APG Expedition for Manali-Leh-Nubra sector The Association of Petroleum Geologists has been providing a unique platform to geoscientists since inception and has been in a pursuit to disseminate knowledge through field trips, invited lectures on specific themes and conferences.

APG has held several field workshops in past, especially in Spiti Valley, rendering thought processes for the exploration of the Higher and Tethyan Himalayan sectors. An Expedition cum Field Workshop was convened during the current year in the Manali-Leh-Nubra sector for the first time with a vision to acquire an overview of the geology and geomorphology of the Himalayan transect from Outer Himalaya through Lesser & Higher Himalaya into the Tethyan and Trans Himalayan regions and to focus on the importance of Field Geology, Stratigraphy, Sedimentation and Tectonics.

The Expedition was attended by participants from Oil India Limited, Birbal Sahni Institute of Palaeontology and ONGC. The participants assembled at Dehradun on 31st July 2010 at Dehradun, where a pre-field session was organized. President APG, Mr. P K Bhowmick graced the function, which was also attended by other office bearers of APG.

The internal faculty Mr. Narendra K. Verma, Vice President APG stressed on the vision behind this Expedition and elucidated upon the India–Asia collision through a meticulously tailored presentation.

The invited faculty Dr. Rajeev Upadhyay from Kumaun University, who owns 22 years of experience working in Tethyan and Trans-Himalaya, touched on the geology of the entire Himalayan sector.

Dr. R J Azmi, Former scientist ‘G’ WIHG also enumerated his experiences of working in the Himalayan domain.

The Expedition was flagged off on 1st August 2010 in the wee hours from Himalaya Building, Frontier Basins and the evening halt was at Manali.

Pre determined key exposures and sections were visited and deliberated upon in the Lesser and Higher Himalayan sectors.

A glimpse of these sites is presented below.

Tectonic dips in the Pliestocene clay & silt, Panchkula Gambhar Thrust juxtaposing Dharamsala with Lower Siwalik

Pre-Tertiary Limestone near Bilaspur, HP

The successive days were spent in understanding the Tethyan domain to the north, beyond Rohtang Pass, and Trans-Himalayan Domain beyond Indus Suture Zone in the Leh-Pangong-Nubra Sectors. These were the new learning experiences especially in the Indus Suture Zone, Shyok Suture Zone and Karakoram fault zone.

Leh and contiguous areas in Indus Valley (Ladakh, J&K) are world renowned as a geological museum of India-Asia collision and rise of the Himalaya. Except some minor interruptions almost the entire Precambrian to Eocene stratigraphic succession is preserved along the Manali–Leh road with ophiolitic mélange in the collision zone which was unravelled through key stratigraphic sections and traverses.

Solang Valley, Manali: readiness to embark into Tethyan Himalaya The vehicle trail at Marhi, half way to Rohtang Pass.

Pre field lessons at Kyelong (Lahaul) The first Cambrian outcrops at Deepak Tal

Resistant Muth Quartzite crowning the peaks in Sarchu Catchment Recumbent folds in Triassic limestone at Sarchu

Oligocene-Miocene Molassic sediments at Hemis; looking west from Karoo

After reaching Leh, a day was spent in the Leh-Pangong Tso sector through the settlements at Shakti, Jingral, Chang-La & Tangtse. Chang-La Pass is known to be the second highest motorable pass. The group observed the outcrops of Ladakh batholith, Tangtse metamorphic and the Pangong Group of rocks comprising slate, mica schist, greenschist/amphibolite, marble, calc silicate and mylonite granite gneiss. The tranquil charm of the Pangong Tso Lake with its myriad colours was a wonderful experience.

The Pangong Tso Lake displaying its myriad colours External faculty discussing the geological map at Pangong

The participants of this expedition also crossed the highest motorable pass at Khardung La (5359m), located about 40 km north of Leh City and obtained a glimpse of the Karakorum Mountain Range.

Khardung La (Participants seen in red & white caps) Panoramic view of Karakoram Batholith (North of Shyok Suture)

The caravan descended into Shyok and Nubra valleys. The Shyok Suture zone which is interpreted as

a suture embodying rocks of a backarc basin is represented by intensely deformed tectonic slices

between the Ladakh and the Karakoram Batholiths. The major tectonic slices from south to north

include: Khardung Formation, Hundri Formation, Shyok volcanics, Saltoro Molasse, Shyok ophiolitic

Melange and Tirit Granitoids.

Volcanics in Khardung Formation Transformation of volcanics into chlorite schist in proximity of Shyok Suture Zone

The Saltoro Limestone within the Shyok Suture is a reefal complex that grew on volcanic basalts and andesites, with ignimbrites forming the seamount of Middle Cretaceous or older age. The Shyok Suture is older than the Indus Suture and was closed around 75 Ma.

Saltoro Hill at the confluence of Shyok (foreground) & Nubra rivers Sand dunes on the bank of Shyok River at Hunder

The varied landforms carved due to weathering and erosion at high altitude cold desert were also witnessed. Traverses throughout the expedition rendered the Geoscientists an insight into the numerous processes involved in carving out the spectacular landscape. The power of glacial, water and wind energy was witnessed by one and all. It was an enlightening experience understanding the India–Asia collision.

RAJEEV BHOJ

Executive Member, APG Coordinator, Manali-Leh-Nubra Expedition 2010