis antarcticus, n=2, and Psychroteuthis glacialis, n=9), remains of 1 unidentified benthic fish species, 16 specimens of Euphausia crystallorophias and 1 mysid species. This is in contrast to the maximum of 17 squid and 4 fish taxa identified from stomachs sampled at Heard and Macquarie Islands, and the 7 squid taxa identified from seals at King George Island in the South Shetland Islands. Elephant seals appear to be a seasonally important component of the Antarctic marine ecosystem. "Antarctic" squid species, such as P. glacialis, may constitute the most important cephalopod prey for southern elephant seals that forage at high latitudes of the Southern Ocean. If the commercial potential for P. glacialis is realised, there is also potential for competition between the fishery and the seals. [ABSTRACT FROM AUTHOR]