Society of Petroleum Geophysicists (SPG), India Organized a Field Trip from Sub-Himalaya to Lesser Himalaya in Dehradun-Mussoorie-Dhanaulti Sector (Garhwal-Himalaya)

It was a proud moment for Society of Petroleum Geophysicists (SPG), India to organize a geological excursion from Sub-Himalaya to Lesser Himalaya in Dehradun-Mussoorie-Dhanaulti Sector (Garhwal-Himalaya) on 27th November 2021.

Geologically the Himalayan mountain chain has been divided into four longitudinal lithotectonic zones. From South to North these zones are as follows: Outer Himalayan Zone or the Himalayan Foothills that comprises mainly the Molasse sediments, the Lesser Himalayan zone comprising low grade metamorphic rocks, the Higher Himalayan Crystalline complex which includes high-grade metamorphic rock and the Tethyan Himalayan sedimentary sequence that encompasses Proterozoic, Palaeozoic and Mesozoic sequences. These zones are longitudinally oriented in West-East direction and extend from Nanga Parbat to Arunachal Pradesh.

A team of 52 geoscientists led by Shri. Vishal Shastri, ED-HoI GEOPIC & vice president SPG, India along with Shri. S. N Chitnis, ED-HoI, KDMIPE & President APG, India, Shri R Tandon GGM-BM, Frontier Basinsand executives from E&D Directorate, GEOPIC, KDMIPE and Frontier Basins, Dehradun participated in the geological excursion. Dr. R Islam, Scientist G (Retd.), Wadia Institute of Himalayan Geology (WIHG), with more than thirty years of vast experience in Himalaya, accompanied the team as an expert to the field.Shri A CNaithani, GGM (Retd.), ONGC also joined the team as co-faculty for the trip. The team assembled at KDMIPE Campus (in front of SPG office) in the early morning of 27th November, 2021 and started their journey to Shahanshai Ashram– Pathanghat – Kolukhet toll checkpost – Jharipani – Bhatta- Barlowganj-Dhanaulti route. The focus of the field trip was to familiarize with different geological sequences from Sub-Himalayan to Lesser Himalayan terrains.

During the field familiarization, participants were taken on a guided traverse through the frontal part of the Himalayan Fold Thrust Belt, in the neighbourhood of the Doon Recess. The objective of the day-long program was to introduce them to the geology of the Great Himalaya, which has fascinated earth scientists of all generations. Starting with the regional perspectives including geographical and stratigraphic aspects, the process was endeavour to introduce structural and tectonic aspects of the study area, covering the frontal lithotectonic zones - the Sub Himalaya and the Lesser Himalaya.Brief descriptions of the covered stoppages are provided below:

First stop is located near the mule track from Shahanshahi Ashram to Jharipani. Here, contact between Siwalik and Lesser Himalaya was observed which demarcate the Main Boundary Thrust (MBT). The Main Boundary Thrust (MBT) is one of the most important tectonic elements of the Himalaya which acts as the boundary between the Sub Himalaya and the Lesser Himalaya. At this stoppage, the different aspects of the MBT and its importance in Himalayan geology were discussed. Also various aspects of Sub-Himalaya and Lesser Himalaya were discussed after familiarization of strati-structural aspects of the study area. The Lesser Himalayan Units viz. ChandpurPhyllite and Nagthat Quartzite were seen along the Shikhar Fall Road section.

Second stop is located at about a distance of 2km from toll barrier at Pathanghat. Contact relationship between Nagthat quartzite and Blainidiamictite were observed in this area. At the contact of Blaini, pyrite bearing and glauconitic quartzite are present. Quartzites are of white in colour in this region. The mixed type of facies (interbedded quartzite, siltstone, rarely shale) indicate they have been deposited in a mixed to sandy tidal flat environment.

Third stop is located 2.7 km from Toll barrier, at the bridge over a nala at Pathanghat. Conglomerate- quartzite-siltstone of the Blaini formation was observed here. Different varieties of conglomerate associated with quartzite, siltstone and shale are present in this area. Both clast supported and matrix supported conglomerate were seen. Clast supported conglomerate contains fragments of limestone, quartzite, siltstone, sandstone, jasper etc. Most of the clasts are similar in lithology to the underlying Nagthat and Chandpur formations.

Fourth stop is located at Kolukhet toll checkpost. In this area, a transitional passage from Infra-Krol to lower Krol were observed. Infra Krol sequence represented by dark grey to black coloured thinly bedded laminated argillites with inter-bedded siltstone and sand stone. Carbonaceous shale were seen. It is transitionally succeeded by a sequence of interbedded calcareous shale, marl and grey fine limestone.

Fifth, sixth and seventh stops are located near abandoned Toll barrier at Jharipani, near Bhattaand near Barlowganj suspension bridge respectively. In the fifth stop, Krol-B, and Krol C Formation were observed. Very high quality limestone, massive gypsum, calcite pockets and oolites are commonly found in this area. In the sixth stop, Krol C, limestones with stromatolitic algal mats and oolites were observed. In the seventh stop, Krol-D limestone with algal mats was observed. Cynobacteria was also observed in this study area.

Finally, a visit to the geologically important outcrop where the Precambrian-Cambrian boundary viz. “from where life begins” had been demarcated. This stop is located at Mussoorie- Tehri by pass road. Approximately 3.5 km from Dehradun –Mussoorie diversion. This road takes off to the east from Dehradun-Mussoorie road, 200 meters before Kingkraig. At this spot, contact between upper Krol and Chert –Phosphatic rocks of lower Tal are exposed. This spot is part of Mussoorie syncline.Second order tight recumbent folds and fault plane are also observed in this area.

The daylong field trip proved to be very educative to all the participants , it gave an insight on the exposures and geology of the sub-Himalaya and lesser Himalaya coupled with the enrichment on the spot with the vast experience of Dr. R Islam and Shri A C Naithani. The geological field trip had been very inspiring for the geoscientists in understanding the Himalayan Geology and structural complexity present therein.

Flag off ceremonyby Shri. Vishal Shastri, Vice President SPG at KDMIPE and journey started to field on 27.11.2021.

Shri. Vishal Shastri, ED-HoI, GEOPIC & Vice President SPG, Shri. S N Chitnis, ED-HoI, KDMIPE & Shri AC Naithani observing Krol formation near Toll barrier

Team observing the MBT (Siwalik and Lesser Himalayan Boundary) near Shahanshai Ashram.

Team assembled near Cambrian-Precambrian Boundary at the onset of Tal formation near Mussoorie- Tehri by pass road.

Faculty Dr. R Islam explaining about the Lesser Himalayan tectonics and geology.

Shri. Vishal Shastri, ED-HoI, GEOPIC & Vice President SPG felicitating faculty Dr. R Islam.

Contact between Siwalik and Lesser Himalayan Formation is inferred by the difference in elevation which demarcate the Main Boundary Thrust (MBT).

Krol-B member observed near Jharipani. Very high quality limestone, Massive gypsum, calcitepockets and oolites are commonly found here.

Krol A formation observed near Kolukhet Toll checkpost. Shows intercalation of Limestones and Shale.

Cambrian-Precambrian Boundary at the onset of Tal formation near Mussoorie- Tehri by pass road. Intercalated Chart and Limestone are found here.