Sylhet, Geology and Packing.

In Bangladesh, we are combining field work using magnetotelluric (MT) to examine subsurface structures and faults in this earthquake-prone region, and a small field school of 11 American and Bangladeshi students over the past two weeks. Magnetotelluric uses the sun’s electromagnetic radiation to probe the subsurface. It requires careful recording of electric and magnetic fields with sensitive equipment. However, we struggled to find it far enough away from the power cord, and mice and foxes would eat the cables. Our solution is to deploy in tea gardens (plantations) and bury cables. Rain and flooding also prevented us from finding good locations for MT. We’ve now finished our work at the Sri Mongar base south of Sylhet, so we’re driving north to a resort on the Sylhet anticline.

Flooded fields in Sylhet with the Shillong massif in the background.

A view of a school flooded by early rain.

After settling into our hotel on the hill, a group of 4 of us went out to scout a remote area of NE Sylhet. We hope the tea gardens there work properly. In order to collect MT data, we need 2 synchronous sites, we want one tea plantation on this anticline and another further NE. Going along the main road, we saw extensive flooding where early rains had already occurred. Many areas were flooded and we saw people raising money to help those who were flooded. Usually, rice fields are flooded, but houses and roads are above normal flood levels and remain dry. We can now see homes and schools flooded even before the start of the monsoon next month. Moving on, we’re on smaller and smaller roads. As we approached our target site, we arrived on a dirt road that the van could not pass through this time of year, with deep mud ruts that we could not drive through. I had hoped that the tea garden would maintain good road traffic, but I was wrong. We had to give up scouting and go back.

Arman, Liza, me, Fahima and Masud at Shaheed Minar at SUST.

Since it was still early, we went to Shahjalal University of Science and Technology (SUST), the university in Shofique. It is located a little west of the city on the edge of the Sylhet anticline. We visited the school, Shofique’s office, a GPS site (not mine) and the local Shaheed Minar on top of the mountain. Shaheed Minar is a memorial to the victims of the Bengali movement in 1952 when Bangladesh was still East Pakistan. It was the precursor to the eventual 1971 War of Independence. Central Shaheed Tower is close to Dhaka University, but there are local ones all over the country. They are at the heart of the annual Language Day celebrations, including a week-long bazaar in Dhaka that celebrates the Bengali language through theatre, poetry, reading and book fairs.

View of the Dawn River flowing into Bangladesh from the Shillong massif in India. Some of us are looking at an outcrop in the lower right.

One of the waterfalls that flows down the Shillong frontage.

We were both dissatisfied with our hotel and in the morning we changed to a better hotel in the city of Sylhet itself. This was also the last day we searched and installed any MT sites that would not have had enough time to deploy for our purposes. Unfortunately, it turned out to be another rainy day. Scouting and deploying electrical equipment in the rain is never a good idea, so we spent the day doing most of the mini field school lectures. Rashed Abdullah of Jahangirnagar University and I lecture in my great room. I had the largest room in the group, big enough for all of us, 10 students and 3 professors (because a few had to leave early) to squeeze in while projecting a PowerPoint onto the wall.

Rash Abdullah on top of Eocene carbonate rocks, flanked by Mohipur and Alman.

Our remaining two days in the field were focused on looking at geology, with some final lectures in the evening. We start at Jaffron, on the Indian border, and on the other side is the huge Shillong massif 2km high and 300km wide. This is the Indian state of Meghalaya, which means the abode of clouds, the rainy place on earth. The Shillong massif is rushing across the Sylhet Basin, pushing it down. It created thicker sediments and many low marsh areas north of Sylhet. Traditionally, the roadbed fault that separates the two regions is located at the boundary between mountains and plains. However, since Nano Seeber and Ellie Ferguson mapped here a few years ago, we’ve suspected that this is not the main Dauki fault. It cannot accommodate the vertical movement of about 7 km along the fault here. It’s a good thing to argue with some Bangladeshi students who have long been taught that this is the Daoji fault.

Masud, Martin, Tomalika, me, Arman, Rashed, Fahima and Liza in Tamabil. When I last came here in winter, it was dry and crowded with rock-digging workers.

Lunch at a restaurant in Jaintipur.

We visited outcrops of limestone and younger shale during the Eocene (about 50 million years ago). This area has been built since my last visit, new stone steps and many tourist shops leading to the river. Jaflong is a mixed-industrial site where rock is mined from the Shillong River along the river as an aggregate source for concrete, as well as touring the steep mountains and rivers that flow from it. We crawled through the rocks and continued eastward, stopping at the Tamabil and Jaintipur outcrops. Jaintipur is the center of the Khasia people, a matriarchal society from Shillong. We had lunch in Jaintipur and then walked through outcrops in the surrounding area, including a government agricultural center that grows a variety of crops to suit the climate of Bangladesh.

Ruven (driver), Martin, Tomalika, Liza, Fahima, Alex and Anna on our Shari River. Others are on the roof.

The next day, we continued our boat ride along the Shari River. No trip to Bangladesh is complete without taking a wooden boat. Unfortunately, many outcrops are underwater this time of year. We can still see the stratigraphy and deformation of the bed. We also got off the bus and almost made it to the Indian border. After the boat ride and some green mangoes, we drove to more outcrops, including some almost vertical beds. These reinforce our belief that the Dougie fault is blind and extends farther south. The deformation we see is most likely the effect of the fault below. This interpretation will be combined with future research.

We all walked cautiously over a bamboo bridge near the Shali River.

Rashed stands on an outcrop and explains its significance.

After the outcrop geology was over, we visited the gas field site where a blowout occurred in 1955, followed by a blowout in the pressure relief well that stopped the leakage. Now, gas can still be seen bubbling in the waters of the two wells, and a small cave nearby is still burning with flames. Then visited the office of Sylhet Gas Field Company. On the way back, we visited Shofique’s home and met his wife and daughter. I thought he was just inviting me, but when I saw the other cars, I realized he invited everyone. We were greeted with a variety of food and fruit. We finally tasted ripe lychees and mangoes.

Since the blowout of the Sylhet-1 well, the gas leaking from the ground has been burning with flames.

A spread of food and fruit awaits us at Shofique’s house.

After a much-needed shower, we went out for a buffet dinner at a restaurant in the city of Sylhet. We then head back to the hotel for a “Longi Party” where all the men are dressed in Lungi while pictures of our trip flash across the walls. The mini field school has come to a successful conclusion. The next morning, drive back to Dhaka. The first stop was the Bangladesh Open University (BOU), where other equipment for our March cruise was stored. The next day, I stayed with Masud, Arman and Biplab’s original crew to pack everything and ship to the US. Everyone else returned to Dhaka, to their homes, relatives or hotels.

Anna took a selfie of Fahima, Masud, Biplab, me, Tomalika, Mohibul, Arman and Liza dressed up for the final buffet dinner.

After driving back to Dhaka from Sylhet, Ana fell asleep on Tomalika’s lap, with Arman watching.

The next day, the students got together at the University of Dhaka to show the Americans their flight while my staff spent the day cleaning and repacking the equipment. After 1400 lbs are scheduled. Equipment on 3 pallets, wrapped in plastic by a team at the furniture factory and shipped back to the US on rope. Then the last few of us can return to Dhaka. I visited Dhaka University on my last day and participated in part of a session on the Bangladesh Delta Plan 2100, a major initiative to create sustainable deltas in this century. Now all that’s left is the long flight home. Although the MT data acquisition encountered many difficulties and our acquisition schedule had to be greatly reduced, I still hope that it will yield important information to complement our seismic data. The Mini Field School, despite its loose organization and dictated by just-in-time MT logistics, was a complete success. Thanks to the mixed contributions of American and Bangladeshi professors, my students and I have learned a lot, both in the classroom and in the field.