Glacial Erratics Research Articles

BRITICE Glacial Map, version 2: a map and GIS database of glacial landforms of the last British–Irish Ice Sheet

During the last glaciation, most of the British Isles and the surrounding continental shelf were covered by the British–Irish Ice Sheet (BIIS). An earlier compilation from the existing literature (BRITICE version 1) assembled the relevant glacial geomorphological evidence into a freely available GIS geodatabase and map (Clark et al. 2004: Boreas 33, 359). New high‐resolution digital elevation models, of the land and seabed, have become available casting the glacial landform record of the British Isles in a new light and highlighting the shortcomings of the V.1 BRITICE compilation. Here we present a wholesale revision of the evidence, onshore and offshore, to produce BRITICE version 2, which now also includes Ireland. All published geomorphological evidence pertinent to the behaviour of the ice sheet is included, up to the census date of December 2015. The revised GIS database contains over 170 000 geospatially referenced and attributed elements – an eightfold increase in information from the previous version. The compiled data include: drumlins, ribbed moraine, crag‐and‐tails, mega‐scale glacial lineations, glacially streamlined bedrock (grooves, roches moutonnées, whalebacks), glacial erratics, eskers, meltwater channels (subglacial, lateral, proglacial and tunnel valleys), moraines, trimlines, cirques, trough‐mouth fans and evidence defining ice‐dammed lakes. The increased volume of features necessitates different map/database products with varying levels of data generalization, namely: (i) an unfiltered GIS database containing all mapping; (ii) a filtered GIS database, resolving data conflicts and with edits to improve geo‐locational accuracy (available as GIS data and PDF maps); and (iii) a cartographically generalized map to provide an overview of the distribution and types of features at the ice‐sheet scale that can be printed at A0 paper size at a 1:1 250 000 scale. All GIS data, the maps (as PDFs) and a bibliography of all published sources are available for download from: https://www.sheffield.ac.uk/geography/staff/clark_chris/britice.

Trilobites from the Rickard Hill facies of the Saugerties Member of the Schoharie Formation, eastern New York (upper Emsian and Lower Devonian): a case study in taphonomy and sequence stratigraphy from glacial erratics

Glacial erratics belonging to the Rickard Hill facies (RHF) of the Saugerties Member of the Schoharie Formation (upper Emsian: Lower Devonian) occur scattered throughout the Piedmont of northern New Jersey and Lower Hudson Valley of New York. These RHF glacial erratics contain an assemblage of trilobites belonging to: Anchiopella anchiops, Burtonops cristatus, Calymene platys, Terataspis grandis, cf. Trypaulites sp. and cf. Coniproetus sp. This RHF glacial erratic trilobite assemblage consists predominately of disarticulated cephala and pygidia that were originally preserved as part of a localized, third-order eustatic sea level lag deposit in the Helderberg Mountains region of central New York State and subsequently transported in glacially plucked blocks by the Hudson-Champlain Lobe of the Laurentide Ice Sheet southward into New Jersey. Physical and chemical weathering during glacial erosion, transportation and deposition of the RHF glacial erratics has revealed some anatomical features of these trilobites in high detail along with other invertebrates. This unique sequence of weathering reveals additional characteristics that bear upon issues of bathymetric controls on upper Schoharie Formation lithology, trilobite faunal abundance and taphonomy during the upper Emsian (Lower Devonian) of eastern New York State.

Graptolites from glacial erratics of the Laerheide area, northern Germany

Ordovician and Silurian glacial erratics of the Laerheide area (Lower Saxony, north-western Germany) bear well-preserved graptolites. The faunas provide important information on the origin and transport direction of the sediments preserved in a kame, representing the Drenthe stadial of the Saalian glaciation. The faunas even include species not commonly encountered in the successions of mainland Sweden, from where the erratics presumably originated. The most common graptolites are from Upper Ordovician (Sandbian to Katian) limestones and from Katian black shales. More common, however, are greenish limestones, sand- and siltstones, often combined in the term ‘Grünlich-Graues Graptolithengestein’, in which upper Wenlock to Ludlow (upper Silurian) graptolites are common.

Cosmogenic nuclide age estimate for Laurentide Ice Sheet recession from the terminal moraine, New Jersey, USA, and constraints on latest Pleistocene ice sheet history

AbstractThe time at which the Laurentide Ice Sheet reached its maximum extent and subsequently retreated from its terminal moraine in New Jersey has been constrained by bracketing radiocarbon ages on preglacial and postglacial sediments. Here, we present measurements of in situ produced10Be and26Al in 16 quartz-bearing samples collected from bedrock outcrops and glacial erratics just north of the terminal moraine in north-central New Jersey; as such, our ages represent a minimum limit on the timing of ice recession from the moraine. The data set includes field and laboratory replicates, as well as replication of the entire data set five years after initial measurement. We find that recession of the Laurentide Ice Sheet from the terminal moraine in New Jersey began before 25.2±2.1 ka (10Be, n=16, average, 1 standard deviation). This cosmogenic nuclide exposure age is consistent with existing limiting radiocarbon ages in the study area and cosmogenic nuclide exposure ages from the terminal moraine on Martha’s Vineyard ~300 km to the northeast. The age we propose for Laurentide Ice Sheet retreat from the New Jersey terminal position is broadly consistent with regional and global climate records of the last glacial maximum termination and records of fluvial incision.

Ballasting the Hanse: Baltoscandian Erratic Cobbles in the Later Medieval Port Landscape of Bruges

The discovery of a remarkable group of vividly coloured rounded cobbles in the fields and monuments of the later medieval outports of Bruges has initiated a multi-disciplinary investigation into their function, provenance, and wider economic meaning. Geological analyses demonstrate that the stones are ballast of exotic lithological nature. A substantial number consist of glacial erratics collected from cobble beaches in the Baltoscandian area. Another group can be traced to north-eastern British coasts. The clustering of stones at Hoeke has drawn particular attention to the Hanseatic connection with Bruges and to the small harbour town of Hoeke, which hosted the staple of stockfish and various other Hanseatic activities. This article contributes to the discussion of ballast stones as a meaningful archaeological object category, especially when studied in a broader methodological context including archaeological, geological, and historical research.

Extreme protomeric development in a burlingiid trilobite from Cambrian glacial erratics of Denmark

AbstractPengia Geyer & Corbacho is a Cambrian burlingiid trilobite with fused trunk segments devoid of any articulation in the anamorphic and epimorphic phases of development. The type species is Pengia fusilis (Peng et al.) from the Wanshania wanshanensis Zone of China. Here we describe a second species, Pengia palsgaardia sp. nov., from the Lejopyge laevigata Zone of the Paradoxides forchhammeri Superzone. It comes from a glacial erratic in Denmark which probably originated in the Alum Shale Formation of Västergötland, Sweden. Pengia palsgaardia is a large burlingiid (~10 mm in length), with 14 fused segments in the trunk whose boundaries are marked by ridges. The axis is narrow, with the axial furrows faintly indicated or effaced across the median. Laterally along the axis and the tapering glabella, symmetrical globular lobes are developed that are pinched at their base. During ontogeny the glabellar furrows are pit‐like adaxially but shallow towards the axial furrow as the globular lobes develop. Their pit‐like appearance in Pengia palsgaardia and some other burlingiid species is not considered similar to the condition seen in oryctocephalid trilobites. A median preglabellar ridge resembling that of Schmalenseeia Moberg develops late in ontogeny but in early ontogeny the preglabellar field resembles that of Burlingia Walcott, Alumenella Geyer & Corbacho and Niordilobites Geyer & Corbacho. This gives Pengia a more basal position in the schmalenseeid lineage, outside the derived Schmalenseeia. In mature specimens the facial sutures in P. palsgaardia are fused, but an ocular suture may have been present. During ontogeny Pengia would have gone through the anamorphic and protomeric protaspid segmental conditions, but articulation between either the cephalon and pygidium, or pygidium and thoracic segments of the trunk never developed so it did not progress beyond the protaspid phase. This extreme protomeric development is considered to be a derived feature in Pengia.

Trace fossils from the Baltoscandian erratic boulders in SW Poland

Many well preserved trace fossils were found in erratic boulders and the fossils preserved in them, occurring in the Pleistocene glacial deposits of the Fore-Sudetic Block (Mokrzeszow Quarry, Świebodzice outcrop). They include burrows ( Arachnostega gastrochaenae , Balanoglossites isp., ? Balanoglossites isp., ? Chondrites isp., Diplocraterion isp., Phycodes isp., Planolites isp., ? Rosselia isp., Skolithos linearis , Thalassinoides isp., root traces) and borings ? Gastrochaenolites isp., Maeandropolydora isp., Oichnus isp., Osprioneides kampto , ? Palaeosabella isp., Talpina isp., Teredolites isp., Trypanites weisei , Trypanites isp., ? Trypanites isp., and an unidentified polychaete boring in corals. The boulders, Cambrian to Neogene (Miocene) in age, mainly came from Scandinavia and the Baltic region. The majority of the trace fossils come from the Ordovician Orthoceratite Limestone, which is exposed mainly in southern and central Sweden, western Russia and Estonia, and also in Norway (Oslo Region). The most interesting discovery in these deposits is the occurrence of Arachnostega gastrochaenae in the Ordovician trilobites (? Megistaspis sp. and Asaphus sp.), cephalopods and hyolithids. This is the first report of Arachnostega on a trilobite (? Megistaspis ) from Sweden. So far, this ichnotaxon was described on trilobites from Baltoscandia only from the St. Petersburg region (Russia). Arachnostega on a trilobite ( Asaphus ), a cephalopod and hyolithids is from Russia or Estonia. Another interesting ichnotaxon is Balanoglossites , which also was encountered in the erratic boulders from the Ordovician Orthoceratite Limestone of Sweden. So far, this ichnotaxon was known only from Russia (St. Petersburg region). Some rare borings (e.g., Osprioneides kampto , ? Palaeosabella isp.) also were found in glacial erratics of Silurian stromatoporoids, excellent outcrops of which are located in Gotland (Sweden) and Saaremaa (Estonia). In addition, stromatoporoid/coral, coral/coral and some new fossil associations are reported. The material studied probably was transported from the N, the NE, and less commonly from the NW.

On the type species of Lingularia, and description of Eolingularia n. gen.

The material under study has previously been identified as Lingula krausei, collected from glacial erratics at Cape Rozewie, Poland. All specimens come from glauconitic sandstone of Cenomanian age. Dames (1874) identified his Lingula sp. as L. krausei which differs in shell outline from Lingula truncata. This species, dedicated to A. Krause, together with L. subovalis, is considered characteristic of the Cenomanian. Several new species and genera have recently been described or redescribed and compared to our specimens, here identified as Lingularia similis. By priority (ICZN, 1999), the type species L. similis is currently synonymized with Lingula krausei. A new genus Eolingularia, within the Family Lingulidae, is here described, with Lingularia siberica Biernat et Emig, 1993, as type species. This new genus ranges from the Carboniferous to the Triassic in Russia, China, and Spain. Possible synonymies are discussed.

Using photogrammetry to interpret human action on Neolithic monument boulders in Ireland's Cavan Burren

Digital technology has been increasingly employed in the documentation and analysis of archaeology in the last ten years. We utilized user-friendly digital photogrammetry and animation to assist in the analysis of archaeological evidence in Ireland. Our tools were commercially available software, a consumer-grade hand-held or tripod-supported digital camera, and a personal computer. The method was developed for and has been subsequently used by local archaeological surveyors in an extensive documentation of prehistoric settlement features within the Marble Arch Caves Global Geopark in Ireland. The boulder monuments are unusual in that they are made from glacial erratics whose surfaces display traditional North Atlantic rock art and a new sculpting art form. Pieces making up two boulder monuments were digitally manipulated via animation into what is believed to be their original source stone configurations. Their matching surfaces were studied in detail. The process was employed to demonstrate, non-invasively, how the monuments might have resulted from some actions other than weathering. The analysis supports the hypothesis that humans worked the monuments, which, in turn, supports protection of the monuments for further study.

Plesiosaurian fossils from Baltic glacial erratics: evidence of Early Jurassic marine amniotes from the southwestern margin of Fennoscandia

Abstract Early Jurassic plesiosaurian fossils are rare in the Scandinavian region, with a few isolated bones and teeth known from Bornholm, and anecdotal finds from East Greenland. The only other identifiable specimens derive from Toarcian-aged (based on ammonites) erratics deposited during Late Pleistocene glacial advances near the town of Ahrensburg, NE of Hamburg in northern Germany. The geographical source of these transported clasts is debated, but reconstructed ice-flow directions and lithofacies comparisons implicate either the offshore Baltic Sea between the Island of Bornholm and Mecklenburg–Vorpommern (Germany) or, less probably, south of the Danish Archipelago (Mecklenburg Bay). These regions collectively bordered the Fennoscandian landmass and adjacent Ringkøbing-Fyn Island in the late Early Jurassic, and were dominated by near-shore marine deltaic to basinal settings. The Ahrensburg plesiosaurian remains include postcranial elements reminiscent of both the microcleidid Seeleyosaurus and the rhomaelosaurid Meyerasaurus . These occur alongside other classic ‘Germanic province’ marine amniotes, such as the teleosaurid crocodyliform Steneosaurus and ichthyosaurian Stenopterygius cf. quadriscissus : thus, advocating faunal continuity between Scandinavia and southern Germany during the Toarcian, and a less pronounced marine reptile faunal provinciality than previously assumed.

Vernacular architecture and traditional rural landscape in new socio-economic realities - a case study from Central Poland

Abstract The article presents the results of the research survey of the old rural constructions in the Koło Basin (Central Poland) and its closest vicinity, conducted by the authors in the period 2011-2013. From the beginning of the 19th century until the late 1960s, the population of that region tended to use for construction limestone, instead of wood which for centuries was the most common building material on Polish lowlands. Using the local deposits of limestone, excavated near Rożaniatow village, various structures were built, with the parts of the building most endangered by degradation made of ceramic bricks (for corners and window/door frames) or glacial erratics (for wall base), thereby forming structures with specific architectural and aesthetic features, unique to that region. The survey was conducted in 165 villages of the region, cataloguing more than 2,000 such structures - residential buildings, farm facilities, industrial buildings. Many of these buildings display a similar elevation style of same-coloured stones, making them one of the most specific elements of the landscape. The analysed area, just like the majority of rural Poland, is currently undergoing socio-economic changes which started in the 1990s and intensified after Poland joined the European Union. Changes in production profiles and farm sizes, migration of rural population to cities or countries of Western and Northern Europe, and progress of suburbanization are some of the main factors which trigger significant changes in the settlement network of the country. This is the right moment to assess whether the traditional solutions applied in the rural construction of the Koło Basin are worth modern application or whether they are only an element of cultural heritage valuable just from the historical perspective.

Notes on the distribution of lichen biota of Podlasie. III. Nowosady village, Podlaskie province (north-eastern Poland)

<p>The present study was undertaken to evaluate the biodiversity of lichen species in Nowosady village and surrounding areas. This work was conducted in 2014 (in August) and biodiversity of lichen species growing on tree bark and bushes, on dead wood (anthropogenic origin), glacial erratics, concrete, mortared walls and other specific substrates like eternit roof slates has been assessed. The lichen species represented morphologically diverse forms: crustose (38%), foliose (38%), fruticose (13%), dimorphous (5%), placodial (3%) and squamulose (3%). They belonged to different ecological types including epiphytes (27 species), epixyles (18) and epilithes (12). Out of 39 species identified in Nowosady village, five are included in the Polish red list of lichens: <em>Bryoria fuscescens</em>, <em>Evernia prunastri</em>, <em>Hypogymnia tubulosa</em>, <em>Ramalina farinacea</em> and <em>Ramalina fraxinea</em>. Four taxons from the study area are under statutory protection of species. One species, <em>Ramalina fraxinea</em> is under full protection and 3 species (<em>Bryoria fuscescens</em>, <em>Evernia prunastri</em> and <em>Hypogymnia tubulosa</em>) are under partial protection.</p>

Characteristics of Macrozoobenthos Lakes of the Barlinek-Gorzów Landscape Park (North-West Poland) on the Basis of the European Union Water Framework Directive

Contamination of lake waters is one of the factors affecting the qualitative and quantitative development of benthic organisms. Aside from contamination, the abundance of macrozoobenthos is determined by other conditions, i.e. predation pressure, phytoplankton biomass, detritus biomass, as well as the accessibility and quality of water reservoir bottom.The Barlinek-Gorzów Landscape Park was established in October 1991. The Barlinek-Gorzów Landscape Park includes more than 55 000 ha of forests, lakes, fields, meadows, and is characterized by a great diversity of habitats and abundant life forms [46].To protect the most valuable plant communities and animal habitats, five nature reserves were created within the boundaries of the Park:“Skalisty Jar Libberta” includes Libbert’s Gorge, and the surrounding moraine hills and glacial erratics. It is the only site featuring lime stones and boulders in Western Pomerania and is surrounded by oak and beech forests [46].“Dębina” forest conservation complex known as the Central European wet-ground forest, featuring stately oaks and beeches with some lime, hornbeam and old pine trees. In its clean environment, as many as 50 species of arboreal lichen have been preserved [46]. “Markowe Błota” – marshland, with its typical vegetation such as the Sphagnopsida, wild rosemary, ordinary cranberry, cottongrass. The site is visited quite often by white-tailed eagles [46].The water reserve of the “River Przyłężek”. It includes a section of the River, the slopes of the riverbank and the surrounding beech stand with some tree specimens that are more than 100 years old. Seen as the watercourse resembles mountain streams, with its pure and cold water, it provides appropriate conditions for Salmonidae to live and spawn [46].The forest reserve “Wilanów” aims to protects the natural mixed forest with vintage beech, oak and pine trees. Thanks to the varied topography, diverse rare types of forests have been preserved here [46].The objective of the research conducted in the course of 2008 – 2012 was to determine the qualitative and quantitative structure of macrozoobenthos in the lakes of the Barlinek-Gorzów Landscape Park in the summer season.The research enabled estimating how far the eutrophication processes have advanced in selected lakes of the Barlinek-Gorzów Landscape Park.Qualitative and quantitative analyses of the macrozoobenthos structure in the lakes Barlinek-Gorzów Landscape Park were conducted in the summer seasons of 2008, 2010 and 2012.By comparing the average density of benthic fauna of the lakes Barlinek-Gorzów Landscape Park with the lakes Western and Northern Polish you can see big changes in the density of taxa studied.In comparison with other lakes Western and Northern Polish in the lakes Barlinek-Gorzów Landscape Park is a large number of taxa, however, as a result of the distribution of non-harmonic doesn't translate to the indicator value of biodiversity index PIE.On the basis of the analysis of research in the Western and Northern Polish Lakes summer macrozoobenthos it can be concluded that in the lakes Barlinek-Gorzów Landscape Park very intensively develop Oligochaeta. While the larvae of Chironomidae subdominants status in the period under review amounting to water, developed in other lakes much more intensely, acting mostly the main ingredient of benthic fauna.

Characteristics of Macrozoobenthos Lakes of the Barlinek-Gorzów Landscape Park (North-West Poland) on the Basis of the European Union Water Framework Directive

Contamination of lake waters is one of the factors affecting the qualitative and quantitative development of benthic organisms. Aside from contamination, the abundance of macrozoobenthos is determined by other conditions, i.e. predation pressure, phytoplankton biomass, detritus biomass, as well as the accessibility and quality of water reservoir bottom.The Barlinek-Gorzów Landscape Park was established in October 1991. The Barlinek-Gorzów Landscape Park includes more than 55 000 ha of forests, lakes, fields, meadows, and is characterized by a great diversity of habitats and abundant life forms [46].To protect the most valuable plant communities and animal habitats, five nature reserves were created within the boundaries of the Park:“Skalisty Jar Libberta” includes Libbert’s Gorge, and the surrounding moraine hills and glacial erratics. It is the only site featuring lime stones and boulders in Western Pomerania and is surrounded by oak and beech forests [46].“Dębina” forest conservation complex known as the Central European wet-ground forest, featuring stately oaks and beeches with some lime, hornbeam and old pine trees. In its clean environment, as many as 50 species of arboreal lichen have been preserved [46]. “Markowe Błota” – marshland, with its typical vegetation such as the Sphagnopsida, wild rosemary, ordinary cranberry, cottongrass. The site is visited quite often by white-tailed eagles [46].The water reserve of the “River Przyłężek”. It includes a section of the River, the slopes of the riverbank and the surrounding beech stand with some tree specimens that are more than 100 years old. Seen as the watercourse resembles mountain streams, with its pure and cold water, it provides appropriate conditions for Salmonidae to live and spawn [46].The forest reserve “Wilanów” aims to protects the natural mixed forest with vintage beech, oak and pine trees. Thanks to the varied topography, diverse rare types of forests have been preserved here [46].The objective of the research conducted in the course of 2008 – 2012 was to determine the qualitative and quantitative structure of macrozoobenthos in the lakes of the Barlinek-Gorzów Landscape Park in the summer season.The research enabled estimating how far the eutrophication processes have advanced in selected lakes of the Barlinek-Gorzów Landscape Park.Qualitative and quantitative analyses of the macrozoobenthos structure in the lakes Barlinek-Gorzów Landscape Park were conducted in the summer seasons of 2008, 2010 and 2012.By comparing the average density of benthic fauna of the lakes Barlinek-Gorzów Landscape Park with the lakes Western and Northern Polish you can see big changes in the density of taxa studied.In comparison with other lakes Western and Northern Polish in the lakes Barlinek-Gorzów Landscape Park is a large number of taxa, however, as a result of the distribution of non-harmonic doesn't translate to the indicator value of biodiversity index PIE.On the basis of the analysis of research in the Western and Northern Polish Lakes summer macrozoobenthos it can be concluded that in the lakes Barlinek-Gorzów Landscape Park very intensively develop Oligochaeta. While the larvae of Chironomidae subdominants status in the period under review amounting to water, developed in other lakes much more intensely, acting mostly the main ingredient of benthic fauna.

Corrigendum: A low-relief hill in eastern Ontario, Canada, covered by the easily erodible Queenston Formation and derived sediments — probably the result of Quaternary tectonic uplift

The Upper Ordovician Queenston Formation is predominantly a brick red, easily erodible, fine-grained clastic sedimentary rock that is not expected to form topographic highs. Nevertheless, the Queenston, overlain by a relatively thin cover of red unconsolidated sediments derived from it, blankets two low-relief hills. Their combined presence at the top of those hills is curious; therefore, Cholowski Hill, the larger of the two, and its surroundings were studied to try to resolve that apparent contradiction. Cholowski Hill is elongated nearly north–south and overlies a similarly shaped, north–south magnetic anomaly, which is a spur off a generally north-northeast-trending magnetic high. The spatial and geometric relationships of the hill to the magnetic anomaly, a feature of the Precambrian basement, suggest that the hill resulted from repeated tectonic uplift along faults that propagated upward from the basement, though many of them show no surface expression. Two notable exceptions are the North Russell and East Ridge faults that are topographically expressed at the surface and extend along the spine of Cholowski Hill. Their presence and that of Cholowski Hill imply geologically recent uplift. Glacial erratics on, and the smooth character of, the hill imply that it had been overridden by continental ice and was an upland prior to at least the last major glacial advance. Champlain Sea sediments surrounding and encroaching on the lowest part of the hill, but absent from the higher elevations, intimate that Cholowski Hill was not completely covered by those sediments, though it is conceivable that deposited sediments were washed away. The precise age of uplift is unknown, but the characteristics of the hill suggest a Quaternary event.

A low-relief hill in eastern Ontario, Canada, covered by the easily erodible Queenston Formation and derived sediments — probably the result of Quaternary tectonic uplift

The Upper Ordovician Queenston Formation is predominantly a brick red, easily erodible, fine-grained clastic sedimentary rock that is not expected to form topographic highs. Nevertheless, the Queenston, overlain by a relatively thin cover of red unconsolidated sediments derived from it, blankets two low-relief hills. Their combined presence at the top of those hills is curious; therefore, Cholowski Hill, the larger of the two, and its surroundings were studied to try to resolve that apparent contradiction. Cholowski Hill is elongated nearly north–south and overlies a similarly shaped, north–south magnetic anomaly, which is a spur off a generally north-northeast-trending magnetic high. The spatial and geometric relationships of the hill to the magnetic anomaly, a feature of the Precambrian basement, suggest that the hill resulted from repeated tectonic uplift along faults that propagated upward from the basement, though many of them show no surface expression. Two notable exceptions are the North Russell and East Ridge faults that are topographically expressed at the surface and extend along the spine of Cholowski Hill. Their presence and that of Cholowski Hill imply geologically recent uplift. Glacial erratics on, and the smooth character of, the hill imply that it had been overridden by continental ice and was an upland prior to at least the last major glacial advance. Champlain Sea sediments surrounding and encroaching on the lowest part of the hill, but absent from the higher elevations, intimate that Cholowski Hill was not completely covered by those sediments, though it is conceivable that deposited sediments were washed away. The precise age of uplift is unknown, but the characteristics of the hill suggest a Quaternary event.

Ross Sea paleo-ice sheet drainage and deglacial history during and since the LGM

Onshore and offshore studies show that an expanded, grounded ice sheet occupied the Ross Sea Embayment during the Last Glacial Maximum (LGM). Results from studies of till provenance and the orientation of geomorphic features on the continental shelf show that more than half of the grounded ice sheet consisted of East Antarctic ice flowing through Transantarctic Mountain (TAM) outlet glaciers; the remainder came from West Antarctica. Terrestrial data indicate little or no thickening in the upper catchment regions in both West and East Antarctica during the LGM. In contrast, evidence from the mouths of the southern and central TAM outlet glaciers indicate surface elevations between 1000 m and 1100 m (above present-day sea level). Farther north along the western margin of the Ross Ice Sheet, surface elevations reached 720 m on Ross Island, and 400 m at Terra Nova Bay. Evidence from Marie Byrd Land at the eastern margin of the ice sheet indicates that the elevation near the present-day grounding line was more than 800 m asl, while at Siple Dome in the central Ross Embayment, the surface elevation was about 950 m asl. Farther north, evidence that the ice sheet was grounded on the middle and the outer continental shelf during the LGM implies that surface elevations had to be at least 100 m above the LGM sea level. The apparent low surface profile and implied low basal shear stress in the central and eastern embayment suggests that although the ice streams may have slowed during the LGM, they remained active.Ice-sheet retreat from the western Ross Embayment during the Holocene is constrained by marine and terrestrial data. Ages from marine sediments suggest that the grounding line had retreated from its LGM outer shelf location only a few tens of kilometer to a location south of Coulman Island by ∼13 ka BP. The ice sheet margin was located in the vicinity of the Drygalski Ice Tongue by ∼11 ka BP, just north of Ross Island by ∼7.8 ka BP, and near Hatherton Glacier by ∼6.8 ka BP. Farther south, 10Be exposure ages from glacial erratics on nunataks near the mouths of Reedy, Scott and Beardmore Glaciers indicate thinning during the mid to late Holocene, but the grounding line did not reach its present position until 2 to 3 ka BP. Marine dates, which are almost exclusively Acid Insoluble Organic (AIO) dates, are consistently older than those derived from terrestrial data. However, even these ages indicate that the ice sheet experienced significant retreat after ∼13 ka BP. Geomorphic features indicate that during the final stages of ice sheet retreat ice flowing through the TAM remained grounded on the shallow western margin of Ross Sea.The timing of retreat from the central Ross Sea remains unresolved; the simplest reconstruction is to assume that the grounding line here started to retreat from the continental shelf more or less in step with the retreat from the western and eastern sectors. An alternative hypothesis, which relies on the validity of radiocarbon ages from marine sediments, is that grounded ice had retreated from the outer continental shelf prior to the LGM. More reliable ages from marine sediments in the central Ross Embayment are needed to test and validate this hypothesis.

Aptian and Albian (Early Cretaceous) ammonites from glacial erratics of the Hamburg area, North Germany

Aptian and Albian (Early Cretaceous) ammonites from glacial erratics of the Hamburg area, North Germany

Controls on interior West Antarctic Ice Sheet Elevations: inferences from geologic constraints and ice sheet modeling

Knowledge of the West Antarctic Ice Sheet (WAIS) response to past sea level and climate forcing is necessary to predict its response to warmer temperatures in the future. The timing and extent of past interior WAIS elevation changes provides insight to WAIS behavior and constraints for ice sheet models. Constraints prior to the Last Glacial Maximum (LGM) however, are rare. Surface exposure ages of glacial erratics near the WAIS divide at Mt. Waesche in Marie Byrd Land, and at the Ohio Range in the Transantarctic Mountains, range from ∼10 ka to >500 ka without a dependence on elevation. The probability distribution functions (PDF) of the exposure ages at both locations, are remarkably similar. During the last glaciation, maximum interior ice elevations as recorded by moraines and erratics were reached between 10 ka and 12 ka. However, most exposure ages are older than the LGM and cluster around ∼40 ka and ∼80 ka. The peak in the exposure age distributions at ∼40 ka includes ages of alpine moraine boulders at Mercer Ridge in the Ohio Range. Comparison of the PDF of exposures ages from the Ohio Range and Mt. Waesche with the temperature record from the Fuji Dome ice core indicates that the youngest peak in the exposure age distributions corresponds to the abrupt warming during the Last Glacial termination. A prominent peak in the Ohio Range PDF corresponds to the penultimate termination (stage 5e). During the intervening glacial period, there is not a consistent relationship between the peaks in the PDF at each location and temperature. A combined ice sheet/ice shelf model with forcing scaled to marine δ18O predicts that interior WAIS elevations near the ice divide have varied ∼300 m over the Last Glacial cycle. Peaks in the PDF correspond to model highstands over the last 200 ka. In the simulated elevation history, maximum ice elevations at Ohio Range (+100 m) and Mt. Waesche (+60 m) occur at ∼10 ka, in agreement with observations from these sites. During collapse of the marine portion of the WAIS, ice elevations at Ohio Range and Mt. Waesche are drawn down at least 200 m below the present ice elevation. The good correspondence between the model results and observations at both the Ohio Range and Mt. Waesche supports the conclusion that interior WAIS highstands do not occur during glacial maximums. Rather, the highstands are controlled primarily by increased accumulation during temperature maximums that occur early in the interglacials. Interior down-draw events follow highstands, resulting from the arrival of a wave of thinning triggered by retreat of the WAIS grounding line coupled with decreasing accumulation rates.

Antarctica and supercontinent evolution: historical perspectives, recent advances and unresolved issues

Abstract The Antarctic rock record spans some 3.5 billion years of history, and has made important contributions to our understanding of how Earth's continents assemble and disperse through time. Correlations between Antarctica and other southern continents were critical to the concept of Gondwana, the Palaeozoic supercontinent used to support early arguments for continental drift, while evidence for Proterozoic connections between Antarctica and North America led to the ‘SWEAT’ configuration (linking SW USA to East Antarctica) for an early Neoproterozoic supercontinent known as Rodinia. Antarctica also contains relicts of an older Palaeo- to Mesoproterozoic supercontinent known as Nuna, along with several Archaean fragments that belonged to one or more ‘supercratons’ in Neoarchaean times. It thus seems likely that Antarctica contains remnants of most, if not all, of Earth's supercontinents, and Antarctic research continues to provide insights into their palaeogeography and geological evolution. One area of research is the latest Neoproterozoic–Mesozoic active margin of Gondwana, preserved in Antarctica as the Ross Orogen and a number of outboard terranes that now form West Antarctica. Major episodes of magmatism, deformation and metamorphism along this palaeo-Pacific margin at 590–500 and 300–230 Ma can be linked to reduced convergence along the internal collisional orogens that formed Gondwana and Pangaea, respectively; indicating that accretionary systems are sensitive to changes in the global plate tectonic budget. Other research has focused on Grenville-age ( c. 1.0 Ga) and Pan-African ( c. 0.5 Ga) metamorphism in the East Antarctic Craton. These global-scale events record the amalgamation of Rodinia and Gondwana, respectively. Three coastal segments of Grenville-age metamorphism in the Indian Ocean sector of Antarctica are each linked to the c. 1.0 Ga collision between older cratons but are separated by two regions of pervasive Pan-African metamorphism ascribed to Neoproterozoic ocean closure. The tectonic setting of these events is poorly constrained given the sparse exposure, deep erosion level and likelihood that younger metamorphic events have reactivated older structures. The projection of these orogens under the ice is also controversial, but it is likely that at least one of the Pan-African orogens links up with the Shackleton Range on the palaeo-Pacific margin of the craton. Sedimentary detritus and glacial erratics at the edge of the ice sheet provide evidence for the c. 1.0 and 0.5 Ga orogenesis in the continental interior, while geophysical data reveal prominent geological boundaries under the ice, but there are insufficient data to trace these features to exposed structures of known age. Until we can resolve the subglacial geometry and tectonic setting of the c. 0.5 and 1.0 Ga metamorphism, there will be no consensus on the configuration of Rodinia, or the size and shape of the continents that existed immediately before and after this supercontinent. Given this uncertainty, it is premature to speculate on the role of Antarctica in earlier supercontinents, but it is likely that Antarctica will continue to provide important constraints when our attention shifts to these earlier events.