As we headed north to our target areas, we have used any extra time to collect some seismics. We got some near Aricha, then again under the Jamuna Bridge. Today we collected data near Bogra, where the transect of wells that we drilled last spring is located. All three pieces of data show reflectors, including a strong one we think is the bottom of the river valley from glacial times when sea level was 120m (393 ft) lower. It seems to shallow as we go north, which fits with our interpretation.
Having to exchange pilots for every stretch of the river made estimating how far we can go each day more confusing. No, we can’t go that far, then perhaps if we hurry. How fast we can go depends on the ever-changing currents. Each pilot only really knows his own stretch of the river. We make multiple contingency plans. We had to change pilots at a little stop just south of Bogra. That cost enough time, we couldn’t make it to our next stop at Bahadurabad Ghat. Option one was we shoot seismics and then return to this place. While shooting, the pilot agreed that we could then go on to some village on the way. If we stop shooting now, we can make it to Islampur only a little south of our target.
A pattern developed of the crew being overly conservative, correctly not wanting to get stuck in the middle of the river at night, but gradually they work hard to get us what we need and plans change. We initially wanted to start continuous shooting from Bogra north, but even we could tell we could not come close to reaching Bahadurabad if we did that. We got a few critical kilometers and steamed north without shooting to the village where we spent the night. Now, they have become more open to sailing and stopping wherever we are at the end of the day, just in time for our continuous profile. Problem solved.
Last night, Dhiman joined the ship and this morning Rafael and I left to return home. The little village is connected by one of the worst roads in Bangladesh. I will miss when the ship crosses the Dauki Fault during the final continuous shooting upstream on the Brahmaputra to the border. The ship will also collect data going downstream, but the speed over the ground will be very fast, perhaps limiting the quality. However, Volkhard and Tilmann are confident as the speed through the water will not be too high. They do not give up.
Overall the cruise has been a mixture of disappointing data in the east combined with the now very good data coming in in the west. And there is a good chance that tomorrow will bring triumphant images of where the Dauki Fault goes west of the Shillong Plateau. We have cemented our ties to the Bremen group, who have worked offshore for many years, but never entered Bangladesh before. Several joint efforts have developed. Mr. Islam, our guide, has been great. Getting to know the Bangladeshis from Dhaka University, the Geologic Survey and the crew has been harder due to language and my status. Last night we bonded more as we waited together for Dhiman’s very late arrival. I am not so good at languages, nor as exuberant as Tommy. Still, two weeks on an 85 ft. boat brings everyone together.
Hi Mike and Nano. If there is time and the current is too fast to get good data going forwards downstream, you can go backwards downstream, although the captain and pilot may not allow that. This was done on the Mississippi River: if there is a 6 knot current, instead of going downstream at 4 knots through the water plus 6 knots = 10 knots over the ground, you can head upstream at 2 knots through the water and end up going downstream over the bottom at 4 knots. OK, I understand that the current may be not that fast. But, it can be faster than that on the Missouri River near where I live, and probably the Mississippi.
If you try it and run aground or tangle up the streaner if you are using one, is still your choice.
Chris