Society of Petroleum Geophysicists (SPG) and Association of Petroleum Geologists (APG) Vadodara Chapter jointly organized one day geological field trip to study the outcrops in the Vastan Lignite Mine and adjoining areas on 15th February 2025. In the area Stratigraphic Sequences from Deccan Trap to Early Eocene marked by the development of lignite-rich sediments and extensive fossil-bearing limestone is exposed. The idea behind the trip was to visualize the scale of workstation seismic sections in geological outcrops, study the different litho stratigraphic divisions and experience the vertical and lateral lithologic variations.

The journey commenced from Gaveshana Bhawan at 7 AM and was flagged off by Shri Priya Ranjan Mishra, ED Basin Manager, WON Basin, ONGC Vadodara & Prof. Atul Vasant Joshi, Head, Department of Geology, MS University, Vadodara. A total of 56 participant which included senior officers of the WON Basin Major Janeshwar Prasad, GGM(Chemistry) Head RGL, Shri K Baskaran, CGM-HGS, President- SPG, Vadodara Chapter, Shri Harsh Vardhan Dave, CGM(Geology)-Retired, Secretary, APG Vadodara Chapter, Smt. Amanjot Kaur, GM(Geology), Block Manger-Block-III and Shri Prasad Kulkarni, GM(Geology)-Head BMG and G & G fraternity from ONGC, Vadodara and life members of SPG & APG actively participated in the field trip

Vastan Lignite and Limestone Mine

The first stop in the trip was at the Vastan open cast mine, operated by Gujarat Industries Power Company Limited (GIPCL). The Company has a diversified power generation portfolio comprising Thermal (Lignite and Gas) and Renewable (Wind and Solar) Power Plants. GIPCL also operates captive Lignite and Limestone Mines to meet the fuel requirement of the 500 MW Surat Lignite Power Plant. It is approx. 50 Km. away from Surat and 40 Km. from Ankleshwar (Dist. Bharuch). The site can be approached from N.H. 8 connecting Bombay-Ahmedabad via Kim.

Vastan Lignite Mine is divided in two pits namely Vastan North Pit and Vastan South Pit. Vastan North Pit is already exhausted and presently GIPCL is operating Vastan Lignite Mine-South Pit. The thickness of the lignite seams varies from 1-2 m in the South pit to upto 11m in the North pit. The seams suddenly pinch out in eastern end and forms the boundary of the basin for the Lignite deposition. The general dip of the seams is 3-4 towards west. Overall Lignite basin is controlled by reverse fault, present part falling under the upthrown portion compared to southern side of Tapi river.

The focus at the mine site was to understand the disposition of the lignite coal seams in the southeastern boundary of the Cambay Basin and its relations to coal seams of early Eocene sequence in the northern part of Cambay Basin. In the mine area the sedimentary deposits consist primarily of sand, clay and lignite seams underlain by Deccan Volcanics. The basin is structurally influenced by faults particularly those associated with the Tapi River.

Shri Hemang T Shukla, DGM(Geology), GIPCL gave a comprehensive overview of the mine’s geological features, including its daily coal extraction, energy production process and mining methods. This was followed by an informative session with Prof. Joshi, who discussed the region’s stratigraphy, highlighting its geological significance and its role in understanding ancient ecosystems and environmental changes. Prof. Joshi thoroughly explained all doubts of participants, providing insightful geological explanations that enhanced the participants' understanding.

Visit to the Limestone Formation Site

After studying the outcrops the in coal mine, the group proceeded to observe the excavated benches of Limestone. Limestone occurs along with shales and sandstone lenses. The extracted limestone, though low grade, is suitable for use in thermal power plant for desulphurization.

Deccan Trap

The outcrops of Deccan Trap rest either over Precambrian or over the Cretaceous sedimentary rocks (Lameta and Baghs) in the study area. The entire terrain to the south of Narmada River, comprising uplands of Rajpipla and Vyara is occupied by Trappean rocks. The area is hilly and shows an undulating topography characterized by E-W trending rows that rise 20-30m above the general ground level. Exposures of Deccan Trap were observed near Netrang Village. The trap is predominantly tholeiitic in nature. Besides tholeiitic basalts and dolerites, felsites, trachytes, diorites and obsidian also occur and beds of scoriaceous breccias are occasionally met with. The other varieties of traps such as amygdaloidal, porphyritic, etc. occur.

At the end of the trip, Shri Priya Ranjan Mishra, Vice President APG Vadodara Chapter presented a token of appreciation to Prof. Atul Vasant Joshi, acknowledging his guidance and contribution to the learning experience. The trip has provided valuable exposure to the geological information of the area and bridging the gap between academia and industry.

Organizers acknowledge ED-Basin Manager Shri Priya Ranjan Misra for encouraging and facilitating the tour. The reconnaissance and planning was done by the executive bodies of SPG and APG, Vadodara chapter for this field excursion.