Fission Track Geochronology of Xiaonanchuan Pluton and the Morphotectonic Evolution of Eastern Kunlun since Late Miocene

Apatite fission track （AFT） thermochronology of seven samples from the Xiaonanchuan （小南川） pluton in the Kunlun （昆仑） pass area was carried out, for the purpose of determining the timing of cooling and the relation between the exhumation and the morphotectonic processes. The AFT ages yield low denudation rates of 0. 020--0. 035 mm/a during the late Miocene, which correspond to a stable geomorphic and weak tectonic uplifting environment. The low denudation rates can be considered as the approximate tectonic uplifting rates. The AFT geochronology shows puroxysmully rapid cooling since the Pliocene and an apparent material unroofing of more than 3 km in the Xiaonanchuan area. This was not the result of simple denudation. The rapid cooling was coupled with the intensive orogeny since the Pliocene, which was driven by tectonic uplifting. The accelerated relief building was accompanied by a series of faulting, which caused the basin and the valley formation and sinking. The space pattern of the AFT ages also shows differential uplifting, which decreases northwardly. This trend is supported by the regional AFT data, which indicate that the exhumation decreases northwardly in eastern Kunlun. This trend also exists in cast-west orientation from the western Kunlun range to the eastern. The uplif- ting trend is also supported by gcomorphic characteristics including the elevation and the relief differences well as the distribution of the Late Cenozoic volcanism.

The morphotectonics and its evolutionary dynamics of the central Southwest Indian Ridge (49° to 51°E)

The morphotectonic features and their evolution of the central Southwest Indian Ridge （SWIR） are dis- cussed on the base of the high-resolution flfll-coverage bathyraetric data on the ridge between 49°-51°E. A comparative analysis of the topographic features of the axial and flank area indicates that the axial topogra- phy is alternated by the ridge and trough with en echelon pattern and evolved under a spatial-temporal mi- gration especially in 49°-50.17°E. It is probably due to the undulation at the top of the mantle asthenosphere, which is propagating with the mantle flow. From 50.17° to 50.7°E, is a topographical high terrain with a crust much thicker than the global average of the oceanic crust thickness. Its origin should be independent of the spreading mechanism of ultra-slow spreading ridges. The large numbers of volcanoes in this area indicate robust magmatic activity and may be related to the Crozet hot spot according to RMBA （residual mantle Bouguer anomaly）. The different geomorphological feature between the north and south flanks of the ridge indicates an asymmetric spreading, and leading to the development of the OCC （oceanic core complex）. The tectonic activity of the south frank is stronger than the north and is favorable to develop the OCC. The first found active hydrothermal vent in the SWIR at 37°47＇S, 49°39＇E is thought to be associated with the detach- ment fault related to the OCC.

Study on Saravan Fault Activities on the Basis of Earthquake and Morphotectonics Evidences

Saravan Fault is the biggest fault in southeast of Iran. It is Right-Slip fault. It has been extended from northwest to southeast. It is important to evaluate tectonic activities along this fault because it is adjacent to the city and various villages. It’s found that there are various tectonic activities along this fault. In this paper, it has been studied on affecting this fault on geomorphology of the zone. Average values of some indices such as Mountain Font Sinuosity and V ratio have been studied that they are 1.76 and 0.77, respectively. It suggests that there are serious tectonic activities in the zone. There are some evidences such as Right-Slip fault along artificial river channel that indicates its youngest stage means Late Cenozoic. According to studies, Saravan Fault is more active in the middle zone than northwest and southeast ends.

Morphotectonic Analysis of Burkh Anticline, North of Bastak (Zagros)

Burkh Anticline having a length of 50 km and a width of 9 km is located 40 km to the north of Bastak City in Internal Fars zone along folded-thrust belt of Zagros. In order to assess the active tectonics in the area of study, morphotectonical indices such as valley index (V), ratio of valley floor to valley height (Vf), channel sinuosity index (S), mountain front faceting index (F%) and mountain front sinuosity(Smf) are studied. These investigations show that the activity is not equal in various sections along Burkh Anticline and the central part of this anticline is the most active one.

Morphotectonic Study of Frontal Siwalik Hills, near Gandhiri, Kangra, Himachal Pradesh, India

The densely populated foothill zone of western Himalaya between the Beas river and the Chakki stream in and around Kangra is being critically examined by us considering the seismo-tectonic destructive potential of the 1905 (Mw 7.8) Kangra earthquake which has not been evaluated so far. We use Resourcesat 1: LISS III Ortho satellite imageries and field studies to qualitatively and quantitatively assess the active tectonic setup of the terrain. Quantitative morphotectonic analysis viz. hypsometric integral, drainage basin asymmetry, stream sinuosity index, ratio of valley floor width to valley height, stream length gradient index, basin shape index and mountain front sinuosity index are being evaluated on high resolution digital elevation model. The five sub-drainage basins of the Gandhiri stream, the Sukar stream and the Duhg stream of Kangra district of Himachal Pradesh, India are being morphotectonically analyzed. The value of hypsometric integral, drainage basin asymmetry, stream sinuosity index, ratio of valley floor width to valley height, stream length gradient index, basin shape index and mountain front sinuosity index reveal that the terrain is tectonically active. An active dextral strike slip fault with significant oblique slip component has been inferred and is being named as the Gandhiri Fault. This fault crosses all the five sub-drainage basins and results in multiple stream offsets. The Index of Relative Tectonic Activity (IRAT) has been established for different sub-drainage basins. The study reveals that the terrain near Gandhiri in Kangra district of Himachal Pradesh is seismo-tectonically active and proper building codes should be followed in construction activity.

Assessment of Recent Tectonic Activity along the Yamuna Basin, Garhwal Region, NW-Himalaya, India: Based on Morphotectonic Analysis

Decoupling between climate and tectonics, transform the elevation of earth surface regionally by denudation and displacement of land. To extract the tectonic footprints on morphology of landform, geormophometry is widely accepted tool due to visible responses in Drainage architecture to an intense tectonic environment. The present morphology of Yamuna basin in the Garhwal Himalaya, India is a result of continuing crustal deformation;erosion and deposition in the area. The drainage system and geomorphic expression of topography have been significantly influenced by active tectonics in this basin. In present study, for numerical modelling to detect the influence of tectonic signals on landform, we used morphotectonic parameters, to gradient index (SL), valley floor height to width ratio (Vf), asymmetry factor (Af), basin shape index (BS) and hypsometric integral (HI), extracted from SRTM DEM with resolution of 30 m. All these morphotectonic parameters are integrated to produce an index of relative active tectonics (IRAT). The Yamuna basin is classified into three groups based on IRAT, very high (<2.0);moderate (2.0 - 2.25) and low (>2.25) based on the degree of tectonic activity. Result shows approx. 56% of Yamuna basin experience high tectonic activity. This along strike deformation pattern pronouncedly emulates subsurface geometry based tectonic model.

Cenozoic Age Counterclockwise Rotation in the Northwest End of the Sierras Pampeanas, Argentina

Investigations into the Andean orocline revealed a counterclockwise rotation of about 37° in the north and a clockwise rotation of about 29° in the south. This rotation would have started in the Eocene because the Nazca and South American plates converged. The transition zone between the Puna and the Sierras Pampeanas has a clockwise rotation pattern. Our new data show that the NE convergence of the Nazca and South American plates caused the counterclockwise rotation around the NW end of the Sierras Pampeanas. The temperature rise during a magmatic activity at 13 Ma would have favored a counterclockwise rotation of the mountain blocks of about 20° on a detachment zone within 10 to 15 km of depth. These range rotations generated local stress tensors trending NE and NW, facilitating the development of valleys, basins, mineralized dikes, mineral deposits, and alluvial fans separated from their origin. The Atajo fault shows both ductile and brittle characteristics. A mylonitic belt from the Sierra de Aconquija was juxtaposed on the rocks of the Ovejería Block and the Farallón Negro Volcanic Complex by reverse vertical displacement, and a dextral horizontal component of displacement resulted in curvatures that gave rise to pull-apart basins and step over features. The Santa Maria Valley, Campo del Arenal, Hualfín Valley, and Pipanaco salt flat most likely constituted a vast early Miocene basin rarely interrupted by low feature relief.

Evidences for Incipient Hydrothermal Event(s) in the Central Indian Basin: A Review

The Central Indian Basin (CIB, 10°-19°S) encompasses morphotectonic features such as seamounts, abyssal hills, faults, fracture zones and lineations and basic to silicic volcanics that were derived from different sources. Instances of incipient hydrothermal event (s) occurred as evident from: (1) spilites that probably formed due to low-temperature hydrothermal action on the precursory basalts, (2) slabs and fragments of zeolitites which are the consequent products of palagonitization of the basaltic glasses, (3) chemical variations in the ferromanganese crusts, and (4) abundance of volcanogenic-hydrothermal material (vhm) that includes ochrous sediments and magnetite spherules. The vhm suggests its origin by interaction of Fe-rich hydrothermal solutions with surrounding sediments. The CIB spherules occur in sediments of~10 ka and ~425 to 650 ka age and are orders of magnitude younger than the 50 to 60 Ma age of the basin. Incidentally, to the north of the basin at ODP Site 717-719(1 °S/81 °E) hydrothermal precipitates of inorganic calcite and deposition of sulphide minerals (~7.5 to 9 Ma and 0.5 Ma) occur as a result of the on-going intraplate deformation. This paper reviews the above evidences that possibly indicate episodes of localized hydrothermal events in the CIB.

Recent tectonic activity in Central Alborz Mountain,Iran:morphometric analysis and knickpoint identification

Alborz,as part of the Alpine-Himalayan orogeny belt,has been the result of the convergence of the Central Iranian and Eurasian plate since the late Triassic.The study area located in Central Alborz encompasses different Quaternary faults.Thus,the present study aimed to evaluate the effect of faults on river landforms through morphotectonic indices and the causes of knickpoints and knickzones in the Bedrock Rivers in part of Central Alborz.To this end,six morphometric indices such as longitudinal gradient(SL),hierarchical anomaly(Δα),the bifurcation index(R),hypsometric integral and hypsometric curve(Hi-Hc),relative relief(Bh),and basin shape(Bs) were calculated and analyzed in38 sub-basins of the area.Finally,the area was divided into extremely high,high,medium,and low tectonic activity areas using the relative tectonic activity(IAT).Normalized steepness and concavity indices along with the longitudinal profiles of the streams were obtained using Matlab and Arc GIS software.Based on the findings,the existence of slope-break knickpoints at the mountain piedmont at the outlet of large rivers through active faults demonstrated that most of these landforms were created by movements along the main faults such as Khazar,Nusha,Soheil,Deylaman,Kashachal,representing high tectonic activity in the central and southern parts of the study area.However,the values of these indices were extremely low and indicated low tectonic activity in the northern parts located in the embayment part of the Caspian Sea.Finally,the findings revealed that these classes correspond well to the areas with landforms such as V-shaped and narrow valleys,gorges,deflected and offset streams,deformed Neogene,and Quaternary units that indicate the post-Neogene activity.

Quaternary tectonic control on channel morphology over sedimentary low land:A case study in the Ajay-Damodar interfluve of Eastern India

The style of active tectonic on the deformation and characterization of fluvial landscape has been investigated on three typical skrike-slip fault zones of the Ajay-Damodar Interfluve（ADI） in Eastern India through field mapping,structural analysis and examination of digital topography（ASTER-30 m）,multispectral imageries,and Google Earth images,Channel morphology in Quaternary sediment is more deformed than Cenozoic lateritic tract and igneous rock system by the neotectonic activities,The structural and lithological controls on the river system in ADI region are reflected by distinct drainage patterns,abrupt change in flow direction,offset river channels,straight river lines,ponded river channel,marshy lands,sag ponds,palaeo-channels,alluvial fans,meander cutoffs,multi-terrace river valley,incised compressed meander,convexity of channel bed slope and knick points in longitudinal profile,Seven morphotectonic indices have been used to infer the role of neotectonic on the modification of channel morphology,A tectonic index map for the ADI region has been prepared by the integration of used morphotectonic indices,which is also calibrated by Bouguer gravity anomaly data and field investigation.

Paleoseismological Analysis Along the Astara Fault System(Talesh Mountain, North Iran)

The Astara Fault System（AFS） is located in the northwest Alborz, east of Talesh Mountain（TM） and west of the South Caspian Basin（SCB）. The AFS is one of the basement rock faults in Iran that is heavily involved in seismotectonic activity of the Talesh region, and to which subsidence of the SCB is attributed. There is little information available concerning previous AFS seismic activities and its properties. In order to elucidate the seismic behavior and activities of the AFS, we conducted a research study on paleoseismology of the fault. Based on paleoseismic evidence, two scenarios could be taken into consideration, one of which has three and another has four seismic events with magnitudes Mw in the range of 6.7 to 7.2. Evidence of these seismic events is within sedimentary succession as they have occurred during the past 3 ka（this age is determined based on the deposition rate of the region）. Six carbon samples were taken for C^14 age determination tests, the results of which clearly demonstrated that the EvIV（scenario A） and EvⅢ（scenario B） had occurred before 27,444 cal BP, while other events occurred in the time period between 27,444 cal BP and 3 ka ago. If we consider the occurrence of three or four seismic events（based on the two scenarios） to be between 27,444 cal BP and 3 ka ago, the average recurrence interval is 7,119 ± 1,017, but evidence for these events has been removed. If we assume EvI to be the youngest event（in both scenarios）, the minimum elapsed time is therefore 3 ka.

Eurasia as the scene of the Late Cenozoic tectogenesis

This paper attempts to review the descriptions on the genetic series of neotectonic forms in Eurasia. Morphotectonically, the Eurasian continental block exhibits a radial-concentric pattern consist- ing of four kinds of tectonic units： platforms, rejuvenated and youthful mobile belts, and the continent- ocean transition zones. Vast areas of young and ancient platforms, such as Siberia, have experienced slow-rate Late-Cenozoic uplift and little interior deformation. The youthful orogenic belts are clustered into the giant Alpine-Himalayan megabelt. The rejuvenated mountain belts are characterized by a variety of structural-morphological types of orogens, such as domelike uplifts, block uplifts and intermountain basins. The continent-ocean transition zones in Eastern Asia, including marginal rifts and extensional basins, are resulted from interaction between the continental block and Pacific Ocean and Philippine Sea since the Late Cenozoic. One of the conspicuous features of Eurasia is that most areas lie in the largest geoid depression of the Earth, and the NS trending Uralian-Oman lineament expresses a break on the geoid slope, implying a relationship to deep structure, including density inhomogeneities, down- ward to the core-mantle interface. Besides, the Eurasian continent fully demonstrates morphotectonic and recent geodynamic features of the Northern Hemisphere of the Earth, just in contrast to that of the Southern Hemisphere. It is best to view the surface morphotectonics and deep structure of the Earth as a geodynamic ensemble which has spawned the large-scale geomorphic features on the surface.

Lithological and tectonic response on catchment characteristics of Rishi Khola, Sikkim, India

Rishi Khola,a sub-watershed of Teesta river,traverses along the Main Central Thrust(MCT)with a multitude of litho units and structural entities.This study examines the impact of tectonic and lithologic controls in configuring the catchment characteristics of Rishi Khola,Sikkim,India.Corrected SRTM 30m DEM and Landsat 8 satellite image have been used for extracting the river network,preparing the sub-catchments,the longitudinal profile and thereby calculating the morphotectonic indices.An aggregated tectonic index(ATI)has been prepared to map the intensity of tectonic perturbations in the fluvial environment using the entropy weightage method(EWM)and Weighted Linear Combination(WLC).The undulating nature of the longitudinal profile with prominent knick points confirms the presence of tectonic disturbances and lithological variations.From all the computed morphotectonic indices and the ATI,it has been evident that the region has experienced surface deformations.When viewed at the entire catchment,the morphotectonic indices suggest ample responses to the tectonic perturbations due to the dominance of lithology-controlled hill slope processes and fluvial erosion.The spatiality of the tectonic sensitiveness is rather concentrated into certain pockets of differential stress field formed due to fault thrusting of the Himalayas.The study chiefly focuses on the peculiarity of the watershed which displays a complex response of tectonic and rock structure;wherein the proposed methodology has been successful in excavating such complex responses around the Himalayan thrusts.

Geomorphological responses of rivers to active tectonics along the Karahay?t Fault, Western Türkiye

Understanding the topography in active tectonic areas and assessing the rates and models of active deformation in the upper crust are primary objectives in tectonic geomorphology studies. The drainage pattern of river systems is highly sensitive to tectonically induced changes, and it often preserves the records of the formation and progression of most tectono-geomorphic processes within its boundaries. Therefore, the evolution of landforms is a consequence of the evolution of individual drainage basins in which they are formed. Assessing the rates of tectonic deformation using geomorphic data is a traditionally adopted method to characterize the nature of active faults. Globally, the Digital Elevation Model(DEM) is widely used as a crucial tool to analyze the morphotectonic features of drainage basins. In this study, some geomorphic indices were applied to investigate the impact of tectonism on landscape along the Karahay?t Fault and its associated drainage areas. These geomorphic indices are mountain front sinuosity(Smf values between 1.17-1.52), valley floor width-to-height ratio(Vf values between 0.25-1.46), basin asymmetry factor(AF values between 15-72), drainage basin shape(Bs values between 3.18-6.01), hypsometric integral and curve(HI values between 0.32-047), channel sinuosity(S values between 1-1.6), normalized steepness index(Ksn values between 1-390) and Chi integral(χ values between 200-4400). The development of drainage areas on the hanging wall and footwall block of the Karahayit Fault differs depending on the uplift. The drainage areas developed on the hanging wall present different patterns depending on the regional uplift caused by the fault. This reveals that the fault contributed significantly to the development of drainage areas and regional uplift in the region. In addition, the maximum earthquake magnitude that may occur in the future on the Karahayit Fault, whose activity is supported by geomorphic indices, is calculated as 6.23. Since an earthquake of this magnitude may cause loss of life and property in the region, precautions should be taken.

Denudation History of South China Block and Sediment Supply to Northern Margin of the South China Sea

On the basis of apatite fission track （AFT） analyses, this article aims to provide a quantitative overview of Cenozoic morphotectonic evolution and sediment supply to the northern margin of the South China Sea （SCS）. Seventeen granite samples were collected from the coast to the inland of the South China block. Plots of AFT age against sample location with respect to the coastline show a general trend of youngling age away from the coast, which implies more prolonged erosion and sediment contribution at the inland of the South China Sea during post break-up evolution. Two-stage fast erosion process, Early Tertiary and Middle Miocene, is deduced from simulated cooling histories. The first fast cooling and denudation during Early Tertiary are recorded by the samples along the coast （between 70 and 60 Ma） and the inland （between 50 and 30 Ma）, respectively. This suggests initial local erosion and deposition in the northern margin of the SCS during Early Tertiary. Fast erosion along the coast ceased since ca. 50 Ma, while it had lasted until ca. 30 Ma inland, indicating that the erosion was transferred from the local coastal zone initially toward the continental interior with unified subsidence of the northern margin, which resulted in the formation of a south-dipping topography of the continental margin. The thermal stasis in the South China block since ca. 30 Ma must define the time at which the northern margin became dynamically disconnected from the active rifting and stretching that was taking place to the south. The lower erosion rate is inconsistent with higher sedimentary rate in the Pearl River Mouth basin during Late Oligocene （ca. 25 Ma）. This indicates that the increased sedimentation in the basin is not due to the erosion of the granite belt of the South China block, but perhaps points to the westward propagation of the paleo-Pearl River drainage related to the uplift of the eastern margin of Tibet plateau and southward jumping of spreading axis of the South China Sea. The second erosion acceleration rate of the Middle Miocene （ca. 14 Ma） cooling could have been linked to the long-distance effect of uplift of the Tibet plateau or due to the enhanced East Asian monsoon.