A fission track thermochronological study of King George and Livingston islands, South Shetland Islands (West Antarctica)

2004 ◽  
Vol 16 (2) ◽  
pp. 191-197 ◽  
Author(s):  
I. SELL ◽  
G. POUPEAU ◽  
J.M. GONZÁLEZ-CASADO ◽  
J. LÓPEZ-MARTÍNEZ
Keyword(s):  
South Shetland Islands ◽  
West Antarctica ◽  
The South ◽  
North West ◽  
The North ◽  
Early Oligocene ◽  
Barton Peninsula ◽  
Bransfield Basin ◽  
Back Arc ◽  
The Antarctic

This paper reports the dating of apatite fission tracks in eleven rock samples from the South Shetland Archipelago, an island arc located to the north-west of the Antarctic Peninsula. Apatites from Livingston Island were dated as belonging to the Oligocene (25.8 Ma: metasediments, Miers Bluff Formation, Hurd Peninsula) through to the Miocene (18.8 Ma: tonalites, Barnard Point). Those from King George Island were slightly older, belonging to the Early Oligocene (32.5 Ma: granodiorites, Barton Peninsula). Towards the back-arc basin (Bransfield Basin), the apatite appears to be younger. This allows an opening rate of approximately 1.1 km Ma−1 (during the Miocene–Oligocene interval) to be calculated for Bransfield Basin. Optimization of the apatite data suggests cooling to 100 ± 10°C was coeval with the end of the main magmatic event in the South Shetland Arc (Oligocene), and indicates slightly different tectonic-exhumation histories for the different tectonic blocks.

Geotectonic evolution of the Bransfield Basin, Antarctic Peninsula: insights from analogue models

2008 ◽  
Vol 20 (2) ◽  
pp. 185-196 ◽  
Author(s):  
M.A. Solari ◽  
F. Hervé ◽  
J. Martinod ◽  
J.P. Le Roux ◽  
L.E. Ramírez ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
South Shetland Islands ◽  
The South ◽  
The West ◽  
Shetland Islands ◽  
Scotia Ridge ◽  
The North ◽  
Analogue Models ◽  
Bransfield Basin ◽  
The Phoenix

AbstractThe Bransfield Strait, located between the South Shetland Islands and the north-western end of the Antarctic Peninsula, is a back-arc basin transitional between rifting and spreading. We compiled a geomorphological structural map of the Bransfield Basin combining published data and the interpretation of bathymetric images. Several analogue experiments reproducing the interaction between the Scotia, Antarctic, and Phoenix plates were carried out. The fault configuration observed in the geomorphological structural map was well reproduced by one of these analogue models. The results suggest the establishment of a transpressional regime to the west of the southern segment of the Shackleton Fracture Zone and a transtensional regime to the south-west of the South Scotia Ridge by at least c. 7 Ma. A probable mechanism for the opening of the Bransfield Basin requires two processes: 1) Significant transtensional effects in the Bransfield Basin caused by the configuration and drift vector of the Scotia Plate after the activity of the West Scotia Ridge ceased at c. 7 Ma. 2) Roll-back of the Phoenix Plate under the South Shetland Islands after cessation of spreading activity of the Phoenix Ridge at 3.3 ± 0.2 Ma, causing the north-westward migration of the South Shetland Trench.

scholarly journals Geodetic Mass Balance of the South Shetland Islands Ice Caps, Antarctica, from Differencing TanDEM-X DEMs

2021 ◽  
Vol 13 (17) ◽  
pp. 3408
Author(s):  
Kaian Shahateet ◽  
Thorsten Seehaus ◽  
Francisco Navarro ◽  
Christian Sommer ◽  
Matthias Braun
Keyword(s):  
Mass Balance ◽  
South Shetland Islands ◽  
The South ◽  
Mass Balance Calculation ◽  
Shetland Islands ◽  
Ice Caps ◽  
The North ◽  
Data Limitations ◽  
Geodetic Mass Balance ◽  
The Antarctic

Although the glaciers in the Antarctic periphery currently modestly contribute to sea level rise, their contribution is projected to increase substantially until the end of the 21st century. The South Shetland Islands (SSI), located to the north of the Antarctic Peninsula, are lacking a geodetic mass balance calculation for the entire archipelago. We estimated its geodetic mass balance over a 3–4-year period within 2013–2017. Our estimation is based on remotely sensed multispectral and interferometric SAR data covering 96% of the glacierized areas of the islands considered in our study and 73% of the total glacierized area of the SSI archipelago (Elephant, Clarence, and Smith Islands were excluded due to data limitations). Our results show a close to balance, slightly negative average specific mass balance for the whole area of −0.106 ± 0.007 m w.e. a−1, representing a mass change of −238 ± 12 Mt a−1. These results are consistent with a wider scale geodetic mass balance estimation and with glaciological mass balance measurements at SSI locations for the same study period. They are also consistent with the cooling trend observed in the region between 1998 and the mid-2010s.

Chapter 3.1a Antarctic Peninsula and South Shetland Islands: volcanology

2021 ◽  
pp. M55-2018-52
Author(s):  
Philip T. Leat ◽  
Teal R. Riley
Keyword(s):  
Antarctic Peninsula ◽  
Continental Margin ◽  
Volcanic Rocks ◽  
South Shetland Islands ◽  
West Antarctica ◽  
The South ◽  
Shetland Islands ◽  
The North ◽  
Climate Cooling ◽  
Tectonic Features

AbstractThe voluminous continental margin volcanic arc of the Antarctic Peninsula is one of the major tectonic features of West Antarctica. It extends from the Trinity Peninsula and the South Shetland Islands in the north to Alexander Island and Palmer Land in the south, a distance of c. 1300 km, and was related to east-directed subduction beneath the continental margin. Thicknesses of exposed volcanic rocks are up to c. 1.5 km, and the terrain is highly dissected by erosion and heavily glacierized. The arc was active from Late Jurassic or Early Cretaceous times until the Early Miocene, a period of climate cooling from subtropical to glacial. The migration of the volcanic axis was towards the trench over time along most of the length of the arc. Early volcanism was commonly submarine but most of the volcanism was subaerial. Basaltic–andesitic stratocones and large silicic composite volcanoes with calderas can be identified. Other rock associations include volcaniclastic fans, distal tuff accumulations, coastal wetlands and glacio-marine eruptions.Other groups of volcanic rocks of Jurassic age in Alexander Island comprise accreted oceanic basalts within an accretionary complex and volcanic rocks erupted within a rift basin along the continental margin that apparently predate subduction.

Hydrology of the Indian Ocean. I. The Water Masses in Intermediate Depths of the South-East Indian Ocean

1961 ◽  
Vol 12 (2) ◽  
pp. 129 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Indian Ocean ◽  
West Indian ◽  
Water Masses ◽  
The South ◽  
North West ◽  
East Indian ◽  
The North ◽  
The Indian Ocean ◽  
The Antarctic ◽  
East Indian Ocean

Three water masses have been identified from maxima and minima in temperature-salinity diagrams for intermediate depths of the south-east Indian Ocean. (1) The Antarctic Intermediate occurred as a salinity minimum within the density range of 7.00-27.28 σt. (2) The North-West Indian Intermediate was found as a salinity maximum within the σt range 27.20-27.50. (3) The Banda Intermediate, lying below the North-West Indian Intermediate, had the characteristic of a salinity minimum within the σt range of 27.28-27.59. Preformed phosphate has been found useful as a third conservative property for the identification of major paths of spreading. The distribution and paths of spreading of the three water masses are shown in charts of the Indian Ocean east of 90�E.

scholarly journals Fungi in the Antarctic cryosphere: using DNA metabarcoding to reveal fungal diversity in glacial ice from the Antarctic Peninsula region

2021 ◽  
Author(s):  
Graciéle de Menezes ◽  
Paulo Câmara ◽  
Otávio Pinto ◽  
Peter Convey ◽  
Micheline Carvalho-Silva ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Fungal Diversity ◽  
High Throughput Sequencing ◽  
South Shetland Islands ◽  
Glacial Ice ◽  
North West ◽  
The North ◽  
Animal Pathogens ◽  
Dna Metabarcoding ◽  
The Antarctic

Abstract We assessed fungal diversity present in glacial of the Antarctic Peninsula using DNA metabarcoding through high throughput sequencing (HTS). We detected a total of 353,879 fungal DNA reads, representing 94 genera and 184 taxa, in glacial ice fragments obtained from seven sites in the north-west Antarctic Peninsula and South Shetland Islands. The phylum Ascomycota dominated the sequence diversity, followed by Basidiomycota and Mortierellomycota. Penicillium sp., Cladosporium sp., Penicillium atrovenetum, Epicoccum nigrum, Pseudogymnoascus sp. 1, Pseudogymnoascus sp. 2, Phaeosphaeriaceae sp. and Xylaria grammica were the most dominant taxa, respectively. However, the majority of the fungal diversity comprised taxa of rare and intermediate relative abundance, predominately known mesophilic fungi. High indices of diversity and richness were calculated, along with moderate index of dominance, which varied among the different sampling sites. Only 26 (14%) of the total fungal taxa detected were present at all sampling sites. The identified diversity was dominated by saprophytic taxa, followed by known plant and animal pathogens and a low number of symbiotic fungi. Our data suggest that Antarctic glacial ice may represent a hotspot of previously unreported fungal diversity; however, further studies are required to integrate HTS and culture approaches to confirm viability of the taxa detected.

Depositional Environment Drive as Overpressure Generation: Study Case in “Gap” Field, North West Java Basin

2020 ◽  
Author(s):  
A., C. Prasetyo
Keyword(s):  
Clay Mineral ◽  
Depositional Environment ◽  
Mineral Content ◽  
Hydrocarbon Generation ◽  
Well Test ◽  
Burial History ◽  
The South ◽  
North West ◽  
The North ◽  
Geological Processes

Overpressure existence represents a geological hazard; therefore, an accurate pore pressure prediction is critical for well planning and drilling procedures, etc. Overpressure is a geological phenomenon usually generated by two mechanisms, loading (disequilibrium compaction) and unloading mechanisms (diagenesis and hydrocarbon generation) and they are all geological processes. This research was conducted based on analytical and descriptive methods integrated with well data including wireline log, laboratory test and well test data. This research was conducted based on quantitative estimate of pore pressures using the Eaton Method. The stages are determining shale intervals with GR logs, calculating vertical stress/overburden stress values, determining normal compaction trends, making cross plots of sonic logs against density logs, calculating geothermal gradients, analyzing hydrocarbon maturity, and calculating sedimentation rates with burial history. The research conducted an analysis method on the distribution of clay mineral composition to determine depositional environment and its relationship to overpressure. The wells include GAP-01, GAP-02, GAP-03, and GAP-04 which has an overpressure zone range at depth 8501-10988 ft. The pressure value within the 4 wells has a range between 4358-7451 Psi. Overpressure mechanism in the GAP field is caused by non-loading mechanism (clay mineral diagenesis and hydrocarbon maturation). Overpressure distribution is controlled by its stratigraphy. Therefore, it is possible overpressure is spread quite broadly, especially in the low morphology of the “GAP” Field. This relates to the delta depositional environment with thick shale. Based on clay minerals distribution, the northern part (GAP 02 & 03) has more clay mineral content compared to the south and this can be interpreted increasingly towards sea (low energy regime) and facies turned into pro-delta. Overpressure might be found shallower in the north than the south due to higher clay mineral content present to the north.

A gold diadem from Aegina

1987 ◽  
Vol 107 ◽  
pp. 182-182
Author(s):  
Reynold Higgins
Keyword(s):  
Bronze Age ◽  
British Museum ◽  
The South ◽  
North West ◽  
The North ◽  
The Dead ◽  
Middle Helladic ◽  
Dead Man ◽  
The Bronze Age ◽  
Grave Goods

A recent discovery on the island of Aegina by Professor H. Walter (University of Salzburg) throws a new light on the origins of the so-called Aegina Treasure in the British Museum.In 1982 the Austrians were excavating the Bronze Age settlement on Cape Kolonna, to the north-west of Aegina town. Immediately to the east of the ruined Temple of Apollo, and close to the South Gate of the prehistoric Lower Town, they found an unrobbed shaft grave containing the burial of a warrior. The gravegoods (now exhibited in the splendid new Museum on the Kolonna site) included a bronze sword with a gold and ivory hilt, three bronze daggers, one with gold fittings, a bronze spear-head, arrowheads of obsidian, boar's tusks from a helmet, and fragments of a gold diadem (plate Va). The grave also contained Middle Minoan, Middle Cycladic, and Middle Helladic (Mattpainted) pottery. The pottery and the location of the grave in association with the ‘Ninth City’ combine to give a date for the burial of about 1700 BC; and the richness of the grave-goods would suggest that the dead man was a king.

Part VI. The Cyclopean Terrace Building and the Deposit of Pottery beneath It

1954 ◽  
Vol 49 ◽  
pp. 267-291
Author(s):  
Elizabeth B. Wace
Keyword(s):  
Contour Line ◽  
The South ◽  
Main Road ◽  
North West ◽  
North East ◽  
The North ◽  
South West

The Cyclopean Terrace Building lies to the north-west of the Lion Gate on the northern end of the Panagia Ridge and faces almost due west across the valley of the Kephissos and modern main road from Corinth to Argos. It lies just below the 200 m. contour line, and one terrace below the houses excavated in 1950–51 by Dr. Papadimitriou and Mr. Petsas to the east at the same end of the ridge. The area contains a complex of buildings, both successive and contemporary, and in view of the discovery of structures both to the south-west and, by the Greek Archaeological Service, to the north-east it is likely that this whole slope was covered by a portion of the outer town of Mycenae. This report will deal only with the structure to which the name Cyclopean Terrace Building was originally given, the so-called ‘North Megaron’, supported by the heavy main terrace wall.The excavation of this structure was begun in 1923. The main terrace wall was cleared and two L.H. IIIC burials discovered in the top of the fill in the south room. In 1950 it was decided to attempt to clear this building entirely in an endeavour to find out its date and purpose. The clearing was not, however, substantially completed until the close of the 1953 excavation season, and this report presents the available evidence for the date as determined by the pottery found beneath the building; the purpose is still a matter for study, though various tentative conclusions can be put forward.

scholarly journals Least limiting water range of Udox soil under degraded pastures on different sun-exposed faces

2017 ◽  
Vol 31 (3) ◽  
pp. 393-400 ◽  
Author(s):  
Renato Ribeiro Passos ◽  
Liovando Marciano da Costa ◽  
Igor Rodrigues de Assis ◽  
Danilo Andrade Santos ◽  
Hugo Alberto Ruiz ◽  
...  
Keyword(s):  
Soil Management ◽  
Sun Exposure ◽  
Soil Samples ◽  
The South ◽  
Undisturbed Soil ◽  
North West ◽  
The North ◽  
Pasture Degradation ◽  
Least Limiting Water Range ◽  
Degraded Pastures

AbstractThe efficient use of water is increasingly important and proper soil management, within the specificities of each region of the country, allows achieving greater efficiency. The South and Caparaó regions of Espírito Santo, Brazil are characterized by relief of ‘hill seas’ with differences in the degree of pasture degradation due to sun exposure. The objective of this study was to evaluate the least limiting water range in Udox soil under degraded pastures with two faces of exposure to the sun and three pedoenvironments. In each pedoenvironment, namely Alegre, Celina, and Café, two areas were selected, one with exposure on the North/West face and the other on the South/East face. In each of these areas, undisturbed soil samples were collected at 0-10 cm depth to determine the least limiting water range. The exposed face of the pasture that received the highest solar incidence (North/West) presented the lowest values in least limiting water range. The least limiting water range proved to be a physical quality indicator for Udox soil under degraded pastures.

Sign in / Sign up

Export Citation Format

Share Document