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1.
In the last decade, even in areas that had been considered tectonically stable, a great amount of Cenozoic, including the Quaternary period, structural data have been collected throughout Brazil. The main goal of this study is to describe the Cenozoic structures and tectonic evolution of an area that is located at the border of the Paraná Basin in the state of São Paulo.The research methods consisted of the analysis of: (1) brittle structure data, mainly conjugate fractures and fault slip data; (2) lineaments traced on air photos and TM Landsat and radar images; and (3) a second-order base surface map.The study area, during the Cenozoic, has been affected by five strike–slip tectonic events, which generated mainly strike–slip faults, and secondarily normal and reverse ones. The events were named, from the oldest to the youngest, E1-NE, E2-EW, E3-NW, E4-NS, and E5-NNE; and the maximum principal stresses σ1 strike approximately NE–SW, E–W, NW–SE, N–S, and NNE–SSW, respectively. Event E2-EW seems to have been contemporaneous with the deposition of the Rio Claro Formation, the most important Cenozoic deposit of probable Neogenic age, and also to have controlled the distribution of its deposits. Event E3-NW was the strongest one in the area, as is pointed out by structural data, and the maximum principal stress σ1 of event E5-NNE is partially concordant with the orientation of σH-max of well break-out data in the Paraná Basin, suggesting a Neotectonic activity for this event. Finally, discontinuities parallel and correlated to the directions of strike–slip faults of the Cenozoic events seem to have actively controlled the sculpturing of the relief in the study area. 相似文献
2.
大兴安岭东坡中段遥感影像特征与区域成矿预测标志 总被引：1，自引：0，他引：1
大兴安岭东坡中段的铜多金属矿产分布，ＮＥ成带，ＥＷ成行，ＮＷ成列，并构成多个矿化－构造带、矿化－构造块体，矿化－构造结。主要是受到区域ＮＥ向与ＥＷ向构造带构成的构造大格局和ＮＷ向与ＳＮ向构造带形成的构造小格局组合而成的“菱格网”状构造所控制。区域构造格局是铜多金属矿成矿构造的基础，据此区域性的遥感成矿预测，指出北段以找铜为主，中段以扩大银铅锌远景为主，深部找铜以及南段深部找铜的找矿方向。 相似文献
3.
Seismicity and neotectonic uplift in the Augrabies Falls National Park,Namaqualand,Northern Cape,South Africa 
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下载免费PDF全文 Kakaba Madi 《地震科学（英文版）》2016,29(5):281-289
Gneissic rocks in the Augrabies Falls National Park are part of the Proterozoic Namaqua-Natal mobile belt. Finding neotectonic evidence in old terranes is always not an easy task. In South Africa, the mid-Miocene is believed to be the beginning of neotectonics. This study investigated the occurrence and recurrence of earthquake activity, occurrence of faulting, jointing, uplift, and potholes in the gneisses cropping out around the Augrabies Falls area that may account for neotectonics. A historic seismic event obtained from the United States Geological Survey(USGS), and seismic epicenters downloaded in October 2015 from IRIS earthquake browser and overlaid on a satellite image with digitised faults and lineaments,indicates that the area is seismically active and is a zone of seismic risk. Potholes occurring today on a dry surface at approximately 613 m above sea level are a direct consequence of the Griqualand-Transvaal neotectonic uplift,which generated a major fault along which water flows continuously. It is concluded that the Augrabies Falls National Park area is a zone of neotectonics. This zone should not be considered for the storage of nuclear wastes. 相似文献
4.
The technique of the wavefield polarization is applied to ambient vibrations recorded in the Mefite d’Ansanto area, an important non-volcanic natural emission of low temperature CO2 enriched gases. Twenty-five measurements were performed in the study area, eleven near the emission site and the other fourteen in different sites within an area of 5 km. Polarization is assessed both in the frequency and time domain through the individual-station horizontal-to-vertical spectral ratio and covariance-matrix analysis, respectively. We find a significant tendency of ground motion in the gas emission area to be polarized in the horizontal plane, with a N115° predominant trend. This polarization tends to disappear while moving far from the site. According to previous papers in other study areas, such a directional effect is likely caused by fault-induced fractures and tends to be orthogonal to the fracture strike. The predominant NW–SE regional faulting does not fit the N115° polarization direction. To explain observations, we propose an interpretation in terms of a NE–SW oriented, local transfer fault as inferred from the lineament analysis. The intersection of the damage zone of this fault with the regional NW–SE normal fault system could easily be the responsible for the gas emissions since it favors a locally increased crustal weakness. 相似文献
5.
G. Neef 《Australian Journal of Earth Sciences》2013,60(5):647-660
The Early Devonian, Maccullochs Range beds (new) of the Winduck Interval largely comprise non-marine fine-grained sheet-flood-deposited sandstones which lie in the southeast sector of the Darling Basin Conjugate Fault System. Deposition of the >2.5 km-thick sequence occurred on the Wilcannia, Towers and Coolabah Bore alluvial fans, that were sourced largely from lightly indurated sandstone caps overlying a large basement high lying north of the Darling River Lineament, and also from west of Maccullochs Range (Coolabah Bore Fan). Four lithofacies are recognised. Lithofacies 1, massive sandstone, is proximal and was deposited from hyperconcentrated sheet floods. The more distal lithofacies 2 is partly massive, partly laminated and partly affected by soft sediment slumping during its deposition. It contains 1.3 – 3.5 m-thick sheet-flood successions that rarely show cross-bedding. Lithofacies 3 and 4 are minor: lithofacies 3, stream-flood deposited, comprises coarse-grained, pebbly sandstone and lithofacies 4, transient playa lake deposits that are locally intercalated with lithofacies 2. In lithofacies 2, thick massive fine-grained sandstone is commonly overlain by laminated sandstone that was deformed when soft. Incised channel deposits in lithofacies 2 deposits are rare and palaeosols were not discovered. Permanency of the positions of two of the alluvial fans, and by inference their feeder streams, remained unchanged for ～9 million years. The fans overlie probable floodplain deposits observed in a quarry in the easternmost part of the study area. Marine fossils are very minor in the range—the brachiopod Howellella jaqueti at one locality indicates an Early Devonian age for one of the brief marine incursions into what was normally an alluvial-fan environment. Very brief marine incursions elsewhere in the group are deduced from the presence of very rare fossil gastropods. 相似文献
6.
Aeromagnetic (AM) and Landsat Thematic Mapper (TM) data from the south-central Zimbabwe Craton have been processed for the purpose of regional structural mapping and thereby to develop strategic models for groundwater exploration in hard-rock areas. The lineament density is greater on TM than on AM images, partly due to the resolution of the different datasets, and also because not all TM lineaments have a magnetic signature. The derived maps reveal several previously undetected lineaments corresponding to dykes, faults, shear zones and/or tectonically-related joints, striking predominantly NNE, NNW and WNW. We suggest the possible hydrogeological significance of some of these patterns as follows: the aeromagnetic data can be used to map faults and fractures of considerable depth which are likely to be open groundwater conduits at depth (typically under tension), while TM lineaments, although not necessarily open (mostly under compression), represent recharge areas.The interpreted persistent lineation and well developed fracture patterns are correlated with existing boreholes and indicate a spatial relationship between regional structures and high borehole yields (> 3 m3/h). This relationship is combined with other lithological and hydrogeological information to identify potential regional groundwater sites for detailed ground investigations. These are defined as dyke margins, faults, fractures/joints or intersections of any combination of these structures. Priority should be given to coincident AM/TM lineaments (e.g., NNW and NNE fractures) and continuous structures with large catchment areas (e.g., NNE and WNW faults). The late Archaean (2.6 Ga) granites are considered the most favourable unit because of their associated long and deep brittle fractures between numerous bornhardts (inselbergs) and kopjes. Several small-scale TM lineaments also form important local sources of groundwater for hand-dug wells. Based on measured rock susceptibilities from the area, we present a model of the typical magnetic responses from the possible groundwater exploration targets. The developed magnetic model could be applicable to similar terrains in other Archaean Cratons. 相似文献
7.
《世界地质(英文版)》2016,(4)
Late Cretaceous sea inundation of major continents,surprisingly did not affect Indian block except by two major subaerial events of Large Igneous Provinces( LIPs). Marion hotspot induced LIP of Mahajanga Flood Basalt( ca. 92 Ma) in Madagascar triggered high intensity earthquake along Narmada Lineament and permitted a short lived marine transgression during late Turonian with spectacular estuarine deposits of limited thickness,preserved as archive of "Greenhouse Climatic Record". Réunion hotspot induced LIP of Deccan Flood Basalt,stretching from western to eastern India around Rajahmundry area attracted worldwide attention for the unique fauna and flora preserved in the intertrappean beds straddling Cretaceous-Palaeogene boundary. This massive subaerial LIP( ca. 66 Ma) permitted fairly deep penetration of sea along collision facing Subathu-Dogadda Lineament during late Maastrichtian-Danian,but due to thick vegetation cover,tectonic disturbance and scarce outcrops the evidence is less straightforward than along Narmada rift. 相似文献
8.
Imag(in)ing the continental lithosphere 总被引：1，自引：0，他引：1
This paper is primarily concerned with seismically imaging details in the mantle at an intermediate scale length between the large scales of regional and global tomography and the small scales of reflection profiles and outcrops. This range is roughly 0.1–1 km < a < 10–102 km, where a is the scale. We consider the implications of several models for mantle evolution in a convecting mantle, and possible scales present in the non-convecting tectosphere. Reflection seismic evidence shows that the structures preserved from continental accretion within and at the margins of the Archean cratons are subduction related, and we use subduction as an analog for scales left by past events. In modern orogenic belts we expect to find subduction structures, small scale upper mantle convection structures, and basalt extraction structures. We examine some of the scales that are likely formed by orogenic processes.We also examine the seismic velocity and density contrasts expected between various upper mantle constituents, including fertile upper mantle, depleted upper mantle, normal and eclogitized oceanic crust, and fertile mantle with and without partial melt. This leads directly to predicting the size of seismic signals that can be produced by specular conversion, and scattering from layers and objects with these contrasts.We introduce an imaging scheme that makes use of scattered waves in teleseismic receiver functions to make a depth migrated image of a pseudo-scattering coefficient. Image resolution is theoretically at least an order of magnitude better than traveltime tomography. We apply the imaging scheme to three data sets from 1) the Kaapvaal craton, 2) the Cheyenne Belt, a Paleoproterozoic suture between a protocontinent and an island arc, and 3) the Jemez Lineament, a series of aligned modern volcanic structures at the site of a Proterozoic suture zone. The Kaapvaal image, although not defining a unique base of the tectosphere, shows complicated “layered” events in the region defined as the base of the tectosphere in tomography images. The image of the transition zone discontinuities beneath the Kaapvaal craton is remarkable for clarity. The migrated receiver function image of the upper mantle beneath the Cheyenne belt is complicated, more so than the tomography image, and may indicate limitations in the receiver function imaging system. In contrast the Jemez Lineament image shows large-amplitude negative-polarity layered events beneath the Moho to depths of 120 km, that we interpret as melt-containing sills in the upper mantle. These sills presumably feed the Quaternary–Neogene regional basaltic volcanic field. 相似文献
9.
V. N. Bajpai 《Journal of Earth System Science》2004,113(3):427-451
The Luni river basin has been evolved as a result of typical hydrogeomorphic processes of arid zone, operating under the influence
of active tectonic lineaments. A detailed analysis of stream morphology in relation to geology and lineaments carried out
on selected windows indicated the morphological control of the streams while flowing over the lineaments from the eastern
to the western part of the basin. Typical valley fills indicated by dark green tone on digitally processed images and the
pediments showing greenish white tone appear in sharp contrast and indicate respectively the graben and horst structures.
A detailed identification of lineaments for the georesources and geological evaluation has been carried out. Earlier analysis
carried out on Bouguer anomalies correlate with graben and horst structures in the subsurface. Quaternary sequences have been
dated from 80 ka to 3 ka indicating a range of fluvial to aeolian deposits reflecting prevailing climatic conditions. However,
the changes in sediment type from coarse and mixed of all size grades to fine in a vertical litho-column warrant further studies
on fine resolution stratigraphy and high resolution stratigraphy for understanding climatic variations in the region 相似文献
10.
A method of seismic zonation based on deterministic modeling of rupture plane is presented in this work. This method is based
on the modeling of finite rupture plane along identified lineaments in the region using the semi-empirical technique, of Midorikawa
[(1993) Tectonophysics 218:287–295]. The modeling procedure follows ω2 scaling law, directivity effects, and other strong motion parameters. The technique of zonation is applied for technoeconomically
important NE part of Brahmaputra valley that falls in the seismic gap region of Himalaya. Zonation map prepared for Brahmaputra
valley for earthquakes of magnitude M > 6.0 show that approximately 90,000 km2 area fall in the highly hazardous zone IV, which covers region that can have peak ground accelerations of order more than
250 cm/s2. The zone IV covers the Tezu, Tinsukia, Dibrugarh, Ziro, North Lakhimpur, Itanagar, Sibsagar, Jorhat, Golaghat, Wokha, Senapati,
Imphal, and Kohima regions. The Pasighat, Daring, Basar, and Seppa region belong to zone III with peak ground accelerations
of the order 200–250 cm/s2. The seismic zonation map obtained from deterministic modeling of the rupture is consistent with the historical seismicity
map and it has been found that the epicenter of many moderate and major earthquakes fall in the identified zones. 相似文献