Vietnam
By Dr. Brooks Ellwood The history of research projects in geology and geophysics at times is fairly rapid, and at other times these take a long time to develop. I have been working in Vietnam for ~25 years, and this year, in International Geology Review, our work on the Permian–Triassic boundary interval (PTBI) at Lung Cam, very near China in the northern-most part of Vietnam, was published. As background, in 1990, I was sent to China by the World Bank, and the National Academy of Sciences, to evaluate geophysical equipment purchases by the China University of Geosciences in Wuhan, using World Bank money. Following this opportunity, I headed to Vietnam to establish a working relationship with the Institute of Geophysics in Hanoi. Initially the Vietnam work started by our sampling Devonian and Cambrian rocks, and then the work evolved into work on five PTBI sections, scattered along the northern boundary of Vietnam with China. Most of these sections were badly altered, weathered and deformed. After many years
we discovered a section at Lung Cam, which became the primary focus of our work. There we found an ideal, expanded section for which we could generate excellent geochemical, biostratigraphic and magnetic susceptibility data sets that we could use in time-series analysis. This work took many years of sampling and resampling, using the conodont biostratigraphy to narrow down the boundary location. When I first visited Hanoi,Vietnam (15 years after the US-Vietnam war ended), the city looked like a classic French country town, with heavily tree-lined streets and dust in the air from all the bicycles. There were very few cars and practically no motorbikes. Lights were dim and power outages were often. (It wasn’t until 1989 that the power generating station on the Red River near Hanoi was finally completely rebuilt after the War.) Westerners were practically non-existent on the streets, and there were thousands of deformed children begging everywhere in the cities – deformed as the result of
birth defects from Agent Orange in the environment. These defects looked very much like the Thalidomide deformation produced in babies in Germany during the late 1950-60s. Today, these children are gone, moved off the streets and placed in homes where they can’t be seen by tourists or the general population. In 1990, many of the men in the North wore the National Vietnamese Army (NVA) shirts, pants, and pith helmets. My hosts were concerned that I was in danger so they assigned a driver to protect me, a veteran of the wars against the US and against China in 1979. He didn’t like me too much, but he did his job. Much of our work was in the north of the country, in the karstic limestone areas that included the famous Hi Long Bay. However, some of the work was in the South. Ho Chi Minh City was a very different place at that time than was Hanoi. The men wore mainly baseball caps and there were thousands of US military vehicles on the road. The first thing to go on such vehicles in a tropical climate is the
Ellwood using a diamond-blade cement saw, brought from LSU, to saw out relatively fresh blocks of limestone for biostratigraphic and geochemical analyses. Bed labels 8 and 10 (fresh limestone beds) are show in the photo, with Bed 9 (exhibiting a slight surface weathering – ‘rusting’ – due to the iron in the mineral ankerite) sandwiched in between. Typical karstic character of the limestone in the region can be seen in the background to the left.
The trail to the Lung Cam section in central, northern-most Vietnam. The outcrop can be seen in the distance on the far left.
radiator, and many of the trucks, “Duce and-a-Halfs”, “3/4 tons”, and other tactical wheeled vehicles, had a 55 gallon drum mounted over the cab filled with water. A hose ran water from the drum through the engine and out into the street, thus replacing the radiator in cooling the engine. Everywhere in the streets had ‘drawn’ thin, wet lines from the water that poured from those engines. These trucks showed a history of US military involvement in Vietnam ranging from vehicles built in the 1950s when we first put troops over there, until the 1970s, when we finally left. Today, all of Vietnam is different. New bridges now cross the rivers in the major cities. Super highways exist for short distances around these cities and massive building projects are underway. Bicycles have been replaced by motor scooters (initially riders rode with no helmets, but then suddenly, in a years time, almost everyone wore a helmet), and many more cars are now on the
roads as people become wealthier. When I first visited in the 1990s, I had to go through Bangkok to get a visa from the Vietnamese embassy there. Now you can get these visas in the airports in Hanoi and Ho Chi Minh City. Things have radically changed in the big cities, but outside the cities, things haven’t changed all that much. When we work in the North we plan two days just for the travel to get to our sections, and these are usually not more than 400 miles away! One of the results of the work we performed, and published this year, was that we were able to develop a time-series curve through the PTBI that correlates very well with published, multiple radiometric age dates using zircons from volcanic ash beds. These ‘absolute’ dates were developed for the Permian–Triassic Global Boundary Stratotype Section and Point (GSSP) located in Meishan, China. This is the global section chosen to represent the
beginning of the Triassic, and therefore the end of the Permian. Our time-series ‘relative age’ data set has allowed us to resolve timing of events through the PTBI to within ~9,000 years. In addition, we have tied, with excellent precision using Graphic Correlation (familiar to some in Oil and Gas), the Lung Cam section to the Meishan GSSP. Because the GSSP is extremely condensed and the Lung Cam section is very expanded, we were able to better define timing of the major extinctions in the latest Permian, and showed that volcanic ash caused global fires during that time. These fires extended from the latest Permian into the Triassic, covering a period of ~85,000 years (our work published in International Geology Review - Nestell et al., 2015). Our research in Vietnam has been very exciting, and the focus on the PTBI here has led to similar work in China, Canada, Slovenia and elsewhere, published and to be published in the near future.