Preparing Updated Geological and Structural Map of Chamba Region Using ArcGIS

1. Centre for Advanced Studies
University of Delhi,
Delhi- 110007, INDIA.
COMPUTER APPLICATIONS IN
GEOSCIENCES – ASSIGNMENT
Integrated [B.Sc. (H) Geology] – M.Sc. Geology 5th
Sem (2016)
PREPARATION OF AN UPDATED GEOLOGICAL AND STRUCTURAL
MAP OF CHAMBA REGION
Submitted To Submitted By (Group B)
Dr. Ningthoujam Pahari Singh 1. Mohammad Imran Khan
Department of Geology 2. Tushar Pande
(Centre for Advanced Studies) 3. Sidhartha Gupta
University of Delhi 4. Shirish Verma
Delhi – 110007 5. Nganaomi Khangrah

2. Procedure for Preparing an Updated
Geological or Structural map
1. CREATING A JPEG FILE FROM THE GIVEN PAPER
1. The map to be taken was selected from the given file and it is zoomed out to such an
extent that all the features on the map are clearly visible.
2. The snapshot of the map was taken by clicking ‘Take a snapshot’ from the edit bar.
3. The snapshot map was copied to the paint and the map was converted to jpeg image.
4. The jpeg image was saved as ‘assignment’.
2. GEOREFERENCING TOPOSHEET IN Arc GIS
Georeferencing is a process of establishing a mathematical relationship between the image
coordinate system to the real world spatial coordinate system.
1. To launch Arc Map, click: Start > All programs> Arc GIS > Arc Map 10.
2. The jpeg image was added by clicking the ‘ Add data’ button after browsing the folder
‘assignment’ and clicking ‘yes’ to create pyramids for the toposheet.
3. Open ‘Georeferencing’ by view >Toolbars > georeferencing.
4. The input X and Y was added by clicking ‘Add control points’on he Georeferencing
Toolbar.
5. Similarly the input x and Y of the diagonals are were added. Also the inputs were added
for other points.
6. The toposheet was then rectified by clicking ‘Rectify’ from the Georeferencing Toolbar.
7. It was saved as – keep ceel size default, Resemple Type- Nearest neighbour.
8. The ‘Output Location Workspace ’and the folder that was made in C: drive was
selected.
9. It was named .img. Format-IMGINE Image, Compression type- None, Compression
quality- 75. It was saved.
10. We click on ‘New Map File’.> Don’t Save Changes to Untitled.
11. We click ‘Add Data’ button and the .img file was added.

3. 3. CREATING A NEW SHAPEFILE IN ArcGIS
Features data are usually organised as points, lines and polygons in vector format. The most
commonly used geospatial data format is shapefile.
1. The ‘Arc Catalog’ was clicked to launch at the window of Arc Catalog.
2. Right click > new >shapefile. A new window ‘Create New Shapefile’ was opened.
3. The shapefile was named as ‘Thrust’. The feature type was selected as polyline by
pulling down the menu below.
4. We clicked on ‘Edit’ to open ‘Spatial reference Properties’ and clicked ‘Select’ to select a
coordinate system.
5. A file ‘Thrust.shp’ was constructed.
6. Similarly the shapefiles for boundary and lithology were constructed by selecting
‘polygon’ as the ‘Feature Type’.
4. EDITING AND LABELLING IN A SHAPEFILE
1. The ‘Thrust.shp’ file was added by clicking on ‘Add Data’.
2. Right click on the Thrust layer and open ‘Attribute Table’.
3. We click on the ‘Options’ and then ‘Add field’.
4. The file was named as ‘Thrust’ and chose the type of field as ‘Text’. And then ‘Ok’.
5. We clicked on ‘Start Editing’ from the pull down ‘Editor’ below in the ‘Editor Toolbars’.
6. Before editing it was made sure that the task is ‘Create new Feature’ and target is
‘Thrust’ in the Editor Toolbars.
7. The ‘Sketch Tool’ was selected and the thrust was edited.
8. After finishing the editing, we right click on the ‘Thrust’ layer and opened the attribute
table.
9. We clicked on the leftmost column to highlight the polyline and named the thrust
accordingly.
10. The ‘Attribute Table’ was then closed.
11. We double click on the ‘Thrust’ layer to open the ‘Layer Properties’ of ‘Thrust’ layer.
Click on the ‘Labels’ and click in ‘Label Feature in this Layer’.
12. The ‘Label Field’ is changed as ‘Thrust’ in ‘Text string’. ‘Apply’and then ‘ok’.
13. Right click on the window and open ‘Labelling Toolbar’. Click on ‘Label Manager’ in
‘Labelling Toolbar’.
14. Click on the ‘Default’ in ‘Label Classes’ and change ‘Label Field ‘as ‘Thrust’ in ‘Text
String’. ‘Apply’ and then ‘ok’.
15. We clicked on ‘Save Edits’ from the pull down ‘Editor’ below in ‘Editor Toolbar’ and then
‘Stop Editing’.
16. Similarly the boundary.shp and lithology.shp file were added in ‘Layers’ and then edited,
labelled and saved.

4. 5. DOWNLOADING THE DATA
We downloaded the DEM data from the USGS.gdex website after registering and
putting the coordinates.
6. REGISTRATION OF SATELLITE DATA WITH TOPOSHEET OF THE AREA
1. We clicked on ‘Add Data’ button and added the .img file.
2. Again we clicked ‘Add Data ‘and added the DEM file and create pyramids for dem.tif file.
3. We double clicked on dem.tif layer and open ‘Layer Properties’ of dem.tif by right
clicking.
4. Open ‘Symbology’ and the click on ‘Classified’ in ‘Show’. We clicked ‘Yes’ as the window
opens asking to build Raster Attribute Table.
5. In ‘Classification ‘the classes was increased by clicking ‘Classify’.
6. The colour ramp was changed to the desired colour.
7.. SURFACE ANALYSIS IN Arc GIS
1. We go to ‘3D Analyst’.
2. Go to Surface Analysis’ and the click on ‘Contour’.
3. We chose dem.tif file in ‘Input Surface’ and changed the contour interval as desired.
4. Click on the save output Feature Button.
5. Click on the folder which contains the file in C: drive.
6. The shapefile was named as ‘Contour’ and then saved.
7. Similarly, the shape files for ‘Slope’ was created by choosing the output measurement
as percentage and saved.
8. Again from ‘Surface Analysis’ the ‘Aspect’ and ‘Hillshade’ were created by clicking ‘Aspect’ and
‘Hillshade’ respectively. The files were saved.
8. CREATING KML FILE FROM THE SHAPE FILE
1. We go to ‘Arc Tool Box’ and choose ‘Conversion Tool’.
2. Click ‘To KML’ and then ‘Layers to KML’.
3. We input the layer as ‘Thrust.shp’ file and the output folder as the folder in C: drive.
We then click ‘Ok’.
4. We then get a .kml file.

5. 9. UPDATING THE THRUST ON GOOGLE EARTH
1. First we drag the ‘.kml’ file on the Google Earth.
2. Click on the ‘Add Path’ and the previous thrust was updated.
3. After updating the thrust we clicked ‘OK’ in the ‘Add Path’ window.
4. Right click on the updated thrust and click on the ‘Save place as’.
5. The updated Thrust was saved as Updated.kmz and then opened in Arc GIS.
10. EXTRACTING LAYER (DEM) FROM THE BOUNDARY
1. Go to ‘Spatial Analyst’ tool in the ‘Arc Toolbox’.
2. Select on the ‘Extraction’.
3. Double click on ‘Extraction by Mask’.
4. Select DEM (.tif file) in ‘Input Raster’.
5. Select ‘Boundary’ in ‘Feature Mask’.
6. Click on ‘Save’.
7. The extracted DEM will open in the Layers.
11. CONVERTING KML FILE INTO THE SHAPE FILE
1. We go to ‘Arc Tool Box’ and choose ‘Conversion Tool’.
2. Click ‘To Shapefile’ and then ‘Feature Class to Shapefile (Multiple)’.
3. We input the layer as ‘Updated.kmz’ file and the output folder as the folder in C: drive.
We then click ‘Ok’.
4. We then get a .kml file.

6. 12. EXPORTING FINAL LAYOUT OF MAP
1. Right click on the window o open ‘Layout’ toolbar.
2. Click on ‘Change Layout’ icon in the ‘Layout Toolbar’. A new window named ‘Select
Templet’ opens.
3. Open ‘General’ menu and lelect ‘Letter Portrait.mxt’ layout and then click ‘Finish’.
4. Zoom the map from the ‘Zoom In’ button on the ‘tools’.
5. Click on the ‘Select Elements’ icon from the ‘Tools’.
6. Mark tick only on the layer to create.
7. Double click on the legends in the map layout. A new window ‘Properties’ of legends
opens. The properties of legends can be changed here.
8. Click on ‘View’ on window and open ‘Data Frame Properties’.
9. Open ‘Grids’ menu and click on ‘New Grid’ button. A new window ‘Grids and Graticules
Wizard’ open asking ‘Which do you want to Create’?
1o. Tick on the ‘Graticules’: divides map by meridians and parallels and then click on ‘Next’.
11. A new window ‘Create a Graticule’ open. Mark tick on ‘Graticules and Labels’ in
‘Appearance’ and then click on ‘Next’.
12. Click on ‘Next’ in ‘Axes and Labels’ window and ‘Create a Graticule’ Window.
13. Click on ‘Properties’ button to open ‘Reference System properties’ window.
14 Click on ‘Labels’ menu and change the label size in ‘Label Style’ and tick on the right in
‘Label Orientation’.
15. Click on ‘Lines’ menu and mark point before ‘Do not show lines or ticks’.
16. ‘Apply’ and Then click ‘Ok’.
17. To export the Map, click on ‘File’ and then ‘Export Map’.
18. Save the Map as ‘JPEG’ with resolution 1000 dpi.
19. Similarly export maps for other layers and close ‘Arc Map’ Layout.

12. Some Geomorhic Indicators of Thrust
in Chamba Region

16. Table 1. Regional Geology of the Chamba
Region
S.No GEOLOGY AGE
1. Cenozoic of Sub-Himalayas Cenozoic
2. Panjal Imbricate Zone(Lesser
Himalayan formations)
2a) Lesser Himalayan formations in
window zone
3. Kalhel/Tandi Formation Mesozoic
4. Salooni Formation Lower-Middle Permian
5. Manjir Formation Carboniferous
6. Lower Palaeozoic Granite Lower Palaeozoic
7. Salkhala/Chamba/Haimanta
Formation
8. Mesozoic ofTethys Himalaya Mesozoic
9. Permian Phe Volcanics Permian
10. Undifferentiated Palaeozoic of
Tethys Himalaya
Palaeozoic

17. TABLE 2. Generalised Stratigraphy of the
Chamba-Dalhousie Area (H.P.) (Updated
from V.C. Thakur, 1998)
FORMATION LITHOLOGY AGE
Kalhel Limestone Dolomitic limestone with quartzite
bands
Lower Triassic-Upper Permian
Salooni Formation Carbonaceous shales, limestone,
quartzite calc-shales
Lower-Middle Permian
Manjir Formation Grey and purple coloured diamictite
with slate and quarzite bands
Carboniferous
Chamba Formation Alternation of slate meta-siltstone and
meta-greywacke
Late Precambrian
Salkhala Formation Quartzite, schist, Late Precambrian
Dalhousie granite (foliated biotite and
muscovite granite), Mylonite gneiss
Late Precambrian 450+/-50 Ma
(dated by Rb/Sr, whole rock)
(Bhanot et al., 1975) 1430+/-50
Ma (dated by Rb/Sr, whole rock)
(Bhanot et al., 1978)
…………………………………………………… Panjal Thrust ……………………………………………………………..
Shali
Formation
Phyllites, slates and limestone Upper Riphean
………………………………………………… Shali Thrust …………………………………………………………….
Mandi-Darla
Volcanics
Basic volcanics with intercalations of
quartzite
Proterozoic (Bhat and LeFort,
1992)
…………………………………………. Main Boundary Thrust ………………………………………………………..
Murree Formation Sandstone and shale Lower Miocene
………………………………………...... Murree Thrust …………………………………………………………………
Upper Siwalik Conglomerates Plio-Pliestocene

18. Structural framework of the Chamba
nappe
Southern contact and closures of the Chamba nappe
The Panjal Thrust (Fig. 3) demarcates the southern boundary of the Chamba nappe bringing
the Salkhala Formation over the LH rocks of the PIZ. A mylonite gneiss band occurs at the
base of the Salkhala Formation. The southeastern closure of the Chamba nappe shows
continuity of the Salkhala Formation towards north and joining into the Haimanta Formation
in Lahaul (Fig. 2). The Salkhala Formation is underlain by the HHC, and further
southeastward in the Rampur Window, the HHC is underlain by the Riphean limestone, and
Proterozoic volcanic, quartzite and gneissose granite of the Lesser Himalaya. Along the
northwestern closure of the Chamba nappe, the Bhadarwah Formation (equivalent of
Chamba Formation) overlies the medium grade rocks of the Warrai Formation of HHC (Fig.
4) which, in turn, overlies rocks of the Kisthwar Window, i.e. Lesser Himalayan formations
with similar lithostratigraphy as that of the Rampur Window zone.
Northern contact and Chenab Normal Fault
The northern contact of the Chamba nappe against the southern boundary of the Zanskar HHC is the
south dipping Chenab Normal Fault (CNF) (Fig. 2), along which the Chamba sequence has moved to
the south with respect to the underlying HHC. The tectonic relationship of the southern margin of
the HHC and the overlying Chamba sequence (Figs 4 and 8) was described in the Bhadarwah (Thakur
et al., 1995), Kilar (Fuchs, 1975; Singh, 1993) and Miyar areas (Pognante et al., 1987; Rawat and
others, WIHG Annual Report, 1993±94). In the LANDSAT TMFCC imagery a sharp linear to curvilinear
boundary trending WNW±ESE is observed in Bhadarwah. This linear boundary corresponds to the
Chenab Normal Fault (locally called Bhadarwah Normal Fault). A mylonite augen gneiss, 300±400 m
thick at the top of the underlying HHC occur along the fault (Fig. 4). Top to-the-south movement of
the hanging wall Chamba sequence is indicated on the basis of Se±Si fabric in garnet porphyroblasts
and S±C fabric in mylonite (Thakur et al., 1995). The CNF is observed in Bhadarwah-Doda and
Bhalesh-Thathri sections where slates of the Bhadarwah Formation lay over garnetiferous schists of
the HHC along the southwest dipping fault. A traverse across Tissa, Sach Pass, Bindrabani and Kilar in
Pangi valley shows Bhadarwah Formation of the Chamba sequence overlies the HHC along south
dipping Chenab Normal Fault (Fig. 7). In its southeastward extension the Chenab Normal Fault was
described as the Miyar Thrust by Pognante and his coworkers (1987). This south dipping fault
between the HHC and Haimanta (= Salkhala) Formation is also mapped by Rawat and his coworkers
(WIHG Annual Report, 1993±94) (Fig. 8). The Chenab Normal Fault (CNF) extends150 km along
regional strike from Badarwah in the west to Lahaul in the east. The fault is moderate to steeply
dipping to the southwest and along this dislocation plane the Salkhala Formation of the Chamba
nappe has moved southwestward.
The southern and northern boundaries of the Chamba nappe sequence demarcated by the Panjal
Thrust and Chenab Normal Fault respectively indicates that the Chamba nappe is an allochthonous
tectonic unit. The late Precambrian to Triassic succession of the Chamba Nappe was detached from
its basement of the HHC and glided southwestward along the Panjal Thrust and the Chenab Normal
Fault in Miocene, the time when the MCT was initiated. NE vergence of the Tandi syncline and other
similar structures with similar vergence on the northern part of the Chamba nappe was due to top-
to-the south movement of the sedimentary cover of the nappe over the HHC.
Extensional tectonics

19. The HHC zone of Zanskar extending in a NW±SE direction and constituting the highest topographic
level forms a huge thermal dome (Searle et al., 1988; Kundig, 1989; Honegger et al., 1982) cored by
highgrade, sillimanite-K-feldspar. Metamorphic grade decreases outward from the core to the ¯anks
of the domes. In the Zanskar valley along the northern margin of the HHC the Tethyan sequence on
the hanging wall has moved top-to-the-north along the Zanskar Shear (Herren, 1987). This type of
extensional tectonics was explained as a result of gravity-controlled collapse of the Himalayan
Miocene topographic front along the northern margin of the Higher Himalaya (Burch®el and Royden,
1985; Royden and Burch®el, 1987). Top-to-the-south movement of the Chamba nappe sequence
along the CNF may also be related to the topographic uplift of the Zanskar HHC along the highest
uplift of the Higher Himalaya. It appears that the extensional regime induced due to uplift of the
Higher Himalayan range caused sliding of the Zanskar Tethys to the north and the Chamba sequence
to the south, thus facilitating the unroo®ng of the HHC. This model is supported by paleotectonic
reconstruction of the Zanskar, Kashmir and Chamba sequences having Tethyan a•nities. Before
collision, the Tethyan sequence were extended from Zanskar southward to Kashmir and Chamba.
The uplift of the Higher Himalaya and crustal shortening of the HHC due to India-Asia collision
caused the tectonic separation of the Zanskar Tethys from the Chamba sequence and this was
facilitated along the Zanskar Shear and the Chenab Normal Fault respectively.
Deformation history
The deformation history of the polyphase deformed rocks has been analysed in the southern
Chamba region (Thakur and Tandon, 1976), the northwestern Churah region (Singh and Thakur,
1987) and the southeastern Tandi-Bhamor region (Powell and Conaghan, 1973 and Rawat and
Thakur, 1988). Three phases of deformation, D1, D2 and D3 were recognised (Figs 3 and 5). D1
deformation is characterised by tight to isoclinal folds with penetrative axial-plane clevage and axes
plunging at 10±208 to NW or SE. A regional planar fabric, the slaty cleavage was formed during D1
deformation. The L1 mineral lineation defined by micas and quartz ®bres and occurring on the
foliation plane plunges 30±558 NE±NNE. The slaty cleavage foliation as well as the mineral lineation
are folded by close to open style folds of D2 deformation (Thakur and Tandon, 1976; Rawat and
Thakur, 1988). The D2 folds are co-axial with D1 folds, plunging NW or SE at 10±308, and they are
associated with development of a crenulation cleavage. The D3 folds are open in style plunging
toward 30±508 N±NNE, some show crenulation cleavage and in the Tandi area they plunge towards
NW. The mylonitic augen gneiss band at the base of the Salkhala Formation shows typical L±S
tectonites characterised by mineral banding on a millimetric scale defining a mylonitic foliation (Sm)
and by linear quartz aggregates on Sm defining a mylonitic lineation (Lm). The mylonitic foliation
strikes NW±SE and dips at moderate angles (358) to the NE. The mineral lineation plunges 20±358
towards NE. The development of Sm and Lm is related to ductile thrusting along the Panjal Thrust
(Rautela and Thakur, 1992). The Manjir Formation, occurring repeatedly as mappable unit across the
entire Chamba Nappe, shows well developed slaty cleavage. The pebbles in the diamictite of this
formation show a strong preferred orientation of their long axes (X) plunging down-dip on the slaty
cleavage towards NE to NNE at low to moderate angles (20±358) (Figs 3 and 5). The slaty cleavage
represents the XY plane and the long axes of the pebbles indicate the X-direction of the finite strain
ellipsoid (Thakur and Tandon, 1976; Singh and Thakur, 1989). The ®nite-strain ellipsoid is of
¯attening-type with elongation values ranging from 50%>1>17% along X direction, 13%>2>5% along
Y direction and shortening along Z direction ranging ÿ38%>3>ÿ22% (Singh and Thakur, 1989). The
Early Palaeozoic Dalhousie granite (500±450 Ma) (Rb±Sr whole rock, Bhanot et al., 1975), occurs
within the Salkhala and shows a penetrative foliation dipping 408 NE and NE to NNE plunging
(25±408) mineral lineation de®ned by felspar phenocrysts. The intensity of foliation as well as the
lineation are strongly developed on both margins and becomes weaker in the centre part of the
granite body, suggesting its deformation in a simple shear regime during southward thrusting of
Chamba Nappe.

20. Major folds
The Chamba Nappe is folded by major folds. The Chamba syncline is a major structure whose axial
trace extends over 100 km from Bhalesh through Kalhel to Bharmor. It is an overturned syncline with
its axial-trace trending NW±SE with axialsurface dipping at an average 308 NE and the width across
the two limbs is about 20 km. The northwestern closure of Chamba syncline is observed in Churah,
(Fig. 4), indicating that the syncline plunges towards NW. The characteristic diamic
tite-bearing lithology of the Manjir Formation occurs both on the normal as well inverted limbs with
the Kalhel Limestone occupying the core of the syncline. The long axes (X) of the deformed pebbles
in the Manjir Formation on the limbs are at right angles to the axial direction of the Chamba syncline
(Fig. 5). The Chamba syncline was formed during D1 and is associated with D1 mesoscopic
structures. The Tissa anticline (Fig. 7) trends NW±SE. The Kugti anticline of the Bharmor area in the
southeastern part of Chamba Nappe represents the southeasterly continuation of the Tissa anticline
(Figs 2 and 6), suggesting that this anticline also has a regional dimension. Farther north of the Tissa
anticline, a syncline occurs with Manjir and Salooni formations in its core. The northern limb of this
syncline dips 40±558 towards SW and rests over the metamorphic HHC through the Chenab Normal
Fault. The Tandi syncline in Lahaul is a tight overturned fold, showing Permian and Jurassic rocks of
the Chamba Nappe (Powell and Conaghan, 1973; Rawat and Thakur, 1986; Parashar and Desraj,
1990) (Fig. 6). Both limbs of the syncline dip toward SW, the axialtrace of this fold extends NW-SE
and axial surface dips 408 SW. Between the north-vergent Tandi syncline and the south-vergent
Bharmor syncline lie the Kugti (Chobia) anticline and a complimentary synclinal structure.
Thrust propagation and development of major folds
A pervasive NE±NNE plunging mineral lineation on the penetrative foliation plane is regionally
distributed and occurs across the entire thickness of the Chamba sequence. The orientation of this
mineral lineation corresponds with the stretching lineation of deformed pebbles and the mylonitic
lineation in the mylonite band at the base of Salkhala Formation. The development of these
lineations is related to southwestward propagation of the Chamba Nappe during D1 deformation
phase (Thakur and Tandon, 1976) The Chamba syncline and its southeastern continuation Bharmor
syncline and Tandi syncline, which have folded the bedding and produced the regional penetrative
foliation were also formed during the D1 deformation. These fold structures were produced during
southwestward propagation of the Chamba Nappe as fault-bend folds. In my interpretation the
sedimentary cover of the Chamba nappe sequence was deformed together with the underlying
basement of the HHC during the southward propagation of the HHC and the overlying Chamba
sequence along the MCT. Southward translation of the MCT was transferred to the PT by upcutting
the section of the HHC. The southward movement of the Chamba nappe along the Chenab Normal
Fault was transferred to the ongoing southward transport along the PT. This means that the MCT, PT
and CNF were developed together with the major folds in a single progressively southward
propagating thrust system during D1 deformation in Miocene time.

21. Position of Main Central Thrust
MCT in Nepal and Kumaun Himalayas
In the eastern Nepal Himalaya, the MCT brings the Higher Himalayan thrust sheet, mainly composed
of kyanite-and sillimanite-bearing metamorphic rocks and granites, over the Lesser Himalayan Shear
Zone (LHSZ) which in turn overrides the Lesser Himalayan Series (Schelling, 1992). The LHSZ consists
of a several hundred metres to several kilometres thick zone of mylonites, phyllonites and mylonitic
augen gneiss. In central Nepal, the Crystalline nappe of the Higher Himalaya is thrust over the Upper
Midland formations along the MCT (Pecher and LeFort 1986). Here the tectonic boundary between
the two tectonic units is characterised by contrasting lithostratigraphy and metamorphism and by
intensity of syn-metamorphic rotational deformation. The MCT has been described as a syn-
metamorphic shear zone with a minimum thickness of 1-2 km in the Annapurna section, and more
than 5 km in the Manaslu section (Pecher and LeFort, 1986). Arita (1983) described stacking of the
Midland metasediment zone by the MCT zone which in turn was thrust over by the Higher
Himalayan gneiss zone. His MCT zone corresponds to the synmetamorphic zone and represents a
thrust package, whose base is designated as the MCT-1 and the top as the MCT-2. In the Kumaun
Himalaya between the rivers Kali and Satluj, three principal thrust sheets of metamorphic rocks and
granites are recognized (Thakur 1992). The Chail Thrust demarcates the base of the lowermost
crystalline of the Chail Group. The Jutogh Thrust is located between the low grade Chail Group and
the overlying medium grade Jutogh Group; and the Vaikrita Thrust, referred to as the MCT by
Valdiya (1980), lies between the Jutogh Group and the overlying high-grade Vaikrita Group (Fig. 9).
The base of the Chail Group invariably contains a mylonitic augen gneiss band, and it overlies either
the carbonate rocks of the Deoban Group or the quartzite±volcanic rocks of the Berinag Group of
the Lesser Himalaya. Gansser (1964) described the thrust at the base of the lowermost crystalline
nappe (the Chail Thrust) as the Main Central Thrust (MCT). The Jutogh Group, also referred to as the
Munsiari Group, is made of an imbricate stack of metasedimentary rocks, together with 2000±1800
Ma dated granitic gneiss and subordinate amphibolite showing Barrovian metamorphism varying
from garnet to kyanite grade (Valdiya, 1980). The Vaikrita Group forms a thrust sheet comprising
kyanite - and sillimanite-bearing metamorphic rocks and granites. The base of this group is
demarcated by the Vaikrita Thrust or MCT.
MCT in Kashmir Himalaya
In their maps earlier workers (Gansser, 1964, 1981; Valdiya, 1980) showed the Panjal Thrust in the
Kashmir Himalaya as representing the western continuation of the MCT by extending the Chail
Thrust westwards into the Panjal Thrust (Fig. 9). This tectonic interpretation is partially correct for
we have observed that the low-grade Salkhala Formation together with PT and the mylonite gneiss
band occurring at its base can be physically traced from the Kulu valley southwestward to the Satluj
valley. But we also find that the Chail Thrust in the Kumaun Himalaya is not the Vaikrita Thrust of
Valdiya (1980) or the MCT defined in Nepal (LeFort, 1975). The Jutogh Thrust exposed in the Rampur
window represents the northwestward extension of the Munsiari Thrust from Kumaun. This thrust
separate the HHC from the underlying window rocks of Riphean carbonate, Proterozoic
volcanic±quartzite and gneissose granite of Lesser Himalayan formations. The Jutogh Thrust is not
exposed on the surface in the Chamba nappe region, but it reappears in the Kishtwar Window. In
Kisthwar Window the thrust separating the HHC from the underlying LH Formation of similar
lithostratigraphy as that of Rampur Window was interpreted as representing the MCT (Kundig, 1989;
Thakur et al., 1990). The Vaikrita Thrust (sensu stricto MCT in Nepal) has been described in Kumaun,
Garhwal and the Satluj valley in eastern Himachal Pradesh; but it is not recognised in its further
westward extension in the Kulu valley and in the Kashmir Himalaya. In the Kisthwar Window the

22. MCT is recognised as a thrust that brings the HHC over the window zone rocks of the Lesser
Himalayan affinity. In its southward propagation, the MCT cuts up-section to the medium- to high-
grade metamorphic rocks of the HHC and its further southward translation is transferred to the
Panjal Thrust at the base of the Chamba Nappe. The mylonite gneiss, occurring at the base of
Salkhala Formation in the frontal part of the Chamba Nappe, is interpreted as representing the
tectonic slice of the HHC brought up by the MCT up-cutting the HHC and transferring it to the PT.