Global warming enhances atmospheric moisture loading and will likely affect the East-Asian monsoon system across Vietnam. The absence of a long written climate history from Vietnam creates a reliance on geological archives of past monsoon history and regional paleoenvironmental changes to provide a framework for evaluating current climatic trends. Biển Hồ lake (14°03′ N, 108°00′ E) is a volcanic crater (i.e. maar) in Vietnam's Central Highlands that has been accumulating sediment since the Pleistocene. Field campaigns between 2016 and 2018 recovered an abundance of gravity and piston sediment cores extending to a depth of ~15 m, covering approximately the last 30 ka BP. The paleoenvironmental interpretation of Pleistocene and Holocene sediment requires knowledge of modern lacustrine and sedimentary conditions, as well as the origin and transport pathways of the catchment material. Here, we focus on a high-resolution sedimentological and geochemical reconstruction of the recent environmental history - from 1950 AD to the present - based on sediment cores from Biển Hồ maar, in direct comparison with local and regional weather and historic records. The uppermost sedimentary record reflects a substantial anthropogenic influence such as deforestation, military use, crater breaching, dam and sill construction, and reforestation that strongly modified the maar's morphology and hydrology. A strong increase in sedimentation rate during the 1960–70s in Biển Hồ cores coincided with U.S. military activities and water withdrawal. A breach in the maar's rim and the connection to a new external reservoir in 1983-1984 AD increased Biển Hồ water level. Reforestation around most of Biển Hồ’s rim in the 1990s curbed erosion and sedimentation rate. Nutrient availability in Biển Hồ declined in the past ~10 years after the installation of a concrete sill between Biển Hồ and the reservoir to limit water exchange with the more nutrient-rich reservoir. This paper is a calibration study on modern sediment to provide an empirical basis for the interpretation of Biển Hồ’s deeper Holocene and pre-Holocene sedimentary record.
Bibliographical noteFunding Information:
The content of this manuscript is based upon work supported by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) grant number 105.99-2018.316 (H.N.). The manuscript benefited from H.N.’s NSF-supported training at the LacCore/CSDCO Drilling and Coring Summer Institute at the University of Minnesota in 2017, as well as continuing analytical support from LacCore. Most figures were plotted using the Generic Mapping Tools ( Wessel et al., 2013 ). We thank Trần Quang Hào from the Tây Nguyên Hydro-Meteorological Center for compiling meteorological weather data. Permissions to use the photographs of Biển Hồ were kindly provided by Don Atwood, Đỗ Ngọc Điệp, Anthony Durbin, Ryan Jolie, Dave Kleinschmidt, Larry Lundeen, Pham Manh Hai, and Phương Tạ-Hòa. We are indebted to Vũ Hoàng, Nùng Văn Minh, Đỗ Văn Thạch, Đỗ Ngọc Điệp, and Phạm Duy Hải Đăng for constructing coring equipment and a coring platform, as well as administrative, logistic, and practical support during coring. Phạm N.Q. Nhi, Phan T.T. Hương, Huỳnh K. Vũ, Nguyễn T. Hoàn, Nguyễn H. Nhật, and Vũ N. Anh provided assistance in the field and in the laboratory. We are grateful for the cultural liaison and logistics facilitated by Minh Ngọc Schimmelmann. The constructive feedback from an expert reviewer and the Guest Editor improved the paper.
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- Central highlands
- Historic records
- Sediment coring