Paleolimnological Training at LacCore in Summer 2017 at the University of Minnesota, USA
Hướng Nguyễn, a lecturer at Vietnam National University, Hanoi (VNU) and founding member of the EOS Geoscience research group was invited for training at the LacCore/CSDCO Drilling and Coring Summer Institute (DCSI) from July 24 to August 4, 2017. DCSI was jointly coordinated by the National Lacustrine Core Facility (LacCore) and the Continental Scientific Drilling Coordination Office (CSDCO), hosted by the University of Minnesota, and funded by the U.S. National Science Foundation. The DCSI application process was extremely competitive, with 143 applicants versus 30 positions (15 for each session). Participants arrived from various countries around the globe.
The Summer Institute was taught by Dr. Amy Myrbo, and other LacCore/CSDCO staff and guest presenters. Topics in the classroom and field included site selection and survey, project planning and management, broader impacts, coring and drilling equipment, initial core description, and downstream analyses. The successful training was transformative for Hướng’s future career as an earth scientist. The following narrative describes Hướng’s paleolimnological experiences from early beginnings in Vietnam to his recent coring success after his training at LacCore.
Chapter 1: Coring in a deep maar lake
Biển Hồ is a cluster of three fused volcanic craters forming a maar lake at about 7 km north of Pleiku City, Gia Lai province in the Central Highland of Vietnam. The maximum water depth is about 21 m. In 2015, Hướng’s group began discussing a possible plaeolimnological survey in Biển Hồ with Dr. Arndt Schimmelmann (Indiana University), his wife Minh Ngọc and his son Jan Schimmelmann (Bremen University). With a shore-string budget and meager equipment, our first visit to Biển Hồ in March 2016 yielded little more than the observation of a bacterial mat on the deep sediment surface. That in itself was encouraging because it proved hypoxic bottom water conditions and made it likely that laminated sediment was accumulating. Our first expedition to Biển Hồ was at times a dramatic comedy. After hours of hard work, we finally lost the sediment core due to clumsy handling. When Jan carried an ‘anchor stone’ from the shore onto the rickety ramp of a boat, he slipped and cut his chin on sharp metal. Jan was brought to a local Vietnamese Army Hospital and received six expert stitches. Regardless, our strong team spirit did not give up.
Follow-up field work with improved home-made equipment in December 2016 utilized an improvised coring platform consisting of two inflatable boats joined together by a central wooden deck. Although the platform was tied to the lake shore with a long rope, the changing wind direction on Biển Hồ made it impossible to hold a steady coring location. Nevertheless, our field work yielded half a dozen 50- to 70-cm long sediment cores using our self-designed and inexpensive “autonomous sediment corer with pneumatically operated core catcher” and “push corer with an extended set of metal rods”. This time we proved the existence of laminated sediment and the recent deposition of a clay-rich flood layer resulting from the unusually strong 2016 monsoon season. The hunt was on to recover and read this valuable paleolimnological archive containing a likely record of paleo-precipitation strength over hundreds and possibly many thousands of years.
At some time in 2016, our group discussed the need for better coring equipment and improved analytical methods in the absence of funding. In Spring 2016, LacCore called for applications for its 2016 Drilling and Coring Summer Institute. Although several members of our group had applied, the applications were not successful because by summer of 2016 we had not yet proven the existence of laminations and the value of the Biển Hồ sedimentary record. Following our coring success in December 2016, Hướng’s renewed application was accepted for the 2017 Drilling and Coring Summer Institute. Since then, the EOS group has greatly benefited from Hướng’s training at LacCore.
November 2017 – the third coring expedition in Biển Hồ
We returned to Biển Hồ maar lake in November 2017 with greatly improved equipment. We were delighted to welcome Dr. Antti Ojala from the Geological Survey of Finland as a new member to our team. Antti’s expertise in lake coring and core-to-core correlation using paleomagnetic sediment properties proved invaluable. Hướng’s training at LacCore had taught him that a stable coring position is mandatory for taking deeper cores. LacCore had used a modified Jaguarundi model cataraft as a coring platform at a cost of several thousand dollars. During training at Lac Core, Hướng learned from Anders Noren that inner tubes of trucks can be used for flotation under a platform for coring in hard-to-reach areas. With limited resources but plenty of Vietnamese ingenuity, Hướng collected six used inner tubes from trucks in Hanoi and sent a sketch of a coring platform to his friend Điệp in Pleiku. Điệp and his friend Đăng organized the construction of a sturdy and re-usable platform (see picture below) from inexpensive steel pipes and plywood. Anchors for the coring platform were made from metal-wire chicken coops that were filled with rocks on the lakeshore. We successfully held our position in about 20 m deep water after dropping four anchors far from the four corners of the platform. The entire platform with anchors cost about $150 and worked extremely well when the wind was moderate. November is the least windy month in Pleiku. Our choice of November 2017 also avoided rain.
At the 2017 DCSI, Hướng witnessed simple sediment coring in shallow lakes with a Griffith drive rod piston surface corer and a Bolivia/Livingstone square rod piston corer. An exchange of e-mails with Ryan O’Grady about prices of commercial piston coring equipment quickly convinced Hướng that his EOS group needed to build their own equipment. After the training at LacCore, Hướng met with aviation engineer Mr. Hoàng, who also happens to be Dương’s husband and thus an unofficial EOS affiliate. As an engineer, Hoàng accepted the challenge to design and build a customized piston corer for use in 20 m water depth. It was probably not necessary that Hướng provided a gypsum model to demonstrate the working principle of a square rod piston corer. By October 2017, Hoàng had produced a working piston corer assembly that was sent via long-distance bus to Pleiku. Hoàng’s design uses a steel pin to lock the piston to the bottom of the core liner before lowering the device into water. Several segments of metal rods with quick-release threads are used to manually lower the piston corer to a pre-determined depth just above or within the sediment. A sharp pull on a steel cable releases the pin, followed by tying of the steel cable to the platform. Further pushing of the rods lowers the core liner while the piston is kept at a stationary depth. The piston corer successfully recovered sediment segments at up to 3.5 depth in sediment, all at a fraction of the cost of commercially available piston coring equipment.
The extremely water-rich and soft, topmost sediment in Biển Hồ lake is difficult to core and transport without disturbance. The microbial mat on the March 2016 cores failed to be preserved after storage of cores in upright condition in the house of a local fisherman and air transport in June 2016 by to Hanoi. Hướng’s training at LacCore offered a superior approach to preserve soft sediment. Mark Shapley and Ryan O’Grady at LacCore kindly introduced Hướng to Zorbitrol, which is the water absorbent sodium polyacrylate used in some baby diapers. Zorbitrol powder is one of the magic things that Hướng learned and brought back to Vietnam. Sprinkling some Zorbitrol on top of water-rich sediment instantly absorbs water and stabilizes the mud underneath, thus minimizing structural disturbance to the sediment surface during transport. Zorbitrol proved to be very beneficial for safely transporting sediment cores horizontally from Pleiku to our lab in Hanoi by airplane.
Our November 2017 coring expedition yielded numerous sediment cores that included well-preserved plant remains. We found our first leaf at a depth of 180 cm in Biển Hồ sediment just below the piston after cutting excess length of the core liner with a pipe cutter. The excellent preservation of this and other plant macrofossils is made possible by the anoxic conditions in the sediment. We are planning to use part of the macrofossils for AMS radiocarbon dating.
At LacCore, Hướng received much support and advice from Mark Shapley and Alex Morrison during the splitting and initial core description of Hướng’s cores from Biển Hồ which had been shipped to LacCore earlier from Việt Nam. Hướng had personal discussions with Mark about our Biển Hồ project before and during the training. Hướng learnt a lot from Mark about diatom abundance, ecological change, technical aspects of coring, finding suitable instruments to sample water, measuring profiles of the oxygen content in the water column, turbidity, temperature of lake water, and about the use of a multi-beam echo sounder to find submerged lake terraces.
Two days of sediment coring in Biển Hồ in November 2017 yielded 17 wonderful piston and gravity cores from up to 21 m water depth with up to 3.5 meter penetration into sediment. Our mobile coring platform and the newly designed coring devices performed better than expected. The logistics worked out better than during previous coring expeditions, because our experienced team members know their duties and don’t require orders from the “boss”. We worked like a well-tuned professional coring team!
Chapter 2: Coring in a swampy maar in Pleiku
The Pleiku volcanic field in Vietnam’s Central Highland is located on a basaltic plateau with an area of ca. 4000 km2. The numerous volcanic craters formed at least 200,000 years ago and have since been fully or partially filled in with sediment. Only few maars still feature lakes or swamps. In addition to coring in Biển Hồ maar lake, we also considered some shallower lakes and dry maars which can record bio-geochemical shifts relating to paleoenvironmental changes. In November 2017, we took short cores in Ia Bang lake and in the Plei Ốp swampy maar near Pleiku City. The picture below shows a special heavy-duty core catcher used in the Plei Ốp swampy maar where we anticipated a hard layer. Following Điệp’s suggestion, a local machine shop in Pleiku lathed the core catcher for us from an old rusty artillery shell at only one hour notice.
Work in the swampy maar was difficult. Điệp was standing on two inflatables and used a section of a tree trunk to hammer the core liner into the sediment. A heavy-duty core catcher was attached to the bottom of the 4 meter long core liner. During extraction of the core, four men used metal bars to slowly lift the core liner. An orange metal clamp provided a point of attachment for successful lifting without the use of a tripod. Hướng learned these valuable ideas from LacCore by closely studying LacCore’s numerous coring devices and specialized tools. The swampy lake exposed the team to brown water, swamp grass with sharp leaves, and the risk of being sucked dry by leeches. At this location in January 2017, Jan had been selectively attacked by leeches and donated plenty of blood. After two hours of hard work, in November 2017 we successfully cored two 1-meter long cores and one shorter core. Next time we may return with a vibracorer for improved recovery and deeper penetration.
Chapter 3: Core documentation and analyses in the laboratory at VNU
Our EOS group at VNU had no laboratory room until we discovered an underutilized stock room full of junk and forgotten rock samples. With the help of VNU students, we cleaned and re-arranged the room to become our EOS paleolimnology lab. The cleanup brought to light some treasures that were kept, such as components of a defunct laboratory fume hood. The image below shows a home-made longitudinal core cutting table made mostly from material of the old fume hood; we only had to invest US $40 for an electric saw and tungsten carbide-tipped broad saw blade to cut core liners longitudially without melting the plastic. In comparison to the high-quality orthopaedic cast cutters used in LacCore, our cutter generates more plastic dust. However, we can work around the problem by carefully adjusting the cutting depth and using tooth picks to clean the cut prior to splitting the core.
We have no walk-in cold room for storing sediment cores. We reduce the access of oxygen to our cores during vertical storage at room temperature by immersing the tightly closed cores under water in a large barrel. This strategy has been successful at Scripps Institution of Oceanography (Arndt Schimmelmann, pers. comm.).
Hướng duplicated some core splitting tools from LacCore for use in our lab. After longitudinally cutting a PVC core liner on opposite sides on the cutting table, the core is placed horizontally between two inclined aluminum bars. A metal nail is connected to the positive pole of a 6 V DC battery and stuck into the end of the sediment core. The negative pole of the battery is connected to a large stainless-steel blade that is slowly pushed through one of the cuts along the core liner into the sediment. Electrolytically deposited hydrogen gas covers the steel blade during entry into the sediment and acts as a lubricant. The nail must never touch the steel blade. After inserting the first blade, the connection from the negative pole of the battery is clamped to a second, identical stainless-steel blade that is pushed into the sediment parallel and close to the first blade. Both electric connections and the nail are removed. With the help of one ore more additional workers, the two halves of the cores are carefully separated, and the steel blades withdrawn from the core halves.
After the splitting of sediment cores, we carefully scraped each half-core’s surface clean and positioned half-cores on a custom-built setup for photography next to a depth scale and a color chart. The image above shows a sliding ‘magic photo box’ that was custom-built by Hướng in the EOS lab. The design was adapted from LacCore’s GeoTek professional imaging device and uses polarizing filters to shield both the light source and the camera lens. Perpendicular orientation of the filters minimizes glare from wet core surfaces. The photo-box glides smoothly on parallel rails along the half-core. The two images below were taken in December 2017 from the same section of freshly split Ia Bang lake sediment without (left) and with (right) polarizing filters. The laminated character of the sediment is revealed only when glare is avoided. Sequences of images along a half-core can be suitably cropped and combined as a composite to photographically document entire core sections in detail. Processing with Photoshop can adjust for any color bias relative to the color chart that is routinely photographed with every half-core.
A ‘smear slide’ is a thin layer of unconsolidated sediment on a glass slide embedded in resin under a thin glass cover for petrographic microscopic examination. Smear slides offer a powerful method for rapidly evaluating tiny quantities of sediment in terms of mineralogy, organic petrography, microfossils, provenance, and grain size. The image below shows VNU graduate student Quỳnh Nhi preparing smear slides from a newly opened sediment core. Hướng’s group adopted Amy Myrbo’s recommended techniques taught at LacCore. The special glue/resin from the small bottle (acquired at LacCore) hardens under UV light prior to the imaging of smear slides and identification of microscopic features with the help of LacCore’s Tool for Microscopic Identification (TMI).
In November 2017, a well-preserved leaf had been found just below the piston when removing a freshly recovered Biển Hồ sediment core from the piston corer assembly. Back in the VNU lab in December, the team carefully inspected each opened half-core and recovered another dozen of floral macrofossils in the form of leaves, clusters of grass fragments, and wood bark from distinct stratigraphic horizons for future AMS radiocarbon dating. We noticed that all plant fossils were positioned ‘flat’ horizontally to presumed bedding in the sediment, especially the grass fragments were deposited like a narrow ‘carpet’ layer. We interpret this as strong indication that bioturbation was limited and the sediment may indeed be laminated even where the eye (or camera) cannot distinguish laminae by color difference.
Resin-embedded and polished sediment thin-sections provide imaging of virtually undisturbed sedimentary structures, fabrics, and components. This technique is used routinely in high-resolution studies of laminated sediment where annual or even seasonal sublaminae can be identified. Whereas thin-sectioning of hard rocks with a rock saw and polishing table is relatively straightforward with little preparation, the soft and fragile nature of unconsolidated sediment (e.g., from Biển Hồ) requires special handling and training, including a critical step of resin-impregnation to make an ‘artificial rock’ prior to polishing.
The EOS lab adapted Amy Myrbo’s ‘frost-biter technique’ where liquid nitrogen is used for shock-freezing of a thin slice of wet sediment onto a glass slide in preparation for making a thin section. After freezing to a shallow depth, the thin layer of sediment on glass is gently detached from the core and placed into a freeze dryer. Low-viscosity ‘Paleo Bond Super-Glue’ had been recommended to Hướng by Amy Myrbo at LacCore. The glue is gently dripped onto dry sediment where it seeps into the matrix and, after hardening, forms a consolidated sediment that can be polished. Luckily Hướng had time during his last afternoon after LacCore training to catch a tram to St. Paul, Minnesota where he walked to a shop on Goodrich Avenue and bought a bottle of Paleo Bond. And even more luckily, no customs officials at airports confiscated the valuable bottle!
Chapter 4: Outreach
In LacCore’s classroom, Hướng saw Amy Myrbo’s fantastic presentations where sediment cores were used for teaching and community outreach. During the 2017 DCSI training, Hướng volunteered for LacCore’s public outreach event at the Richfield Farmer’s Market. Within 24 hours after having returned from our November 2017 coring expedition, three members of our EOS group had little more than one hour preparation time to successfully show-case some of our field work equipment at a Student Scientific Event organized by Vietnam National University in Hanoi. VNU students were interested to learn about the use of our inflatable, the under-water GoPro camera, a sediment core from Biển Hồ lake, a gravity corer, Zorbitrol, water-sampling equipment, a Secchi disk, the Garmin Echo fish finder, and various special tools.
Chapter 5: Our best wishes for everybody!
“We cored! We cored! We cored!” Our EOS group thankfully acknowledges the immense value of Hướng’s training at LacCore, which laid the foundation for our latest coring success with our home-built platform and sediment coring devices. Hướng has his sights on building a “little LacCore” at VNU, Hà Nội. Whenever we climb over the first mountain, we begin seeing even higher mountains in the distance. EOS understands that huge challenges are waiting for us in the future.
Our experience shows that scientists in developing countries with limited resources can achieve wonderful results when they rely on hard work, ingenuity, and practical advice from outside experts like the staff of LacCore. The power of improvisation and working within a close network of friends and family are essential virtues of the Vietnamese culture that made our success possible. Other helpful ingredients for success are a good dose of stubbornness, persistence, and resilience when something does not work well the first time. Always keep some band-aids handy in the field 😊. The EOS group will be happy to help/train other geoscientists from developing countries to build the necessary low-cost hardware for lake sediment coring and analyses.
In November 2017, Arndt Schimmelmann shared two pictures and a brief report about our sediment coring activities with his colleagues at Indiana University. One picture showed our mobile coring platform, whereas the other picture showed the lathing of a core catcher from an old rusty artillery shell. One Indiana University professor responded: “These are amazing pictures, and the story of making a core-catcher from an old shell is amazing as well. People who can do this kind of thing at short notice give me hope for the world.” We love this message! The last three years of close collaboration with the Schimmelmanns also led to numerous international contacts, including Amy Myrbo and her colleagues at LacCore, and in November 2017 with Dr. Antti Ojala from the Geological Survey of Finland. For our next coring campaign in March 2018 we expect the visit of Dr. Ingmar Unkel from Kiel University. We are lucky to have so many supportive friends in academia around the world, immensely talented friends in Pleiku, and a pool of hard-working and enthusiastic VNU students.
Thank you all for your invaluable support and guidance for our research project on the paleolimnology of maars near Pleiku! We are convinced that the best is yet to come.
The EOS group,
Vietnam National University
Christmas 2017, Hanoi, Vietnam
Hướng’s Personal Acknowledgements
I am deeply indebted to Amy Myrbo, Mark Shapley, Anders Noren, Shane Loeffler, Ryan O’Grady, Alexander Morrison and Aaron “Wally” Lingwall for guidance and assistance before, during, and after my trainning at LacCore. I would like to thank my DCSI II classmates Elise Farrington, Shauna Rainford, Heidi Tanttu, Julianna McDonnell, Bess Koffman, Liz Bunin, Bryce Mitsunaga, Spencer Staley, Julio Quevedo, Ben Keenan, Kellen McArthur, Karen Saunders and Teresa Wriston for their kind help and friendship.
Thank you, NSF, for this grand opportunity and thank you, Amy, for making it happen!