scholarly journals Geodynamic conditions for Cenozoic activation of tectonic structures in Southeastern Mongolia

2018 ◽  
Vol 9 (3) ◽  
pp. 855-888 ◽  
Author(s):  
A. V. Parfeevets ◽  
V. A. Sankov
Keyword(s):  
Late Cretaceous ◽  
Strike Slip ◽  
Tectonic Deformation ◽  
Published Data ◽  
Plate Boundaries ◽  
Tectonic Structures ◽  
History Of ◽  
The Impact ◽  
The Western Pacific ◽  
Early Cenozoic

The knowledge of the neotectonic structures inSoutheastern Mongolia, that is considerably distant from the active plate boundaries, is important for determining a source of tectonic deformation and regular features of activation in the intracontinental setting. Our research was focused on the East Gobi and South Gobi depressions located inSoutheastern Mongolia, which developed since the Mesozoic and were activated to various degrees in the neotectonic stage. The study aimed to assess the paleostress state of the crust inSoutheastern Mongolia, identify the stages, factors and mechanisms of the Cenozoic activation of the regional structures of different strike, and determine the sources of activation. The analysis of the available literature suggests a similar history of their development in the Late Jurassic – Early Cretaceous (rifting) and Late Cretaceous – Paleogene (tectonic quiescence). In the Cenozoic stage, the depressions experienced activation of completely different styles. In theEast Gobidepression, left-lateral strike-slip faults were activated in the Tertiary, and the post-Late Cretaceous thrusting took place along the northeastern faults on the northern slope of the Totoshan uplift. In the Early Cenozoic, the N-S and N-W compression was dominant as evidenced by the deformed Late Cretaceous sediments and the reconstructed stress tensors typical of the compression and transpression regimes. An overview of the published data suggests that the most probable cause of such deformation was the impact of the Western Pacific zone of plate interaction. However, a potential influence of compression at the early stages of the Indo-Asian collision cannot be completely excluded. TheEast Gobidepression was low active in the second half of the Cenozoic. In contrast to the East Gobi depression, theSouth Gobiactivation began in the Late Cenozoic (Late Miocene – Early Pliocene). Young uplifts and forbergs (Gobi Altai eastern termination) developed actively and ‘cut’ the sediments of the basins originating from the Mesozoic. The W-E and N-W strike-slip and thrust faults were active in the Pliocene–Quaternary. The stress field reconstructions show compression, transpression and strike-slip regimes with the NE-trending axis of compression. Deformation in the East Goby Altay (as well as in Western andSouthwestern Mongolia) is driven by the India-Eurasia collision.

scholarly journals Tectonic and Geologic Evolution of Syria

GeoArabia ◽  
2001 ◽  
Vol 6 (4) ◽  
pp. 573-616 ◽  
Author(s):  
Graham Brew ◽  
Muawia Barazangi ◽  
Ahmad Khaled Al-Maleh ◽  
Tarif Sawaf
Keyword(s):  
Late Cretaceous ◽  
Eastern Mediterranean ◽  
Regional Scale ◽  
Dead Sea ◽  
Hydrocarbon Exploration ◽  
Fault System ◽  
Tectonic Deformation ◽  
Plate Boundaries ◽  
History Of ◽  
The Dead

ABSTRACT Using extensive surface and subsurface data, we have synthesized the Phanerozoic tectonic and geologic evolution of Syria that has important implications for eastern Mediterranean tectonic studies and the strategies for hydrocarbon exploration. Syrian tectonic deformation is focused in four major zones that have been repeatedly reactivated throughout the Phanerozoic in response to movement on nearby plate boundaries. They are the Palmyride Mountains, the Euphrates Fault System, the Abd el Aziz-Sinjar uplifts, and the Dead Sea Fault System. The Palmyrides include the SW Palmyride fold and thrust belt and two inverted sub-basins that are now the Bilas and Bishri blocks. The Euphrates Fault System and Abd el Aziz-Sinjar grabens in eastern Syria are large extensional features with a more recent history of Neogene compression and partial inversion. The Dead Sea transform plate boundary cuts through western Syria and has associated pull-apart basins. The geological history of Syria has been reconstructed by combining the interpreted geologic history of these zones with tectonic and lithostratigraphic analyses from the remainder of the country. Specific deformation episodes were penecontemporaneous with regional-scale plate-tectonic events. Following a relatively quiescent early Paleozoic shelf environment, the NE-trending Palmyride/Sinjar Trough formed across central Syria in response to regional compression followed by Permian-Triassic opening of the Neo-Tethys Ocean and the eastern Mediterranean. This continued with carbonate deposition in the Mesozoic. Late Cretaceous tectonism was dominated by extension in the Euphrates Fault System and Abd el Aziz-Sinjar Graben in eastern Syria associated with the closing of the Neo-Tethys. Repeated collisions along the northern Arabian margin from the Late Cretaceous to the Late Miocene caused platform-wide compression. This led to the structural inversion and horizontal shortening of the Palmyride Trough and Abd el Aziz-Sinjar Graben.

Mineral assemblages and xenolith cargo in the Storkwitz carbonatite (Delitzsch Complex, Germany)

2020 ◽  
Author(s):  
Hripsime Gevorgyan ◽  
Sascha Schmidt ◽  
Ilja Kogan ◽  
Manuel Lapp
Keyword(s):  
Late Cretaceous ◽  
Early Stage ◽  
Soft Rock ◽  
Core Material ◽  
Compositional Variation ◽  
Published Data ◽  
Fine Grained ◽  
Ultramafic Lamprophyre ◽  
The Matrix ◽  
History Of

<p>The multi-compositional carbonatite body of Storkwitz is one of several purported diatremes of the Late Cretaceous Delitzsch Complex, which comprises carbonatites and ultramafic lamprophyres emplaced into a heterogeneous series of volcanic and sedimentary rocks of Precambrian to Early Permian age (Krüger et al., 2013; Seifert et al., 2000). The Late Cretaceous peneplain is covered with about one hundred meters of Tertiary soft rock. According to Röllig et al. (1990), the Delitzsch Complex developed in six stages: (i) hidden intrusion of a dolomite carbonatite (rauhaugite) that led to the formation of a fenite aureole; (ii) ultramafic and alkaline lamprophyre intrusion (alnöite, aillikite, monchiquite); (iii) formation of beforsitic diatremes (intrusive breccias), including xenoliths of dolomite carbonatite and ultramafic lamprophyre; (iv) ultramafic and alkali lamprophyres (dykes within diatremes of 3<sup>rd</sup> stage); (v) formation of beforsite and (vi) alvikite dykes.</p><p>The Storkwitz carbonatite is mainly characterized by beforsitic breccias containing abundant angular xenoliths of metasediments form the complete underlying stratigraphic succession, metamorphic and igneous rocks, as well as rounded xenoliths of ultramafic lamprophyre, rauhaugite, fenite, and glimmerite, which suggest the existence of a deep-seated carbonatite pluton (Seifert et al., 2000). It is remarkable that the fenites exhibit a different degree of fenitization and show occurrence of phlogopite in the strongly fenitized samples. The matrix of the Storkwitz carbonatite is mainly composed of ankerite and calcite/siderite, which corresponds to ferro- or silico-carbonatites.</p><p>Detailed petrographical observations on extensive drill core material, new analyses and a reinterpretation of published data confirm the existence of compositional variation and zonation within the carbonatite body that reflect independent crystallization history and formation due to multiple magmatic events. The different generations of apatite and phlogopite from the early stage of the plutonic dolomite carbonatite through the late-stage beforsite dykes and fine-grained calcite carbonatite veins shed light on the crystallization history and magma development of carbonatites.</p><p> </p><p>References</p><p> </p><p>Krüger, J.C., Romer, R.L., Kämpf, H., 2013. Late Cretaceous ultramafic lamprophyres and carbonatites from the Delitzsch Complex, Germany. Chemical Geology, 353, 140-150.</p><p>Röllig, G., Viehweg, M., Reuter, N., 1990. The ultramafic lamprophyres and carbonatites of Delitzsch/GDR. Zeitschrift für Angewandte Geologie, 36, 49-54.</p><p>Seifert, W., Kämpf, H., Wasternack, J., 2000. Compositional variation in apatite, phlogopite and other accessory minerals of the ultramafic Delitzsch complex, Germany: implication for cooling history of carbonatites. Lithos, 53, 81-100.</p>

A seismotectonic study and minimum 1D velocity model for the Greater Geneva Basin, Western Switzerland

2020 ◽  
Author(s):  
Verónica Antunes ◽  
Thomas Planès ◽  
Jiří Zahradník ◽  
Anne Obermann ◽  
Celso Alvizuri ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Large Scale ◽  
Detection Threshold ◽  
Velocity Model ◽  
Strike Slip ◽  
Tectonic Deformation ◽  
Geothermal Exploration ◽  
Area Of Interest ◽  
The Impact ◽  
1D Velocity Model

<p>In the framework of the Geothermie2020 project, the canton of Geneva and the Industrial Services of Geneva (SIG) are currently developing geothermal exploration in the Greater Geneva Basin (GGB), located in south-western Switzerland and neighbouring France. Before geothermal exploration begins, it is important to investigate the ongoing seismic activity, its relationship with local tectonic features, and the large-scale kinematics of the area. Background seismicity suggest that the local tectonic structures affecting the basin may still be active. Moderate-magnitude earthquakes have been identified along the Vuache fault, a major strike-slip structure crossing the basin. In this context we deployed a dense temporary network of 20 broadband stations around and within the GGB, during ~1.5 years, and reaching a detection threshold 0.5M<sub>L</sub>. </p><p>Using a new coherence-based detector (LASSIE), we detected and located 158 events in our area of interest. However, only 20 events were located in the GGB, with local magnitudes ranging from 0.7 to 2.2M<sub>L</sub>. We found no earthquakes in the Canton of Geneva where geothermal activities are taking place. We constructed a local minimum 1D velocity model with VELEST, using the recorded seismicity together with earthquakes from adjacent regions, in a total of 1263 P- and S-picks. The new velocity model allowed to relocate micro-seismic activity up to 11km depth along the main fault systems (i.e. Vuache, Cruseilles, Le Coin, and Arve) offsetting the GGB. We retrieved 8 new focal mechanisms for the area, using a combination of polarities and waveform inversion techniques (CSPS method). A stress inversion shows a tectonic deformation dominated by a quasi-pure strike-slip regime in the GGB, consistent with structural and geological data.</p><p>The study of microseismicity in a quiet sedimentary basin is challenging due to the scarce occurrence of seismic events combined with low signal-to-noise ratios and the often strong attenuation. However, the investigation of the sporadic (yet present) natural seismicity with dedicated dense networks could provide useful information about the GGB, even with a short-term experiment. We propose a newly-computed 1D velocity model that can be used in the GGB for seismic monitoring purposes throughout the geothermal project. This model can be easily improved later on, whenever more data is available. Monitoring the evolution and dispersion of the seismic-activity through the identified seismogenic areas during the geothermal project is essential. Quantifying the seismic rate in the basin before geothermal operations start will help to quantify the impact that geothermal energy extraction might have on the GGB. </p>

scholarly journals Geomorphic expression and slip rate of the Fairweather fault, southeast Alaska, and evidence for predecessors of the 1958 rupture

Geosphere ◽  
2021 ◽  
Author(s):  
Robert C. Witter ◽  
Adrian M. Bender ◽  
Katherine M. Scharer ◽  
Christopher B. DuRoss ◽  
Peter J. Haeussler ◽  
...  
Keyword(s):  
Active Faults ◽  
Plate Boundary ◽  
Slip Rate ◽  
Strike Slip ◽  
Tectonic Deformation ◽  
Plate Boundaries ◽  
Slip Rates ◽  
Southeast Alaska ◽  
The Past ◽  
Show Evidence

Active traces of the southern Fairweather fault were revealed by light detection and ranging (lidar) and show evidence for transpressional deformation between North America and the Yakutat block in southeast Alaska. We map the Holocene geomorphic expression of tectonic deformation along the southern 30 km of the Fairweather fault, which ruptured in the 1958 moment magnitude 7.8 earthquake. Digital maps of surficial geology, geomorphology, and active faults illustrate both strike-slip and dip-slip deformation styles within a 10°–30° double restraining bend where the southern Fairweather fault steps offshore to the Queen Charlotte fault. We measure offset landforms along the fault and calibrate legacy 14C data to reassess the rate of Holocene strike-slip motion (≥49 mm/yr), which corroborates published estimates that place most of the plate boundary motion on the Fairweather fault. Our slip-rate estimates allow a component of oblique-reverse motion to be accommodated by contractional structures west of the Fairweather fault consistent with geodetic block models. Stratigraphic and structural relations in hand-dug excavations across two active fault strands provide an incomplete paleoseismic record including evidence for up to six surface ruptures in the past 5600 years, and at least two to four events in the past 810 years. The incomplete record suggests an earthquake recurrence interval of ≥270 years—much longer than intervals <100 years implied by published slip rates and expected earthquake displacements. Our paleoseismic observations and map of active traces of the southern Fairweather fault illustrate the complexity of transpressional deformation and seismic potential along one of Earth’s fastest strike-slip plate boundaries.

scholarly journals Cycad Toxins and Neurological Diseases in Guam: Defining Theoretical and Experimental Standards for Correlating Human Disease with Environmental Toxins

HortScience ◽  
2005 ◽  
Vol 40 (6) ◽  
pp. 1598-1606 ◽  
Author(s):  
Thomas E. Marler ◽  
Vivian Lee ◽  
Christopher A. Shaw
Keyword(s):  
Human Disease ◽  
Neurological Diseases ◽  
Empirical Studies ◽  
Medical Science ◽  
Past Research ◽  
Published Data ◽  
Science Standards ◽  
Community Factors ◽  
History Of ◽  
The Impact

Consumption of Cycas micronesica seed tissue has been associated with the amyotrophic lateral sclerosis–parkinsonism dementia complex (ALS–PDC) of the Western Pacific. However, failures to document vital plant and neighborhood descriptors and pronounced variability in toxin concentrations noted within and among studies obfuscate decades of research on this subject. We discuss the theoretical and experimental constraints of plant tissue sampling in relation to human disease research. Comparisons are made between this approach and methods used throughout the history of ALS–PDC research, most notably very recent reports concerning β-methyl-amino-alanine. Methods for studying possible plant neurotoxins need to be standardized and must follow rigorous criteria to be valid in principle. Our discussions reveal why these criteria are essential and highlight the impact that natural variations have on environmental toxin quantification and interpretation. Past research on cycad toxins is deficient on experimental and theoretical grounds, and interpretation of published data is dominated by ambiguities. This area of study as conventionally conceived and carried out needs transforming. We argue that future empirical studies should honor appropriate plant science standards concomitantly with medical science standards. This dual focus will ensure appropriate sampling scheme, sample size, and reporting of background plant and community factors known to influence phenotypic plasticity.

Seismicity and structure of the Zagros (Iran): the Main Recent Fault between 33 and 35° N

1974 ◽  
Vol 277 (1262) ◽  
pp. 1-25 ◽  
Keyword(s):  
Relative Motion ◽  
Late Quaternary ◽  
Strike Slip ◽  
Arabian Plate ◽  
Tectonic Deformation ◽  
Tectonic History ◽  
History Of ◽  
Slip Deformation ◽  
The Individual ◽  
First Time

The most recent tectonic deformation of the Zagros, and in particular the late Quaternary right-lateral wrench movement along the Main Recent Fault, is summarized in the context of the general tectonic history of the range. The seismicity along the Main Recent Fault between latitudes 33 and 35° N is examined, and details are given for several destructive earthquakes, including the 1909 Selakhor earthquake which was associated with over 40 km of surface faulting along a segment of the Main Recent Fault and which is described here for the first time. The relation between the seismicity and the individual fault segments forming the Main Recent Fault is studied and interpreted in terms of a continuing right-lateral strike slip deformation. The implications of this contemporary deformation for the seismotectonics of the Zagros are considered, and in particular its bearing on the problem of the relative motion of the Arabian Plate with respect to Central Iran.

The interplay between geodynamics and flooding drives the dynamics of the inner Okavango Delta (North Botswana)

2020 ◽  
Author(s):  
Olivier Dauteuil ◽  
Marc Jolivet ◽  
Mike Murray-Hudson ◽  
laurie Barrier ◽  
Aziliz Audran ◽  
...  
Keyword(s):  
Ground Deformation ◽  
East African Rift ◽  
Strike Slip ◽  
Okavango Delta ◽  
Tectonic Deformation ◽  
Strain Partitioning ◽  
East African ◽  
Half Graben ◽  
African Rift ◽  
The Impact

<p><span>The southwestward propagation of the East African Rift System inside the southern African plateau generated the Okavango basin in a strike-slip context. This setup generates one of the largest endoreic ecosystem in Africa: the Okavango Delta alluvial fan. The sedimentary and topography dynamics of that system are driven by both annual flooding and strike-slip geodynamics. To evaluate the impact of ground deformation on the long-term evolution of the Okavango ecosystem, we estimated the 3D strain field from the deformation of a geodetic network composed of 7 dual-frequency GPS semi-permanent stations measured during 4 years. The Okavango basin is a half-graben: its SE edge being limited by a set of normal faults, while the NW limit is bounded by a right-lateral fault. This fault pattern generates strain partitioning with a stretching direction that changes from oblique to parallel to the graben trend and with the highest dilation to the NE and shortening to the SW. Integrating geophysical data, we propose a crustal model describing a strike-slip basin with a normal detachment zone connected to a steep strike-slip shear zone in the lower crust. We show that strain partitioning lead to dilating and shortening domains, which favors water flow toward the NE and progressively restricts water discharge into Lake Ngami, SW of the Delta.</span></p><p><span>At regional scale, the vertical component of the ground deformation recorded over 10 years reveals annual variations generated by the cyclic flooding, this process acting in addition to the ground deformation induced by the regional geodynamics. A preliminary numerical modeling of the ground flexure induced by the floods constrains the rheological properties of the crust. It highlights two domains with high subsidence limiting a domain with lower subsidence allowing differential water storage.</span></p><p><span>We conclude that the geodynamic deformation linked to the propagation of the East African Rift into the Okavango half-graben is a key factor controlling the hydrodynamics and ecosystem evolution of the Okavango Delta fan. This control is super-imposed to the effects of variations in sediment and water supply linked to regional climate change. More generally, we show that intra-continental endoreic systems can be highly sensible to low amplitude tectonic deformation.</span></p><p> </p>

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