Abstracts:

1. *Dhiman A, Singh S, MUKHERJEE S. 2023. Micromorphology of basalt alterite for understanding of geological processes during quiescence period of Deccan volcanism. 39th Convention/international conference of Indian Association of Sedimentologists. 06-08 December. Scientific Theme- Forces Beneath: Exploring Tectonics and Volcano-Sedimentology. (*- Presenting author)
2. Kar NK, Mani D, MUKHERJEE S*, Dasgupta S, Puniya MK, Kaushik AK, Biswas M, Babu EVSSK. 2023. Source rock characterization of Eocene shales from Giral lignite mine, Rajasthan, India. (Abstract id: 198). 14th International Conference & Exposition: New Age Geosciences: A Fulcrum for Energy Trilemma. SPG, Kochi. (Poster Presentation)  (*- Presenting author) S. Mukherjee’s trabvel, stay etc. funded by COE-OGE (IIT Bombay).
3. Biswas T, Bose N, Dutta D, MUKHERJEE S.* 2023. Arc-parallel shears in collisional orogens: Global review and paleostress analyses from the NW Lesser Himalayan Sequence (Garhwal region, Uttarakhand, India). Centtral University of Himachal Pradesh. Dharamshala. GEOHIM 2023.  (*- Presenting author, KEYNOTE SPEECH)
4. Pensirini B, Morell KD, Godard V, Cordilean A, Fulop RH, Wilcken K, Maheo G, MUKHERJEE S, ASTER team. 2022. Exploring Spatiotemporal Variability in Denudation in the Dhauladhar Range, Northwest Himalaya. AGU Fall Meeting, Chicago, 12-16 December.
5. Vidal CS, Reber J, McLafferty S, MUKHERJEE S. 2020. Relationship between Himalayan topography, crustal viscosity,and channel flow. AGU Fall Meeting.
6. Vanik N, Shaikh M, Maurya DM, MUKHERJEE S. 2018. Kinematics studies in Saurashtra and Kachchh: implications for paleostress patterns at teh western continental margin of India. In: Recent Studies on the Geology of Kachchh Basin. 30 Dec 2018 to 01 Jan 2019. KSKV Kachchh University. Bhuj. Gujarat
7. Godard V, Maheo G, MUKHERJEE S, Sterb M, Maleappane E, Leloup H, Team ASTER. Rapid denudation at the Dhauladhar range front, Himachal Pradesh, India. Abstract Volume of the 33rd Himalaya-Karakoram-Tibet Workshop. 10-12 September, Lausanne, Switzerland. pp. 56. Hetenyi G et al. (Eds) DOI: 10.5281/zenodo.1403887 [PDF]
8. Vanik N, Shaikh M, Maurya DM, MUKHERJEE S, Chamyal LS. (Submitted in RDS Delhi 2018). Temporal change in stress orientations over SW Saurashtra, Gujarat, western India: indicators from paleostress analysis. [PDF]
9. Shaikh M, Padmalal A, Maurya DM, MUKHERJEE S, Vanik N, Tiwari P, Chamyal LS. (Submitted in RDS, Delhi, 2018) Paleostress analysis and Ground Penetrating Radar (GPR) studies along the intra-uplift Vigodi Fault in western part of Kachchh Mainland, Gujarat, western India. [PDF]
10. Dutta D, MUKHERJEE S. 2017. Structural and Mineralogical Studies of the Tso Morari Dome, Insight into the deformation kinematics of the eclogitic gneiss, Ladakh Himalaya, India. GSA
11. Biswas T, Bose N, MUKHERJEE S. 2017. Shear fabrics reveal orogen-parallel deformations, NW Lesser Garhwal Himalaya, Uttarakhand, India. GSA
12. MUKHERJEE S. 2017. Revisiting role of shear heating in Himalayan inverted metamorphism through thermo-mechanical models. In the session: “The Metamorphic Architecture of Orogenic Belts”. GAC-MAC 2017. 2017 Geological Association of Canada-Mineralogical Association of Canada Annual Meeting, Kingston, Ontario. 14-18 May 2017. http://www.kingstongacmac.ca/ Organizers: Dawn Kellett & Natasha Wodicka. [PDF]
13. Gogoi RK, MUKHERJEE S, Jadhav GN. 2016. Microstructural and fluid inclusion studies on (ductile sheared) quartz lenses, Main Central Thrust Zone in the Sutlej river section, Sarahan, Himachal Pradesh, India. In: Rock, Deformation and Structures (National conference). Kathgodam. 18-20 Nov
14. Joshi AU, Sant DA, Parvez I, Rangarajan G, Limaye MA, MUKHERJEE S, Charola MJ, Bhatt MN, Mistry SP.(2016) Subsurface profiling of granite pluton using microtremor method: A case study from southern Aravalli mountain belt, Gujrat, India. RDS. In: Rock, Deformation and Structures (National conference). 18-20 Nov
15. Bose N, Dutta D, MUKHERJEE S. 2016. Quantification of competency contrast from refraction of shear-induced micro-fractures, Gangori Shear Zone, Bhagirathi river section, NW Indian Lesser Himalaya. AGU. (Submitted) [PDF]
16. Joshi A, MUKHERJEE S, Limaye M. 2016. Opaques as a shear sense indicator: An example of shear sense reversal. In: Rock, Deformation and Structures. National Conference, Haldwani. 18-20 Nov
17. Das T, MUKHERJEE S. 2016. Detection of abnormal pressures from well logs. In: Rock Deformation and Structures”, National Conference, Department of Geology, Centre of Advanced Study, Kumaun University, Nainital, 18-20 Nov.
18. MUKHERJEE S. 2016. Review on Symmetric Structures in Ductile Shear Zones. Tectonic Studies Group 2016 Annual Meeting. University College London. 06-08 January 2016. https://tsg2016.wordpress.com/ [PDF]
19. Dasgupta S, MUKHERJEE S. 2016. Review on tectonics of Barmer rift basin, India. Tectonic Studies Group 2016 Annual Meeting. University College London. 06-08 January 2016. https://tsg2016.wordpress.com/ [PDF]
20. Misra AA, MUKHERJEE S. 2016. Review on spheroidal weathering and associated fractures. Tectonic Studies Group 2016 Annual Meeting. University College London. 06-08 January 2016. https://tsg2016.wordpress.com/[PDF]
21. Bose N, MUKHERJEE S. 2015. Back structures (back-faults and back-folds) from collisional orogen: field findings from Lesser Himalaya, Sikkim, India. 30th Himalaya-Karakoram-Tibet Workshop, Wadia Institute of Himalayan Geology, 06-08 Oct, Dehradun, India. pp. 13-14.  [PDF]
22. MUKHERJEE S. 2015. A review on out-of-sequence deformation in the Himalaya. 30th Himalaya-Karakoram-Tibet Workshop, Wadia Institute of Himalayan Geology, 06-08 Oct, Dehradun, India. pp. 36-38.  [PDF]
23. Bose N, MUKHERJEE S. 2015. First Report and Microstructural Studies of Phyllonite of Gangori Shear Zone, Inner Lesser Himalaya, Bhagirathi Section, India. Geomechanical and Petrophysical Properties of Mudrocks. Geological Society, London, Burlington House, UK. 16-17 November 2015. [PDF]
24. Mulchrone KF, MUKHERJEE S. 2015. Kinematics and shear heat pattern of ductile simple shear zones with ‘slip boundary condition’: application in Himalayan tectonics. Submitted in the 30th Himalaya-Karakoram-Tibet Workshop, Wadia Institute of Himalayan Geology, 06-08 Oct, Dehradun, India. pp. 1.  [PDF]
25. Bose N. MUKHERJEE S. 2015. Back-structures (backfolds and backthrusts) in the Lesser Himalaya, Bhagirathi river section, NW Himalaya, India: field findings. Tectonic Studies Group Annual Meeting 2015, Grant Institute, University of Edinburg, UK.[PDF]
26. Misra AA, MUKHERJEE S. 2015. Dyke-­‐brittle shear relation in the western Deccan Traps near Mumbai, India. Tectonic Studies Group Annual Meeting 2015, Grant Institute, University of Edinburg, UK.[PDF]
27. Misra AA, Sarkar S, MUKHERJEE S. 2015. Tectonic inheritance in rifting: example from western Indian passive margin near Mumbai, India. Tectonic Studies Group Annual Meeting 2015, Grant Institute, University of Edinburgh, UK.[PDF]
28. Biswas T, Dutta D, MUKHERJEE S. (2014) Tectonics of Siwalik Himalaya in Dehradun-Roorkee section, India. GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014). Topical Session: T.23 Exploring the Development of the Himalayan-Karakorum- Tibet Orogenic System from the Mantle to Mountain Peaks. Conveners: Delores Robinson, SOUMYAJIT MUKHERJEE, Barun Kumar Mukherjee.
29. MUKHERJEE S, Ghosh A. (Submitted) Rock Texture Classification for Geocellular Modelling. Third International Conference on Petroleum Science and Technology 2014 (ICPST-2014). IIT Madras. Supported by Petrotech Society, India.
30. Dey J, MUKHERJEE S. (Submitted) Review on hydrocarbon occurrences in the Indian Himalaya. Third International Conference on Petroleum Science and Technology 2014 (ICPST-2014). IIT Madras. Supported by Petrotech Society, India.
31. Biswas T, MUKHERJEE S. (2014) A review of polygonal fault systems and their hydrocarbon prospects. Tectonic Studies Group, 06-08 January, Cardiff University, UK. (POSTER)
32. Ghosh A, MUKHERJEE S. (2014) Modified P/z approach to address dry gas reservoir performance. Devex. Aberdeen.  06-07 May. Organized jointly by the Petroleum Exploration Society of Great Britain (PESGB), the Society for Petroleum Engineers (SPE), and the Aberdeen Formation Evaluation Society (AFES).
33. Ghosh A, MUKHERJEE S. (2014) Remote sensing analyses to decipher trend of lineaments at Mount Abu Granitoid, Rajasthan (India). Tectonic Studies Group, 06-08 January. Cardiff University, UK. (POSTER)
34. Misra AA, Sinha N, MUKHERJEE S. (2014) Repeat ridge jumps and microcontinent separation: insights from NE Arabian Sea. Symposium in Honour of Davis Robert. Basin Dynamics and Petroleum Systems: Geophysics, Structure, Stratigraphy, Sedimentology and Geochemistry. 14-16 April 2014. Windsor Building, Royal Holloway University of London. (ORAL)
35. Misra AA, MUKHERJEE S. (2014) Role of tectonic inheritance in passive margin architecture: A review. Symposium in Honour of Davis Robert. Basin Dynamics and Petroleum Systems: Geophysics, Structure, Stratigraphy, Sedimentology and Geochemistry. 14-16 April 2014. Windsor Building, Royal Holloway University of London. (ORAL)
36. MUKHERJEE S., Ghosh R. (2013) Nyalam Detachment, Nyalam Shear Zone and Nyalam Thrust around south central Tibet. 28th Himalaya Karakoram Tibet Workshop & 6th International Symposium on Tibetan Plateau 2013. Tuebingen University. Germany. [PDF]
37. MUKHERJEE, S., Dixit S, Bose N. (2013) Shear heating of brittle reverse fault- an analytical model applied to the Main Boundary Thrust and cross-check by Raman thermometry. 28th Himalaya Karakoram Tibet Workshop & 6th International Symposium on Tibetan Plateau 2013. Tuebingen University. Germany. [PDF]
38. MUKHERJEE, S., Dixit, S. 2013. Surficial erosion governs deformation pattern at depth- an example of channel flow and the case of the Greater Himalayan Crystallines. 28th Himalaya Karakoram Tibet Workshop & 6th International Symposium on Tibetan Plateau 2013. Tuebingen University. Germany. [PDF]
39. MUKHERJEE, S., Ghosh R. 2013. Both channel flow and critical taper operated on the Greater Himalayan Crystallines (GHC)- a review. 28th Himalaya Karakoram Tibet Workshop & 6th International Symposium on Tibetan Plateau 2013. Tuebingen University. Germany. [PDF]
40. MUKHERJEE, S. 2013. Genesis of out-of-sequence thrust inside the Greater Himalayan Crystallines: the case of Nyalam Thrust, and ‘restricted channel flow’. 28th Himalaya Karakoram Tibet Workshop & 6th International Symposium on Tibetan Plateau 2013. Tuebingen University. Germany. [PDF]
41. MUKHERJEE, S., Biswas, R. 2013.Kinematics of simple shear zones with curved boundaries applied on Greater Himalayan Crystallines. 28th Himalaya Karakoram Tibet Workshop & 6th International Symposium on Tibetan Plateau 2013. Tuebingen University. Germany. [PDF]
42. MUKHERJEE, S., Biswas, R. 2013. Analytical models for shear senses & viscous dissipation of layered ductile simple shear zones: applications on the Greater Himalayan Crystallines. 28th Himalaya Karakoram Tibet Workshop & 6th International Symposium on Tibetan Plateau 2013. Tuebingen University. Germany. [PDF]
43. Bose, N., Bhattacharya, G., MUKHERJEE, S. 2013. Temperature predicted from quartz microstructures from the Main Boundary Thrust Zone, Dehradun-Mussourie region, western Himalaya. In: Geophysical Research Abstract. European Geosciences Union, Vienna, Austria. Vol. 15.  http://meetingorganizer.copernicus.org/EGU2013/EGU2013-4516.pdf
44. Bhattacharya, G., Misra, A.A., Bose, N., MUKHERJEE, S. 2013. Strike-slip brittle shear zone from Deccan in and around Mumbai, India: Evidence for N-S extension. In: European Geosciences Union, Vienna, Austria. Vol. 15. http://meetingorganizer.copernicus.org/EGU2013/EGU2013-2594.pdf
45. MUKHERJEE, S. 2013. Implications of the southern Tethyan Himalaya (Sutlej section, India) for the extrusion of the Higher Himalaya and the geometry of the mid-crustal channel. In: Geophysical Research Abstract. European Geosciences Union, Vienna, Austria. Vol. 15.   http://meetingorganizer.copernicus.org/EGU2013/EGU2013-2584.pdf
46. MUKHERJEE, S. 2013. Symmetric and near-symmetric objects in ductile shear zones- examples from Higher Himalaya, Bhagirathi river section, India. In: Geophysical Research Abstract. European Geosciences Union, Vienna, Austria. Vol. 15.  http://meetingorganizer.copernicus.org/EGU2013/EGU2013-2585.pdf
47. MUKHERJEE, S., 2012. Viscous dissipations in simple shear zones- analytical models and a Himalayan example. ABSTRACT. National Seminar on Multidisciplinary Approach in Sedimentary Basin Studies. March, Dibrugarh University, Assam. India. 15-16 March. pp. 21. [PDF]
48. MUKHERJEE, S. 2012. Channel flow extrusion model to constrain viscosity and Prandtl number of the Higher Himalayan Shear Zone. Geophysical Research Abstracts Vol. 14, EGU2012-3381, 2012 European Geosciences Union, General Assembly. [PDF]
49. Ghosh, R., MUKHERJEE, S., 2012. Mechanism of drag folding. National Conference: “Recent Researches in Earth System Science”. Asutosh College, Kolkata. 10-11 Feb-2012. [DOC]
50. Mukherjee, B., MUKHERJEE, S. 2012. Prograde fluid in Tso Morari UHP rocks, Ladakh India. Geophysical Research Abstracts Vol. 14, EGU2012-3582, 2012 European Geosciences Union, General Assembly.
51. Koyi, HA, Schmeling, H, Burchardt S, Sjöström H, Talbot C, MUKHERJEE, S. ., Chemia, Z. 2011. Shear zones between blocks with no differential movement. Geological Society of America. 27 June–02 July 2011. Spain.Cadaqués & Cap de Creus Peninsula, Catalonia, Spain.       URL: http://www.geosociety.org/penrose/11spain.htm [PDF]
52. MUKHERJEE, S. , Bandyopadhyay A (submitted) Structural geology of the Bhagirathi section of the Higher Himalayan Shear Zone with special reference to back-thrusting “International Conference on Indian Monsoon and Himalayan Geodynamics” 02-05 Nov 2011. Wadia Institute of Himalayan Geology. Dehradun. India. [DOC]
53. MUKHERJEE, S. , Mukherjee, T. (Submitted) Serial thin-section study of ductile shear S-fabrics to decipher their 3D geometries. “International Conference on Indian Monsoon and Himalayan Geodynamics.” 02-05 Nov 2011. Wadia Institute of Himalayan Geology. Dehradun. India. [DOC]
54. MUKHERJEE, S. . (Submitted) Morphology and Chemistry of Columnar rocks,formed during India-Madagaskar breakup, at the Coconut Island near west coast of India, Udupi district, Karnataka, India. GEO Conference,04-07 March, Baharin. AAPG. [DOC]
55. MUKHERJEE, S. (Submitted) An example of Modelling in Structural Geology for better understanding of structural history of a terrain: Shear senses developed in a ‘top-to-down’ simple shear on a Newtonian viscous rheology- a reinterpretation. GEO Conference, 04-07 March,Baharin. AAPG. [DOC]
56. MUKHERJEE, S. (Submitted) Reversal of shear sense in ductile shear zones. 7th International Conference on Asian Marine Geology. Session: Tectonics of Asian Continental Margins. National Institute of Oceanography. Goa. India. 11-14 October 2011. [PDF]
57. MUKHERJEE, S. (Submitted) Channel flow extrusion model to constrain viscosity and Prandtl number of the Higher Himalayan Shear Zone. Tectonic Studies Group Annual Meeting: “Our Dynamic Earth”. Edinburg, UK. 04-06 January 2012. [DOC]
58. MUKHERJEE, S. (Submitted) Simple shear is not so simple! Kinematics of incompressible Newtonian viscous ductile simple shear zones. “National Seminar On Geodynamics and Metallogenesis of the Indian Lithosphere”.Banaras Hindu University. Varanashi. Sept 22-24, 2011. [PDF]
59. MUKHERJEE, S. Estimation of Viscosity of Salt Diapirs of the Persian Gulf & a Himalayan Gneiss Dome. Will be submitted in the DRT-2011, Spain (Deformation, Rheology & Tectonics Conference).
60. MUKHERJEE, S., , Mulchrone, K. (Submitted) Estimating viscosity of the Tso Morari Gneiss Dome, western Indian Himalaya. Tectonic Studies Group Conference, 05-07 January 2011, Durham, UK. [PDF]
61. MUKHERJEE, S., SUBMITTED. Principles of Hydrostratigraphic Correlation. ‘8th Washington Hydrogeology Symposium’ April 26-28, 2011; Takoma, Washington.
62. MUKHERJEE, S., SUBMITTED. Tectonic Problems the Higher Himalayan Shear Zone, Bhagirathi Section, Indian Himalaya. Annual Meeting of the “Tectonic Studies Group”, Durham, UK, 05-07 January 2011. [PDF]
63. MUKHERJEE, S., SUBMITTED. Morphometric Textural Analyses of Sigmoidal & Zygmoidal Objects in Sheared Rocks. 16th International Conference on the Texture of Materials (ICOTOM 16)” to be held at IIT Bombay during 12-17 December 2011.
64. MUKHERJEE, S., SUBMITTED. Tectonic implications and morphology of trapezoidal mica grains from the Sutlej section of the Higher Himalayan Shear Zone, Indian Himalaya. 16th International Conference on the Texture of Materials (ICOTOM 16)” to be held at IIT Bombay in December 2011.
65. MUKHERJEE, S., 2010. Applicability of Channel flow as an extrusion mechanism of the Higher Himalayan Shear Zone from Sutlej, Zanskar, Dhauliganga and Gorigang Sections, Indian Himalaya. Vol. 12, EGU2010-14 , 2010. Geophysical Research Abstracts. EGU General Assembly 2010. URL: http://meetingorganizer.copernicus.org/EGU2010/EGU2010-14.
66. MUKHERJEE, S., 2009. Flanking Microstructures from the Western Indian Himalaya. 17th Deformation, Rheology and Tectonics. Martin Casey Memorial Meeting. Liverpool. [PDF]
67. MUKHERJEE, S., 2009. Channel Flow Model of Extrusion of the Higher Himalaya- Successes & Limitations. Vol. 11, EGU2009-13966 . Geophysical Research Abstract. European Geosciences Union General Assembly. Vienna, Austria, 19-24 April. URL: http://meetingorganizer.copernicus.org/EGU2009/EGU2009-13966. [PDF]
68. MUKHERJEE, S., Koyi, H.A., Talbot, C.J., 2009. Out-of-Sequence Thrust in the Higher Himalay

Abstract of my Ph.D. thesis: Please refer it as: “MUKHERJEE, S., 2007. Geodynamics, deformation and mathematical analysis of metamorphic belts, NW Himalaya. Unpublished Ph.D. thesis. pp. 1-267. ”

Abstracts:

1. 1. Vanik N, Shaikh M, Maurya DM, MUKHERJEE S, Chamyal LS. (Submitted in RDS Delhi 2018). Temporal change in stress orientations over SW Saurashtra, Gujarat, western India: indicators from paleostress analysis. [PDF]
   2. Shaikh M, Padmalal A, Maurya DM, MUKHERJEE S, Vanik N, Tiwari P, Chamyal LS. (Submitted in RDS, Delhi, 2018) Paleostress analysis and Ground Penetrating Radar (GPR) studies along the intra-uplift Vigodi Fault in western part of Kachchh Mainland, Gujarat, western India. [PDF]

1. The thesis was evaluated by Prof. Mary Leech (San Francisco State University) and Dr. A.K. Dubey (Wadia Institute of Himalayan Geology):

   Abstract

   • Intra-continental collision between the Indian- and the Eurasian Plates since ~ 55 Ma remobilized the Indian crust and resulted in the exhumation of different parts of the mountain in various episodes. The Higher Himalayan Shear Zone (HHSZ), a part of the Himalayan Metamorphic Belt, was deformed and exhumed as a delayed response to the post-collisional crustal shortening. The ductile extensional shearing at the top of the HHSZ took place simultaneously with the ductile compressional shearing at the lower boundary of this shear zone. Based on structural geology, mathematical analyses and analogue modelling, models of exhumation of the HHSZ are proposed taking the Zanskar- and the Sutlej sections of the shear zone in the NW Indian Himalaya as the study areas. Additionally, flanking structures in micro-scales from the Sutlej section of the HHSZ are studied and their compatibility with the proposed exhumation model is addressed.
   • Thin-section studies of the rocks of the Zanskar Shear Zone (ZSZ) reveal (a) an initial top-to-SW sense of ductile shearing; (b) subsequent top-to-NE sense of ductile shear coeval with the ongoing top-to-SW sense of ductile shearing; (c) top-to-NE sense of ductile synthetic secondary shearing; (d) brittle-ductile extension; (e) top-to-SW sense of brittle shear; (f) northeasterly steeply dipping brittle faults; and (g) brittle extension. A two-phase model of exhumation of the HHSZ is proposed. The first phase represented top-to-SW sense of non-coaxial shearing same as the Couette flow during the Neo-Himalayan Period. The second phase was guided by combined top-to-SW sense of simple shear and the channel flow during the Middle Miocene Period. This simulated a thin ZSZ characterized by a top-to-NE sense of ductile shearing. Variation in the ratio of relative velocity of the boundaries of the HHSZ to the pressure gradient explains the variable thickness of the ZSZ.
   • Fieldwork and micro-structural studies of the HHSZ in the Sutlej section reveal (a) initial top-to-SW sense of ductile shearing; (b) late stage top-to-NE sense of ductile shearing in two zones- the ‘Himalayan Detachment-1’ (HD1) and the ‘Himalayan Detachment-2’ (HD2); (c) uniform top-to-SW sense of brittle shearing; and (d) brittle-ductile extension. A three-phase model of exhumation of the HHSZ is proposed. The first phase represented top-to-SW sense of non-coaxial shearing, similar to what is proposed for the Zanskar section of the HHSZ, during the Neo-Himalayan Period. The second phase was guided by combined top-to-SW sense of simple shear and channel flow in two pulses. One of the pulses took place throughout the HHSZ during the Middle Miocene Period; the other pulse was restricted within the lower sub-channel. Thin HD1 and HD2 were produced during the respective pulsed flows. The third phase of exhumation is idealized by brittle slip of markers in a top-to-SW sense.
   • The channel flow component had differentially acted in various sections of the HHSZ. For example, while a single pulse of channel flow is deciphered from the Zanskar section; two distinct spatially and temporally separated pulses acted in the Sutlej section. The models of exhumation of the HHSZ for both these sections predict that (i) the base of the ZSZ (or the HD1) exhumed with highest rate; and (ii) the ZSZ (or the HD1) might be missing in certain sections of the HHSZ even if channel flow was active.
   • The exhumation mechanism of the HHSZ is studied with 10 analogue models of channel flow initiating from a horizontal channel and extrusion through a linked inclined channel. The inclined channel is the model HHSZ and is of parallel, gently diverging-up and strongly diverging-up geometries in different considerations. In these experiments, Polydimethylsiloxane (PDMS) is used as the model material and only geometric similarity is maintained with the prototype. Six flow zones are deciphered in the two channels. The flow zone-4, formed nearly at the middle of the inclined channel, reveals a single zone of ductile extensional shearing similar to that in the South Tibetan Detachment System (or the HD1). This indicates that, in certain sections of the HHSZ, exhumation of the HHSZ took place by channel flow in two distinct pulses and gave rise to two ductile extensional shear zones, even when non-parallel geometry of the walls of the inclined channel is considered. A blind ductile secondary thrust, formed in zone-4, rotates while moving up and finally crops to the surface. In Sutlej section of the HHSZ, this thrust may be correlated with the Chaura Thrust with the recorded activation at least 13 Ma after the ongoing extrusion of the HHSZ by channel flow mechanism 18 Ma ago. The analogue models generate intrafolial folds within the ductile extensional shear zone, which is similar to the field observations from the detachments from different sections of the HHSZ.
   • Ductile sheared rocks of the HHSZ in Sutlej section outside the HD1and the HD2, in micro-scale, reveal ‘microflanking structures’ (MFS) defined by the nucleated minerals (the crosscutting elements- CEs), and deflected cleavages and grain margins (the host fabric elements- HEs). Depending on whether the drag of HEs across the CE is different or same, the MFS are grouped into the Type-(i) and the Type-(ii) varieties, respectively. The Type-(ii) MFS indicates directional growth of the CE. The Type-(i) MFS indicates non-coaxial shearing, where the external HEs bounding the CEs act as the C-plains, and that the CE minerals undergo crystal-plastic deformation. Salient morphological variations in the MFS are: (1) variable intensity and senses of drag along the single- and the opposite CE margins; (2) HE defined only at one of the sides of the CE; and (3) presence of thin hazy zone at the HE-CE contact. The HEs are dragged even in absence of rheological softening at the CE boundaries. The Type-(i) MFS from the HHSZ reveals top-to-SW sense of shearing, which matches with other shear sense indicators. This also supports a channel flow model of exhumation of the studied shear zone. Rheological possibilities, except for a weaker CE mineral within a stronger host grain, have been encountered in the present study, and are represented in a graph of its constitutive equation.
   • Conclusions of my Ph.D. thesis: Please refer it as: “MUKHERJEE, S., 2007. Geodynamics, deformation and mathematical analysis of metamorphic belts, NW Himalaya. Unpublished Ph.D. thesis. pp. 1-267. ”

   Conclusions

   • The Zanskar Shear Zone (ZSZ) in the Suru and Doda valleys of the NW Indian Himalaya demarcates the northern boundary of the Higher Himalayan Shear Zone (HHSZ), and is characterized by a top-to-NE sense of ductile shearing. The deformation phases of the rocks of the ZSZ, identified under a microscope, are: (i) ‘shearing-1’- initial top-to-SW sense of ductile shearing, survived as remnants, along the northeasterly dipping C-planes (the main foliation); (ii) ‘shearing-2’- subsequent top-to-NE sense of ductile shearing along the main foliation; (iii) ‘shearing-3’- strong extensional ductile shearing along northeasterly steeply dipping shear planes at an angle to the previous shear fabrics; (iv) brittle-ductile extension parallel to the main foliation, indicated by boudins of different varieties; (v) top-to-SW sense of brittle shearing along the main foliation, deciphered from asymmetric duplexes of a number of minerals and V-pull aparts of originally single mineral grains; (vi) northeasterly steeply dipping brittle faulting that cuts and displaces individual minerals; and (vii) brittle extension parallel to the main foliation, given by parallel pull apart of minerals. Different phases of ductile deformation are deciphered using S-C fabric, mineral fishes of different morphological types, intrafolial folds, Type-1 microflanking structures and preferred orientation of grains.
   • Within the ZSZ, reversal of ductile sense of shearing from a top-to-SW into a top-to-NE sense is confirmed with the documentation of rare hook shaped minerals. ‘Shearing-2’ and hook-shaped minerals are new findings from this study from the ZSZ, hitherto not reported from macro-scales. ‘Shearing-3’ is interpreted as secondary and synthetic to ‘shearing-2’. Duplexes in grain-scales are also new observations. It seems that the thrust-up mineral grains, in micro-scales, acquire the characteristic shape of a trapezium or a hat. Hat-shaped grains that are (i) isolated from the underthrust grain, and (ii) produced due to migration of boundaries of the adjacent grains were not used to determine the brittle shear sense.
   • The deformation phases deciphered from the ZSZ, and those previously reported from the HHSZ are summarized in a schematic cross-section. The top-to-SW sense of ductile shearing within the Higher Himalayan Shear Zone was initiated during the early Neo-Himalayan Period and continued during the Middle Miocene Period when the top-to-NE sense of ductile shearing of the ZSZ was also active. Existing models of exhumation of the HHSZ do not take into account of these constraints. A two-phase exhumation model E=(E1+E2) is, therefore, proposed. Velocity profiles of these phases are derived assuming incompressible Newtonian viscous rheology of the rocks of the HHSZ. The E1 phase, same as the ‘ductile shear model’, is represented by a top-to-SW sense of simple shearing of the parallel walls of the HHSZ. This Neo-Himalayan event can take into account the top-to-SW sense of ductile shearing throughout the HHSZ. The E2 phase, during the middle-Miocene Period, represented the flow of the HHSZ like a fluid by a combination of top-to-SW simple shear of the walls of the shear zone and a component of channel flow guided by the pressure gradient. This combined flow gave rise to a thin ZSZ at the upper part of the HHSZ and was characterized by apparent top-to-NE ductile shearing in a bulk southwestward flow. Metamorphic isograds within the HHSZ were deformed into the same geometries as of the velocity profiles of the respective phases, and gave rise to inverted metamorphism within the shear zone. The spatially variable thickness of the ZSZ along the Himalayan trend is explained by varying the ratio of the relative velocity of the walls of the HHSZ to the pressure gradient driving the channel flow. The E2 phase predicts that (i) the base of the ZSZ underwent the highest rate of exhumation; and (ii) the top-to-NE sense of ductile shearing might be absent in some sections of the HHSZ even with the presence of a component of channel flow.
   • Modeling the exhumation of the HHSZ in the Sutlej section is attempted as follows. The HHSZ rocks that underwent post-collisional deformation are grouped into two types: rocks of higher viscosities consisting mainly of granites, schists and quartzites- all in solid states, and that of lower viscosities comprising of migmatites, gneisses, (leuco)granites and pegmatites with the presence of granitic material in a (partially)molten stage. Field- and micro-structural studies of the HHSZ reveal (i) initial top-to-SW sense of ductile compressional shearing throughout the shear zone; (ii) top-to-NE sense of extensional ductile shearing dominantly present in two distinct zones named as- the ‘Himalayan Detachment-1’ (HD1) and the ‘Himalayan Detachment-2’ (HD2); (iii) uniform top-to-SW sense of brittle shearing along the pre-existing ductile primary shear planes; and (iv) brittle-ductile extension parallel to the main foliation. The first two senses of ductile shearing are deciphered mainly from S-C fabrics, mineral fishes and intrafolial folds. The S-planes are defined by discrete mineral grains, leucosomes and melanosomes of different thicknesses, and bulges of sigmoid shaped leucosomes and quartz veins. The brittle sense of shearing is deciphered in the field from duplexes of different dimensions. On micro-scales, hat-shaped minerals with their longest grain boundaries dipping northeasterly are examples of such duplexes. Brittle-ductile extension is represented by boudins of different morphologies in the field. The HD1 occurs at the top of the HHSZ and is the continuation of the South Tibetan Detachment System. The HD2 occurs inside the HHSZ. Both the HD1 and HD2 are thinner than the remainder of the HHSZ, and are absent in some Himalayan sections. Extensional shearing within the HD1 was contemporaneous with the compressional shearing of the MCT during the Middle Miocene Period. The absolute timing of ductile extensional shearing within the HD2 is indeterminate.
   • None of the recent models of the exhumation of the HHSZ, viz. (i) ‘ductile shear model’, (ii) channel flow model, (iii) ‘combined flow model’, and (iv) ‘general shear model’ can explain the presence of the two detachments within it. Therefore, a three-phase model of exhumation, E=E1+E2+E3, is proposed for the study area. The velocity profiles of the first two phases are derived assuming the HHSZ to be of incompressible Newtonian rheology and bonded by very long parallel walls. The E1 phase stands for the uniform top-to-SW sense of non-coaxial shearing within the HHSZ.
   • The E2 phase is represented by a combined top-to-SW sense of simple shearing and upward channel flow mode of exhumation in two pulses. One of these pulses occupied the whole of the HHSZ, i.e. from the MCT to the top of HD1, during the Middle Miocene Period. The other pulse was restricted within the lower part of the HHSZ -from the MCT to the top of HD2. During the respective pulses, thin HD1 and HD2 were produced characterized by a top-to-NE sense of ductile extensional shearing in bulk southwestward flow within them. The relative time relation between these two pulses is unconstrained. The HD2 might be absent in some sections of the Himalaya even with the presence of a component of channel flow. Further, mathematical analyses of the two pulses predict that (i) the bases of HD1 and the HD2 underwent the highest rates of exhumations in respective flows; and (ii) the HD1 might also be absent in particular sections of the Himalaya even when simple shear and channel flow were active. In the two mathematical analyses- one incorporating the constraints of viscosity, and the other with a possible flow partitioning, it is shown that the extensional ductile shearing can never be produced simultaneously within the two detachments. The development of extensional shearing in the two detachments is therefore sequential, and not simultaneous. The E3 phase represents consistent top-to-SW sense of brittle shearing, and is idealized in terms of markers disrupted into a top-to-SW sense in the shear zone/channel of the same geometry. The brittle-ductile extensional phase parallel to the main foliation planes is not brought into the tectonic modeling.
   • The channel flow model takes into account exhumation, inverted metamorphism, and ductile extensional shearing coeval to ductile compressional shearing at the base of the Higher Himalayan Shear Zone. However, a pure channel flow mode of exhumation cannot explain the presence of two detachments that has recently been reported from a few sections of the HHSZ. The classical channel flow model assumes parallel wall geometry of the HHSZ. On the other hand, seismic studies reveal that the geometry of the walls might also be diverging-up. To explore the geometry of flow within non-parallel walls, ten analogue models of channel flow were performed. The considered situations are a horizontal channel and linked with it an inclined channel with parallel, gently divergent-up and strongly divergent-up geometries of the walls of the later in different considerations. The inclined channel is the model HHSZ. Very slow flow parameters of the exhumation of the HHSZ in one hand, and the limitations of the instruments in the laboatory on the other, did not allow dynamic- and kinematic similarities to achieve between the prototype and the model. However, only the geometric similarity was maintained.
   • In these experiments, the flow within the horizontal channel was initiated by pushing polydimethylsiloxane (PDMS), a transparent incompressible Newtonian viscous polymer model material, by a piston with a constant rate. The induced flow in the inclined channel gave rise to extrusion of the PDMS on the free surface. Six flow domains were visually deciphered from all these experiments. Gradually away from the piston, these zones are as follows. Zone-1: velocity profile of inverted pitcher shape. Zone-2: plane Poiseuille flow given by parabolic velocity profiles. Zone-3: the profile at the contact between the horizontal and the inclined channel. In the inclined channel the following zones are produced sequentially away from the corner. Zone-4: parabolic profiles. Zone-5: rounded profiles. The extruded PDMS define parabola-shaped zone-6. Pressure gradients in zone-2 and -4 linearly increase with time. The shear strain at any moment at a fixed point is linearly related with the pressure gradient in these zones. Therefore, shear strain at any point in zone-2 and -4 also increase linearly with time. However these relations are instrument-specific and are not related with the extrusion of the HHSZ. Intrafolial folds showing top-to-NE sense of ductile shearing is formed inside the inclined channel at the later stages of all the experiments. Similar intrafolial folds have also been documented in this work from the Himalayan Detachments.
   • The PDMS in the horizontal channel enters the inclined channel and moves at a faster rate than the part of the PDMS that is already in the inclined channel. This in effect defines a blind secondary ductile thrust inside the inclined channel. The thrust rotates while moving up and finally comes to the surface. This thrust may be correlated with the Chaura Thrust in the Sutlej section of the HHSZ that was active at least 13 Ma after the ongoing channel flow event ~18 Ma ago. In all the analog models a single broad zone of top-to-NE sense of shear sense is produced equivalent to that in the South Tibetan Detachment System (or the HD1). This confirms that a single pulse of channel flow throughout the HHSZ cannot give rise to two ductile extensional shear zones even when extrusion takes place through diverging-up walls. These two shear zones, therefore, must be sequentially produced by channel flow in two distinct pulses.
   • XZ oriented thin-sections from the Sutlej section of the HHSZ reveal that nucleated minerals (the cross-cutting elements-CEs) cut and drag cleavages and grain-margins (the host fabric elements-HEs) of the host mineral(s). The HE-CE composite is designated as the ‘microflanking structure’ (MFS). Unavailability of HE as marker in most cases precludes deciphering its sense of slip across the CE. Depending on whether the sense of drag of the HE at the two sides of the CE is different or same, the MFS are grouped into the Type-(i) and the Type-(ii) varieties, respectively. The later type indicates preferential growth of the CE from the convex- towards the concave direction of the internal HE. The former types are a product of ductile shearing. Their CEs are parallelogram or sigmoid shaped, non-coaxially sheared; and are bounded by HEs that act as the C-plains. The shape of the CE is an alternative criterion to identify the Type-(i) MFS.
   • Variation in the intensity- and sense of drag of internal HEs has been noted, and may be due to (a) considerable rotation of the CE in simple shearing; (b) heterogeneous displacement field around the CE; or (c) mechanical anisotropy imposed by the HEs. The internal HE may be defined only at one side of the CE when one of the host minerals lacks cleavages. A thin hazy zone may mark the HE-CE contact, with the internal HEs strongly swerved and penetrating the CE within it. Lack of rheological weakening at the HE-CE contacts for the studied MFS indicates that it is not to an essential criterion for the drag (and slip) of the HE. This, along with the fact that the reported CEs are non-rigid, indicates that the CEs are strongly coupled with the host minerals. Top-to-SW ductile shear sense is deduced from the inclination of the CE of the Type-(i) MFS, which matches with that given by other shear sense indicators. This supports the channel flow mode of exhumation of the HHSZ. The Type-(i) MFS with (I) rigid CE and a weaker host mineral, and (II) CE and the host of the same minerals, have been observed. The second observation indicates that little variation in viscosities between the CE- and the host mineral must exist even if they belong to the same species.
   • Abstract of my M.Tech. thesis: Please refer it as: “Mukherjee, S., 2002. Geological investigations prerequisite to flow modelling in the arsenic affected groundwater zones in the Yamuna sub-basin, West Bengal. Unpublished M.Tech. thesis. Indian Institute of Technology Roorkee. pp. 1-51. ”

   Abstract

   • This dissertation zeros in on the geological investigations prerequisite to locate safe drinking water wells in the zone of arsenic polluted groundwater in the Yamuna sub basin, West Bengal. With the unavailability of set rules for aquifer delineation based on litho-log data, a review on ‘hydro-stratigraphy’ was done and the principles of hydro-stratigraphic correlation were established. Subsequently, lithologic descriptions of the study domain were simplified and three sets of multiple aquifer-aquitard systems along with the depth to each of the hydro-stratigraphic units were conceptualized. Arsenic concentration in waters of deeper tube wells at selected locations in the study domain in January 2002 went undetected (instrumental detection limit: 0.083ppm). Installing deeper tube wells in the study area is not a permanent solution to arsenic polluted waters. Compilation of chemical data on the depth-wise distribution of ‘As’ in sediments and groundwater, and also, a newly defined parameter ‘Deviation Factor’ (DF) in the study domain, fail to reveal any definite trend in depth wise arsenic concentration variation. It is, therefore, emphasized that future contaminant transport modeling in the study domain in order to locate safe drinking water wells has to incorporate (i) conceptualized disposition of hydro-stratigraphic units along with their depth specifications, and (ii) insitu sporadic nature of depth wise arsenic concentration variation.
   • Conclusions of my M.Tech. thesis: Please refer it as: “Mukherjee, S., 2002. Geological investigations prerequisite to flow modelling in the arsenic affected groundwater zones in the Yamuna sub-basin, West Bengal. Unpublished M.Tech. thesis. Indian Institute of Technology Roorkee. pp. 1-51. ”

   Conclusions

   • ‘Hydro-stratigraphy’ has been reviewed and few principles of it have been worked out for ‘hydro-stratigraphic correlation’. Accordingly, down to 140m depth in the Yamuna sub basin, West Bengal, three sets of multiple aquifer-aquitard systems along with the depth range of each hydro-stratigraphic units have been envisaged. All these six units are of variable thickness with the presence of patches/pockets/windows of pinched out sediments/rocks of different hydraulic conductivities. From bottom to top, these are Sand and Gravel (aquifer, 100-140m depth)- Clay Group (aquitard, 90-100m depth)- Sand (aquifer, 70-90m depth)-Clay Group (aquitard, 42-70m depth)-Sand (aquifer, 25-42m depth)-Clay Group (aquitard, 0-25m depth). (/p>
   • In January 2002, deeper tube well waters at selected locations in the study domain were found giving no ‘As’ (with the instrumental detection limit of 0.083ppm).
   • Distribution of ‘As’ in the sediments and groundwater at various depths in the study domain is sporadic and cannot be represented by any generalized statement. Deviation Factor (DF) has been defined. Calculated DF values for a few litho-logs also do not reveal any depth-wise trend.
   • Installing deeper tube wells do not give a permanent solution to ‘As’ contaminated groundwater in the study domain.
   • Tube-wells are the commonest means of getting water in the study area. The borers of the tube wells are broadly of four categories: (i) Municipal Corporation, (ii) Public Health Engineering Department (PHED), (iii) Panchayat, and (iv) Private. Information like locations, depth range of water extraction etc. for the private tube wells are not available. Shallow tube wells, which, after prolonged use give red waters are abandoned and new deeper tube wells are installed. (Red colour is taken as the indication of high amount of ‘As’ in waters.) However, with time, those deeper tube wells also start giving ‘As’ contaminated waters. Such an event can be delayed if the load on the new tube well is reduced, for example, by mining ‘As’ contaminated waters from old tube wells and using them for household works, and new deeper tube well waters for drinking purpose. ‘As’ concentration variation in groundwater in the study domain vary both spatially and temporally.

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