Trip Notes on Exploring the Ombilin Basin

The journey starts from the search for the oldest coal mine in Indonesia, the Ombilin coal mine, to visit the basement of Sumatra Island.

This research trip visited West Sumatra. Some of the locations that are targeted for this research trip are visited to further uncover the geological potential in the West Sumatra. The three-day trip was still not enough to explore targeted locations in West Sumatra, starting from the basement to the latest deposit.

Coal Potential in Ombilin

The first trip was to visit one of the oldest mines in Indonesia which is also a world heritage site; the Ombilin coal mine, located in Sawahlunto City, West Sumatra. On the first trip we had the opportunity to visit PT. Bukit Asam Ombilin Mining Unit to take samples for research. The journey begins with safety induction. Dark conditions, narrow alleys, wet, and occasional lorries passing by make us have to be more careful. The mine is still in production, but since it has been established as a World Heritage site, several functions switch for educational and tourism purposes.

The geothermal manifestations in Sawahlunto

Not far from Ombilin’s coal mine, precisely in the area of Padang Ganting, there are several geothermal manifestation in the form of hot water found in some locations. The hot spring is used as a tourism destination, but it is still unknown whether the manifestation actually holds a significant potential of geothermal energy in West Sumatra. The water pH observation and measurement was also performed by Dr. Nukman, one of the researchers that focused on geothermal energy. The manifestation is quite unique because the location is quite far from the existing volcano and raises curiosity towards the formation of such manifestations.

Recent Volcanic Deposits

On the way to the inn, we stopped in Tanah Datar regency to visit quarry outcrop. Due to the high curiosity, we approached and observed the quarry. Surprisingly, the quarry is a product of volcanism that is interpreted as a product of Malintang and Singgalang volcanism. Not only doing observations, sampling in the form of pumice, charcoal and bulk samples are also performed mainly by Dr. Esti who was very interested in the outcrop. The sample is planned to be further investigated for deposit characterization to reveal its origin and potential in the future.

Harau Valley Geotourism

Moving westward, precisely in the Lima Puluh Kota Regency, we also visited one of the famous tourist sites in West Sumatra; the Harau Valley. Harau Valley presents a rural atmosphere surrounded by steep cliffs with breccia and conglomerates lithologies . Not only presents a beautiful view, in the Harau Valley there are also several waterfalls that further complement the tourist destinations in this area.

The Granitoid Basement of Sumatra Island

At the end of this trip, we took the time to visit the city of Solok to take some granite samples for further research on the potential of granite on the island of Sumatra. This outcrop is one of the ideal outcrops and we also found several types of granitoid stones that have been broken through basalt intrusion, making the second trip this time closed with a sense of satisfaction and fun.