10 April 2018

Geologist Dr Yani Najman explains how she travelled with researcher Dr Gwladys Govin to the remote kingdom of Bhutan to solve a Himalayan mystery - how the Shillong Plateau was formed

It had long been my dream to do field work in the Himalayan Kingdom of Bhutan, both because of its remoteness and isolation, and because it provides an unparalleled opportunity to understand how topography develops. However, Bhutan is also a country that will cripple anyone’s research budget, and so it was not until I was awarded a European FP7 grant that the dream could become reality.

My first job was to pick a research student from an impressive list of applicants who had been invited to interview at the Consortium’s “welcome event”. It was not an easy task, particularly as I had a headache and wanted to go to bed. But up popped Gwladys with her cheeky cheery smile that no-one can ignore, and soon my headache was forgotten; it was clear who I would pick as my student. And so the partnership began.

The concept behind the project was simple. The only raised topography in the Himalayan foreland is the 2000 metre high Shillong Plateau. To understand how and why it formed, we first needed to know when it rose up. But how could we date when it uplifted?

Our idea was that, millions of years ago, the Brahmaputra River flowed over the region where the plateau is today: when the plateau rose, it shunted the river northward towards Bhutan.

The Brahmaputra sands have zircon mineral grains of very characteristic age. So, by searching for Brahmaputra-like zircons in sedimentary rocks of Bhutan, deposited by rivers over a time span of many millions of years, we can discover if and when the Brahmaputra flowed further north.

Field work started with a hair-raising landing at one of the most difficult landing strips in the world, for which Gwladys had somehow managed to secure front row seats in the cockpit with the pilot! We landed in a country unlike any other I have known: Bhutan has only recently emerged into the 21st century (television and the internet only came in 2000) and it measures its progress by its Gross National Happiness (GNH) index.

There is also a total ban on smoking, a situation Gwladys described with a few flowery French phrases of disgust. 

Bhutan is a land of extremes, from lowland jungle with rivers we waded through and swam in, to snowy mountain passes over which we trekked in the icy cold, nearly setting fire to our tent in a failed bid to keep warm on one memorable occasion.  And finally we dragged back over 200 kg of rocks, which we presented to a rather perplexed office clerk at DHL's shipping depot in Thimphu, the capital city of Bhutan.

After the field work, the hard grind of intricate lab work began. Gwladys had to hand pick each tiny zircon grain and analyse it to determine its age, searching for that elusive signal of the Brahmaputra River. She analysed more than 500 grains in all, and, when the analytical instruments were acting up, taught the lab-managers an “interesting” new collection of French phrases.  Finally we found the evidence we were looking for: the Brahmaputra was shunted north by the rising Shillong Plateau 5 million years ago.

Having dated the time when the plateau rose up, we could then consider the mechanism involved. The Shillong Plateau, which is bounded on both sides by major faults in the Earth’s crust, is part of the Indian plate. The Indian plate is moving northwards and being pushed beneath the Himalaya, a process which causes the plate to be subject to “stresses” in the region next to the mountains. 

Since we know how fast the Indian plate is moving north we can calculate when the area that was to become Shillong Plateau entered the stressed region.

We discovered that this happened at the same time that the Plateau rose up. So we concluded that the creation of the Shillong Plateau was due to accelerated movement on the Plateau’s bounding faults, caused by the Indian plate entering the stressed region.

With this success began the final hurdle; writing up and submitting the work for publication. We decided to go for the journal Geology, one of the most prestigious in our field. Twice the paper was rejected. After the second rejection, Gwladys’ rapidly tiring co-authors were prepared to give up the fight and submit the work to a journal with lower entry requirements. But not Gwladys. A fighter ‘til the end, she was determined to persevere, and was making the final amendments when her life was tragically cut short in a car accident.

In the following turbulent weeks I found it cathartic to finalise the work Gwladys all-but-completed. We resubmitted her work in her name, and… finally… success… it was accepted.

You can read the paper here. This is Gwladys’ story. We celebrate her life as we celebrate her achievement.


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