194 results on '"Smellie, John L."'
Search Results
152. Merrick Mountains
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Le Masurier, W.E., Thomson, J.W., Rowley, P.D., Vennum, W.R., Smellie, John L., Le Masurier, W.E., Thomson, J.W., Rowley, P.D., Vennum, W.R., and Smellie, John L.
- Published
- 1990
153. Alexander Island, Palmer Island, and Ellsworth Land. Summary
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Le Masurier, W.E., Thomson, J.W., Rowley, P.D., Smellie, John L., Laudon, T.S., LaPrade, K.E., LeMasurier, W.E., Le Masurier, W.E., Thomson, J.W., Rowley, P.D., Smellie, John L., Laudon, T.S., LaPrade, K.E., and LeMasurier, W.E.
- Published
- 1990
154. Seal Nunataks
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Le Masurier, W.E., Thomson, J.W., Smellie, John L., Le Masurier, W.E., Thomson, J.W., and Smellie, John L.
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- 1990
155. Southeastern Alexander Island
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Le Masurier, W.E., Thomson, J.W., Rowley, P.D., Smellie, John L., Le Masurier, W.E., Thomson, J.W., Rowley, P.D., and Smellie, John L.
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- 1990
156. Cain and Abel Nunataks, Trinity Peninsula
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Le Masurier, W.E., Thomson, J.W., Smellie, John L., Le Masurier, W.E., Thomson, J.W., and Smellie, John L.
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- 1990
157. Preliminary stratigraphy of volcanoes in the Executive Committee Range, central Marie Byrd Land
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Smellie, John L., McIntosh, W.C., Gamble, J.A., Panter, K.T., Smellie, John L., McIntosh, W.C., Gamble, J.A., and Panter, K.T.
- Abstract
Marie Byrd Land is amongst the most inaccessible and least visited regions of Antarctica. It contains a large alkaline volcanic province, with 18 large central volcanoes and numerous small satellitic centres, ranging in age from late Oligocene (c. 28–30 Ma) to Recent (LeMasurier 1990). The volcanic rocks provide an outstanding record of the late Cenozoic glacial and volcanic history of Antarctica. The volcanism has been described within a region-wide model of hot-spot impingent at the base of the crust, widespread eruption of mafic plateau lavas and the sequential release of more evolved magmas from crustal chambers beneath central volcanoes situated along a series of reactivated, orthogonal basement fractures (LeMasurier & Rex 1989). Most of the volcanoes have been studied only on a reconnaissance level.
- Published
- 1990
158. Lithostratigraphy of volcanic and sedimentary sequences in central Livingston Island, South Shetland Islands
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Willan, Robert C.R., primary, Smellie, John L., additional, Sàbat, Francesc, additional, and Muñoz, Josep A., additional
- Published
- 1996
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159. Products of subglacial volcanic eruptions under different ice thicknesses: two examples from Antarctica
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Smellie, John L., primary and Skilling, Ian P., additional
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- 1994
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160. 'A'ālava-fed deltas: A new reference tool in paleoenvironmental studies.
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Smellie, John L., Wilch, Thomas I., and Rocchi, Sergio
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DELTAS , *LAVA , *FOSSILS , *ICE sheets , *PALEOENVIRONMENTAL studies - Abstract
Lava-fed deltas are extraordinarily useful indicators of fossil water (and ice) levels in glacial, marine, and lacustrine environments. Deltas fed by 'a'a lava should be at least as common as those sourced in pahoehoe, yet they have been rarely described. Although facies models for pahoehoe lava-fed deltas are well established, the architecture and lithofacies of 'a'a-fed equivalents are substantially different and have thus far largely been unrecognized. This can have profound consequences for paleoenvironmental investigations, particularly those attempting to reconstruct past ice sheets. Essential features of 'a'a lava-fed deltas include (1) a subaerial 'a'a lava capping unit comprising massive internal sheet lava overlain by clinkers; (2) a crudely developed subaerial to subaqueous transition (passage zone); (3) a chaotic subaqueous association of abundant lava lobes and hyaloclastite with admixed vesicular, often reddened (oxidized) lava clinkers; and (4) rare subaqueous stratification with predominantly lower dips (~10°-20°) than in deltas fed by pahoehoe lava (~25°-40°). We develop a generic facies model and investigate the emplacement conditions of 'a'a lava-fed deltas in order to facilitate the recognition and environmental interpretation of these important sequence types in ancient successions. [ABSTRACT FROM AUTHOR]
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- 2013
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161. Neogene glacigenic debris flows on James Ross Island, northern Antarctic Peninsula, and their implications for regional climate history
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Nelson, Anna E., Smellie, John L., Hambrey, Michael J., Williams, Mark, Vautravers, Maryline, Salzmann, Ulrich, McArthur, John M., and Regelous, Marcel
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NEOCENE stratigraphic geology , *LANDSLIDES , *CLIMATOLOGY , *SEDIMENTS , *MIOCENE stratigraphic geology - Abstract
Abstract: Detailed sedimentological and microtextural analyses of newly-discovered late Neogene diamictites and other coarse-grained facies, mostly sandwiched between hyaloclastite of the James Ross Island Volcanic Group and Cretaceous sandstone and mudstone, indicate deposition mainly by glacigenic debris flows. The deposits on James Ross Island (northern Antarctic Peninsula) constrain the depositional setting, ice–bed dynamics and regional palaeoclimate. The sequences on James Ross Island vary in age but are mainly late Miocene and Pliocene. Unlike Neogene sedimentary sequences elsewhere in Antarctica, those on James Ross Island are unusually well-dated by a combination of 40Ar/39Ar and 87Sr/86Sr analyses on fresh interbedded lavas and pristine bivalve molluscs, respectively. The Sr isotopic ages of the debris flows cluster around 4.74, 4.89, 5.44, 5.78, and 6.31Ma and probably date relatively warm periods in the northern Antarctic Peninsula region, when the bivalves lived under ice-poor or seasonally ice-free conditions. The bivalves are often remarkably well-preserved, lack adhering lithified sediment and, in at least two locations, are large, mainly unfragmented and sometimes articulated, suggesting that they were alive immediately prior to their incorporation in subaqueous debris flows at the margins of an advancing glacier. These fossiliferous glacigenic debris flows signify episodes of ice expansion during relatively warm periods, or “interglacials”, of the late Miocene and Pliocene. The James Ross Island glacigenic sedimentary successions attain thicknesses of up to 150m and extend over 4km laterally. The high volume of glacigenic sediment delivery implicit in the James Ross Island successions indicates that a series of dynamic ice fronts crossed the region during the late Miocene and Pliocene epochs. Associated evidence, in the form of clast abrasion (including striations and faceting) and bedrock erosion, is indicative of basal sliding and subglacial sediment deformation active at the ice–bed interface and wet-based temperate or polythermal regimes, prior to remobilisation. The evidence further suggests two local ice caps on James Ross Island during the warm periods, as well as ice-overriding by the Antarctic Peninsula Ice Sheet from the west and northwest. [Copyright &y& Elsevier]
- Published
- 2009
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162. History of the Antarctic Peninsula Ice Sheet since the early Pliocene—Evidence from cosmogenic dating of Pliocene lavas on James Ross Island, Antarctica
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Johnson, Joanne S., Smellie, John L., Nelson, Anna E., and Stuart, Finlay M.
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ICE sheets , *PLIOCENE stratigraphic geology , *COSMOCHRONOLOGY , *COSMOGENIC nuclides , *LAVA , *CLIMATE change , *GLACIAL erosion - Abstract
Abstract: Knowledge of the thickness, extent and basal thermal conditions of ice cover on Antarctica during past climatic fluctuations is essential if we are to accurately predict the contribution from the Antarctic ice sheets to future global sea level rise. When combined with geomorphological evidence, terrestrial cosmogenic nuclides are a powerful tool for palaeo-ice sheet reconstructions. Here we present results from the first terrestrial cosmogenic nuclide study on James Ross Island, northern Antarctic Peninsula. We measured cosmogenic 3He concentrations in primary flow surface features of Pliocene basalt lavas which are exposed more than 600m above present-day sea level. Our results suggest that the lava surfaces have been ice-free for no more than 15kyr since their eruption at 4.69Ma. This implies that a glacial cover has persisted on James Ross Island since 4.69Ma, even during interglacial periods, and much (if not all) of the warm Pliocene (5–3Ma, when average global temperatures were up to 3°C higher than today). This is consistent with results of recent modelling studies, but contradicts General Circulation Models that suggest an ice-free Antarctic Peninsula during that time. Field observations of striated lava surfaces found adjacent to primary volcanogenic features, such as ropy textures, combined with cosmogenic 3He data suggest that the ice cover was locally wet-based, and relatively thin (not exceeding 45–200m) for the majority of the past 4.69Myr. The ice temporarily reached a thickness sufficient to cause some localised erosion in hollows, but this erosion was not widespread. Although the pristinely-preserved lavas found on upstanding tumuli appear never to have been eroded, our exposure age data show that they were covered by ice for most of their history, and therefore could not have been refugia for terrestrial organisms during glacial periods. [Copyright &y& Elsevier]
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- 2009
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163. Subglacial intermediate volcanism at Kerlingarfjöll, Iceland: Magma–water interactions beneath thick ice
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Stevenson, John A., Smellie, John L., McGarvie, David W., Gilbert, Jennie S., and Cameron, Barry I.
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VOLCANISM , *GLACIERS , *MAGMAS , *ICE sheets , *LAVA flows , *DACITE , *ANDESITE - Abstract
Abstract: The products of andesite and dacite glaciovolcanism at Kerlingarfjöll are unlike others previously described in the literature. Three sequences of lithofacies are described and interpreted here. The andesitic deposits at “Campsite Gully” are divided into: massive vitriclastic lapilli tuff with intrusions; fluidal-clast-bearing vitriclastic lapilli tuff; and stratified, pumice-rich vitriclastic lapilli tuff. At Tindur, andesitic eruptions produced contorted pillow fragment breccia and the clast-supported lithic breccia. Finally, pillow lava with intrusions and crudely-bedded vitriclastic lapilli tuff of dacitic composition are described at Haraldur. Abundant vitriclasts, the presence of pillow lavas, hackly fracturing of lava bodies and lack of oxidation of clasts demonstrate that each of these lithofacies formed in the presence of abundant water. This contrasts with all other descriptions of subglacially-erupted intermediate magmas, which are characterised by jointed and glassy lava flows and domes with a marked scarcity of fragmental material. The Kerlingarfjöll sequences therefore demonstrate that it is possible for intermediate magmas to generate and interact with significant volumes of water at the base of a glacier. Preliminary estimates of volatile contents in glassy clasts correspond to quenching pressures equivalent to >500 m water or >550 m ice. This is consistent with eruption beneath an ice sheet that was thick enough to overwhelm the underlying topography and where meltwater drainage was controlled by the morphology of the glacier surface. It is argued that the drainage of water due to steep topography and/or thin and fractured ice, as opposed to thermodynamic considerations, is the most likely explanation for the absence of evidence for significant magma–water interaction in previously described instances of intermediate glaciovolcanism. The apparent low viscosity of the Kerlingarfjöll magmas may relate to relatively high eruption temperatures and/or the inhibition of degassing of the magma due to high ambient pressures and the consequent limitation of groundmass crystallisation. [Copyright &y& Elsevier]
- Published
- 2009
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164. Nature of the Antarctic Peninsula Ice Sheet during the Pliocene: Geological evidence and modelling results compared
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Smellie, John L., Haywood, Alan M., Hillenbrand, Claus-Dieter, Lunt, Daniel J., and Valdes, Paul J.
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ICE sheets , *PLIOCENE paleoecology , *METEOROLOGICAL precipitation , *GEOLOGY ,ENVIRONMENTAL aspects - Abstract
Abstract: In this paper, we examine the nature of the Pliocene Antarctic Peninsula Ice Sheet by comparing the terrestrial and marine geological records of the Antarctic Peninsula and surrounding sea floor with estimated net snow accumulation in the region derived from numerical palaeoclimate model experiments. Pliocene geological data and our new modelling results are consistent and mutually supportive in suggesting that an ice sheet was present even during the warmest episodes of the Pliocene. The combined results suggest that the ice sheet in the Antarctic Peninsula is more robust to globally warmer conditions than is generally assumed, at least up to the climatic limits examined in our study. [Copyright &y& Elsevier]
- Published
- 2009
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165. Basaltic subglacial sheet-like sequences: Evidence for two types with different implications for the inferred thickness of associated ice
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Smellie, John L.
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GLACIERS , *ICE sheets , *HYDRAULIC engineering , *ICE caps - Abstract
Abstract: Subglacially-erupted volcanic sequences provide proxies for a unique range of palaeo-ice parameters and they are potentially highly useful archives of palaeoenvironmental information, particularly for pre-Quaternary periods. They can thus be incorporated by climate and ice sheet modellers in the same way as other environmental proxies, yet they remain largely under-utilised. Basaltic volcanic sequences erupted subglacially consist empirically of two major types, corresponding to eruptions under “thick” and “thin” ice, respectively. The latter are called subglacial sheet-like sequences and only one generic type of sequence has been described so far. However, there is now evidence that there are at least two generic types, with significantly different implications for interpretations of associated palaeo-ice sheet thicknesses. One type, which is relatively well described, is believed to be a diagnostic product of eruptions associated with a relatively thin glacial cover (
1000 m). Eruptions that form the Dalsheidi-type of sequence commence with the injection and inflation of a sill along the ice:bedrock interface. Such “interface sills” were predicted theoretically but had no known geological example, until now. Subsequent evolution commonly involves floating of the ice cover, catastrophic meltwater drainage and emplacement of widespread sheets of hyaloclastite, as cohesionless mass flows and hyperconcentrated flows. The water-saturated hyaloclastite is characteristically intruded by apophyses sourced in the underlying “interface sill”. Eruptions are commonly not explosive until their later stages. Dalsheidi-type deposits are outflow sequences probably linked to subglacial pillow volcanoes, which in Iceland were erupted along fissures. They only provide an indication of minimum thicknesses of the associated overlying ice, although theoretical considerations suggest substantial ice thicknesses in excess of 1000 m. However, they are likely to be characteristic products of eruptions under the thick West Antarctic Ice Sheet, but are currently inaccessible. Such eruptions may be capable of destabilising that ice sheet. [Copyright &y& Elsevier] - Published
- 2008
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166. Late Cenozoic glacier-volcano interaction on James Ross Island and adjacent areas, Antarctic Peninsula region.
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Hambrey, Michael J., Smellie, John L., Nelson, Anna E., and Johnson, Joanne S.
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GEODYNAMICS , *VOLCANOES ,ANTARCTIC glaciers - Abstract
The northern Antarctic Peninsula region has undergone ~10 m.y. of eruptive activity by basaltic volcanoes, mainly in subglacial settings. Spectacular exposures of lava-fed deltas, capped by basalt flows and commonly underlain by glacigenic sediments on top of a Cretaceous sedimentary "basement," characterize James Ross, Vega, and other islands and promontories in the region. Neogene strata are collectively known as the James Ross Island Volcanic Group and record a cryptic history of glaciation, with the timing of events determinable by argon-isotope dating. Focusing especially on the glacigenic sediments themselves, and their relationships with overlying or bounding volcanic rocks, we define facies associations related to (1) eruptions beneath thick ice (>200 m) that produced lava-fed deltas resting on, and intermingling with, diamictite; and (2) eruptions under marine conditions that typically culminated in the development of several tuff-cone successions, some on top of presumably relict glacially striated surfaces. A combination of provenance studies on clasts in the glacigenic sediments, some of which are derived from the Antarctic Peninsula, and geochronology, leads to the conclusion that an Antarctic Peninsula Ice Sheet extended over James Ross and Vega Islands at about the time that the main volcanic edifices began to grow, i.e., prior to ca. 6.2 Ma at least. Much of the subsequent development of the succession is attributed to the interaction between the growing volcanoes and local ice caps. Full resolution of glacial-interglacial events in this region promises to inform the debate about the stability of the most climatically sensitive part of the Antarctic Ice Sheet during the Neogene Period. [ABSTRACT FROM AUTHOR]
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- 2008
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167. Antarctic terrestrial life – challenging the history of the frozen continent?
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Convey, Peter, Gibson, John A. E., Hillenbrand, Claus-Dieter, Hodgson, Dominic A., Pugh, Philip J. A., Smellie, John L., and Stevens, Mark I.
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QUALITY of life ,ICE sheets ,GLACIERS ,MESOZOIC paleobiogeography - Abstract
Antarctica is a continent locked in ice, with almost 99.7% of current terrain covered by permanent ice and snow, and clear evidence that, as recently as the Last Glacial Maximum (LGM), ice sheets were both thicker and much more extensive than they are now. Ice sheet modelling of both the LGM and estimated previous ice maxima across the continent give broad support to the concept that most if not all currently ice-free ground would have been overridden during previous glaciations. This has given rise to a widely held perception that all Mesozoic (pre-glacial) terrestrial life of Antarctica was wiped out by successive and deepening glacial events. The implicit conclusion of such destruction is that most, possibly all, contemporary terrestrial life has colonised the continent during subsequent periods of glacial retreat. However, several recently emerged and complementary strands of biological and geological research cannot be reconciled comfortably with the current reconstruction of Antarctic glacial history, and therefore provide a fundamental challenge to the existing paradigms. Here, we summarise and synthesise evidence across these lines of research. The emerging fundamental insights corroborate substantial elements of the contemporary Antarctic terrestrial biota being continuously isolated in situ on a multi-million year, even pre-Gondwana break-up timescale. This new and complex terrestrial Antarctic biogeography parallels recent work suggesting greater regionalisation and evolutionary isolation than previously suspected in the circum-Antarctic marine fauna. These findings both require the adoption of a new biological paradigm within Antarctica and challenge current understanding of Antarctic glacial history. This has major implications for our understanding of the key role of Antarctica in the Earth System. [ABSTRACT FROM AUTHOR]
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- 2008
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168. Palaeomagnetic, 40Ar/39Ar, and stratigraphical correlation of Miocene-Pliocene basalts in the Brandy Bay area, James Ross Island, Antarctica.
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Jánsson, Leó Krist, Gudmundsson, Magnús T., Smellie, John L., Mcintosh, William C., and Esser, Richard
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LANDFORMS ,CELL polarity ,DELTAS ,LAVA - Abstract
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
40 Ar/39 Ar 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. Our40 Ar/39 Ar 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]- Published
- 2005
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169. Petrogenesis of a Phonolite–Trachyte Succession at Mount Sidley, Marie Byrd Land, Antarctica.
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Panter, Kurt S., Kyle, Philip R., and Smellie, John L.
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PHONOLITE ,TRACHYTE ,PETROGENESIS ,SILICA ,CRYSTALLIZATION - Abstract
The 1.5 Ma evolution of the Late Pliocene (5.7 to 4.2 Ma) Mt Sidley volcano, Marie Byrd Land, is examined using major and trace elements, Sr, Nd, O and Pb isotopic data. A large (5 km × 5 km) breached caldera exposes lavas and tephras, deep within Mt Sidley, and allows its magmatic evolution to be elucidated. Two alkaline rock series are distinguished: (a) a strongly silica-under-saturated basanite to phonolite series; (b) a more silica-saturated to -oversaturated alkali basalt to trachyte series. Rock compositions in both series fall within a narrow range of 77Sr/86Sri (0.7028–0.7032), 143Nd/144Ndi (0.51285–0.51290) and δ18O (5.0–6.0‰), and with 206Pb/204Pb (>19.5), suggest an asthenospheric source containing a strong mantle plume component. Partial melting models require ≤2% melting to produce primary basanite and ≤5% melting to produce alkali basalt from the same mantle source. The differentiation of the phonolitic series is modeled by fractionation of diopside, olivine, plagioclase, titaniferous magnetite, nepheline and/or apatite from basanite to derive 35% mugearite, 25% benmoreite and 20% phonolite as residual liquids. Fractional crystallization of a similar mineral assemblage from alkali basalt is modeled for compositions in the trachyte series. However, many trachytes have variable 87Sr/86Sri (0.7033–0.7042), low 143Nd/144Ndi (0.51280–0.51283), high δ18O (6.5–8.4‰) and are silica oversaturated, suggesting they are contaminated by crust. The trachytes evolved by a two-step assimilation–fractional crystallization process (AFC). The first step involved contamination of alkali basalt by calc-alkaline granitoids within the middle crust where high assimilation to crystallization rates (high-r AFC) produced trachytic magmas characterized by depletions in Ta and Nb relative to K and Rb. The second step involved further fractionation of these magmas by low-r AFC within the upper crust to produce another suite of trachytes showing extreme incompatible element enrichment (e.g. Zr>1000 p.p.m/ and Th>100 p.p.m.). [ABSTRACT FROM AUTHOR]
- Published
- 1997
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170. First recorded eruption of Mount Belinda volcano (Montagu Island), South Sandwich Islands
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Patrick, Matthew R., Smellie, John L., Harris, Andrew J. L., Wright, Robert, Dean, Ken, Izbekov, Pavel, Garbeil, Harold, and Pilger, Eric
- Abstract
The MODVOLC satellite monitoring system has revealed the first recorded eruption of Mount Belinda volcano, on Montagu Island in the remote South Sandwich Islands. Here we present some initial qualitative observations gleaned from a collection of satellite imagery covering the eruption, including MODIS, Landsat 7 ETM+, ASTER, and RADARSAT-1 data. MODVOLC thermal alerts indicate that the eruption started sometime between 12 September and 20 October 2001, with low-intensity subaerial explosive activity from the island’s summit peak, Mount Belinda. By January 2002 a small lava flow had been emplaced near the summit, and activity subsequently increased to some of the highest observed levels in August 2002. Observations from passing ships in February and March 2003 provided the first visual confirmation of the eruption. ASTER images obtained in August 2003 show that the eruption at Mount Belinda entered a new phase around this time, with fresh lava effusion into the surrounding icefield. MODIS radiance trends also suggest that the overall activity level increased significantly after July 2003. Thermal anomalies continued to be observed in MODIS imagery in early 2004, indicating a prolonged low-intensity eruption and the likely establishment of a persistent summit lava lake, similar to that observed on neighboring Saunders Island in 2001. Our new observations also indicate that lava lake activity continues on Saunders Island.
- Published
- 2005
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171. Syn-plutonic and Tertiary age for the (?) Precambrian False Bay schists of Livingston Island, South Shetland Islands
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Smellie, John L.
- Subjects
Earth Sciences - Published
- 1983
172. Geology of Hugo Island, Quintana Island, Sooty Rock, Betbeder Islands and parts of the Biscoe and Outcast Islands
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Smellie, John L., Moyes, A.B., Marsh, P.D., and Thomson, Janet W.
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Earth Sciences - Published
- 1985
173. Geology of a Mesozoic intra-arc sequence on Byers Peninsula, Livingston Island, South Shetland Islands
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Smellie, John L., Davies, R.E.S., and Thomson, M.R.A.
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Earth Sciences - Published
- 1980
174. Geological observations on Rugged Island, South Shetland Islands
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Smellie, John L. and Thomson, Janet W.
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Earth Sciences - Published
- 1985
175. the geology of Low Island, South Shetland Islands and Austin Rocks
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Smellie, John L.
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Earth Sciences - Published
- 1980
176. Recent observations on the volcanic history of Deception Island, South Shetland Islands
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Smellie, John L.
- Published
- 1988
177. Age, distribution and eruptive conditions of late Cenozoic alkaline volcanism in the Antarctic Peninsula and eastern Ellsworth Land: a review
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Smellie, John L., Pankhurst, R.J., Hole, M.J., and Thomson, J.W.
- Published
- 1988
178. A geochemical overview of subduction-related igneous activity in the South Shetland Islands, Lesser Antarctica
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Oliver, R.L., Jame, P.R., Jago, J.B., Smellie, John L., Oliver, R.L., Jame, P.R., Jago, J.B., and Smellie, John L.
- Published
- 1983
179. K-Ar geochronology of the South Shetland Islands, Lesser Antarctica: apparent lateral migration of Jurassic to Quaternary island arc volcanism
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Pankhurst, R.J., Smellie, John L., Pankhurst, R.J., and Smellie, John L.
- Abstract
Approximately 70 K-Ar whole-rock ages for low-K tholeiitic and andesitic volcanic and intrusive rocks from the South Shetland Islands, Antarctica, including about 50 not previously published, are reviewed. Activity mainly spanned the range 130 to 30 Ma (Jurassic/Cretaceous to Oligocene/Miocene) with a very recent (∼ 2 Ma), more alkaline, renewal. Throughout the main period of activity magmatism (or, perhaps, its cessation) migrated continuously northeastwards along the length of the island chain.
- Published
- 1983
180. A complete arc-trench system recognized in Gondwana sequences of the Antarctic Peninsula region
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Smellie, John L. and Smellie, John L.
- Abstract
Prior to Late Triassic–Early Jurassic times, the geological history of the Antarctic Peninsula region was dominated almost entirely by Gondwana sequences that together comprised a major arc-trench system. Subduction complex, trench-slope-break and fore-arc basin sedimentation can all be recognized, and deposition was at least partly on early Palaeozoic or older continental crust. The only evidence for a contemporaneous magmatic arc situated in the Antarctic Peninsula at this time consists of patchy occurrences of metavolcanic rocks, possibly representing the frontal edge of the arc, and the major outcrop area of these rocks is believed to lie under the broad shallow continental shelf E of the Antarctic Peninsula. This is contrary to most current hypotheses in which a marginal basin, presumably floored by oceanic crust, is thought to crop out close to the E coast of the Antarctic Peninsula. However, the complete absence of substantial outcrops of pre-Jurassic volcanic rocks anywhere in eastern Antarctica and South Africa, which are the closest and most likely places in which these should exist, supports the new proposal. Moreover, the identification of back-arc elements of the arc-trench system (foreland fold-thrust belt and retro-arc foreland basin) in eastern Antarctica and South Africa greatly strengthens the likelihood of the arc cropping out in the area suggested. Towards the end of the Triassic and during the Early Jurassic Periods, an intense diastrophic event, or culmination of events, of orogenic magnitude occurred (Gondwanian orogeny), causing substantial redistribution of the pre-existing elements of the arc-trench system. In particular, all the fore-arc sequences were strongly deformed, some possibly for the first time (e.g. in the fore-arc basin), and became firmly accreted to the continental margin. Moreover, the magmatic foci migrated trenchwards to intrude the deformed rocks in the Antarctic Peninsula. Because many of the plutons were emplaced synkine
- Published
- 1981
181. Geochemistry and tectonic setting of alkaline volcanic rocks in the Antarctic Peninsula: A review
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Smellie, John L. and Smellie, John L.
- Abstract
The numerous Miocene-Recent alkaline volcanic outcrops in the Antarctic Peninsula form a substantial volcanic province, the least well-known part of a major belt of alkaline volcanism that extends between South America and New Zealand. The outcrops consists mainly of aa and pahoehoe lavas and hyaloclastites which locally contain accidental nodules of spinel lherzolite and other mantle-derived lithologies. The province is predominantly basaltic with two major differentiation lineages: (1) a sodic series of olivine and alkali basalt, hawaiite, mugearite, trachy-phonolite and trachyte; and (2) a relatively potassic, highly undersaturated series of basanite, tephrite and phono-tephrite. All the lavas show varying effects of fractionation by crystallization of olivine and clinopyroxene, joined by plagioclase in the hawaiites to trachytes. Fractional crystallization can probably explain most of the chemical variation observed within each outcrop, but variable partial melting is necessary to account for the differences in incompatible element enrichment between the two series, and between the individual outcrops. The degree of partial melting may not have exceeded 3%, as is the case for many other alkaline magmas. The volcanism is an intraplate phenomenon but there is no correlation in timing between the cessation of subduction and the inception of alkaline volcanism. The activity cannot be related to the passage of the coupled Pacific-Antarctic plate over a stationary mantle hot-spot. Although the precise causal relationship with tectonic setting is unknown, regional extension was a prerequisite for giving the magmas rapid access to the surface.
- Published
- 1987
182. Cretaceous angiosperms from an allegedly Triassic flora at Williams Point, Livingston Island, South Shetland Islands
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Rees, P.M., Smellie, John L., Rees, P.M., and Smellie, John L.
- Abstract
A terrestrial sequence on Livingston Island, South Shetland Islands, known as the Williams Point Beds contains a well-preserved, diverse fossil flora previously assigned a Triassic age. Because of their supposed age, volcanic provenance and evidence for active volcanism, the Williams Point Beds have occupied a unique position in Gondwana (pre-Jurassic) stratigraphy in the Antarctic Peninsula region. However, a large new collection of plant specimens obtained at Williams Point has yielded several species of angiosperm leaves, which are abundant and occur at all levels within the Williams Point Beds sequence. Thus, a Triassic age is no longer tenable. On the basis of the plants present and published radiometric ages for associated strata, the Williams Point Beds fossil flora is reassigned to the Cretaceous, and there is some evidence for a more restricted Albian–Cenomanian age. This revision of the age of the Williams Point Beds removes all direct evidence for an active Triassic volcanic arc in the Antarctic Peninsula region.
- Published
- 1989
183. Deception Island
- Author
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Dalziel, I.W.D., Smellie, John L., Dalziel, I.W.D., and Smellie, John L.
- Published
- 1989
184. Sandstone detrital modes and basinal setting of the Trinity Peninsula Group, northern Graham Land, Antarctic Peninsula: a preliminary survey
- Author
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McKenzie, Garry D., Smellie, John L., McKenzie, Garry D., and Smellie, John L.
- Abstract
Sandstone detrital modes for a representative sample of the Trinity Peninsula Group in northern Graham Land are described and assessed. Whereas the volumetrically dominant quartz and feldspar were derived principally from erosion of a plutonic and high‐rank metamorphic terrane, the lithic population was derived mainly from a volcanic cover. The data clearly indicate the presence of two major sandstone suites (petro‐facies I and II) with distinctive and probably separate provenances. Further scope for subdivision is limited by the small sample set, but four petrofacies (Ia, Ib, IIa, and IIb) may be present, three of which correspond with previously described lithostratigraphical units (Legoupil, Hope Bay, and View Point formations). The sample distribution and detrital modes enable approximate geographical limits to be assigned to each petrofacies for the first time, although the nature of the boundaries (stratigraphical or structural) is unknown. Petrofacies II could have been derived from an active magmatic arc and deposited in a forearc basin (sensu lato) or series of basins at a major consuming margin. Petrofacies I is a much more quartzose suite, although otherwise petrographically very similar to petrofacies II. Its depositional setting is ambiguous on the basis of the data presently available, and deposition can only be said to have occurred at either an active or a passive continental margin. Finally, there is the possibility that strike‐slip faulting has structurally shuffled the Trinity Peninsula Group, causing the pronounced age and compositional contrasts observed.
- Published
- 1987
185. The timing and widespread effects of the largest Holocene volcanic eruption in Antarctica
- Author
-
Antoniades, Dermot, Giralt, Santiago, Geyer, Adelina, Álvarez-Valero, Antonio M, Pla-Rabes, Sergi, Granados, Ignacio, Liu, Emma J, Toro, Manuel, Smellie, John L, and Oliva, Marc
- Subjects
0403 Geology ,13. Climate action ,0406 Physical Geography and Environmental Geoscience - Abstract
The caldera collapse of Deception Island Volcano, Antarctica, was comparable in scale to some of the largest eruptions on Earth over the last several millennia. Despite its magnitude and potential for far-reaching environmental effects, the age of this event has never been established, with estimates ranging from the late Pleistocene to 3370 years before present. Here we analyse nearby lake sediments in which we identify a singular event produced by Deception Island's caldera collapse that occurred 3980 ± 125 calibrated years before present. The erupted tephra record the distinct geochemical composition of ejecta from the caldera-forming eruption, whilst an extreme seismic episode is recorded by lake sediments immediately overlying the collapse tephra. The newly constrained caldera collapse is now the largest volcanic eruption confirmed in Antarctica during the Holocene. An examination of palaeorecords reveals evidence in marine and lacustrine sediments for contemporaneous seismicity around the Antarctic Peninsula; synchronous glaciochemical volcanic signatures also record the eruption in ice cores spread around Antarctica, reaching >4600 km from source. The widespread footprint suggests that this eruption would have had significant climatic and ecological effects across a vast area of the south polar region.
186. Antarctic Peninsula Ice Sheet evolution during the Cenozoic Era
- Author
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Davies, Bethan J., Hambrey, Michael J., Smellie, John L., Carrivick, Jonathan L., and Glasser, Neil F.
- Subjects
- *
GLACIAL climates , *ICE sheets , *BIOLOGICAL evolution , *CENOZOIC Era , *ICE shelves , *HOLOCENE paleoclimatology , *CONTINENTAL margins , *HOLOCENE Epoch - Abstract
Abstract: The Antarctic Peninsula region is currently undergoing rapid environmental change, resulting in the thinning, acceleration and recession of glaciers and the sequential collapse of ice shelves. It is important to view these changes in the context of long-term palaeoenvironmental complexity and to understand the key processes controlling ice sheet growth and recession. In addition, numerical ice sheet models require detailed geological data for tuning and testing. Therefore, this paper systematically and holistically reviews published geological evidence for Antarctic Peninsula Ice Sheet variability for each key locality throughout the Cenozoic, and brings together the prevailing consensus of the extent, character and behaviour of the glaciations of the Antarctic Peninsula region. Major contributions include a downloadable database of 186 terrestrial and marine calibrated dates; an original reconstruction of the LGM ice sheet; and a new series of isochrones detailing ice sheet retreat following the LGM. Glaciation of Antarctica was initiated around the Eocene/Oligocene transition in East Antarctica. Palaeogene records of Antarctic Peninsula glaciation are primarily restricted to King George Island, where glacigenic sediments provide a record of early East Antarctic glaciations, but with modification of far-travelled erratics by local South Shetland Island ice caps. Evidence for Neogene glaciation is derived primarily from King George Island and James Ross Island, where glaciovolcanic strata indicate that ice thicknesses reached 500–850 m during glacials. This suggests that the Antarctic Peninsula Ice Sheet draped, rather than drowned, the topography. Marine geophysical investigations indicate multiple ice sheet advances during this time. Seismic profiling of continental shelf-slope deposits indicates up to ten large advances of the Antarctic Peninsula Ice Sheet during the Early Pleistocene, when the ice sheet was dominated by 40 kyr cycles. Glacials became more pronounced, reaching the continental shelf edge, and of longer duration during the Middle Pleistocene. During the Late Pleistocene, repeated glacials reached the shelf edge, but ice shelves inhibited iceberg rafting. The Last Glacial Maximum (LGM) occurred at 18 ka BP, after which transitional glaciomarine sediments on the continental shelf indicate ice-sheet retreat. The continental shelf contains large bathymetric troughs, which were repeatedly occupied by large ice streams during Pleistocene glaciations. Retreat after the LGM was episodic in the Weddell Sea, with multiple readvances and changes in ice-flow direction, but rapid in the Bellingshausen Sea. The late Holocene Epoch was characterised by repeated fluctuations in palaeoenvironmental conditions, with associated glacial readvances. However, this has been subsumed by rapid warming and ice-shelf collapse during the twentieth century. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
187. Sea ice extent and seasonality for the Early Pliocene northern Weddell Sea
- Author
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Williams, Mark, Nelson, Anna E., Smellie, John L., Leng, Melanie J., Johnson, Andrew L.A., Jarram, Daniel R., Haywood, Alan M., Peck, Victoria L., Zalasiewicz, Jan, Bennett, Carys, and Schöne, Bernd R.
- Subjects
- *
SEA ice , *PLIOCENE stratigraphic geology , *BIVALVES , *ISOTOPE geology , *BIVALVE shells , *DETRITUS , *MARINE sediments - Abstract
Abstract: Growth increment analysis coupled with stable isotopic data (δ 18O/δ 13C) from Early Pliocene (ca 4.7Ma) Austrochlamys anderssoni from shallow marine sediments of the Cockburn Island Formation, northern Antarctic Peninsula, suggest these bivalves grew through much of the year, even during the coldest parts of winter recorded in the shells. The high frequency fluctuation in growth increment width of A. anderssoni appears to reflect periodic, but year-round, agitation of the water column enhancing benthic food supply from organic detritus. This suggests that Austrochlamys favoured waters that were largely sea ice free. Our data support interpretation of the Cockburn Island Formation as an interglacial marine deposit and the previous hypothesis that Austrochlamys retreated from the Antarctic as sea ice extent expanded, this transition occurring during climate cooling in the Late Pliocene. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
188. Ice-dammed lateral lake and epishelf lake insights into Holocene dynamics of Marguerite Trough Ice Stream and George VI Ice Shelf, Alexander Island, Antarctic Peninsula.
- Author
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Davies, Bethan J., Hambrey, Michael J., Glasser, Neil F., Holt, Tom, Rodés, Angél, Smellie, John L., Carrivick, Jonathan L., and Blockley, Simon P.E.
- Subjects
- *
HOLOCENE Epoch , *ICE streams , *ICE shelves , *GLACIERS , *COSMOGENIC nuclides - Abstract
We present new data regarding the past dynamics of Marguerite Trough Ice Stream, George VI Ice Shelf and valley glaciers from Ablation Point Massif on Alexander Island, Antarctic Peninsula. This ice-free oasis preserves a geological record of ice stream lateral moraines, ice-dammed lakes, ice-shelf moraines and valley glacier moraines, which we dated using cosmogenic nuclide ages. We provide one of the first detailed sediment-landform assemblage descriptions of epishelf lake shorelines. Marguerite Trough Ice Stream imprinted lateral moraines against eastern Alexander Island at 120 m at Ablation Point Massif. During deglaciation, lateral lakes formed in the Ablation and Moutonnée valleys, dammed against the ice stream in George VI Sound. Exposure ages from boulders on these shorelines yielded ages of 13.9 to 9.7 ka. Following recession of the ice stream, George VI Ice Shelf formed in George VI Sound. An epishelf lake formed at 15–20 m asl in Ablation and Moutonnée valleys, dated from 9.4 to 4.6 ka, suggesting that the lake was stable and persistent for some 5000 years. Lake-level lowering occurred after this, with the lake level at 12 m at 3.1 ± 0.4 ka and at 5 m asl today. A readvance of the valley glaciers on Alexander Island at 4.4 ± 0.7 ka is recorded by valley glacier moraines overlying epishelf lake sediments. We speculate that the glacier readvance, which occurred during a period of warmth, may have been caused by a dynamic response of the glaciers to a lowering in surface elevation of George VI Ice Shelf. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
189. DecTephra: A new database of Deception Island's tephra record (Antarctica).
- Author
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Hopfenblatt, Joaquín, Geyer, Adelina, Aulinas, Meritxell, Álvarez-Valero, Antonio M., Sánchez, Antonio Polo, Giralt, Santiago, and Smellie, John L.
- Subjects
- *
VOLCANIC ash, tuff, etc. , *VOLCANIC hazard analysis , *DECEPTION , *PALEOENVIRONMENTAL studies , *ISLANDS , *SOIL sampling - Abstract
Deception Island (South Shetland Islands) is one of the most active volcanoes in Antarctica, with more than 20 explosive eruptive events registered over the past few centuries. Recent eruptions (1967, 1969, and 1970) and volcanic unrest episodes (1992, 1999, and 2014–2015) demonstrate that volcanic activity will likely occur in the future. Despite this, there has been a considerable increase in the number of scientific bases, tourist activities and air and vessel traffic in the region during the last several decades. The escalation in interest has increased the amount of infrastructure and population numbers exposed to a future eruption. Thus, there is an urgent need to develop an accurate long-term assessment of the volcanic hazard of the island. However, past attempts have always been limited by the incompleteness of the eruptive record. Volcanic ash layers found in marine and lacustrine sediment cores and glaciers outside Deception Island are a fundamental source of information for reconstructing the explosive eruptive record of the volcano. The spatial distribution of the tephra layers, as well as their physicochemical analysis are invaluable for determining the size and explosiveness of past eruptive events, as well as for assessing the extent and impact of their related hazards (e.g., ash fall out). In order to overcome the dispersion of existing data among numerous publications and to facilitate the analysis of available information on tephra layers sourced in Deception Island, we present the DecTephra (Deception Island Tephra Record) database. The current database version contains 362 tephra layers (including cryptotephras) located at sites up to 3115 km distant from the island. For each tephra layer, the database includes: (i) the location and simple description of the sampling site; and (ii) the key petrologic and geochemical features of each tephra layer. A preliminary analysis of the information contained in the DecTephra database (e.g., magma composition, explosiveness, eruptive recurrence, etc.), validates it as a key tool for evaluating past explosive activity of the volcano. In addition, it can function as a valuable resource for paleoenvironmental and paleoclimatic studies requiring tephrostratigraphical and tephrochronological control at local and regional scales. DecTephra also has the potential to help to assess the contribution of volcanic forcing to Holocene climate variability in the Southern Hemisphere. • Deception Island is one of the most active volcanoes in Antarctica. • The eruptive record is incomplete hindering a complete volcanic hazard assessment. • Volcanic ash layers are fundamental for reconstructing the explosive eruptive record. • DecTephra compiles existing data on tephra layers sourced in Deception Island. • DecTephra is a valuable resource for paleoenvironmental and paleoclimatic studies. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
190. Explosive rhyolite tuya formation: classic examples from Kerlingarfjöll, Iceland
- Author
-
Stevenson, John A., Gilbert, Jennie S., McGarvie, David W., and Smellie, John L.
- Subjects
- *
RHYOLITE , *MOUNTAINS , *VOLCANIC eruptions , *VOLCANIC ash, tuff, etc. , *MELTWATER , *LAKES , *ICE caps - Abstract
Abstract: Rhyolite eruptions in Iceland mostly take place at long-lived central volcanoes, examples of which are found associated with each of the present-day rift-zone ice caps. Subglacial eruptions at Kerlingarfjöll central volcano produced rhyolite tuyas that are notable for their exposures of early-erupted pyroclastic material. Observations from a number of these edifices are synthesised into a general model for explosive rhyolite tuya formation. Eruptions begin with violent phreatomagmatic explosions that generate massive tuff (mT), but the influence of water quickly declines, leading to the formation of massive lapilli-tuffs (mLT) containing magmatically-fragmented vesicular pumice and ash. These are deposited rapidly near the vent, probably by moist pyroclastic density currents, confined by ice but not within a meltwater lake. The explosive-effusive transition is controlled by the ascent rate and gas content of the magma. An unusual obsidian-rich massive lapilli-tuff lithofacies (omLT) is identified and interpreted as pyroclastic material that was intruded into gas-fluidised deposits at the explosive-effusive transition. The effusive phase of eruption involves the emplacement of intrusions and lava caps. Intrusions of lava into the early-erupted phreatomagmatic deposits are characterised by peperitic margins and the formation of hyaloclastite. Intrusions into stratigraphically higher levels of the pyroclastic material show more limited interaction with the host tephra and have microcrystalline cores. Large lava bodies with columnar-jointed margins cap the tuyas and have intrusive basal contacts with the tephras. The main influence of the ice is to confine the rhyolite eruptive products to immediately above the vent region. This is in contrast to subglacial basaltic tuya-forming eruptions, which are characterised by the formation of meltwater lakes, phreatomagmatic fragmentation and subaqueous deposition. The lack of meltwater storage may reduce the potential for large jökulhlaups. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
191. Exploring biological constraints on the glacial history of Antarctica
- Author
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Convey, Peter, Stevens, Mark I., Hodgson, Dominic A., Smellie, John L., Hillenbrand, Claus-Dieter, Barnes, David K.A., Clarke, Andrew, Pugh, Philip J.A., Linse, Katrin, and Cary, S. Craig
- Subjects
- *
GLACIAL Epoch , *BIOLOGICAL evolution , *LIFE history theory , *MARINE biology , *MOUNTAINS , *HUMAN geography - Abstract
Abstract: The evolutionary and biogeographic history of the contemporary Antarctic terrestrial and marine biotas reveals many components of ancient origin. For large elements of the terrestrial biota, long-term isolation over timescales from hundreds of thousands to tens of millions of years, and thus persistence through multiple glacial cycles, now appears to be the norm rather than the exception. For the marine biota there are some parallels with benthic communities also including ancient components, together with an incidence of species-level endemism indicating long-term isolation on the Antarctic continental shelf. Although it has long been known that a few ice-free terrestrial locations have existed in Antarctica for up to 10–12 million years, particularly in the Dry Valleys of Victoria Land along with certain nunataks and higher regions of large mountain ranges, these do not provide potential refugia for the majority of terrestrial biota, which occur mainly in coastal and/or low-lying locations and exhibit considerable biogeographic regionalisation within the continent. Current glacial models and reconstructions do not have the spatial resolution to detect unequivocally either the number or geographical distribution of these glacial refugia, or areas of the continental shelf that have remained periodically free from ice scouring, but do provide limits for their maximum spatial extent. Recent work on the evolution of the terrestrial biota indicates that refugia were much more widespread than has been recognised and it is now clear that terrestrial biology provides novel constraints for reconstructing the past glacial history of Antarctica, and new marine biological investigations of the Antarctic shelf are starting to do likewise. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
192. Exploring biological constraints on the glacial history of Antarctica
- Author
-
Dominic A. Hodgson, Andrew Clarke, S. Craig Cary, Claus-Dieter Hillenbrand, John L. Smellie, David K. A. Barnes, P. J. A. Pugh, Mark I. Stevens, Katrin Linse, Peter Convey, Convey, Peter, Stevens, Mark I, Hodgson, Dominic A, Smellie, John L, Hillenbrand, Claus-Dieter, Barnes, David KA, Clarke, Andrew, Pugh, Philip JA, Linse, Katrin, and Cary, S Craig
- Subjects
Archeology ,Global and Planetary Change ,geography ,geography.geographical_feature_category ,Continental shelf ,Regionalisation ,Geology ,Biota ,Glaciology ,Oceanography ,Biological constraints ,Benthic zone ,Glacial period ,Endemism ,Ecology, Evolution, Behavior and Systematics - Abstract
The evolutionary and biogeographic history of the contemporary Antarctic terrestrial and marine biotas reveals many components of ancient origin. For large elements of the terrestrial biota, long-term isolation over timescales from hundreds of thousands to tens of millions of years, and thus persistence through multiple glacial cycles, now appears to be the norm rather than the exception. For the marine biota there are some parallels with benthic communities also including ancient components, together with an incidence of species-level endemism indicating long-term isolation on the Antarctic continental shelf. Although it has long been known that a few ice-free terrestrial locations have existed in Antarctica for up to 10–12 million years, particularly in the Dry Valleys of Victoria Land along with certain nunataks and higher regions of large mountain ranges, these do not provide potential refugia for the majority of terrestrial biota, which occur mainly in coastal and/or low-lying locations and exhibit considerable biogeographic regionalisation within the continent. Current glacial models and reconstructions do not have the spatial resolution to detect unequivocally either the number or geographical distribution of these glacial refugia, or areas of the continental shelf that have remained periodically free from ice scouring, but do provide limits for their maximum spatial extent. Recent work on the evolution of the terrestrial biota indicates that refugia were much more widespread than has been recognised and it is now clear that terrestrial biology provides novel constraints for reconstructing the past glacial history of Antarctica, and new marine biological investigations of the Antarctic shelf are starting to do likewise. Refereed/Peer-reviewed
- Published
- 2009
193. The timing and widespread effects of the largest Holocene volcanic eruption in Antarctica.
- Author
-
Antoniades D, Giralt S, Geyer A, Álvarez-Valero AM, Pla-Rabes S, Granados I, Liu EJ, Toro M, Smellie JL, and Oliva M
- Abstract
The caldera collapse of Deception Island Volcano, Antarctica, was comparable in scale to some of the largest eruptions on Earth over the last several millennia. Despite its magnitude and potential for far-reaching environmental effects, the age of this event has never been established, with estimates ranging from the late Pleistocene to 3370 years before present. Here we analyse nearby lake sediments in which we identify a singular event produced by Deception Island's caldera collapse that occurred 3980 ± 125 calibrated years before present. The erupted tephra record the distinct geochemical composition of ejecta from the caldera-forming eruption, whilst an extreme seismic episode is recorded by lake sediments immediately overlying the collapse tephra. The newly constrained caldera collapse is now the largest volcanic eruption confirmed in Antarctica during the Holocene. An examination of palaeorecords reveals evidence in marine and lacustrine sediments for contemporaneous seismicity around the Antarctic Peninsula; synchronous glaciochemical volcanic signatures also record the eruption in ice cores spread around Antarctica, reaching >4600 km from source. The widespread footprint suggests that this eruption would have had significant climatic and ecological effects across a vast area of the south polar region.
- Published
- 2018
- Full Text
- View/download PDF
194. Fossil proxies of near-shore sea surface temperatures and seasonality from the late Neogene Antarctic shelf.
- Author
-
Clark NA, Williams M, Hill DJ, Quilty PG, Smellie JL, Zalasiewicz J, Leng MJ, and Ellis MA
- Subjects
- Animals, Antarctic Regions, Climate, Geologic Sediments, Oceans and Seas, Fossils, Models, Theoretical, Seasons, Temperature
- Abstract
We evaluate the available palaeontological and geochemical proxy data from bivalves, bryozoans, silicoflagellates, diatoms and cetaceans for sea surface temperature (SST) regimes around the nearshore Antarctic coast during the late Neogene. These fossils can be found in a number of shallow marine sedimentary settings from three regions of the Antarctic continent, the northern Antarctic Peninsula, the Prydz Bay region and the western Ross Sea. Many of the proxies suggest maximum spring-summer SSTs that are warmer than present by up to 5 °C, which would result in reduced seasonal sea ice. The evidence suggests that the summers on the Antarctic shelf during the late Neogene experienced most of the warming, while winter SSTs were little changed from present. Feedbacks from changes in summer sea ice cover may have driven much of the late Neogene ocean warming seen in stratigraphic records. Synthesized late Neogene and earliest Quaternary Antarctic shelf proxy data are compared to the multi-model SST estimates of the Pliocene Model Intercomparison Project (PlioMIP) Experiment 2. Despite the fragmentary geographical and temporal context for the SST data, comparisons between the SST warming in each of the three regions represented in the marine palaeontological record of the Antarctic shelf and the PlioMIP climate simulations show a good concordance.
- Published
- 2013
- Full Text
- View/download PDF
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