Structural Evolution of the Kohat and Potwar Fold and Thrust Belts of Pakistan Dissertation Von Humaad Ghani zur Erlangung des akademischen Grades DOCTOR RERUM NATURALIUM »DR. RER. NAT.« in der Wissenschaftsdisziplin Geologie eingereicht an der Mathematisch-Naturwissenschaftlichen Fakultät der Universität Potsdam Potsdam, im June 2019 Datum der Disputation: 20.11. 2019 This work is licensed under a Creative Commons License: Attribution – Non Commercial 4.0 International. This does not apply to quoted content from other authors. To view a copy of this license visit https://creativecommons.org/licenses/by-nc/4.0/ Supervisors apl Prof. Edward Sobel Dr Gerold Zeilinger Institute of Geosciences, University of Potsdam, Germany Referees 1: Dr Gerold Zeilinger Institute of Geosciences, University of Potsdam, Germany 2: Prof. Delores Robinson Department of Geological Sciences, University of Alabama, USA 3: Prof. Peter van der Beek ISTerre Université Grenoble Alpes, France Published online at the Institutional Repository of the University of Potsdam: https://doi.org/10.25932/publishup-44077 https://nbn-resolving.org/urn:nbn:de:kobv:517-opus4-440775 To my father who left, when I started to understand him Table of Contents Abstract………………………………………….………………………………………...i Zussamenfassung ……………………………………………………………………… iii Preface……………………………………………………………………………………vi Acknowledgments……………………………………………………………………....vii Chapter 1 …………………………………………………………………………………1 Introduction 1.1 Research statement.……………………………………………………………………1 1.2 Aim and objectives of the research………………………………………………........3 1.3 Research methods…...………………………………………………….……….…….3 1.4 Significance of the research…………………………………….……………………..4 1.5 Thesis outline………………………………………………………………………….5 Chapter 2……………………………………………………………………………..5 Chapter 3…………………………………………………………………………......5 Chapter 4…………………………………………………………………………......6 Chapter 5…………………………………………………………………………......6 Chapter 6…………………………………………………………………………......7 Chapter 2………………………………………………………………………………….8 Tectonic framework of northwestern Pakistan 2.1 Hindukush and Karakoram……………………………………………………………8 2.2 Kohistan Arc .........…………………………………………………………………...8 2.3 Himalaya………………………………………………………………………………9 2.3.1 Western Hinterland (metamorphic zone)……………………………………….9 2.3.2 Nanga Parbat Syntaxis………………………………………………………….9 2.3.3 Lesser Himalaya…...………………………………………………………….10 2.3.4 Subhimalaya and Hazara Syntaxis...………………………………………….10 2.4 Himalayan western axial fold and thrust belt..………………………………………11 2.5 Development of the Himalayan fold and thrust belt..……………………………….11 Chapter 3………………………………………………………………………………...13 Structural variation within the Himalayan fold and thrust belt: A case study from the Kohat-Potwar fold thrust belt of Pakistan Abstract……………………………………………………………………………….….13 3.1 Introduction…………………………………………………………………………..13 3.2 Tectonic framework and previous structural interpretations…………………………15 3.3 Stratigraphy and décollements……………………………………………………….18 3.4 Structural style of KP-FTB...………………………………………………………...22 3.4.1 Kohat- Surghar………………………………………………………………..23 3.4.1.1 Seismic profiles...……………………………………………....23 3.4.1.2 Cross-sections…………………………………………………..23 3.4.1.3 Restored sections……………………………………………….25 3.4.2 Potwar, Salt Range and Kalabagh fault zone……………………………………..27 3.4.2.1 Seismic profiles………………………………...………………27 3.4.2.2 Cross-sections…………………………………………………..29 3.4.2.3 Restored sections……………………………………………….30 3.5 Discussion………………………………………………………………...………….31 3.6 Conclusions…………………………………………………………………………..39 Acknowledgments.……………………………………………………………………….39 Chapter 4………………………………………………………………………………...40 Paleozoic to Pliocene tectonic evolution of the Salt Range constrained by low temperature thermochronology Abstract……………………………………………………………………….………….40 4.1 Introduction…………………………………………………………………………..40 4.2 Tectonic framework and stratigraphy…………...…………………………………...41 4.3 Thermochronologic data………………………………………………...…………...42 4.4 Thermal modelling…………………………………………………………………...43 4.5 Discussion and conclusions…………………………………………………………..46 4.5.1 Pre-Himalayan basin history…………………………………………………..46 4.5.2 Development of the Salt Range……………………………………………….47 Acknowledgments……………………………………………………………………......49 Chapter 5………………………………………………………………………………...50 Structural evolution of the Kohat fold and thrust belt, Pakistan Abstract………………………………………………………………….……………….50 5.1 Introduction…………………………………………………………………………..50 5.2 Tectonic framework and stratigraphy.………………………………………………..51 5.3 Apatite low temperature thermochronology…………………………………….……55 5.3.1 Sampling and mineral separation…………………………………………...…55 5.3.2 Analytical methods…………………………………………………………....55 5.3.2.1 U-Th-Sm/He dating (AHe)……………………………………..55 5.3.2.2 Apatite Fission Track dating (AFT)………………………...….56 5.3.3 Results……………….………………………………………………………...56 5.4 Thermal modelling……………………………………………………...……………58 5.5 Balanced cross-section...……………………………………………………………..61 5.6 Discussion…………………………………………………………………...……….63 5.6.1 Sequential structural evolution of Kohat from the MBT to the SGT………....63 5.6.2 Early accretion of the foreland: implications for the Trans Indus Ranges……67 5.6.2.1 Burial and exhumation mechanisms in the Surghar Ranges…...67 5.6.2.2 Development of the Surghar and Khisor Ranges…………..…..68 5.6.3 Thick vs. thin skinned structures……..……………………………………….70 5.7 Conclusions……………………………………………………………………….….71 Acknowledgments……………………………………..……………………………….…71 Chapter 6……………………………………………………………................................72 Synthesis and conclusions 6.1 Pre-Himalayan history of the Salt Range and the adjoining areas……………………72 6.2 Development of the Main Boundary Thrust (MBT)………………………………….73 6.3 Temporal evolution of the structural style and exhumation in the Kohat and Potwar..74 6.4 Spatiotemporal development of the Kohat and Potwar range fronts…………..……...75 6.5 Comparative shortening in the Kohat, Potwar and transfer zone kinematics…............76 6.6 Conclusions……………………………………………………………………………77 6.7 Recommendations for future work……………………...………………………….....78 References………………………………………………………………………………...80 Appendix 1 (Chapter 4).….....…………………………………………...………………...91 1) Section SM 4.1. Sample location and collection strategy………………………….....91 2) Section SM 4.2. Analytical methods……………………………...…………………..94 a) Mineral Separation……………………………………………………………….94 b) Apatite (U-Th-Sm)/He methods and data analysis………………………….……94 c) AFT dating methods and data analysis………………………..…………………96 3) Section SM 4.3. Thermal history modeling………………………………...……….102 4) References…………………………………………………………………………...112 Appendix 2 (Chapter 5)..……………………………………………………………........115 1) Section SM 5.1. Sample locations and characteristics………………...…………….115 2) Section SM 5.2. Low temperature thermochronology data………………………….117 List of Figures Chapter 1 Figure 1.1. Regional tectonic map of the Himalaya and surrounding regions (modified after Beck et al. (1995); Badshah et al. (2000); DiPietro and Pogue, (2004)……………………..….5 Chapter 2 Figure 2.1. Regional tectonic map of the Himalaya and surrounding regions. The inset shows the geographic location………………………………………………………………………..12 Chapter 3 Figure 3.1. Generalized tectonic map of northern Pakistan, showing major geological features………………………………………………………..……………………………….15 Figure 3.2. Evolutionary models of the Kohat and Potwar…………………………………….17 Figure 3.3. Geological map of the study area revised after Meissner et al. (1974) and Gee (1980)…………………………………..………………………………………………….......20 Figure 3.4. Stratigraphic column and correlation chart showing north to south thickness variations of different stratigraphic packages……………………............................................21 Figure 3.5. a) Un-interpreted seismic profiles from the Kohat. b) Interpreted seismic profiles………………………………………………………………………...........................24 Figure 3.6. Cross sections traversing the Kohat (see Figure. 3.3 for location of sections) … .26 Figure 3.7. a) Un-interpreted seismic profiles from the Potwar and the Kalabagh re- entrant…………………………………………………..…………………………………… 28 Figure 3.8. Cross sections through the Potwar, Kalabagh Fault Zone and the Kohat………. ..31 Figure 3.9. Proposed sequential structural evolution within the Kohat………………………..36 Figure 3.10. Field photographs of the Kalabagh Fault Zone. a) Salt diapir in the Molasse sequence. b) KF1 fault shows dextral shear and normal slip movement………………………37 Figure 3.11. Deformed and restored model of the KP-FTB……………………………………37 Figure 3.12. Sketch to show the sequence of thrusting that shaped the Kohat Potwar range front…………………………………………………………………………………………....38 Figure 3.13. 3-D diagram of the KP-FTB illustrating two possible geometries for the basal decollement and the basement normal fault and how these could influence the deflection of the range front……………………………………………………………………………………..38 Chapter 4 Figure 4.1. Structural map of Salt Range and surrounding regions. The inset shows Pakistan and neighboring countries (modified after Gee, (1980); Ghani et al., (2018))……………………...41 Figure 4.2. Geological block diagram showing geometry of the stratigraphic wedge in the Salt Range………………………………………………………………………………………….43 Figure 4.3. QTQt thermal model and age - elevation profile for ten Cambrian and Permian samples combined into a single thermal model……………………………………………….45 Figure 4.4. Development of the Salt Range based on MOVE modeling (Ghani et al., 2018) and our new thermochronologic results……………………………………………………………48 Chapter 5 Figure 5.1. Regional tectonic map of northwestern Pakistan and eastern Afghanistan. Inset map in the lower right shows map location…………………………………………………………52