scholarly journals Transversal folding in Himalaya foothill ranges

2019 ◽  
Vol 149 (3) ◽  
pp. 255
Author(s):  
László Csontos ◽  
István Dunkl ◽  
Gábor Vakarcs ◽  
Abid H. Abbaso
Keyword(s):  
Seismic Data ◽  
Seismic Analysis ◽  
Regional Scale ◽  
Time Frame ◽  
Indian Plate ◽  
Thrust Faults ◽  
Lateral Shear ◽  
Shear Component ◽  
Major Break ◽  
Thrust Sheets

The Himalayan foreland in N Pakistan, dissected by Main Frontal Thrust (MFT) and Main Boundary Thrust (MBT) contains spectacular salients and syntaxes. The lateral (N-S) boundaries between these salients and syntaxes around Kalabagh city and east-southeast of Islamabad were believed to host deep-seated lateral ramps with strike slip movements. However, seismic data in these two sectors suggest that there are N-S trending folds and locally east- or west-vergent thrusts that affect the Paleozoic-Paleogene cover of the Indian shield, as well as the Miocene-Pliocene molasse sediments. The proposed lateral ramps cannot be followed on the seismic and on maps either; instead, both maps and seismic data suggest folding, often on a regional scale of harder Paleo-Mesozoic-Paleogene and softer Oligo-Miocene-Pilo-Pleistocene cover. The NE corner of Surghar range is proposed to be formed of relaying thrust sheets with emergent heads composed of Paleozoic-Paleogene and its slightly detached Miocene molasse. These relaying imbricates are taken in a southward flexure generated by a major right lateral shear of a wide zone, where transpressive Riedel shears, en echelon anticlines and southwards flexed earlier thrust faults are the main elements (but a single, through-going Kalabagh fault is missing). The generation of mapped N-S trending folds and east-vergent thrusts preceded the formation of the wide shear zone and southwards flexing.Hazara syntaxis is interpreted as a major antiform that re-folded MBT and Panjal thrust around Oligo-Miocene molasse, itself forming an antiform (BOSSART ET AL. 1988). In our model we propose that the west-vergent Balakot thrust and deeper blind thrusts are in the core of this antiform. In the southern continuation we propose that folds in Miocene molasse continue from eastern Potwar region to western Kashmir and there appears no major break. These structures are also re-folded in a major antiform with N-S axial trend. Map analysis also suggests that N-S trending folds bending earlier main thrusts are occurring in a wide area south of the Indus-Tsangpo suture.Several independent geological and geophysical observations including mapping, seismic analysis, earlier measurements of strain axes and of paleomagnetic declinations suggest that the salients and syntaxes may have been much more linear in the past (although a total linearity is not realistic). It is proposed that the present-day undulating pattern may have been generated by N-S trending folds due to general (and episodic) E-W shortening. If the main fault zones were more linear, the relay pattern along their segments suggests a left lateral shear component along MBT and a mixed, locally left, locally right lateral component along MFT. Earlier (ZEITLER 1985) and now provided low temperature thermochronological ages strongly suggest a rather general episode of E-W shortening between 4-5 Ma for the whole northern Indian margin. However, there should have been original transversal dome formation as early as Oligocene (DIPIETRO ET AL. 2008). It is also clear that longer N-S shortening and shorter E-W shortening episodes should alternate eventually in a very short time frame, since earthquake focal mechanisms (LISA AND KHWAJA 2004, BURG ET AL. 2005) suggest the coexistence of E-W compression and NW-SE compression in Potwar.There are several potential explanations for generating E-W shortening and related structures in a general N-S shortening regime. Possibilities range from fault terminations of thrust faults at high angles in a particular zone (TREOLAR ET AL. 1992) to en echelon folding along a major right lateral E-W fault zone. However, we speculate that E-W shortening could be much more general, suggesting a mechanism that affects the whole of Indian plate. Possibly the best explanation is given by analogue models (REPLUMAZ ET AL. 2012) proposing major, slightly convergent confining boundaries. If applied to the northwards advance of India, the northwards converging boundaries generate secondary E-W shortening and east-or west-vergent orogens parallel to these boundaries.

scholarly journals Controls of Deep-Seated Faults and Folds on Hydrocarbon Fluid Migration and Accumulation in Sedimentary Basins: A Case Study from the Northwestern Sichuan Basin, China

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Xi Wang ◽  
Yin Liu ◽  
Jian Cao ◽  
Yiduo Liu ◽  
Bing Luo ◽  
...  
Keyword(s):  
Seismic Data ◽  
Sichuan Basin ◽  
Horizontal Direction ◽  
Late Triassic ◽  
Fluid Migration ◽  
Thrust Faults ◽  
Hydrocarbon Accumulation ◽  
3D Seismic ◽  
Thrust Sheets ◽  
3D Seismic Data

Deep-seated faults and folds of foreland basin systems have become important exploration targets in the recent years because they are crucial in controlling fluid migration and hydrocarbon accumulation. In this study, we analyzed the characteristics and formation history of these structures in the northwestern Sichuan Basin using recently acquired two-dimensional (2D) and three-dimensional (3D) seismic data. The seismic interpretation revealed that the thrust sheets, tectonic wedges, and foredeep were well developed in the northwestern Sichuan Basin from the mountain to the basin. Forward thrusts, fault-bend folds, and wedges are the main types of structures in the thrust sheets and tectonic wedges. The deep-seated faults and folds were easily recognized in the high-resolution 3D seismic data. The imbricate thrust faults that merged into detachment layers of the Lower Cambrian are the main types of structures in the foredeep, and they show a prominent strike-slip influence in the horizontal direction. The formation of these structures in the foredeep in the northwestern Sichuan Basin mainly endured two stages of thrusting, including those during the Middle-to-Late Triassic and Cenozoic. Based on the tectonic evolution and seismic data, we infer that these deep-seated faults and folds in the foredeep may have formed earlier than the northern Longmen Shan fold-and-thrust belts and they may have been initially active in the late of Early Triassic and reactive during the Cenozoic. Furthermore, evaporites in the Lower and Middle Triassic were crucial in forming these structures. The petroleum exploration data suggested that the deep-seated faults can facilitate hydrocarbon accumulation. The thrust faults in the foredeep were more likely to act as migration pathways for fluids instead of sealing barriers along the horizontal direction. The interconnected reservoirs of deep-seated folds possess a great potential to allow large-scale hydrocarbon accumulation. Our study provides a good example for evaluating the hydrocarbon exploration potential in the deeply buried area in the sedimentary basin.

scholarly journals No mafic layer in 80 km thick Tibetan crust

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gaochun Wang ◽  
Hans Thybo ◽  
Irina M. Artemieva
Keyword(s):  
Seismic Data ◽  
P Wave ◽  
Indian Plate ◽  
Low Velocity ◽  
Crustal Earthquakes ◽  
Tectonic Processes ◽  
P Wave Velocity ◽  
Juvenile Crust ◽  
Mafic Lower Crust ◽  
Thick Crust

AbstractAll models of the magmatic and plate tectonic processes that create continental crust predict the presence of a mafic lower crust. Earlier proposed crustal doubling in Tibet and the Himalayas by underthrusting of the Indian plate requires the presence of a mafic layer with high seismic P-wave velocity (Vp > 7.0 km/s) above the Moho. Our new seismic data demonstrates that some of the thickest crust on Earth in the middle Lhasa Terrane has exceptionally low velocity (Vp < 6.7 km/s) throughout the whole 80 km thick crust. Observed deep crustal earthquakes throughout the crustal column and thick lithosphere from seismic tomography imply low temperature crust. Therefore, the whole crust must consist of felsic rocks as any mafic layer would have high velocity unless the temperature of the crust were high. Our results form basis for alternative models for the formation of extremely thick juvenile crust with predominantly felsic composition in continental collision zones.

scholarly journals LOS MAMIFEROS DE MICHOACÁN

2014 ◽  
Vol 4 (2) ◽  
pp. 1 ◽  
Author(s):  
Tiberio C. Monterrubio-Rico ◽  
Juan Felipe Charre Medellín ◽  
Cristina Z. Colín-Soto ◽  
Livia León Paniagua
Keyword(s):  
Regional Scale ◽  
Time Frame ◽  
The State ◽  
Limiting Factor ◽  
Current Estimate ◽  
Mammal Species ◽  
Wild Mammals ◽  
Lack Of Information ◽  
Potos Flavus ◽  
Tamandua Mexicana

 RESUMEN Los mamíferos silvestres han sido estudiados en Michoacán desde el siglo XVIII por renombrados zoólogos y naturalistas. Sin embargo, todavía en 1949 se reconocía solo 85 especies, y hasta el año 2005 se proporcionó estimaciones completas basadas en integración de registros disponibles tanto nacionales como de colecciones científicas internacionales, ya que la información disponible para el estado se encontraba dispersa. Como resultado de proyectos recientes con nuevos registros, el objetivo de este análisis es proporcionar una cifra actualizada sobre la riqueza taxonómica de los mamíferos silvestres terrestres en el estado de Michoacán. Existen registros de 161 especies en 9 Ordenes, 25 familias, y 94 géneros que representan el 32% de las especies de México. El Orden con mayor número de especies es Chiroptera con 74 especies que representan el 53% de las especies del Orden en México. A pesar de la ubicación central de Michoacán en el país, y ser un estado muestreado por numerosos investigadores, todavía existe carencia de información para regiones remotas, y en algunos grupos de mamíferos. Por ejemplo, el jaguar, que a pesar de ser el mayor felino del país, se carecía de confirmación para el estado, afortunadamente durante 2010 se localizó una población en el estado. Otro aspecto limitante para la interpretación adecuada de la estimación actual, es la antigüedad de muchos registros, ya que los estudios más completos realizados a escala regional, como en la costa Michoacana son de hace 30 años, y durante ese periodo se ha incrementado la deforestación de selvas tropicales, por lo que desconocemos la situación actual que presentan las poblaciones de mamíferos en el estado. En Michoacán encuentran su límite más norteño en el Pacífico tres especies de amplia distribución en el Neotrópico, Tamandua mexicana,  Potos flavus y Sphiggurus mexicanus, por lo que deben limitarse áreas que protejan sus poblaciones. Palabras clave: Distribución, Mochoacán, mamíferos, especies.ABSTRACT The wild mammals in Michoacan state have been studied since the XVIII century by reknown zoologists and naturalists. However, still in 1949 only 85 mammals species were recognized, and until 2005 a complete estimate based on the integration of national and international data bases records available from Scientific collections, since all available information was scattered. As a result of recent surveys with new records, the aim of this analysis was to provide an updated statistic of the terrestrial wild mammals taxonomic richness in the Michoacan state. Available records correspond to 161 species in 9 Orders, 25 families and 94 genera which represent 32% of the Mexican mammal species. The Order with the major number of species is Chiroptera that includes 74 species thet represent 53% of the Order in Mexico. Despite its central location in the country, and considering that the state has been surveyed by several prestigious academics, there is still a lack of information for remote regions, and for some mammal groups. For example, the jaguar, even though constitute the largest wild felid in the country, no information was available for the state, fortunately during 2010 a population was localized in the state. Another limiting factor for the adequate interpretation of the current estimate is that many records are outdated, since the most complete studies performed at a regional scale, like in the Michoaca coast, are 30 years old, and during that time-frame, tropical forest loss increased dramatically, for instance, the current situation that present the mammal populations in the state are unknown. In Michoacan three species with a broad neotropical distribution present its northernmost limit on the Pacific, Tamandua mexicana, Potos flavus, and Sphiggurus mexicanus and there is the need to establish protected areas oriented to protect their populations. Key words: Distribution, Michoacan, mammals, species.

scholarly journals Characterizing Seismo-stratigraphic and Structural Framework of Late Cretaceous-Recent succession of offshore Indus Pakistan

2018 ◽  
Vol 10 (1) ◽  
pp. 174-191 ◽  
Author(s):  
Majid Khan ◽  
Yike Liu ◽  
Asam Farid ◽  
Muhammad Owais
Keyword(s):  
Seismic Data ◽  
Late Eocene ◽  
Indian Plate ◽  
Processing Scheme ◽  
Structural Growth ◽  
Seismic Records ◽  
Exploratory Wells ◽  
Well Data ◽  
Seismic Reflection Profiles ◽  
Push Up

Abstract Regional seismic reflection profiles and deep exploratory wells have been used to characterize the subsurface structural trends and seismo-stratigraphic architecture of the sedimentary successions in offshore Indus Pakistan. To improve the data quality, we have reprocessed the seismic data by applying signal processing scheme to enhance the reflection continuity for obtaining better results. Synthetic seismograms have been used to identify and tie the seismic reflections to the well data. The seismic data revealed tectonically controlled, distinct episodes of normal faulting representing rifting during Mesozoic and transpression at Late Eocene time. A SW-NE oriented anticlinal type push up structure is observed resulted from the basement reactivation and recent transpression along Indian Plate margin. The structural growth of this particular pushup geometry was computed. Six mappable seismic sequences have been identified on seismic records. In general, geological formations are at shallow depths towards northwest due to basement blocks uplift. A paleoshelf is also identified on seismic records overlain by Cretaceous sediments, which is indicative of Indian-African Plates rifting at Jurassic time. The seismic interpretation reveals that the structural styles and stratigraphy of the region were significantly affected by the northward drift of the Indian Plate, post-rifting, and sedimentation along its western margin during Middle Cenozoic. A considerable structural growth along the push up geometry indicates present day transpression in the margin sediments. The present comprehensive interpretation can help in understanding the complex structures in passive continental margins worldwide that display similar characteristics but are considered to be dominated by rifting and drifting tectonics.

Seismic Qualitative and Quantitative Analysis for Reservoir Characterization of Globigerina BH Gas Field, North East Java Basin.

2021 ◽  
Author(s):  
I. Sumantri
Keyword(s):  
Quantitative Analysis ◽  
Seismic Data ◽  
Quantitative Methods ◽  
Reservoir Characterization ◽  
Seismic Analysis ◽  
Analysis Model ◽  
Gas Reservoir ◽  
Qualitative And Quantitative ◽  
North East ◽  
Exploration Well

BH field is one of the Globigerina limestone gas reservoir that exhibits strong seismic direct hydrocarbon indicator (DHI). This field is a 4-way dip faulted closure with Globigerina limestone as the main reservoir objective. The field was discovered back in 2011 by BH-1 exploration well and successfully penetrated about 350ft gross gas pay. BH-1 well was plugged and abandoned as Pliocene Globigerina limestone Mundu-Selorejo sequence gas discoveries. The laboratory analysis of sampled gas consists of 97.8% of CH4 and indicating a biogenic type of gas. This is the only exploration well drilled in this field and located on the crest of the structure. Seismic analysis both qualitative and quantitative, are common tools in delineating and characterizing reservoir. These methods usually make use of seismic data and well log collaboratively in the quest to reveal reservoir features internally. The lack of appraisal well in the area of study made the reservoir characterization process must be carried out thoroughly, incorporating several seismic datasets, both PSTM and PSDM, seismic gathers and stacks. Bounded by appraisal well limitation, this research looks into Gassmann's fluid substitution modeling, seismic forward modeling to confirm the DHI flat spot presence in the seismic, as well as seismic AVO analysis. Meanwhile, for quantitative analysis, model-based seismic post-stack inversion and simultaneous seismic pre-stack inversion were conducted in order to delineate the distribution of Globigerina limestone gas reservoir in BH Field. Through comprehensive analyses of qualitative and quantitative methods, this research may answer the challenge on how to intensively utilize seismic data to compensate the lack of appraisal well data in order to keep delivering a proper subsurface reservoir delineation.

Applications of quantitative prestack seismic analysis to unconventional resource play characterization in the Permian/Delaware Basin

2019 ◽  
Vol 38 (2) ◽  
pp. 106-115 ◽  
Author(s):  
Phuong Hoang ◽  
Arcangelo Sena ◽  
Benjamin Lascaud
Keyword(s):  
Hydraulic Fracturing ◽  
Seismic Data ◽  
Reservoir Characterization ◽  
Seismic Analysis ◽  
Seismic Inversion ◽  
Reservoir Properties ◽  
Yield Attributes ◽  
Horizontal Drilling ◽  
Delaware Basin ◽  
Unconventional Resource

The characterization of shale plays involves an understanding of tectonic history, geologic settings, reservoir properties, and the in-situ stresses of the potential producing zones in the subsurface. The associated hydrocarbons are generally recovered by horizontal drilling and hydraulic fracturing. Historically, seismic data have been used mainly for structural interpretation of the shale reservoirs. A primary benefit of surface seismic has been the ability to locate and avoid drilling into shallow carbonate karsting zones, salt structures, and basement-related major faults which adversely affect the ability to drill and complete the well effectively. More recent advances in prestack seismic data analysis yield attributes that appear to be correlated to formation lithology, rock strength, and stress fields. From these, we may infer preferential drilling locations or sweet spots. Knowledge and proper utilization of these attributes may prove valuable in the optimization of drilling and completion activities. In recent years, geophysical data have played an increasing role in supporting well planning, hydraulic fracturing, well stacking, and spacing. We have implemented an integrated workflow combining prestack seismic inversion and multiattribute analysis, microseismic data, well-log data, and geologic modeling to demonstrate key applications of quantitative seismic analysis utilized in developing ConocoPhillips' acreage in the Delaware Basin located in Texas. These applications range from reservoir characterization to well planning/execution, stacking/spacing optimization, and saltwater disposal. We show that multidisciplinary technology integration is the key for success in unconventional play exploration and development.

scholarly journals Implication of methodological uncertainties for mid-Holocene sea surface temperature reconstructions

2014 ◽  
Vol 10 (6) ◽  
pp. 2237-2252 ◽  
Author(s):  
I. Hessler ◽  
S. P. Harrison ◽  
M. Kucera ◽  
C. Waelbroeck ◽  
M.-T. Chen ◽  
...  
Keyword(s):  
Climate Model ◽  
Time Window ◽  
Planktonic Foraminifera ◽  
Regional Scale ◽  
Time Frame ◽  
Sea Surface ◽  
Model Simulations ◽  
Climate Model Simulations ◽  
Analytical Approaches ◽  
Baseline Climate

Abstract. We present and examine a multi-sensor global compilation of mid-Holocene (MH) sea surface temperatures (SST), based on Mg/Ca and alkenone palaeothermometry and reconstructions obtained using planktonic foraminifera and organic-walled dinoflagellate cyst census counts. We assess the uncertainties originating from using different methodologies and evaluate the potential of MH SST reconstructions as a benchmark for climate-model simulations. The comparison between different analytical approaches (time frame, baseline climate) shows the choice of time window for the MH has a negligible effect on the reconstructed SST pattern, but the choice of baseline climate affects both the magnitude and spatial pattern of the reconstructed SSTs. Comparison of the SST reconstructions made using different sensors shows significant discrepancies at a regional scale, with uncertainties often exceeding the reconstructed SST anomaly. Apparent patterns in SST may largely be a reflection of the use of different sensors in different regions. Overall, the uncertainties associated with the SST reconstructions are generally larger than the MH anomalies. Thus, the SST data currently available cannot serve as a target for benchmarking model simulations. Further evaluations of potential subsurface and/or seasonal artifacts that may contribute to obscure the MH SST reconstructions are urgently needed to provide reliable benchmarks for model evaluations.

Occurrence of the ophiolitic complexes along the Indoburman orogenic belt

1983 ◽  
Vol 120 (2) ◽  
pp. 175-182 ◽  
Author(s):  
R. Duarah ◽  
M. M. Saikia ◽  
C. C. Bhattacharjee
Keyword(s):  
Upper Mantle ◽  
Deep Sea ◽  
Lower Cretaceous ◽  
Late Jurassic ◽  
Orogenic Belt ◽  
Indian Plate ◽  
Mantle Material ◽  
Crust And Upper Mantle ◽  
Thrust Sheets ◽  
Ophiolitic Belt

SummaryThe ophiolitic complexes within the Indoburman orogenic belt form a conspicuous N-S line along the eastern margins of Manipur and Nagaland. The rock assemblages consisting of mafic-ultramafics are associated with deep sea pelagic sediments of the Disang Group (Lower Cretaceous-Eocene). The ultramafics in part, represent the oceanic crust and upper mantle material that formed the basement on which the radiolarites and other pelagic sediments were deposited. The fossil radiolaria present in the cherts suggest that the orogen took its foundation during late Jurassic-Lower Cretaceous time. The westward obduction of the flysch ophiolites in the form of large thrust sheets was possible during underthrusting of the Indian plate beneath the Burmese. The position of the ophiolitic belt defines the Indoburman suture zone.

East-directed imbrication and oblique-slip faulting in the Humber Arm Allochthon of western Newfoundland: structural and tectonic significance

1985 ◽  
Vol 22 (9) ◽  
pp. 1351-1360 ◽  
Author(s):  
William Bosworth
Keyword(s):  
Structural Features ◽  
Strike Slip ◽  
Thrust Faults ◽  
High Angle ◽  
Structural Geometry ◽  
Tectonic Significance ◽  
Thrust Sheets ◽  
Internal Deformation ◽  
Fold Formation ◽  
Slip Motion

Many of the dominant outcrop-scale structural features in the lower, clastic thrust sheets of the Humber Arm Allochthon were not generated during the westerly emplacement of the allochthonous terranes of western Newfoundland. Two general groups of structures are abundant in the Humber Arm rocks: (1) east-verging folds accompanied by a weakly to moderately developed slaty cleavage and cut by west-dipping thrust faults; and (2) northeast–southwest-striking high-angle faults, with predominantly normal oblique-slip motion and with larger faults down-stepping to the northwest. Evidence of the earlier, west-directed thrusting (refolded and downward-facing folds, folded thrusts, etc.) is uncommon in the Humber Arm area. Slaty cleavage-generation structures, however, appear to overprint the phacoidal fabrics of the mélange zones that exist between and within thrust slices of the allochthon, making the mélange fabrics the most readily identified features associated with the initial east over west imbrication and emplacement of the allochthon.These observations suggest that the original detachment of the rocks of the Humber Arm Supergroup from their basement (early Taconian deformation) occurred with only limited internal deformation. Mélange zones presently define some or all of the early surfaces of movement. The fully assembled and emplaced allochthonous terrane was subsequently reimbricated on a smaller scale through east-directed thrusting, at which time the allochthon was more pervasively deformed (regional slaty cleavage and fold formation). This may represent late Taconian back thrusting or Acadian shortening. The youngest deformation of the Humber Arm region appears to have been a regional extensional event, with a significant northeast–southwest strike-slip component of movement. This may correlate with the development of Carboniferous strike-slip basins in the present Gulf of St. Lawrence and western Newfoundland. Much of the present structural geometry in the Humber Arm region, including the contacts between ophiolitic and clastic thrust sheets, may have originated during these later two deformational sequences, rather than as a consequence of the initial emplacement history.

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