- 2080 Bhadra · 4 marks
Discontinuities; Siwalik and Higher Himalaya lithology
Short answer
The major discontinuities are the Main Frontal Thrust (MFT/HFT), Main Boundary Thrust (MBT), Main Central Thrust (MCT), and South Tibetan Detachment System (STDS). The Siwalik zone comprises Miocene-Pleistocene sandstone, mudstone, and conglomerate in lower, middle and upper divisions. The Higher Himalaya is composed of high-grade metamorphic rocks: kyanite-sillimanite schist/gneiss, calc-silicate gneiss and marble, and augen gneiss with leucogranite.
What are the major discontinuities of the Nepal Himalaya? Describe the lithological characteristics of the Siwaliks and Higher Himalayan zone.
Major discontinuities of the Nepal Himalaya
| Thrust | Between | Tentative location | Age of last movement |
|---|---|---|---|
| MFT / HFT | Terai and Siwalik | Along the southern foot of the Churiya hills | Active (Holocene) |
| MBT | Siwalik and Lesser Himalaya | Along the northern edge of the Siwaliks / foot of the Mahabharat range | Late Pleistocene, reactivated |
| MCT | Lesser and Higher Himalaya | Along the foot of the Higher Himalaya, mostly north of Kathmandu | Miocene, partly active |
| STDS | Higher Himalaya and Tethys | Along the northern slopes of the Great Himalaya | Normal fault, Miocene |
Siwalik zone
Lithology (three divisions)
- Lower Siwalik: alternation of fine-grained sandstone, mudstone and siltstone; red, purple and grey colours (Miocene).
- Middle Siwalik: thick, massive, coarse "salt and pepper" sandstone with some mudstone and conglomerate lenses (Mio-Pliocene).
- Upper Siwalik: poorly cemented boulder-pebble conglomerate with sandstone and clay (Plio-Pleistocene).
Structure: the strata are folded into anticlines and synclines with strike roughly parallel to the Himalaya (WNW-ESE), often steeply dipping or overturned in the north near the MBT, and cut by thrust faults such as the MBT and MFT.
Higher Himalaya
Lithology (three formations)
- Formation I (lower): kyanite-sillimanite schist and gneiss, with migmatite.
- Formation II (middle): calc-silicate gneiss, marble and diopside bearing rocks.
- Formation III (upper): augen gneiss, quartzite, and Manaslu and other leucogranite intrusions.
✓ Answer checked by Claude Opus 5.5 (high effort)
Related questions
- Lithology of Higher Himalaya and Tethys zone · Engineering Geology I, chapter 7 · asked 3×
- Lithology of Lesser and Tethys Himalaya; Siwalik difference · Engineering Geology I, chapter 7
- Physiographic division; Siwalik and Higher Himalaya · Engineering Geology I, chapter 7
- Discontinuities and engineering problems in Nepal Himalaya · Engineering Geology I, chapter 7
- Siwalik zone in detail · Engineering Geology I, chapter 7 · asked 2×
- Tectonic zones and major discontinuities · Engineering Geology I, chapter 7 · asked 2×
- Problems of Siwalik and Higher Himalaya · Engineering Geology II, chapter 2 · asked 2×
- Major discontinuity systems of Nepal Himalaya · Engineering Geology II, chapter 2 · asked 12×
- Geological hazards of Higher Himalaya · Engineering Geology II, chapter 2
- Engineering geological problems of Siwalik zone · Engineering Geology II, chapter 2 · asked 4×