The Brahmaputra River in Assam: Geomorphology, Hazards, and Natural Resources

Cover
Half Title
Title Page
Copyright Page
Dedication
Table of Contents
List of Figures
List of Tables
Preface
Acknowledgements
Author
1. Introduction
The Upper Reach of the Brahmaputra Valley
Precipitation and Hydrology
Natural Hazards
Essential Objectives
2. A Quick Review: Geoscientific Understanding of the Brahmaputra Valley
General Geology and Geomorphology
Stratigraphy
Archaean
Precambrian
Mesozoic
Tertiary
Paleogene Strata
Neogene Strata
Quaternary Deposits
Structural and Tectonic Setting
Seismicity
Tectonic Setting of the Brahmaputra Valley
Limitations of 'Geosynclinal Theory'
Implications of 'Pop-Up' Theory
Different Collision Models and Their Influence on the Basin Evolution
Neotectonic Elements
Geomorphic Evidence
Structural Evidence
Fluvial Dynamics and Morphotectonics
3. Tools and Methods: A Brief Appraisal
Common Geological Problems
Questions of Usual Concern in Geophysical Exploration
Inverse Nature of Geophysical Problems
Effect of Size and Depth of the Causative Body
Planning Geophysical Investigations
'Noise' and the Problems of Enhancing 'Signal'
Resolution
Data Reduction
Data Presentation
Geological Objects and Their Geophysical Generalizations
Geophysical Data Integration
Gravity Data
Bouguer Anomaly
Regional–Residual Separation
Seismic data analysis and basic principles of interpretation
The 'Seismic Data'
Noise Reduction
2D Seismic Data Interpretation
Shallow Subsurface Geophysical Field Data Samples
Uphole Data
Shallow Refraction Data
Remote Sensing and GIS
Data Used
Data Integration
4. Fluvial Dynamics and the Changing Interfluves
Data and Approach
Dynamics of the Main Brahmaputra River
Bank-Line Shift
Basin Asymmetry and Bank-Line Shift
Planar and Temporal Variability of Width
Trend Analysis of the Bank-Line Shift and Width Variation
Channel Avulsion and Migration
Morphodynamics of the Brahmaputra River
Major Changes in River Islands
Majuli Island
Geomorphology, History, and Mechanism of Erosion of Majuli Island
Thalweg Migration
Subansiri Effect
Effect of Erosion of Majuli Island on BB Formation
Erosion of Majuli Island and the Aggradation Tendency
Existing Hypothesis for the Genesis of Majuli Island and Related Questions
Dibru-Saikhowa Island – the New Majuli
Bank erosion in Rohmoria
Dynamics of the Brahmaputra Tributaries
South Bank Tributaries
North Bank Tributaries
Morphotectonic Zonation of the Upper Reach of the Brahmaputra Valley
Recent Seismicity and Fluvial Dynamics
Morphotectonic Model for Morphodynamics
5. Quaternary Geomorphology, Shallow Subsurface Stratigraphy, and Neotectonics
Theoretical Aspects
A 'Layer'
Velocity as an Attribute for Basin Analysis
Micro-Zonation of the Basin
Significance of Tectonogeomorphic-Type Areas
Type 1 Areas [V[sub(3 (High))] V[sub(2 (High))] V[sub(1 (High))]]
Type 2 Areas [V[sub(3 (High))] V[sub(2 (High))] V[sub(1 (Low))]]
Type 3 Areas [V[sub(3 (High))] V[sub(2 (Low))] V[sub(1 (High))]]
Type 4 Areas [V[sub(3 (High))] V[sub(2 (Low))] V[sub(1 (Low))]]
Type 5 Areas [V[sub(3 (Low))] V[sub(2 (High))] V[sub(1 (High))]]
Type 6 Areas [V[sub(3 (Low))] V[sub(2 (High))] V[sub(1 (Low))]]
Type 7 Areas [V[sub(3 (Low))] V[sub(2 (Low))] V[sub(1 (High))]]
Type 8 Areas [V[sub(3 (Low))] V[sub(2 (Low))] V[sub(1 (Low))]]
Multi-Parametric Attributes for Basin Analysis
Choosing 'Threshold' Values
Study 'Windows'
Window 1: Amguri
The Amguri Data
Fluvial dynamics in Amguri Window
Oldest Channel Belt in Layer 3
Older Channel Belt in Layer 2
Old Channel Belt in Layer 1
Tectonic Controls and the River Dynamics
Neotectonics and Oil Migration
Multi-Parametric Micro-Zonation
Window 2: Namrup–Sapekhati
Namrup–Sapekhati data
Landform Variability and Quaternary Geomorphology
Fluvial Dynamics and Quaternary Basin Evolution
Neotectonics and Valley–Range Relationship
Multi-Parametric Micro-Zonation and the Oil Fields
Window 3: Matikhana
Matikhana Data
Salient Features in Window 3
Window 4: Mechaki
Window 4 Mechaki Data
Salient Features in Window 4
Discussion
6. Basin Evolution and Fluvial Dynamics
Seismic Sections
Profile A-A'
Profile B-B'
Profile C-C'
Profile D-D'
Profile E-E'
Profile F-F'
Discussion
Generalized Lithostratigraphy and Basin Evolution
Basin-Forming Tectonics
Sequence 1: Margin Sag (MS-321)
Sequence 2: Margin Sag–Interior Sag (MSIS-321)
Sequence 3: Interior Sag (IS-31)
Sequence 4: Shear or Wrench Initiation (LL1)
Sequence 5: Wrench Deformation (LL3)
Sequence 6: Basin Upliftment (LL3)
Basin-Modifying Tectonics
Tectonics and Sedimentation
Unconformity in the Fluvial Sediments
Basin Evolution and Directional Shift in the Major Fluvial System
Accommodation Space Generation and Residence Time of Rivers
Morphotectonic Evolution of Majuli Island
7. Bed–Bank Relationship and Flood Vulnerability
Bed–Bank Relationship
Assumptions for Flood Characterization
Data and Interpretation
Flood Characterization
8. The Golden Corridor
Surface Resources
Gold on the Surface
Hydropower
Alternative Energy Resources like Using Solar Power and Wind Power
Shallow Subsurface Resources
Gold in the Shallow Subsurface
Coal in the Shallow Subsurface
Coal Bed Methane (CBM)
Deep Subsurface Resources
Gold in the Deep Subsurface
Deeper Oil Prospects
9. Epilogue
Morphodynamics of the Brahmaputra River and Tributaries
Erosional and Evolutionary History of Majuli Island
Multi-Parametric Micro-Zonation in the Shallow Subsurface: Implications for Palaeo-Fluvial Dynamics
Cyclic Evolution of the Poly-History Basin
Characterization of Changing Bed–Bank Relations
Natural Resources of Geological Significance
Major Conclusions
Scope for Further Work
Appendix 1: Field Visit
Appendix 2: Tables (Additional for Chapter 4)
Glossary
References
Index