Fold pattern analysis around Kanjamalai Salem district Tamilnadu

Kanjamalai one of the fascinating location in Southern Granulite Terrain (SGT) for studying Archaean geology and structures as the entire hill is made up of variety of rock types like two pyroxene granulite, amphibolites, quartzo - feldsapthic gneisses, banded iron formation, and intrusive rocks like dunite, peridotite and pegmatite and beautifully carved structures. The entire hill resembles a canoe shape with doubly plunging fold structure with E-W elongation. The entire hillock seems to sit pretty on mylonitised hornblende biotite gneisses which also have a common N70-95 degree trend and sub vertical dip with NE plunge which is in contradiction to centrally plunging lineations of the hill. The SW part of Kanjamalai near Chinasrirangapadi was displaying beautiful fold structures, with interference pattern out of which six domains were selected for detailed study and analysis. The multiple generation folded structure will have a clue in reconstructing the deformation history of this Kanjamalai. The observed f1, f2 and f3 folds show significant Type III interference pattern as that of Ramsay and 01 and 03 type folds of Bernhard Grasemann.   Wavelength –amplitude analysis was made to generalize and regroup the observed folds in to high amplitude, high wavelength or open folds, low wavelength and Mesoscopic folds. And visual harmonic analysis was made to analyse the symmetry of the folds and analyze the geometry, symmetry and harmony and genesis of the fold in terms of relative timing of the events

Contrasting mineralogy and strain partitioning across N-S oriented Sitampundi - Kanjamalai Shear in Sitampundi Anorthosite Layered Complex

Sitampundi Anorthosite Layered Complex (SALC) is a complexly folded and metamorphosed terrain that shows different metamorphic grade separated by a regional linear divide. In the north-eastern part of the complex, the anorthosites contain green-colored clinozoisites that are strikingly absent in the western part of the limb. Based on the presence of the clinozoisites, the entire SALC can be divided into two zones. The Sitampundi-Kanjamalai shear zone (SKSZ) separates mega crystals of clinozoite bearing anorthosites from clinozoisite free anorthosites. To add furthermore, strain analysis of different samples of anorthosite on either side of the zones was conducted by employing Flinn method. In general, anorthosites fall into the flattening field. The clinozoisite free anorthosites are more flattening and clinozoisite bearing anorthosites exhibit a slight difference in their strain ratio, ie., it is comparatively less flattening.  Geochemistry of clinozoisites was studied using EPMA & XRD methods. The percentage of oxides obtained from EPMA coincides with that of epidote. But, XRD confirms the mineral to be clinozoisite indicating the transition phase of epidote to clinozoisite. Zoning has had occurred in clinozoisites with aluminium oxide rich core and FeO rich rim. This could be related to a retrogression corresponding to a shearing event

Seasonal Variation of Groundwater Quality for Irrigational uses in Gadilam River Basin, Tamil Nadu, India

The present research work pertains to the Gadilam river basin groundwater quality for irrigation uses with respect to the Archaean formation, the Quaternary formation, the Tertiary formation and the Cretaceous formation. Experiments were carried out for two seasons (rainy season and summer season) for two successive years (November 2018 and June 2019). Overall, 120 groundwater samples were collected from the Gadilam river basin, excluding the reserved forest area. The 50 samples were collected from the Archaean formation, 34 samples from the Quaternary formation, and 35 samples from the Tertiary Formation. The remaining sample is from the Cretaceous formation. Based on the obtained analysed data, the following agricultural water quality parameters were calculated using the following expressions: The irrigational quality parameters are used, such as sodium percentage (Na%), sodium adsorption ratio (SAR), Kelly’s ratio (KR), permeability index (PI), magnesium ratio (MR), residual sodium carbonate (RSC), and potential salinity (PS) are calculated and assessed for irrigation purposes

Strain Pattern Analysis of Mylonites From Sitampundi-Kanjamalai Shear Zone, Thiruchengode, South India

This study aims to investigate the petrography and strain pattern of mylonites from parts of N-S trending Sitampundi-Kanjamalai Shear Zone (SKSZ) around Thiruchengode. The petrographic study indicates the presence of recrystallized quartz, K-feldspar, plagioclase, biotite and some hornblende. The kinematic analysis of Mylonites was done with the help of shear sense indicators such as recrystallized type quartz (quartz ribbon) around the cluster of feldspar, S-C fabric shows dextral shear sense and some sinisterly shear sense in some parts of SASZ which can be considered as a product of partitioning of both strain and vorticity between domains. These all indicates the simple shear extension along E-W direction and the mylonitic foliation shows the pure shear compression along N-S direction. Further the study of bulk strain analysis by Flinn plot method using L and T section of mylonite shows k<1 which lies in the field of flattening zone of finite strain. The kinematic vorticity number is calculated by Rxz/β method which gives the value of 0.36 indicating the general shear. The rigid grain graph shows that the pure shear component is more ­­­­dominant than the simple shear component. The analysis leads to the conclusion that the mylonite has experienced a high temperature shearing of above 700°cat deep crustal level

Strain Analysis of the Salem-Attur Shear Zone of Southern Granulite Terrane Around Salem, Tamil Nadu

Salem-Attur shear zone in the Southern Granulite Terrane demarcates the tectonic boundary between Archaean granulites of Dharwar craton and the Palaeoproterozoic granulites of Salem area. The shear zone marks a low angle thrust which has been steepened at places due to late stage folding. Static recrystallisation during late stage folding has removed the strain marker of mylonites to large extent. However, in a few places S-C angle and porphyroclasts are preserved and have been used to compute the strain. The strain shows apparent flattening by simple shear deformation with 35 % volume loss. A minimum displacement along the thrust has been computed to be 2.7 km. The strain k values increases with r suggesting the strain approaching towards prolate field with increase in strain intensity. The above study suggests the Salem-Attur shear zone is a thrust with low to moderate deformation and volume loss

Geoinformatic Modeling of Groundwater Resource Mapping of Shear Zone Regions- A Case Study on Attur Valley, Tamil Nadu, India

The general tendency of mapping groundwater resource using remote sensing and Geographic Information System (GIS) techniques involve assigning higher weightage to geomorphology. But this cannot be used as a thumb rule everywhere, especially an area where many ductile and brittle zones are prevalent. The influence of texture and structure of sheared rocks might play a control over retaining and permitting groundwater to flow. Attur valley is characterized by the presence of many shear zones and faults and hence the rocks are highly fissile within the shear zones. The present study tries to establish a new ranking and weightage scheme and hence a new spatial model for groundwater resource mapping in shear zone area like Attur Valley. This spatial model can be verified with field data such as water level data, pump test and resistivity data

ASSESSING THE IMPACTS OF CLIMATE CHANGE ON TERRESTRIAL ECOSYSTEMS IN BHAVANISAGAR RESERVOIR AND ITS SURROUNDINGS, USING MULTITEMPORAL SATELLITE DATA AND GIS TECHNIQUES

Despite the warnings against climate change since the early century, recent human activities are still geared towards enhancing them. Because of climate change coupled by other human activities, natural ecosystems are facing difficulties in coping with the impacts of climate change. The evaluation of the impact of climate change on ecosystems implies studying a multi-component system in which the complexity of links is high enough to present doing it as a whole. Because of this, it is a reasonable approach to study separately the behavior of each element, to be afterwards linked into a general conceptual model for ecosystems behavior. Moreover, in the case of largely regulated region, the main impacts of climatic change will be fluvial-related since those related to the catchment areas will be severely damped by river regulation and management policies. This fact implies that Terrestrial fringes may become the main frontier between the ecosystems and climatic change effects. This paper describes the potential impacts of warming temperatures and changing precipitation on vegetation, wildlife, land use/ land covers, and agricultural ecosystems across the Bhavanisagar Reservoir region centered on Coimbatore district, Tamilnadu. We examine a geographic area that captures much of Reservoir, including a complex mosaic of urbanization and agriculture surrounding the Bhavanisagar Reservoir. The comparative study of land cover and soil status are provided using space images with middle resolution. Multitemporal satellite data provide the capability for mapping and monitoring land cover and land use change, but require the development of accurate and repeatable techniques that can be extended to a broad range of environments and conditions. The Landsat TM and ETM+ and SRTM-DEM images are included in analysis. The unsupervised and supervised classifications are applied for determination of different types of land cover. The research present here has focus on devising a simple and operational rule-based approach to map land cover changes, based on the classification of Landsat imagery and the conceptual analysis of the information regarding change detection. The use of ancillary GIS data such as Digital Elevation Model, existing thematic maps and the knowledge of the ecosystem dynamics, formed the basis for setting the rules for the post-processing of the classified Multitemporal images that led to a more accurate assessment and mapping of land cover changes. The above framework has proved to be a promising and practical approach in order to quantify, understand, conceptualize and better present the dynamics of land cover/use changes in Terrestrial Ecosystems

Study of the Salem-Attur shear zone, east of Salem, Tamil Nadu: a new kinematic interpretation

A study of the mylonites of the Salem-Attur shear zone at Udayapatti and Sarkar Nattar Mangalam reveals that the shear zone developed in the form of a northeasterly vergent subhorizontal thrust which has been refolded into variable attitude due to late stage folding. The subhorizontal mylonitic foliation with NE trending stretching lineation bears testimony to such an explanation. The earlier impression that the shear zone is vertical comes from the folded part of the thrust as the mylonites have assumed a vertical attitude on the limb of the fold

Size distribution and roundness of clasts within pseudotachylytes of the Gangavalli Shear Zone, Salem, Tamil Nadu: An insight into its origin and tectonic significance

Gangavalli (Brittle) Shear Zone (Fault) near Attur, Tamil Nadu exposes nearly 50 km long and 1-3 km wide NNE-SSW trending linear belt of cataclasites and pseudotachylyte produced on charnockites of the Southern Granulite Terrane. Pseudotachylytes, as well as the country rock, bear the evidence of conjugate strike slip shearing along NNE-SSW and NW-SE directions, suggesting an N-S compression. The Gangavalli Shear Zone represents the NNE-SSW fault of the conjugate system along which a right lateral shear has produced seismic slip motion giving rise to cataclasites and pseudotachylytes. Pseudotachylytes occur as veins of varying width extending from hairline fracture fills to tens of meters in length. They carry quartz as well as feldspar clasts with sizes of few mm in diameter; the clast sizes show a modified Power law distribution with finer ones ( 0.4) due to thermal decrepitation. In a large instance, devitrification has occurred producing albitic microlites that suggest the temperature of the pseudotachylyte melt was > 1000 degrees C. Thus, pseudotachylyte veins act as a proxy to understand the genetic process involved in the evolution of the shear zone and its tectonic settings

A Study of Mylonites from parts of the Salem-Attur Shear Zone (Tamil Nadu) and its Tectonic Implications

The E-W running Salem-Attur shear zone demarcates the tectonic boundary between Archaean Dharwar Craton in the north and Proterozoic Southern granulite terrane in the south. This study reveals that the shear zone is a low angle thrust. The thrust zone is around 10 m thick and it merges with the main shear zone along the strike. The thrust is developed on charnockite near Odyarpatti, which is retrograded into schists. Further, it is marked by gently dipping mylonitic foliation and subhorizontal lineation. The S-C fabric, mantled porphyroclasts and intragranular faults indicate northeasterly slip along the thrust. Recumbent shear folds SF 1 are developed within the thrust zone. The thrust has been folded by late stage F 2 fold which has brought variation in the orientation of the mylonitic foliation from subhorizontal to vertical attitude; the mylonitic lineations have been rotated to subvertical orientation also. Additionally, the F 2 crenulations and shear cleavages and intersection lineations are superimposed on the mylonitic fabric. Thrusting along the Salem-Attur shear zone is probably the cause for upliftment of the charnockites to the upper crust. Post-upliftment stage has witnessed brittle deformation in the form of development of shear fractures in NNE-SSW and E-W directions. Pseudotachylites are emplaced along these fractures