Geodynamic implications of the Cenozoic stress field on Seymour Island, West Antarctica

2008 ◽  
Vol 20 (2) ◽  
pp. 173-184 ◽  
Author(s):  
A. Maestro ◽  
J. López-Martínez ◽  
F. Bohoyo ◽  
M. Montes ◽  
F. Nozal ◽  
...  
Keyword(s):  
Stress Field ◽  
Antarctic Peninsula ◽  
Horizontal Stress ◽  
Weddell Sea ◽  
Scotia Sea ◽  
Compressional Stress ◽  
The North ◽  
Stress States ◽  
Bransfield Basin ◽  
Minimum Horizontal Stress

AbstractPalaeostress inferred from brittle mesostructures in Seymour (Marambio) Island indicates a Cenozoic to Recent origin for an extensional stress field, with only local compressional stress states. Minimum horizontal stress (σ3) orientations are scattered about two main NE–SW and NW–SE modes suggesting that two stress sources have been responsible for the dominant minimum horizontal stress directions in the north-western Weddell Sea. Extensional structures within a broad-scale compressional stress field can be linked to both the decrease in relative stress magnitudes from active margins to intraplate regions and the rifting processes that occurred in the northern Weddell Sea. Stress states with NW–SE trending σ3are compatible with back-arc extension along the eastern Antarctic Peninsula. We interpret this as due to the opening of the Larsen Basin during upper Cretaceous to Eocene and to the spreading, from Pliocene to present, of the Bransfield Basin (western Antarctic Peninsula), both due to former Phoenix Plate subduction under the Antarctic Plate. NE–SW σ3orientations could be expressions of continental fragmentation of the northern Antarctic Peninsula controlling eastwards drifting of the South Orkney microcontinent and other submerged continental blocks of the southern Scotia Sea.

scholarly journals Cenozoic stress field in the southwestern Antarctic Peninsula from brittle mesostructures in Wright Peninsula, Adelaide Island

2011 ◽  
Vol 32 (1) ◽  
pp. 39-58 ◽  
Author(s):  
Adolfo Maestro ◽  
Jerónimo López-Martínez
Keyword(s):  
Stress Field ◽  
Antarctic Peninsula ◽  
Bimodal Distribution ◽  
Horizontal Stress ◽  
Early Miocene ◽  
Western Antarctic Peninsula ◽  
Compressional Stress ◽  
Stress States ◽  
Maximum Horizontal Stress ◽  
Adelaide Island

Cenozoic stress field in the southwestern Antarctic Peninsula from brittle mesostructures in Wright Peninsula, Adelaide IslandPalaeostresses inferred from brittle mesostructures in the southern Wright Peninsula show a stress field characterized by compressional, strike-slip and extensional regime stress states. The compressional stress (σ1) shows a main NW-SE direction and the extensional stress (σ3) shows a relative scattering with two main modes: NE-SW to E-W and NW-SE. The maximum horizontal stress (σy) has a bimodal distribution with NW-SE and NE-SW direction. The compressional orientation is related to subduction of the former Phoenix Plate under the Antarctic Plate from the Early Jurassic to the Early Miocene. Extensional structures within a broad-scale compressional stress field can be related to both the decrease in relative stress magnitudes from active margins to intraplate regions and stretching processes occurring in eastern Adelaide Island, which develop a fore-arc or intra-arc basin from the Early Miocene. Stress states with NW-SE-trending σ1are compatible with the dominant pattern established for the western Antarctic Peninsula. NW-SE orientations of σ3suggest the occurrence of tectonic forces coming from fore-arc extension along the western Antarctic Peninsula.

Fractures in the northern plains, stream patterns, and the midcontinent stress field

1987 ◽  
Vol 24 (6) ◽  
pp. 1086-1097 ◽  
Author(s):  
Mel R. Stauffer ◽  
Don J. Gendzwill
Keyword(s):  
Stress Field ◽  
Horizontal Stress ◽  
The Body ◽  
North American Plate ◽  
Plate Motion ◽  
Viscous Drag ◽  
Near Surface ◽  
The North ◽  
Elastic Rebound ◽  
Western North Dakota

Fractures in Late Cretaceous to Late Pleistocene sediments in Saskatchewan, eastern Montana, and western North Dakota form two vertical, orthogonal sets trending northeast–southwest and northwest–southeast. The pattern is consistent, regardless of rock type or age (except for concretionary sandstone). Both sets appear to be extensional in origin and are similar in character to joints in Alberta. Modem stream valleys also trend in the same two dominant directions and may be controlled by the underlying fractures.Elevation variations on the sub-Mannville (Early Cretaceous) unconformity form a rectilinear pattern also parallel to the fracture sets, suggesting that fracturing was initiated at least as early as Late Jurassic. It may have begun earlier, but there are insufficient data at present to extend the time of initiation.We interpret the fractures as the result of vertical uplift together with plate motion: the westward drift of North America. The northeast–southwest-directed maximum principal horizontal stress of the midcontinent stress field is generated by viscous drag effects between the North American plate and the mantle. Vertical uplift, erosion, or both together produce a horizontal tensile state in near-surface materials, and with the addition of a directed horizontal stress through plate motion, vertical tension cracks are generated parallel to that horizontal stress (northeast–southwest). Nearly instantaneous elastic rebound results in the production of second-order joints (northwest–southeast) perpendicular to the first. In this manner, the body of rock is being subjected with time to complex alternation of northeast–southwest and northwest–southeast horizontal stresses, resulting in the continuous and contemporaneous production of two perpendicular extensional joint sets.

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 A semi-quantitative method to combine tectonic stress indicators: example from the Southern Calabrian Arc (Italy)

2020 ◽  
Vol 56 (1) ◽  
pp. 280
Author(s):  
Salvatore Scudero ◽  
Giorgio De Guidi ◽  
Riccardo Caputo ◽  
Vincenzo Perdicaro
Keyword(s):  
Stress Field ◽  
Original Data ◽  
Horizontal Stress ◽  
Tectonic Stress ◽  
Structural Features ◽  
Interesting Case ◽  
Stress Indicators ◽  
Spatial And Temporal Scales ◽  
Independent Information ◽  
Minimum Horizontal Stress

Databases of tectonic stress indicators are commonly based on different types of observations at different spatial and temporal scales. Each single indicator can be variously representative of the real stress field and the relative importance of all the indicators should be accounted for before any following elaboration. We propose a semi-quantitative procedure which assigns weights to each indicator on the basis of its quality and its representative volume. In this way the indicators can be reliably combined to produce, for example, stress field maps or stress trajectories. The proposed weighting criterion has been applied to a dataset of 440 crustal stress indicators specifically compiled, gathering focal mechanisms and geological data from the literature, and original data from structural features derived from devoted fieldwork, for the southern part of the Calabrian Arc (Italy). This area represents an interesting case study because of its complex geodynamic and structural arrangement. Data were ranked and the orientation of the minimum horizontal stress (Sh) has been interpolated and smoothed on a regular grid. We drew maps of the principal stress axes and inferred the stress regimes over the investigated area. Results are in agreement with independent information from the literature and display the non-uniform orientation of the tectonic stresses and the occurrence of perturbations both at regional and local scale.

THE OTWAY BASIN: EARLY CRETACEOUS RIFTING TO NEOGENE INVERSION

1995 ◽  
Vol 35 (1) ◽  
pp. 494 ◽  
Author(s):  
A.J. Buffin ◽  
A.J. Sutherland ◽  
J.A. Gorski
Keyword(s):  
Stress Field ◽  
Normal Fault ◽  
Horizontal Wells ◽  
Horizontal Stress ◽  
Natural Fracture ◽  
Water Flooding ◽  
Hydraulic Fractures ◽  
Vertical Wells ◽  
Minimum Horizontal Stress ◽  
Maximum Horizontal Stress

Borehole breakouts and hydraulic fractures in­ferred from dipmeter and formation microscanner logs indicate that the minimum horizontal stress (σh) is oriented 035°N in the South Australian sector of the Otway Basin. Density and sonic check-shot log data indicate that vertical stress (σv) increases from approximately 20 MPa at a depth of one km to 44 MPa at two km and 68 MPa at three km. Assum­ing a normal fault condition (i.e. σy > σH > σh), the magnitude of σh is 75 per cent of the magnitude of the maximum horizontal stress (σH), and the magni­tude of σH is close to that of av. Sonic velocity compaction trends for shales suggest that pore pressure is generally near hydrostatic in the Otway Basin.Knowledge of the contemporary stress field has a number of implications for hydrocarbon produc­tion and exploration in the basin. Wellbore quality in vertical wells may be improved (breakouts sup­pressed) by increasing the mud weight to a level below that which induces hydraulic fracture, or other drilling problems related to excessive mud weight. Horizontal wells drilled in the σh direction (035°N/215°N) should be more stable than those drilled in the σH direction, and indeed than vertical wells. In any EOR operations where water flooding promotes hydraulic fracturing, injectors should be aligned in the aH (125°N/305°N) direction, and off­set from producers in the orthogonal σh direction. Any deviated/horizontal wells targeting the frac­tured basement play should be oriented in the σh (035°N/215°N) direction to maximise intersection with this open, natural fracture trend. Hydrocar­bon recovery in wells deviated towards 035°N/215°N may also be enhanced by inducing multiple hydrau­lic fractures along the wellbore.Considering exploration-related issues, faults following the dominant structural trend, sub-paral­lel to σH orientation, are the most prone to be non-sealing during any episodic build-up of pore pres­sure. Pre-existing vertical faults striking 080-095°N and 155-170°N are the most prone to at least a component of strike-slip reactivation within the contemporary stress field.

Latest Jurassic–earliest Cretaceous age for a fossil flora from the Latady Basin, Antarctic Peninsula

2006 ◽  
Vol 18 (2) ◽  
pp. 261-264 ◽  
Author(s):  
Morag A. Hunter ◽  
David J. Cantrill ◽  
Michael J. Flowerdew
Keyword(s):  
Antarctic Peninsula ◽  
Plant Material ◽  
Weddell Sea ◽  
Detrital Zircons ◽  
Fossil Flora ◽  
Fossil Plant ◽  
The North ◽  
Depositional Age ◽  
The Antarctic ◽  
Basin Margin

Dating Jurassic terrestrial floras in the Antarctic Peninsula has proved problematic and controversial. Here U–Pb series dating on detrital zircons from a conglomerate interbedded with fossil plant material provide a maximal depositional age of 144 ± 3 Ma for a presumed Jurassic flora. This is the first confirmed latest Jurassic-earliest Cretaceous flora from the Latady Basin, and represents some of the youngest sedimentation in this basin. The presence of terrestrial sedimentation at Cantrill Nunataks suggests emergence of the arc closer to the Latady Basin margin in the south compared to Larsen Basin in the north, probably as a result of the failure of the southern Weddell Sea to undergo rifting.

Multiproxy climate and sea ice reconstruction of the industrial era at the Western Antarctic Peninsula

2020 ◽  
Author(s):  
Maria-Elena Vorrath ◽  
Paola Cárdenas ◽  
Lorena Rebolledo ◽  
Xiaoxu Shi ◽  
Juliane Müller ◽  
...  
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
System Analysis ◽  
Ice Cover ◽  
Weddell Sea ◽  
Water Masses ◽  
Western Antarctic Peninsula ◽  
Climate Conditions ◽  
Ice Conditions ◽  
Bransfield Basin

<p>Recent changes and variability in climate conditions leave a significant footprint on the distribution and properties of sea ice, as it is sensitive to environmental variations. We investigate the rapidly transforming region of the Western Antarctic Peninsula (WAP) focusing on the conditions and development of sea ice in the pre-satellite era. For this study on past sea ice cover we apply the novel proxy IPSO<sub>25</sub> (Ice Proxy for the Southern Ocean with 25 carbon atoms; Belt et al., 2016). Three sampling sites were selected to cover areas near the Antarctic mainland, in the Bransfield Basin (2000 m depth) and the deeper shelf under an oceanographic frontal system. Analysis of short cores (multicores) resolving the last 200 years (based on <sup>210</sup>Pb<sub>ex</sub> dating) focused on geochemical bulk parameters, biomarkers (highly branched isoprenoids, GDGTs, sterols) and diatoms. These results are compared to multiple climate archives and modelled data. This multiproxy based approach provides insights on changes in spring sea ice cover, primary production regimes, subsurface ocean temperature (SOT based on TEX<sup>L</sup><sub>86</sub>) and oceanographic as well as atmospheric circulation patterns. While environmental proxies preserved in two cores near the coast and in the Bransfield Basin reflect the properties of water masses from the Bellingshausen Sea and Weddell Sea, respectively, data from the third core at the deeper shelf depict mixed signals of both water masses. Our study reveals clear evidence for warm and cold periods matching with ice core records and other marine sediment data at the WAP. We observe a general decrease in SOT and an increase in sea ice cover overprinted by high decadal fluctuations. Trends in SOT seem to be decoupled from atmospheric temperatures in the 20<sup>th</sup> century, and this is supported by previous studies (e.g. Barbara et al., 2013), and may be related to the Southern Annual Mode. We consider numerical modelling of sea ice conditions, sea surface temperature and SOT for further support of our findings.</p><p> </p><p>References:</p><p>Barbara, L., Crosta, X., Schmidt, S. and Massé, G.: Diatoms and biomarkers evidence for major changes in sea ice conditions prior the instrumental period in Antarctic Peninsula, Quat. Sci. Rev., 79, 99–110, doi:10.1016/j.quascirev.2013.07.021, 2013.</p><p>Belt, S. T., Smik, L., Brown, T. A., Kim, J. H., Rowland, S. J., Allen, C. S., Gal, J. K., Shin, K. H., Lee, J. I. and Taylor, K. W. R.: Source identification and distribution reveals the potential of the geochemical Antarctic sea ice proxy IPSO25, Nat. Commun., 7, 1–10, doi:10.1038/ncomms12655, 2016.</p>

New records of Antarctic and Sub-Antarctic sea anemones (Cnidaria, Anthozoa, Actiniaria and Corallimorpharia) from the Weddell Sea, Antarctic Peninsula, and Scotia Arc

Zootaxa ◽  
2013 ◽  
Vol 3624 (1) ◽  
pp. 1-100 ◽  
Author(s):  
ESTEFANÍA RODRÍGUEZ ◽  
PABL J. LÓPEZ-GONZÁLEZ
Keyword(s):  
Antarctic Peninsula ◽  
New Records ◽  
Sea Anemone ◽  
Weddell Sea ◽  
External Morphology ◽  
Sea Anemones ◽  
Antarctic Species ◽  
Scotia Sea ◽  
Distribution Maps ◽  
Scotia Arc

Herein we provide new records for 22 Antarctic species of sea anemone sensu lato (Anthozoa: Actiniaria and Corallimorpharia) from the Weddell Sea, Antarctic Peninsula, and the Scotia Sea. We provided short descriptions, images of the external morphology of preserved specimens (but also of living specimens in most cases), cnida data, and distribution maps for each studied species. New records are presented for nine species in the Weddell Sea and the geographic or bathymetric distributions for 19 of the 22 studied species are extended.

scholarly journals Adult male southern elephant seals from King George Island utilize the Weddell Sea

2008 ◽  
Vol 21 (2) ◽  
pp. 113-121 ◽  
Author(s):  
C.A. Tosh ◽  
H. Bornemann ◽  
S. Ramdohr ◽  
M. Schröder ◽  
T. Martin ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Adult Male ◽  
Weddell Sea ◽  
Adult Males ◽  
King George Island ◽  
Elephant Seals ◽  
The North ◽  
Southern Elephant Seals ◽  
Ice Shelf Water ◽  
The Antarctic

AbstractAdult male southern elephant seals instrumented in 2000 on King George Island (n = 13), travelled both to the north (n = 2) and to the east (n = 6) of the Antarctic Peninsula. Five males remained within 500 km of the island focusing movements in the Bransfield Strait and around the Antarctic Peninsula. Sea surface temperatures encountered by these animals showed little variation. While animal trajectories appeared unaffected by sea ice cover, areas of shallow depths were frequented. Three males moved as far as 75°S to the east of the Peninsula with maximum distances of more than 1500 km from King George Island. They travelled into the Weddell Sea along the western continental shelf break until they reached the region of the Filchner Trough outflow. Here the sea floor consists of canyons and ridges that support intensive mixing between the warm saline waters of the Weddell Gyre, the very cold outflow waters and ice shelf water at the Antarctic Slope Front. The need for re-instrumentation of adult males from King George Island is highlighted to investigate whether males continue to travel to similar areas and to obtain higher resolution data.

scholarly journals The Crustal Stress Field of Germany - A Refined Prediction

2021 ◽  
Author(s):  
Steffen Ahlers ◽  
Luisa Röckel ◽  
Tobias Hergert ◽  
Karsten Reiter ◽  
Oliver Heidbach ◽  
...  
Keyword(s):  
Stress Field ◽  
Sedimentary Basins ◽  
Horizontal Stress ◽  
Rock Properties ◽  
Upper Rhine Graben ◽  
Calibration Data ◽  
Directional Drilling ◽  
In Situ Data ◽  
The North ◽  
The Absolute

Abstract Information about the absolute stress state in the upper crust plays a crucial role in the planning and execution of e.g., directional drilling, stimulation and exploitation of geothermal and hydrocarbon reservoirs. Since many of these applications are related to sediments, we present a refined geomechanical-numerical model for Germany with focus on sedimentary basins, able to predict the complete 3D stress tensor. The lateral resolution of the model is 2.5 km, the vertical resolution about 250 m. Our model contains 22 units with focus on the sedimentary layers parameterized with individual rock properties. The model results show an overall good fit with magnitude data of the minimum (Shmin) and maximum horizontal stress (SHmax) that are used for the model calibration. The mean of the absolute stress differences between these calibration data and the model results is 4.6 MPa for Shmin and 6.4 MPa for SHmax. In addition, our predicted stress field shows good agreement to several supplementary in situ data from the North German Basin, the Upper Rhine Graben and the Molasse Basin.

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