--- title: "Tectonic division and Lesser Himalaya geology" subject: "Engineering Geology I" chapter: 7 key: "semester_3/engineering_geology_i:tectonic-division-and-lesser-himalaya" source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/tectonic-division-and-lesser-himalaya site: BCT Engineering --- # Tectonic division and Lesser Himalaya geology Engineering Geology I · Chapter 7: Geology of Nepal - Asked in: 2068 Chaitra, 5 marks - Video: [Subdivisions of Himalayas: TransHimalaya, Greater Himalaya, Lesser Himalaya, Shivalik with Animation](https://www.youtube.com/watch?v=er9fqvm1Qcs) — Zeta Axis (UPSC-SSC) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/tectonic-division-and-lesser-himalaya - Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-7 ## Question What are the tectonic divisions of Nepal? Explain the geology of the Lesser Himalaya zone. ## Short answer Tectonic zones are Terai, Sub-Himalaya (Siwalik), Lesser Himalaya, Higher Himalaya, and Tethys Himalaya, separated by MFT, MBT, MCT, and STDS. The Lesser Himalaya zone comprises low-grade metamorphic rocks (slate, phyllite, quartzite, limestone) of the Nawakot and Kathmandu Complexes, with granites. It is intensely folded, faulted, and thrust, featuring synclinoria and klippen. ## Answer From south to north, Nepal is divided into five **tectonic zones**, separated by major thrusts and faults (discontinuities): ```text S N Terai | Sub-Him | Lesser Him | Higher Him | Tethys |(Siwalik)| | | MFT/HFT MBT MCT STDS ``` 1. **Terai (Gangetic plain):** Quaternary alluvium. 2. **Sub-Himalaya (Siwalik zone):** Miocene to Pleistocene molasse sediments. 3. **Lesser Himalaya:** Precambrian to Palaeozoic low-grade metamorphic rocks and sediments. 4. **Higher Himalaya (Great Himalaya):** high-grade metamorphic rocks and granites. 5. **Tibetan-Tethys Himalaya:** Palaeozoic to Cretaceous fossiliferous marine sediments. **Boundaries (major discontinuities)** - **Main Frontal Thrust (MFT) / Himalayan Frontal Thrust (HFT):** between the Terai and Siwalik. - **Main Boundary Thrust (MBT):** between the Siwalik and Lesser Himalaya. - **Main Central Thrust (MCT):** between the Lesser and Higher Himalaya. - **South Tibetan Detachment System (STDS):** between the Higher Himalaya and the Tethys zone. #### Geology of the Lesser Himalaya **Lithology** - **Nawakot Complex:** slate, phyllite, quartzite, limestone, dolomite and metasandstone. Lower Nawakot Group: Kuncha, Fagfog, Dandagaon, Nourpul and Dhading formations; Upper Nawakot Group: Benighat, Malekhu and Robang formations. - **Kathmandu Complex (nappe):** the **Bhimphedi Group** of schist, quartzite and marble (Raduwa, Bhainsedobhan, Kalitar, Chisapani, Kulekhani and Markhu formations), overlain by the **Phulchauki Group** of slate, sandstone and limestone (Tistung, Sopyang, Chandragiri, Chitlang and Godavari formations). - **Granite and gneiss bodies:** Palung granite and other granites, and the Ulleri augen gneiss. **Structure:** intensely folded, faulted and thrust. There are synclinoria (e.g. the Mahabharat synclinorium of the Kathmandu nappe) with klippen, and anticlinoria, with many thrusts and tectonic windows. The beds mostly dip northward. **Engineering problems:** landslides in weathered phyllite and slate, karst and seepage in limestone and dolomite, and shear zones along the thrusts. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How many tectonic zones does Nepal have and which is the southernmost? A. Four; Siwalik B. Five; Terai C. Six; Terai D. Five; Tethys Answer: B. Nepal has five tectonic zones, starting with the Terai (Gangetic plain) in the south. (Key point: Number and order of zones) 2. Which zone consists of Palaeozoic to Cretaceous fossiliferous marine sediments? A. Sub-Himalaya B. Lesser Himalaya C. Higher Himalaya D. Tibetan-Tethys Himalaya Answer: D. The Tibetan-Tethys Himalaya holds Palaeozoic to Cretaceous fossiliferous marine sediments. (Key point: Rocks of zones) 3. Which feature describes the Lesser Himalaya structure? A. Synclinoria with klippen and anticlinoria, many thrusts and tectonic windows, beds dipping northward B. Horizontal undisturbed beds C. Only normal faults D. A single simple anticline Answer: A. It is intensely folded and thrusted with synclinoria, klippen, anticlinoria and tectonic windows; beds mostly dip north. (Key point: Lesser Himalaya structure) 4. Which problem is associated with limestone and dolomite of the Lesser Himalaya? A. Karst and seepage B. Glacial outburst C. Liquefaction of alluvium D. Avalanches Answer: A. Limestone and dolomite give karst and seepage, while weathered phyllite and slate give landslides. 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