1,721,025 research outputs found
Evidences of carbonate preservation on the outer continental slope in the Western Ross Sea (Hallett Ridge and Central Basin, Antarctica)
No full textLate Quaternary Antarctic Ice Sheet (AIS) changes can be investigated by analyzing marine sediments (gravity and box cores) collected on the continental shelves and along the continental margins of Antarctica. These sites are strongly influenced by the ice sheet/shelf sediment drainage and inflow/outflow of polar water masses. In this respect, the continental slope of the Western Ross Sea (WRS) is still poorly studied, in particular its history is affected by uncertainties due to the scarcity of well-preserved calcareous foraminifera preventing the production of reliable age models.
We present the results of a study made on one gravity core (KI13-C2; Melis et al., 2021) and three box-cores (KI13-bc2, bc3 and bc4; Torricella et al., 2021) located on the Hallett Ridge and in the Central Basin where the presence of carbonate-rich intervals offers the opportunity, to time-reconstruct the AIS evolving changes since the Marine Isotopic Stage (MIS) 2. These intervals correlated with other carbonate layers identified in cores collected along the WRS continental slope provide important insights about a large-scale break-up of the ice shelf/sea ice system.
This study has been conducted in the framework of the STREAM Project (Late Quaternary evolution of the ocean-ice sheet interactions: the record from the Ross Sea continental margin, Antarctica; period 2019-2021), funded by the Italian Ministry of Foreign Affairs and International Cooperation and the National Research Foundation of Korea, and thanks to a grant approved by the Department of Mathematics and Geoscience, University of Trieste.
Bibliographic references
Melis R., Capotondi L., Torricella F., Ferretti P., Geniram A., Hong J.K., Kuhn G., Khim B.-K., Kim S., Malinverno E., Yoo K.C. and Colizza E. (2021) - Last Glacial Maximum to Holocene: paleoceanography of the northwestern Ross Sea inferred from sediment core geochemistry and micropaleontology at Hallett Ridge. J. of Micropal., 40, 15-35.
Torricella F., Melis R., Malinverno E., Fontolan G., Bussi M., Capotondi L., Del Carlo P., Di Roberto A., Geniram A., Kuhn G., Khim B.-K., Morigi C., Scateni B. and Colizza E. (2021) – Environmental and Oceanographic Conditions at the Continental Margin of the Central Basin, Northwestern Ross Sea (Antarctica) Since the Last Glacial Maximum. Geosciences, 11, 155
Geomorphological characterization of the coastal and marine area between primera and segunda angostura, Strait of Magellan (Chile)
No full textA detailed geomorphological study of the Chilean coastal area of the Strait of Magellan aimed at the determination and description of different coastal environments and related processes. The survey data have been compiled in a map that outlines the influence of glacial history in the coastal landscape development. Sea-bed characteristics such as bathymetry and sedimentology, together with information on tides, direction and magnitude of currents are also presented in the map. A subdivision of the coastal area was carried out dividing the coastline into 40 homogeneous segments, each described by 15 representative morphological and physical variables. By means of multivariate analyses of the data matrix six coastal groups subdivision was obtained. Groups were reviewed and re-interpreted in order to highlight relationships between coastal landforms and variables. Three factors fully describe the main coastal types and constraints. First factor groups the inherited coastal landforms, that..
Multidisciplinary analysis of three box cores collected east to the Hillary Canyon (Eastern Ross Sea, Antarctica)
No full textThe LGM and post-LGM history of the Antarctic Ice Sheet (AIS) can be reconstructed by studying cores and box cores collected along the continental slope of Antarctica. According to several authors (Shipp et al., 1999; Mosola & Anderson, 2006; Halberstadt et al., 2016; Anderson et al., 2018; Gales et al., 2021) the Western Antarctic Ice Sheet (WAIS) was grounded near the shelf break in many sectors of the Eastern Ross Sea (ERS) during the Last Glacial Maximum (LGM). However, the post-LGM retreat is characterized by lacks and uncertainties.
Three box cores were collected east of the Hillary Canyon, which carves the ERS continental slope south-east to the Iselin Bank, during the XXIX PNRA (Italian National Antarctic Research Program) expedition (2013-2014). The samples were studied in the frame of the ROSSLOPE II (2013/AN2.01) PNRA project and then in the frame of the STREAM Project (Late Quaternary evolution of the ocean-ice sheet interactions: the record from the Ross Sea continental margin, Antarctica (project funded by the Italian Ministry of Foreign Affairs and International Cooperation and the National Research Foundation of Korea). Grain size, organic matter, biogenic silica and water content, magnetic susceptibility and chemical composition (XRF core scanner) were analyzed in order to reconstruct the paleoclimate of Late Quaternary. Organic matter (14C AIO dates) was used to date each box core. The results of these analyses are presented here.
References
Anderson J.B., Simkins L.M., Bart P.J., De Santis L., Halberstadt A.R.W., Olivo E. & Greenwood S.L. 2018. Seismic and geomorphic records of Antarctic Ice Sheet evolution in the Ross Sea and controlling factors in its behaviour. In: Le Heron, D.P., Hogan, K.A., Phillips, E.R., Huuse, M., Busfield, M.E. & Graham, A.G.C. Eds., Glaciated Margins: The Sedimentary and Geophysical Archive. Geological Society, London, Special Publications, 475, 223-240.
Gales J., Rebesco M., De Santis L., Bergamasco A., Colleoni F., Kim S., Accettella D., Kovacevic V., Liu Y., Olivo E., Colizza E., Florindo-Lopez C., Zgur F. & McKay R. 2021. Role of dense shelf water in the development of Antarctic submarine canyon morphology. Geomorphology, 372, 107453.
Halberstadt A.R.W., Simkins L.M., Greenwood S.L. & Anderson J.B. 2016. Past ice-sheet behaviour: retreat scenarios and changing controls in the Ross Sea, Antarctica. The Cryosphere, 10, 1003-1020.
Mosola A.B. & Anderson J.B. 2006. Expansion and rapid retreat of the West Antarctic Ice Sheet in Eastern Ross Sea: possible consequence of over-extended ice stream. Quat. Sci. Rev., 29, 2177-2196.
Shipp S., Anderson J.B. & Domack E.W. 1999. Late Pleistocene/Holocene retreat of the West Antarctic ice-sheet system in the Ross Sea. Part 1. Geophysical results. GSA Bulletin, 111, 1486–1516
Geomorphic setting and geohazard-related features along the Ionian Calabrian margin between Capo Spartivento and Capo Rizzuto (Italy)
No full textThe aim of this work is to describe the morpho-dynamic processes of coastal and submarine areas based on morpho-bathymetric data and sub-bottom acoustic profiles from the Calabrian Ionian margin (from Capo Spartivento to Capo Rizzuto). We describe some of the most significant geo-hazard features and show some examples of their complex interactions and related potential risk. The relationship between these geo-hazard features and the active tectonics and some severe historical earthquakes and tsunamis is also discussed. The studied area is characterized by several well developed canyon systems. The retrogressive erosion of the canyon heads affects the continental shelf and interacts with the coastal morpho-sedimentary processes, evidencing the intense geomorphic activity of this sector of Ionian margin. The widespread evidence of mass wasting processes and slope instability, together with the historical seismicity, makes this area also an ideal case study for investigating on the possible relationship between earthquakes and landslide-triggered tsunamis and assessing the potential risk. © 2011 Springer Science+Business Media B.V
The Pacific entrance of the Magellan Strait: Preliminary Result of a seismic and sampling survey
No full textDuring Spring 1995, in the frame of the Italian Programma Nazionale di Ricerche in Antartide (PNRA) 290 km of intermediate-resolution multichannel reflection profiles have been acquired in the Pacific entrance of the Magellan Strait with the RN OGS Explora.
The survey was carried out with two principal aims: a) to verify the occurrence and effects of the Magellan Fault along the western part of the South America-Scotia plate boundary, and b) to investigate the sedimentary architecture of the sequences of this sector of the Strait, with particular interest to those concerning the Pleistocene glacial events.
The survey herein described has been carried out in a marine enlargement of the Strait north of Isla Desolaciòn, between Cabo Pilar and Isla Tamar. Seismicenergy was provided by two G.I. Guns of 210 cubic inches each, with shot interval of 25m. The cable was a 48 channels -600 m streamer which furnished a 1200% coverage.
Record length was kept at 8 seconds and sampling interval at 1 ms. Three gravity cores were also collected from the bottom sediments. These data are integrated b a high-resolution seismic line longitudinal to the Strait recorded in 1991 and other three cores collected during different surveys in 1991 and 1995.
This work describes the preliminary results of the survey in terms of both tectonic and palaeoenvironmental frame. Its original aspect consists in documenting for the first time the location and characterization of the Magellan Fault along the westernmost arm of the Strait.
This result fills the gap with the central-eastern tract of the fault for which a number of works have been issued in the last years. Another aspect concerns the sedimentological data from core analyses that constrain the environmental evolution of the Pacific mouth of the Strait about the last 21 000 years
LGM – Holocene sedimentary dynamics by multidisciplinary analysis of three box cores collected east to the Hillary Canyon (Eastern Ross Sea, Antarctica)
No full textThe presence of different types of glacial and sub-glacial features near the shelf edge indicates that the
Western Antarctic Ice Sheet (WAIS) was grounded near the shelf break in many sectors of the Eastern Ross Sea
(ERS) during the Last Glacial Maximum (LGM) (Shipp et al., 1999; Mosola & Anderson, 2006; Halberstadt et
al., 2016; Anderson et al., 2018; Gales et al., 2021). However, mechanisms and timing of the post-LGM retreat
are still debated. Studying sediments collected along the continental slope could help to reconstruct the LGM
and post-LGM history of the ice sheet.
This study focused on the analysis of three box cores collected east of the Hillary Canyon, which carves the
ERS continental slope and is connected to the Glomar Challenger and Pennell Troughs on the shelf, south-east
to the Iselin Bank. Multidisciplinary analysis (grain size, organic matter, biogenic silica and water content,
magnetic susceptibility and chemical composition (XRF core scanner)) were conducted in order to reconstruct
the sedimentary dynamics. Three samples for each box core were dated by using organic matter (14C AIO
dates). Here, we present the results of these analysis.
These box cores were collected during the XXIX PNRA (National Antarctic Research Program) expedition
(2013-2014) and studied in the frame of the ROSSLOPE II (2013/AN2.01) PNRA project and the STREAM
Project (Late Quaternary evolution of the ocean-ice sheet interactions: the record from the Ross Sea continental
margin, Antarctica; period 2019-2021). The latter is funded by the Italian Ministry of Foreign Affairs and
International Cooperation and the National Research Foundation of Korea.
Anderson J.B., Simkins L.M., Bart P.J., De Santis L., Halberstadt A.R.W., Olivo E. & Greenwood S.L. (2018) - Seismic
and geomorphic records of Antarctic Ice Sheet evolution in the Ross Sea and controlling factors in its behaviour. In:
Le Heron, D.P., Hogan, K.A., Phillips, E.R., Huuse, M., Busfield, M.E. & Graham, A.G.C. Eds., Glaciated Margins:
The Sedimentary and Geophysical Archive. Geological Society, London, Special Publications, 475, 223-240.
Gales J., Rebesco M., De Santis L., Bergamasco A., Colleoni F., Kim S., Accettella D., Kovacevic V., Liu Y., Olivo
E., Colizza E., Florindo-Lopez C., Zgur F. & McKay R. (2021) - Role of dense shelf water in the development of
Antarctic submarine canyon morphology. Geomorphology, 372, 107453.
Halberstadt A.R.W., Simkins L.M., Greenwood S.L. & Anderson J.B. (2016) - Past ice-sheet behaviour: retreat scenarios
and changing controls in the Ross Sea, Antarctica. The Cryosphere, 10, 1003-1020.
Mosola A.B. & Anderson J.B. (2006) - Expansion and rapid retreat of the West Antarctic Ice Sheet in Eastern Ross Sea:
possible consequence of over-extended ice stream. Quat. Sci. Rev., 29, 2177-2196.
Shipp S., Anderson J.B. & Domack E.W. (1999) - Late Pleistocene/Holocene retreat of the West Antarctic ice-sheet
system in the Ross Sea. Part 1. Geophysical results. GSA Bulletin, 111, 1486-1516
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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