The geomorphology of the Denton Hills provides insight into the timing and magnitude of glacial retreats in a region of Antarctica isolated from the influence of the East Antarctic ice sheet. We present 26 Beryllium-10 surface exposure ages from a variety of glacial and lacustrine features in the Garwood and Miers valleys to document the glacial history of the area from 10 to 286 ka. Our data show that the cold-based Miers, Joyce and Garwood glaciers retreated little since their maximum positions at 37.2 ± 6.9 (1σ n = 4), 35.1 ± 1.5 (1σ, n = 3) and 35.6 ± 10.1 (1σ, n = 6) ka respectively. The similar timing of advance of all three glaciers and the lack of a significant glacial expansion during the global LGM suggests a local LGM for the Denton Hills between ca. 26 and 51 ka, with a mean age of 36.0 ± 7.5 (1σ, n = 13) ka.

The relevance of the term "Gondwanian orogeny" to deformation within upper Paleozoic to Mesozoic rocks of the Antarctic Peninsula is reviewed, and the tectogenesis of deformation within this time frame is discussed. The term, originally applied by du Toit to deformation of middle Paleozoic to lower Mesozoic rocks in the Samfrau geosyncline, has been used extensively in Antarctic literature . However, the Gondwanian fold belt includes deformed regions of significantly different ages. For example, in southern Africa the Gondwanide Cape folding is a singlephase multiple-event period of deformation which spanned the beginning of the Permian to the Middle Triassic, a period of approximately 50 m.y. In the Antarctic Peninsula, although data are insufficient to reconstruct a full tectonic history, the Gondwanian orogen is now known to include rocks and structures of a younger age. The only ages which presently fall within the above time frame are some estimates of a period of metamorphism whose tectonic significance is uncertain. The authors favor the use of the term "Peninsula orogeny" for deformation of Triassic and Early Jurassic rocks below the "Peninsula unconformity" in preference to the term Gondwanian orogeny.

We present direct terrestrial evidence of ice volume change of the Darwin and Hatherton glaciers which channel ice from the Transantarctic Mountains into the Ross Ice Shelf. Combining glacial geomorphology with cosmogenic exposure ages from 25 erratics indicates a pre-LGM ice volume at least 600m thicker than current Hatherton ice elevation was established at least 2.2 million years ago. In particular, five erratics spread across a drift deposit at intermediate elevations located below a prominent moraine feature mapped previously as demarcating the LGM ice advance limits, give a well-constrained single population with mean 10 Be age of 37.0 +/- 5.5 ka (1 sigma). At lower elevations of 50-100m above the surface of Lake Wellman, a further five samples from within a younger drift deposit range in exposure age from 1 to 19 ka. Our preferred age model interpretation, which is partly dependent on the selection of a minimum or maximum age-elevation model, suggests that LGM ice volume was not as large as previously estimated and constrains LGM ice elevation to be within +/-50 m of the modern Hatherton Glacier ice surface, effectively little different from what is observed today.

The Theron Mountains, Antarctica expose Jurassic mafic sills intruded into flatlying Permian sedimentary rocks. The sills form some 30% of the outcrop and most are highly concordant, although there are a few cross-cutting relationships. New fieldwork and analytical data suggest that there are four types of sills. The most abundant group chemically correlates with the Mount Fazio Chemical Type of Ferrar tholeiites from Victoria Land, and a second correlates with the distinctive Scarab Peak Chemical Type of Ferrar tholeiites. Two other chemical groups are compositionally close to certain low-Ti-Zr and high-Fe, high Ti-Zr lavas and intrusions in the central Lebombo Monocline and in Dronning Maud Land. The sills provide evidence for long-distance transport of magmas during initial stages of Gondwana break-up.

Newly acquired aeromagnetic data indicate the presence of a dike swarm that may have acted as a magma transport and feeder system from the plume impact site up to 3,500 km to the Ferrar Large Igneous Province (FLIP). The Dufek and Forrestal intrusions, cover approximately 6,600 km2, and may form a ponding station between a mantle superplume responsible for Gondwana breakup and the FLIP sills and lavas along the Transantarctic Mountains into Tasmania and New Zealand. Prior to this survey, no feeder dike swarms or sills connecting with the Ferrar have been found in the Pensacola Mountains. Similarities with the Mackenzie dikes and intrusions of Northwest Canada imply that Jurassic dikes may have been emplaced into the pre‐existing Ross orogeny trend during doming above a mantle plume. However, our survey area is too small to show the dikes convincingly radiating from a focal point that would indicate the plume position.

The Neptune Range of the Pensacola Mountains, East Antarctica, exposes a record of Early Palaeozoic to Early Mesozoic polyphase deformation along the former East Antarctic margin of Gondwana that is unique within the 3500 km length of the Transantarctic Mountains. The earliest of these orogenic events is the polyphase Early Palaeozoic Ross orogeny. Following two phases of intense pre-late Mid-Cambrian deformation (D 1 and D 2 ), a succession of volcanic and sedimentary rocks (sequences 2 and 3) were deposited in late Mid- to Late Cambrian time during a transient period of back-arc rifting. New stratigraphical and structural relationships suggest that the Cambrian succession was deformed during latest Cambrian time while at or near the palaeosurface in a foreland basin setting (D 3 ). D 3 deformation is characterized by thrust faulting and folding without the development of a widespread coeval cleavage, with evidence for syntectonic deposition of the basal Neptune Group (sequence 4). The main regional cleavage developed through the Palaeozoic cover rocks (sequences 2–5) is also developed in rare Permo-Carboniferous clastic dykes that cut down through the stratigraphy from the base of the Gale Mudstone. The dyke–cleavage relationship, together with observations of the conglomerate cobbles from throughout the stratigraphical succession, suggests that the most intense deformation within the Cambrian sequences is Permo-Triassic (Gondwanian orogeny) rather than latest Cambrian (late Ross orogeny) as previously concluded. Our data corroborate recent suggestions that the main phase of Ross orogenic deformation is pre-late Mid-Cambrian and not Late Cambrian or Early Ordovician.

Primitive magmas representing mantle partial melts minimally affected by fractionation and assimilation are rare in the magmatic arc environment. Most examples are either associated with high rates of arc-parallel extension, or occur along faults and dykes perpendicular to the trend of the arc and related to arc compression. In two cases, the Vanuatu and Solomon Islands arcs, such arc compression is being caused by collision of seamounts. In the Antarctic Peninsula. primitive mafic dykes were emplaced perpendicular to the continental arc. Ar-Ar and K-Ar data suggest intrusion of the dykes at c. 126-106 Ma, possibly during mid-Cretaceous regional compression of the arc. The dykes form two compositional groups, One group has low La-N/Yb-N ratios (0.31-0.49), lower Nb/Yb and higher Th/Nb than N-MORB, age-corrected epsilonNd values of +7.3 to +7.9, and are interpreted as melts of subduction modified sub-arc asthenosphere. The other has high La-N/Yb-N ratios (3.86 8.92), higher Nb/Yb and Th/Nb than N-MORB, age-corrected epsilonNd values of -2.8 to +3.4, and are interpreted as melts of sub-arc lithosphere. The absence of dykes compositionally between these groups suggests that the primitive magmas avoided storage and mixing in magma chambers.

Ar–Ar dating of high-strain ductile mylonites of the Eastern Palmer Land Shear Zone in the southern Antarctic Peninsula indicates that reverse movement on the shear zone occurred in late Early Cretaceous times (Albian), and not latest Jurassic times as previously supposed. The Eastern Palmer Land Shear Zone forms a major tectonic boundary, separating suspect arc terranes from rocks of Gondwana continental affinity. The dated mylonites are developed in Lower Jurassic plutonic rocks at Mount Sullivan, eastern Palmer Land, and form part of a zone of ductile reverse deformation up to 25 km wide. Biotite from a fine-grained mafic mylonite yields an Ar–Ar cooling age of 102.8±3.3 Ma. Movement of this age on the Eastern Palmer Land Shear Zone is coeval with circum-Pacific deformation, possibly related to a mantle superplume event, and provides support for allochthonous-terrane models for the Antarctic Peninsula with accretion in post-Early Cretaceous times.

Remotely located sites have become more accessible and therefore more valuable and profitable to investors and entrepreneurs. Typically these sites are environmentally sensitive. For the designer, these sites offer a unique challenge conceptually, in terms of the physical and cultural constraints. The built environment research community has yet to seriously take up the challenge of developing theoretical models for the management of the design and construction processes for remotely located projects. Such models would explore efficiency and efficacy management for projects in remote and often hostile areas, in an integrated and sustainable manner. There are varying degrees of remoteness experienced in nearly all construction projects and therefore a clearer definition of the characteristics of remote sites is required. Towards this definition, a typology is initiated for the concept of remotely located construction projects related to environmental sustainability and the management of the design process. The characteristics of the typology are drawn from a selected literature review of the fields of design management and environmental sustainability, and from an exploratory investigation of two case studies.

New isotopic ages and a fresh understanding of stratigraphic relations among siliciclastic strata in the Pensacola Mountains along the northern margin of the East Antarctic craton result in removal of some constraints for the Proterozoic break-up of Rodinia and necessitate revision of the subsequent history of the East Antarctic margin. These rocks, formerly all included in the Patuxent Formation, were thought to be of mid-Neoproterozoic age, to have formed as a consequence of Rodinia rifting, and to have been deformed during a Neoproterozoic orogenic event. Our data show, in contrast, that these siliciclastic strata were deposited in two chronologically distinct basins. The older basin, in which the Hannah Ridge Formation (new name) accumulated, received sediment that contains detrital zircons of latest Neoproterozoic or Early Cambrian age. It was deformed and its contents uplifted and eroded prior to the late Mid-Cambrian in an orogenic event that we interpret as the early stage(s) of the Ross orogeny. The second basin formed later, accumulated turbidite-rich sediments of the redefined Patuxent Formation of Mid- and probably Late Cambrian age, and was subsequently deformed, possibly in Ordovician time. Review of both biostratigraphic and isotopic ages along the length of the Transantarctic Mountains indicates that almost everywhere the main episodes of deformation predate 500 Ma and are thus older than latest Mid-Cambrian, rather than Ordovician, as they are commonly considered to be. Only in the accreted Bowers and Robertson Bay terranes of northern Victoria land, which reveal no clear record of pre-latest Mid-Cambrian or older folding, is the principal episode of Ross orogenic deformation demonstrably younger than Late Cambrian.

This paper reviews some of the main criteria that are important in locating the original position of mantle plumes in large igneous provinces in the geologic record. The criteria are applied to three large Middle Jurassic igneous provinces-the Karoo province in southern Africa, the Ferrar province in Antarctica, and the Chou Aike province in Patagonia-that formed prior to initial breakup of Gondwana. Although the Karoo province has been most clearly linked to a mantle plume, links between the Ferrar and Chon Aike provinces and mantle-plume centers are by no means certain. On the basis of evidence from the uplift and subsidence history in southern Africa and Antarctica, volcanic margins in the Weddell Sea region, and plume-derived alkalic magmas, we conclude that the presence of a large thermal anomaly or super-plume in the South Atlantic (Weddell Sea) sector of Gondwana seems the most appropriate interpretation at present. Within this regional anomaly, three individual hotspots may have existed beneath the Mozambique Basin (Discovery hotspot), beneath the Weddell Sea embayment region (Shona hotspot), and beneath the Dufek intrusion in the Pensacola Mountains (Bouvet hotspot).

Cambrian volcanic rocks of the Liv Group, defined here as including the Wyatt, Ackerman, Taylor, Fairweather, and Leverett Formations, occur along the paleo-Pacific margin of Gondwana, in the Queen Maud Mountains, Transantarctic Mountains. The Ackerman and Wyatt Formations are dominated by massive dacite lava flows and were erupted ca, 525 Ma. The Taylor, Fairweather, and Leverett Formations form a bimodal assemblage of basalts and rhyolites and were erupted ca, 515 Ma. The dacites of the Ackerman and Wyatt Formations are the most light rare earth element (REE) and large ion lithophile element (LILE) enriched rocks (La-N/Yb-N = 6.6-10.2; Th/Nb = 0.9-1.8) of the Liv Group. They have the lowest epsilon Nd-i (-1.8 to -3.1) of all the Liv Group volcanic rocks and are interpreted to be partial melts of continental crust, Sm-Nd model ages suggest that some of this crust may be as old as 1.5 Ga. The volumetrically minor basalts and basaltic andesites of the Taylor, Fairweather, and Leverett Formations are variably light REE and LILE enriched (varying from La-N/Yb-N = 1.5 to 6.0) and have epsilon Nd-i between 5.7 and -1.1, The most depleted of these basalts are transitional between normal midocean ridge basalt (MORB) and enriched MORB and are interpreted as melts of asthenospheric mantle that were variably enriched in light REE and LILE by melts from lithospheric mantle and/or continental crust, The rhyolites of the Taylor, Fairweather, and Leverett Formations have La-N/Yb-N = 2.8-6.0, Th/Nb = 1.0-1.6, and epsilon Nd, between 2.1 and -2.8 and are interpreted as mixtures of fractionated mafic magma and crustal partial melt. The Liv Group rhyolites were probably generated in response to the mafic magmatism, The most likely tectonic setting for the Liv Group was in an extensional rift environment within or behind an active volcanic are.

Constraining the paleogeography of the Ediacaran is crucial for understanding the extensive tectonic, biological and geochemical changes that occurred during that epoch. Paleomagnetism is an essential tool for reconstructing the Ediacaran paleogeography but it is complicated because the paleomagnetic data of that age display unusually fast and large directional oscillations. Two main competing hypotheses have been proposed: the occurrence of very fast True Polar Wander (TPW) episodes, which correspond to the motion of the planetary spin axis relative to the solid Earth, or strong geomagnetic field disturbances that could potentially be dominated by an equatorial dipole field. Their implications for paleogeographic reconstructions are radically different as TPW would result in a major latitudinal shift of continents of up to ∼ 90°. In this study, we focus on one rapid paleomagnetic change recorded in pyroclastic rocks of the Ouarzazate Group in the Anti-Atlas Belt (Morocco) that has been interpreted to reflect an exceptionally fast episode of True Polar Wander between ∼ 575 and 565 Ma. To further test this hypothesis, tight constraints on the rate of the paleomagnetic directional change are needed, as TPW is speed-limited by mantle viscosity. Here, we present high-resolution Chemical Abrasion Isotope-Dilution Thermal Ionization Mass Spectrometry (CA-ID-TIMS) U-Pb dates on zircons from seven pyroclastic levels distributed stratigraphically below, in between and above the horizons where the large paleomagnetic change is observed. Based on these new data, we estimate the associated lower bound rate of the apparent polar motion related to this abrupt paleomagnetic change to be 11.6°/Myrs [5.5 – 17.9]. This value is much higher than the TPW speed limit estimated from numerical simulations, suggesting that this large paleomagnetic change cannot be explained by TPW. It could rather be associated with intense perturbations of the Ediacaran geomagnetic field potentially oscillating from an axial to an equatorial dipole. The paleomagnetic pole that we interpret as referring to the axial dipole field would imply that West Africa was located at high latitude during the mid-Ediacaran.

A major ductile fault zone, the eastern Palmer Land shear zone, has been identified east of the spine of the southern Antarctic Peninsula. This shear zone separates newly identified geological domains, and indicates that during Late Jurassic terrane accretion and collision, two and possibly three separate terranes collided, resulting in the Palmer Land orogeny. The orogeny is best developed in eastern Palmer Land and eastern Ellsworth Land. There, shallow-marine sedimentary rocks of the Latady Formation, and a metamorphic and igneous basement complex of possible Lower Palaeozoic to pre-Early Jurassic age, are thrust and folded. This forms an arcuate, east-directed, foreland, fold and thrust belt up to 100 km wide and 750 km long, parallel to the axis of the Antarctic Peninsula. The newly identified Antarctic Peninsula domains include: (1) a parautochthonous Eastern Domain that represents part of the margin of the Gondwana continent, comparable to the Western Province of New Zealand, the Ross Province superterrane of Marie Byrd Land, the Eastern Series of south-central Chile, the Pampa de Agnía and Tepuel rocks of north Patagonia, and the Cordillera Darwin rocks of Tierra del Fuego, (2) a suspect Central Domain that represents an allochthonous, microcontinental, magmatic arc terrane, comparable to the Median Tectonic Zone of New Zealand, the Amundsen Province superterrane of Marie Byrd Land, and Coastal Cordillera of north Chile and (3) a suspect Western Domain, with strong similarities to the Eastern Province of New Zealand, Western Series of south-central Chile, and Chonos metamorphic complex of north Patagonia, that represents either a subduction–accretion complex to the Central Domain, or another separate crustal fragment. Although an allochthonous terrane hypothesis for the Antarctic Peninsula remains to be fully tested, this has much in common with models for the New Zealand and South American parts of the Pacific margin of Gondwana. The identification of a potential allochthonous terrane–continent collision zone allows us to define the edge of the Gondwana continent in the Antarctic Peninsula sector of the supercontinent margin, which has implications for Mesozoic reconstructions of Gondwana.

AbstractAn ultramafic lamprophyre dyke is described from the otherwise tholeiitic Ferrar magmatic province of Antarctica. We report an Ar-Ar age of 183 ± 2.2 Ma for the dyke, indistinguishable from those of the Ferrar tholeiites. However, the dyke has mineralogical and major and trace element compositions, and radiogenic isotopes ratios, very different from the Ferrar tholeiites. The sample consists of olivine and rare clinopyroxene phenocrysts with perovskite and spinel microphenocrysts in a groundmass of amphibole, nepheline and biotite. Carbonatitic globules contain calcite, dolomite, Fe-rich carbonate, nepheline, biotite, orthoclase, pyrite, clinopyroxene, apatite and silicate glass, and were formed by liquid immiscibility. The rock is mildly potassic and classifies as an ouachitite. It is strongly enriched in both moderately and highly incompatible trace elements and is the first high-Ti rock to be described from the Ferrar magmatic province. The rock has similar initial 143Nd/144Nd to OIB, notably Bouvet, Crozet and Réunion, but significantly higher initial 87Sr/86Sr. The lamprophyre magma is interpreted as having been generated by low-degree partial fusion of metasomatized lithospheric mantle as a result of heat conducted from an underlying Jurassic mantle plume. The same mantle plume was probably also responsible for generating one of the world’s largest layered gabbro bodies, the Dufek-Forrestal intrusions.

Interpretation of an airborne magnetic data compilation containing a key, new survey, together with re-tracked satellite gravity data from the Weddell Sea embayment (WSE), West Antarctica, suggests Rift–Rift–Rift triple junction formation at the onset of Gondwana breakup in the Early Middle Jurassic. A complex system of northwest–southeast rifts was active contemporaneously with an east–west trending rift. This rift activity led to northward separation of the Falkland Plateau, and formation of the Weddell Sea by sea floor spreading. Atypically, the Jurassic passive margin of Gondwana shows evidence for coeval extension in two directions and a large volume of interpreted magmatic material. This is consistent with initial doming above a mantle plume and we suggest that this resulted in the formation of a triple junction. Magnetic anomalies indicate a series of faults perpendicular to igneous intrusions and extrusions with outlines that range in shape from lozenges to parallel ridges. They show remarkably good spatial correlation with free air gravity anomalies, even in areas of sea ice. We base a structural elements map and timing sequence for the events in the WSE during early Gondwana breakup on anomaly cross-cutting relationships.