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Journal articles on the topic 'East Scotia ridge'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Prasetyawan, Indra Budi. "The Origin of Back-Arc Spreading in The Eastern Edge of Scotia Plate." BULETIN OSEANOGRAFI MARINA 5, no. 1 (April 3, 2016): 21. http://dx.doi.org/10.14710/buloma.v5i1.11292.

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The origin and evolution of back-arc spreading in the eastern edge of Scotia Plate will be discussed in this paper. The Scotia Plate is a tectonicplate on the edge of the South Atlantic and Southern Ocean, located between the South American and Antartic plates. The East Scotia Ridge (ESR) in the eastern edge of Scotia Plate, forned due to subduction of the South American plate beneath the South Sandwich plate along the South Sandwich Island arc. The methods and techniques of data acquisition used were data from absolution motions and data from magnetic anomalies and bathymetric data. Magnetic anomalies and bathymetric data that used in this paper consist of two sets data. First, magnetic anomalies and bathymetric data which were obtained by aboard HMS Endurance in the 1969-70 austral summer, and the second, magnetic anomalies and bathymetric data which were obtained after removal of the International Geomagnetic Reference Field (IGRF). Absolution motion analyses in the subduction zones of Sandwich plate results that form back-arc spreading in East Scotia Ridge showing high deformation for slow moving upper plates. Where back-arc spreading is associated with upper plate retreat that reaches 26.9 mm/year and have back-arc deformation style consistent with upper plate absolute. Key Words: Geological oceanography, Scotia plate, back-arc spreading

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2

Livermore, Roy, Alex Cunningham, Lieve Vanneste, and Robert Larter. "Subduction influence on magma supply at the East Scotia Ridge." Earth and Planetary Science Letters 150, no. 3-4 (August 1997): 261–75. http://dx.doi.org/10.1016/s0012-821x(97)00074-5.

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3

FRETZDORFF, S. "Petrogenesis of the Back-arc East Scotia Ridge, South Atlantic Ocean." Journal of Petrology 43, no. 8 (August 1, 2002): 1435–67. http://dx.doi.org/10.1093/petrology/43.8.1435.

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4

Thompson, Andrew F., Karen J. Heywood, Sally E. Thorpe, Angelika H. H. Renner, and Armando Trasviña. "Surface Circulation at the Tip of the Antarctic Peninsula from Drifters." Journal of Physical Oceanography 39, no. 1 (January 1, 2009): 3–26. http://dx.doi.org/10.1175/2008jpo3995.1.

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Abstract An array of 40 surface drifters, drogued at 15-m depth, was deployed in February 2007 to the east of the tip of the Antarctic Peninsula as part of the Antarctic Drifter Experiment: Links to Isobaths and Ecosystems (ADELIE) project. Data obtained from these drifters and from a select number of local historical drifters provide the most detailed observations to date of the surface circulation in the northwestern Weddell Sea. The Antarctic Slope Front (ASF), characterized by a ∼20 cm s−1 current following the 1000-m isobath, is the dominant feature east of the peninsula. The slope front bifurcates when it encounters the South Scotia Ridge with the drifters following one of three paths. Drifters (i) are carried westward into Bransfield Strait; (ii) follow the 1000-m isobath to the east along the southern edge of the South Scotia Ridge; or (iii) become entrained in a large-standing eddy over the South Scotia Ridge. Drifters are strongly steered by contours of f /h (Coriolis frequency/depth) as shown by calculations of the first two moments of displacement in both geographic coordinates and coordinates locally aligned with contours of f /h. An eddy-mean decomposition of the drifter velocities indicates that shear in the mean flow makes the dominant contribution to dispersion in the along-f /h direction, but eddy processes are more important in dispersing particles across contours of f /h. The results of the ADELIE study suggest that the circulation near the tip of the Antarctic Peninsula may influence ecosystem dynamics in the Southern Ocean through Antarctic krill transport and the export of nutrients.

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5

LEAT, P. T., R. A. LIVERMORE, I. L. MILLAR, and J. A. PEARCE. "Magma Supply in Back-arc Spreading Centre Segment E2, East Scotia Ridge." Journal of Petrology 41, no. 6 (June 1, 2000): 845–66. http://dx.doi.org/10.1093/petrology/41.6.845.

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6

German, C. R., R. A. Livermore, E. T. Baker, N. I. Bruguier, D. P. Connelly, A. P. Cunningham, P. Morris, I. P. Rouse, P. J. Statham, and P. A. Tyler. "Hydrothermal plumes above the East Scotia Ridge: an isolated high-latitude back-arc spreading centre." Earth and Planetary Science Letters 184, no. 1 (December 2000): 241–50. http://dx.doi.org/10.1016/s0012-821x(00)00319-8.

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7

Wilson, Rory P., Boris M. Culik, Piotr Kosiorek, and Dieter Adelung. "The over-winter movements of a chinstrap penguin (Pygoscelis antarctica)." Polar Record 34, no. 189 (April 1998): 107–12. http://dx.doi.org/10.1017/s0032247400015242.

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AbstractA single chinstrap penguin (Pygoscelis antarctica), which had moulted at the South Shetland Islands, was subsequently tracked during 120 days at sea in the austral winter using a global location system (geolocation) based on light intensity. The bird moved east along the Scotia Ridge to a point approximately 300 km west of the South Sandwich Islands and approximately 1600 km away from the colony in which it had moulted. It spent more than 60% of its time in open water north of the edge of the pack ice.

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8

Linse, Katrin, Verity Nye, Jonathan T. Copley, and Chong Chen. "On the systematics and ecology of two new species of Provanna (Gastropoda: Provannidae) from deep-sea hydrothermal vents in the Caribbean Sea and Southern Ocean." Journal of Molluscan Studies 85, no. 4 (October 16, 2019): 426–39. http://dx.doi.org/10.1093/mollus/eyz024.

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ABSTRACT The recent discovery and exploration of deep-sea hydrothermal vent fields in the Mid-Cayman Spreading Centre, Caribbean Sea (Beebe Vent Field, 4956–4972 m depth) and the East Scotia Ridge, Southern Ocean (E2 and E9 vent fields, 2394–2641 m depth) have yielded extensive collections of two new provannid species, Provanna beebei n. sp. and P. cooki n. sp. Morphological and molecular taxonomy (530 bp of the mitochondrial cytochrome c oxidase subunit I gene) confirm P. beebei n. sp. and P. cooki n. sp. as distinct species; these species are formally described, and details are provided of their distribution, habitat and species associations. Bayesian and maximum likelihood analyses support the placement of P. beebei n. sp. and P. cooki n. sp within the genus Provanna and show that these two new deep-sea species form a well-supported clade with the abyssal West Pacific P. cingulata. Provanna beebei n. sp. and P. cooki n. sp. represent the first records of Provanna from hydrothermal vents in the Caribbean Sea and Southern Ocean, respectively, and extend the known geographic range of the genus. For the first time, intraspecific phenotypic variation in size and sculpture has been reported for Provanna. At the East Scotia Ridge, shell-size frequency distributions and median shell size of P. cooki n. sp. varied significantly between the E2 and E9 vent fields, as well as between diffuse flow and high-temperature venting habitats within each field. The variation in shell sculpture in relation to habitat was also observed in P. cooki n. sp.

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9

Millard, Andrew D., Ian Hands-Portman, and Katrin Zwirglmaier. "Morphotypes of virus-like particles in two hydrothermal vent fields on the East Scotia Ridge, Antarctica." Bacteriophage 4, no. 3 (April 2, 2014): e28732. http://dx.doi.org/10.4161/bact.28732.

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10

Bruguier, N. J., and R. A. Livermore. "Enhanced magma supply at the southern East Scotia Ridge: evidence for mantle flow around the subducting slab?" Earth and Planetary Science Letters 191, no. 1-2 (August 2001): 129–44. http://dx.doi.org/10.1016/s0012-821x(01)00408-3.

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11

Nicholson, B., and J. Georgen. "Controls on crustal accretion along the back-arc East Scotia Ridge: constraints from bathymetry and gravity data." Marine Geophysical Research 34, no. 1 (March 2013): 45–58. http://dx.doi.org/10.1007/s11001-013-9172-x.

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12

Reid, William D. K., Christopher J. Sweeting, Ben D. Wigham, Katrin Zwirglmaier, Jeffrey A. Hawkes, Rona A. R. McGill, Katrin Linse, and Nicholas V. C. Polunin. "Spatial Differences in East Scotia Ridge Hydrothermal Vent Food Webs: Influences of Chemistry, Microbiology and Predation on Trophodynamics." PLoS ONE 8, no. 6 (June 7, 2013): e65553. http://dx.doi.org/10.1371/journal.pone.0065553.

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13

Harrison, D., P. T. Leat, P. G. Burnard, G. Turner, S. Fretzdorff, and I. L. Millar. "Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands." Geological Society, London, Special Publications 219, no. 1 (2003): 333–44. http://dx.doi.org/10.1144/gsl.sp.2003.219.01.16.

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14

James, Rachael H., Darryl R. H. Green, Michael J. Stock, Belinda J. Alker, Neil R. Banerjee, Catherine Cole, Christopher R. German, Veerle A. I. Huvenne, Alexandra M. Powell, and Douglas P. Connelly. "Composition of hydrothermal fluids and mineralogy of associated chimney material on the East Scotia Ridge back-arc spreading centre." Geochimica et Cosmochimica Acta 139 (August 2014): 47–71. http://dx.doi.org/10.1016/j.gca.2014.04.024.

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15

Thatje, Sven, Leigh Marsh, Christopher Nicolai Roterman, Mark N. Mavrogordato, and Katrin Linse. "Adaptations to Hydrothermal Vent Life in Kiwa tyleri, a New Species of Yeti Crab from the East Scotia Ridge, Antarctica." PLOS ONE 10, no. 6 (June 24, 2015): e0127621. http://dx.doi.org/10.1371/journal.pone.0127621.

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16

Reid, WDK, CJ Sweeting, BD Wigham, RAR McGill, and NVC Polunin. "Isotopic niche variability in macroconsumers of the East Scotia Ridge (Southern Ocean) hydrothermal vents: What more can we learn from an ellipse?" Marine Ecology Progress Series 542 (January 19, 2016): 13–24. http://dx.doi.org/10.3354/meps11571.

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17

Djurhuus, Anni, Svein-Ole Mikalsen, Helge-Ansgar Giebel, and Alex D. Rogers. "Cutting through the smoke: the diversity of microorganisms in deep-sea hydrothermal plumes." Royal Society Open Science 4, no. 4 (April 2017): 160829. http://dx.doi.org/10.1098/rsos.160829.

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There are still notable gaps regarding the detailed distribution of microorganisms between and within insular habitats such as deep-sea hydrothermal vents. This study investigates the community composition of black smoker vent microorganisms in the Southern Hemisphere, and changes thereof along a spatial and chemical gradient ranging from the vent plume to surrounding waters. We sampled two hydrothermal vent fields, one at the South West Indian Ridge (SWIR), the other at the East Scotia Ridge (ESR). Samples were collected across vent fields at varying vertical distances from the origin of the plumes. The microbial data were sequenced on an Illumina MiSeq platform for the 16SrRNA gene. A substantial amount of vent-specific putative chemosynthetic microorganisms were found, particularly in samples from focused hydrothermal venting. Common vent-specific organisms from both vent fields were the genera Arcobacter , Caminibacter and Sulfurimonas from the Epsilonproteobacteria and the SUP05 group from the Gammaproteobacteria. There were no major differences in microbial composition between SWIR and ESR for focused plume samples. However, within the ESR the diffuse flow and focused samples differed significantly in microbial community composition and relative abundance. For Epsilonproteobacteria, we found evidence of niche-specificity to hydrothermal vent environments. This taxon decreased in abundance by three orders of magnitude from the vent orifice to background water. Epsilonproteobacteria distribution followed a distance–decay relationship as vent-effluents mixed with the surrounding seawater. This study demonstrates strong habitat affinity of vent microorganisms on a metre scale with distinct environmental selection.

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18

Thatje, S., KE Smith, L. Marsh, and PA Tyler. "Evidence for protracted and lecithotrophic larval development in the yeti crab Kiwa tyleri from hydrothermal vents of the East Scotia Ridge, Southern Ocean." Sexuality and Early Development in Aquatic Organisms 1, no. 2 (April 28, 2015): 109–16. http://dx.doi.org/10.3354/sedao00011.

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19

Zwirglmaier, Katrin, William D. K. Reid, Jane Heywood, Christopher J. Sweeting, Benjamin D. Wigham, Nicholas V. C. Polunin, Jeff A. Hawkes, Douglas P. Connelly, David Pearce, and Katrin Linse. "Linking regional variation of epibiotic bacterial diversity and trophic ecology in a new species of Kiwaidae (Decapoda, Anomura) from East Scotia Ridge (Antarctica) hydrothermal vents." MicrobiologyOpen 4, no. 1 (December 16, 2014): 136–50. http://dx.doi.org/10.1002/mbo3.227.

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20

Linse, Katrin, Jonathan T. Copley, Douglas P. Connelly, Robert D. Larter, David A. Pearce, Nick V. C. Polunin, Alex D. Rogers, et al. "Fauna of the Kemp Caldera and its upper bathyal hydrothermal vents (South Sandwich Arc, Antarctica)." Royal Society Open Science 6, no. 11 (November 2019): 191501. http://dx.doi.org/10.1098/rsos.191501.

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Faunal assemblages at hydrothermal vents associated with island-arc volcanism are less well known than those at vents on mid-ocean ridges and back-arc spreading centres. This study characterizes chemosynthetic biotopes at active hydrothermal vents discovered at the Kemp Caldera in the South Sandwich Arc. The caldera hosts sulfur and anhydrite vent chimneys in 1375–1487 m depth, which emit sulfide-rich fluids with temperatures up to 212°C, and the microbial community of water samples in the buoyant plume rising from the vents was dominated by sulfur-oxidizing Gammaproteobacteria. A total of 12 macro- and megafaunal taxa depending on hydrothermal activity were collected in these biotopes, of which seven species were known from the East Scotia Ridge (ESR) vents and three species from vents outside the Southern Ocean. Faunal assemblages were dominated by large vesicomyid clams, actinostolid anemones, Sericosura sea spiders and lepetodrilid and cocculinid limpets, but several taxa abundant at nearby ESR hydrothermal vents were rare such as the stalked barnacle Neolepas scotiaensis . Multivariate analysis of fauna at Kemp Caldera and vents in neighbouring areas indicated that the Kemp Caldera is most similar to vent fields in the previously established Southern Ocean vent biogeographic province, showing that the species composition at island-arc hydrothermal vents can be distinct from nearby seafloor-spreading systems. δ 13 C and δ 15 N isotope values of megafaunal species analysed from the Kemp Caldera were similar to those of the same or related species at other vent fields, but none of the fauna sampled at Kemp Caldera had δ 13 C values, indicating nutritional dependence on Epsilonproteobacteria, unlike fauna at other island-arc hydrothermal vents.

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21

Leat, Philip T., Peter T. Fretwell, Alex J. Tate, Robert D. Larter, Tara J. Martin, John L. Smellie, Wilfried Jokat, and Gerhard Bohrmann. "Bathymetry and geological setting of the South Sandwich Islands volcanic arc." Antarctic Science 28, no. 4 (March 18, 2016): 293–303. http://dx.doi.org/10.1017/s0954102016000043.

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AbstractThe South Sandwich Islands and associated seamounts constitute the volcanic arc of an active subduction system situated in the South Atlantic. We introduce a map of the bathymetry and geological setting of the South Sandwich Islands and the associated East Scotia Ridge back-arc spreading centre that consists of two sides: side 1, a regional overview of the volcanic arc, trench and back-arc, and side 2, detailed maps of the individual islands. Side 1 displays the bathymetry at scale 1:750 000 of the intra-oceanic, largely submarine South Sandwich arc, the back-arc system and other tectonic boundaries of the subduction system. Satellite images of the islands on side 2 are at scales of 1:50 000 and 1:25 000 with contours and main volcanological features indicated. These maps are the first detailed topological and bathymetric maps of the area. The islands are entirely volcanic in origin, and most have been volcanically or fumarolically active in historic times. Many of the islands are ice-covered, and the map forms a baseline for future glaciological changes caused by volcanic activities and climate change. The back-arc spreading centre consists of nine segments, most of which have rift-like morphologies.

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22

MAGALHÃES, WAGNER F., KATRIN LINSE, and HELENA WIKLUND. "A new species of Raricirrus (Annelida: Cirratuliformia) from deep-water sunken wood off California." Zootaxa 4353, no. 1 (November 22, 2017): 51. http://dx.doi.org/10.11646/zootaxa.4353.1.3.

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The genus Raricirrus is characterized by the absence of feeding palps, presence of filamentous branchiae, posterior segments shorter and wider than preceding ones, and by having diverse types of chaetae, including serrate capillaries, long natatory capillaries, falcate and finely pectinate, coarsely serrate chaetae and simple curved spines. A new species of Raricirrus is proposed based on morphological and mitochondrial DNA data. The K2P distance comparison of 16S and COI sequences from Raricirrus specimens collected from sunken wood in the deep-sea (3100 m) off Monterey, California, differed in less than 0.02 in both loci from those of another undescribed Raricirrus species collected at deep-sea hydrothermal vents in the East Scotia Ridge, Southern Ocean, and they are considered conspecific. This species is unique among its congeners by the lack of serrate chaetae, presence of acicular spines and neuropodial capillaries. Raricirrus jennae sp. nov. has only long capillaries on anterior notopodia, straight acicular spines with companion capillaries on posterior notopodia (from chaetigers 15–20), and similar acicular spines and companion capillaries throughout neuropodia. Raricirrus jennae sp. nov. appears to be an opportunistic and widely distributed species. The genus Raricirrus is emended to include the presence of acicular spines and keys to all cirratulid and ctenodrilid genera and Raricirrus species are presented.

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23

McTaggart-Cowan, Ron, Eyad H. Atallah, John R. Gyakum, and Lance F. Bosart. "Hurricane Juan (2003). Part I: A Diagnostic and Compositing Life Cycle Study." Monthly Weather Review 134, no. 7 (July 1, 2006): 1725–47. http://dx.doi.org/10.1175/mwr3142.1.

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Abstract A detailed analysis of the complex life cycle of Hurricane Juan (in 2003) is undertaken to elucidate the structures and forcings that prevailed over the period leading up to the hurricane’s landfall in Halifax, Nova Scotia, Canada. Despite the presence of easterly wave precursors, Hurricane Juan’s initial development is shown to occur in a baroclinic environment beneath a low-latitude potential vorticity streamer. This feature interacts with a lower-level shear line as the incipient vortex begins to effectively focus ascent and convection. The system undergoes a slow tropical transition over a period of several days as the deep-layer shear over the developing storm decreases. The hurricane is repeatedly perturbed by subsynoptic-scale waves traveling along the leading edge of a large upstream trough. However, Hurricane Juan maintains its tropical structure despite its relatively high formation latitude (28°N) and its northward trajectory. The unusual persistence of the storm’s tropical nature as it propagates northward is of primary interest in this study. In particular, the role of persistent ridging along the east coast of North America is investigated both in high-resolution analyses for Hurricane Juan and in a compositing framework. Dynamic tropopause, quasigeostrophic, and modified Eady model diagnostics are used to elucidate the interactions between Hurricane Juan and this amplified midlatitude flow. Given the strength and persistence of the anomalous ridge–trough couplet both in the case diagnosis and in the composite fields, the study concludes that the presence of prestorm, high-amplitude ridging along the east coast likely reinforced by diabatic ridging downshear of the storm itself produces an environment both dynamically and thermodynamically conducive to the high-latitude landfall of hurricanes still in the tropical phase.

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24

Jutras, Pierre, J. Brendan Murphy, Dennis Quick, and Jaroslav Dostal. "Evolution of Subduction Dynamics beneath West Avalonia in Middle to Late Ordovician Times." Lithosphere 2020, no. 1 (September 23, 2020): 1–22. http://dx.doi.org/10.2113/2020/8837633.

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Abstract Middle to Upper Ordovician volcanic rocks in the Arisaig area of Nova Scotia, Canada, constitute the only known record of volcanism in West Avalonia during that interval. Hence, they have been extensively studied to test paleocontinental reconstructions that consistently show Avalonia as a drifting microcontinent during that period. Identification of volcanic rocks with an intermediate composition (the new Seaspray Cove Formation) between upper Darriwilian bimodal volcanic rocks of the Dunn Point Formation and Sandbian felsic pyroclastic rocks of the McGillivray Brook Formation has led to a reevaluation of magmatic relationships in the Ordovician volcanic suite at Arisaig. Although part of the same volcanic construction, the three formations are separated by significant time-gaps and are shown to belong to three distinct magmatic subsystems. The tectonostratigraphic context and trace element contents of the Dunn Point Formation basalts suggest that they were produced by the high-degree partial melting of an E-MORB type source in a back-arc extensional setting, whereas trace element contents in intermediate rocks of the Seaspray Cove Formation suggest that they were produced by the low-degree partial melting of a subduction-enriched source in an arc setting. The two formations are separated by a long interval of volcanic quiescence and deep weathering, during which time the back-arc region evolved from extension to shortening and was eventually onlapped by arc volcanic rocks. Based on limited field constraints, paleomagnetic and paleontological data, this progradation of arc onto back-arc volcanic rocks occurred from the north, where an increasingly young Iapetan oceanic plate was being subducted at an increasingly shallow angle. Partial subduction of the Iapetan oceanic ridge is thought to have subsequently generated slab window magmatism, thus marking the last pulse of subduction-related volcanism in both East and West Avalonia.

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25

McClenaghan, M. B., and R. N. W. DiLabio. "Ice-flow history and glacial dispersal patterns, southeastern Cape Breton Island, Nova Scotia: implications for mineral exploration." Canadian Journal of Earth Sciences 33, no. 2 (February 1, 1996): 351–62. http://dx.doi.org/10.1139/e96-026.

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Regional till sampling and stratigraphic studies were completed in southeastern Cape Breton Island, Nova Scotia, in 1990 and 1991 to document the directions and distances that successive ice-flow events have dispersed material and to document regional till geochemical patterns to aid mineral exploration in this heavily drift-covered area. Three major Wisconsinan ice-flow events affected the area: an early eastward flow, followed by a northeastward flow, and finally a southward flow. The shape and magnitude of dispersal trains in the area are the net result of the three ice-flow events, which are variable from north to south. In the north, the northeast ice flow was the dominant erosive and depositional event, producing a large northeast-trending drumlin field. Salmon River porphyry clasts and Pb- and Zn-rich till from the Yava Pb mine were dispersed more than 15 km to the northeast. In the south, eastward ice flow was the dominant erosive and depositional event, producing large east-trending till ridges. Dispersal in this area is difficult to detect because exotic red silty till in the giant till ridges masks underlying mineralized bedrock and dilutes the locally derived glacial debris. Many precious and base metal anomalies and dispersal trains were identified in the regional till samples, several of which are related to unknown mineralized sources.

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26

Druitt, T. H., R. A. Mellors, D. M. Pyle, and R. S. J. Sparks. "Explosive volcanism on Santorini, Greece." Geological Magazine 126, no. 2 (March 1989): 95–126. http://dx.doi.org/10.1017/s0016756800006270.

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AbstrctSantorini volcanic field has had 12 major (1–10 km3 or more of magma), and numerous minor, explosive eruptions over the last ~ 200 ka. Deposits from these eruptions (Thera Pyroclastic Formation) are well exposed in caldera-wall successions up to 200 m thick. Each of the major eruptions began with a pumice-fall phase, and most culminated with emplacement of pyroclastic flows. Pyroclastic flows of at least six eruptions deposited proximal lag deposits exposed widely in the caldera wall. The lag deposits include coarse-grained lithic breccias (andesitic to rhyodacitic eruptions) and spatter agglomerates (andesitic eruptions only). Facies associations between lithic breccia, spatter agglomerate, and ignimbrite from the same eruption can be very complex. For some eruptions, lag deposits provide the only evidence for pyroclastic flows, because most of the ignimbrite is buried on the lower flanks of Santorini or under the sea. At least eight eruptions tapped compositionally heterogeneous magma chambers, producing deposits with a range of zoning patterns and compositional gaps. Three eruptions display a silicic–silicic + mafic–silicic zoning not previously reported. Four eruptions vented large volumes of dacitic or rhyodacitic pumice, and may account for 90% or more of all silicic magma discharged from Santorini. The Thera Pyroclastic Formation and coeval lavas record two major mafic-to-silicic cycles of Santorini volcanism. Each cycle commenced with explosive eruptions of andesite or dacite, accompanied by construction of composite shields and stratocones, and culminated in a pair of major dacitic or rhyodacitic eruptions. Sequences of scoria and ash deposits occur between most of the twelve major members and record repeated stratocone or shield construction following a large explosive eruption.Volcanism at Santorini has focussed on a deep NE–SW basement fracture, which has acted as a pathway for magma ascent. At least four major explosive eruptions began at a vent complex on this fracture. Composite volcanoes constructed north of the fracture were dissected by at least three caldera-collapse events associated with the pyroclastic eruptions. Southern Santorini consists of pryoclastic ejecta draped over a pre-volcanic island and a ridge of early- to mid-Pleistocene volcanics. The southern half of the present-day caldera basin is a long-lived, essentially non-volcanic, depression, defined by topographic highs to the south and east, but deepened by subsidence associated with the main northern caldera complex, and is probably not a separate caldera.

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27

Lenat, Jean-Francois, Patrick Bachelery, and Frederic Desmulier. "Genese du champ de lave de l'Enclos Fouque; une eruption d'envergure exceptionnelle du Piton de la Fournaise (Reunion) au 18 e siecle." Bulletin de la Société Géologique de France 172, no. 2 (March 1, 2001): 177–88. http://dx.doi.org/10.2113/172.2.177.

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Abstract A large lava flow field, essentially constituted of "pahoehoe" flows, forms a relatively monotonous area on the north-west flank of the terminal cone of Piton de la Fournaise and on a large part of the Enclos floor. We named this unit "champ de lave de l'Enclos Fouque" (CLEF). To the east, more recent lava flows almost completely cover the CLEF. Mapping of the CLEF has been attempted using satellite imagery. Radar (SIR-C) and SPOT images have been used. Both types of images lead to comparable results for the surface of the CLEF, estimated to 11 km 2 . On satellite images, only a general map of the facies of the CLEF can be done. Air photos and ground observations allow to characterize more precisely the facies defined from satellite images. On the slopes of the Central Cone, the surface of the CLEF is mostly composed of tumuli that may produce small lava flows at their downhill base. On the floor of the Enclos, the CLEF is constantly formed by a multitude of intricate small flows. Except for small "aa" patches, surfaces are "pahoehoe". Tumuli, pressure ridges and collapsed plates are common features of the CLEF. Near the NW border of Enclos, the surface becomes less regular, with a higher proportion of "aa" patches and tilted slabs. This is probably due to the increase of slope in this area. In the vicinity of Bory crater contemporaneous welded scoria cover a zone extending 150-200 m from the crater. Several elements, found in various historical documents collected by Lacroix [1936 and 1938], bring evidence that the CLEF may result from a succession of events between the years 1750's to the 1790's. During this period, the volcano has been virtually continuously in eruption. Bory crater was the only active crater until 1766, when a new summit crater was formed by collapse, 400 m east of Bory crater. In the following years, this 1766 crater was filled by lava emissions which erected a gigantic tumulus, 50 m high, called Mamelon central. Several large lava flows, some of them reaching the sea, are unambiguously described as emitted from the summit craters. One of the main event appears to be the phase that occurred in 1753 (or 1759 according to different authors). This phase was associated to felt earthquakes and widespread ash-falls in the island. Lava flows covered most the western part of Enclos and reached the sea to the east. Whereas the activity of 1753 (1759 ?) appears as paroxysmal, extensive lava flows are described until 1794. In 1791, a new crater formed south of the 1766 crater. In 1801, Bory de St-Vincent [1804] observed an active lava lake inside this 1791 crater. In summary, it appears that quasi-continuous activity took place during the second half of the 18th century at Piton de la Fournaise, with lava flows covering almost all the Enclos and Grand Brule areas. It is obvious that the presently outcropping surface of the CLEF is only a fraction of its former extension. From the above-mentioned historic descriptions, it is reasonable to assume the CLEF may have recovered the entire surface of the Enclos Fouque and the Grand Brule depression. The surface extension of the CLEF would thus lie between 11 km 2 , its presently observed area, to ca. 90 km 2 . The compounded thickness of the CLEF has not been directly observed. In the rim of Dolomieu crater, a series of lava flows thought to represent the CLEF is about 25 m thick, but this thickness is that of the shield built around the vents and not that of the lava field. Using statistical laws for strombolian cones morphometry from Wood [1980], the thickness of the CLEF may be approached considering the crater diameter of 3 cones located in the north-western part of Enclos and partially flooded by the CLEF. We obtain estimates of 5 to 15 m. If Enclos has been entirely covered by the CLEF and for a mean thickness of 5 to 10 m, then the volume of the CLEF eruption is 450 to 900X10 6 m 3 . Mineralogical and chemical compositions of the CLEF lavas are similar to those of the transitional olivine basalts of the historic period [steady-state basalts, Albarede et al, 1997]. The chemical compositions vary somewhat due to variable modal olivine phenocrysts abundances and are characteristic of a rapid transfer of magma from deep reservoirs with virtually no low-pressure evolution. Major changes of the summit craters were associated to this eruption as a result of the unusually prolonged magmatic activity at Piton de la Fournaise during decades. The occurrence of similar phases at Piton de la Fournaise in the future can be appraised with reference to Kilauea. Holcomb [1987] reports 7 long-lived eruptions at Kilauea in the last 3 centuries. Thus, although not frequent, this type of event is not uncommon for Kilauea. By analogy, it must be considered as probable that Piton de la Fournaise will experience new long-lived eruptions in the future.

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Reid, W. D. K., B. D. Wigham, L. Marsh, J. N. J. Weston, Y. Zhu, and J. T. Copley. "Trophodynamics at the Longqi hydrothermal vent field and comparison with the East Scotia and Central Indian Ridges." Marine Biology 167, no. 10 (September 3, 2020). http://dx.doi.org/10.1007/s00227-020-03755-1.

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Abstract The Longqi vent field, situated on the Southwest Indian Ridge, is ecologically distinct among known hydrothermal vents fields. It hosts a combination of previously unknown species and those shared at species or genus level with other hydrothermal vents on the Central Indian Ridge (CIR) and East Scotia Ridge (ESR). We investigate the size-based and trophodynamics of consumers at Longqi vent field and compared these with ESR and CIR vent fields using stable isotope analysis. Intra-specific variability in δ13C and δ15N values in relationship to shell length was observed in Gigantopelta aegis but absent in Chrysomallon squamiferum. A model-based clustering approach identified four trophic groupings at Longqi: species with the lowest δ13C values being supported by carbon fixed via the Calvin–Benson–Bassham cycle, the highest δ13C values being supported by the reductive tricarboxylic acid cycle and intermediate values potentially supported by a mix of these primary production sources. These clusters were driven by potential differences in resource partitioning. There were also differences in the spread of stable isotope values at the vent field level when comparing Bayesian stable isotope ellipse areas among Longqi, CIR and ESR vent fields. This was driven by a combination of the range in δ13C value of macrofauna, and the negative δ15N values which were only observed at Longqi and CIR vent fields. Many of the shared species or genera showed inter-vent field differences in stable isotope values which may be related to site-specific differences in food sources, geochemistry or potential intra-field competition. This study provides important information on the trophic ecology of hydrothermal vent macrofauna found within an area of seabed that is licensed for seabed mining exploration.

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29

Occhietti, Serge. "The Saint-Narcisse morainic complex and early Younger Dryas events on the southeastern margin of the Laurentide Ice Sheet." 61, no. 2-3 (February 3, 2010): 89–117. http://dx.doi.org/10.7202/038987ar.

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Abstract The Saint-Narcisse morainic complex extends over 750 km along the southern margin of the Laurentian Highlands in Québec, north of the St. Lawrence Valley, between the Ottawa and Saguenay Rivers. To the east, the Laurentide Ice Sheet margin was located in the present St. Lawrence Estuary. To the west, the morainic complex is extended 235 km west of the Ottawa River to the Algonquin Highlands, in Ontario. The general outline of the morainic complex comprises large lobes and reentrants, related to major topographic features. In the lower Saint-Maurice River area, the moraine is composed of reworked clay and till and proximal glaciomarine deposits (Yamachiche Diamicton) and melt-out till and ice-marginal outwash (Charette Drift). The Saint-Narcisse Event can be subdivided in several phases: local readvance in low areas, main phase at the origin of the Saint-Narcisse Moraine s.s., melting-out of the marginal ice with compressive structures and large proglacial outwash features, and slow retreat with secondary ridges. The accuracy of the chronological data is limited by several factors: and a floating chronology is proposed. Two landmarks constrain the age and range of duration of the main Saint-Narcisse phase. The main ridge deposition occured after the onset, ca. 12.9 cal ka, of Champlain Sea in the St. Lawrence Valley, and a rapid ice retreat on the southern edge of the Laurentians. It ended before the drawdowm, in the Lake Huron basin, of Glacial Lake Algonquin ca. 12.5 cal ka. The Saint-Narcisse Event is related to the early cold phase of Younger Dryas, as evidenced by other YD ice readvances in Maine, Nova Scotia, and ice cover on the Gaspé Peninsula. It corresponds to a positive change of the budget of the Laurentide Ice Sheet as a result of climate forcing. After a slow ice front retreat during about 900-700 yr, the final phase of YD is marked by the Mars-Batiscan Moraine, located 17 to 70 km north of the Saint-Narcisse Moraine.

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