Abstract
In response to the need for lightweight and affordable sediment coring and high-resolution structural documentation of unconsolidated sediment, we developed economical and fast methods for (i) recovering short sediment cores with undisturbed topmost sediment, without the need for a firmly anchored coring platform, and (ii) rapid epoxy-impregnation of crayon-shaped subcores in preparation for thin-sectioning, with minimal use of solvents and epoxy resin. The ‘Autonomous Gravity Corer’ (AGC) can be carried to remote locations and deployed from an inflatable or makeshift raft. Its utility was tested on modern unconsolidated lacustrine sediment from a ~21 m deep maar lake in Vietnam’s Central Highlands near Pleiku. The sedimentary fabric fidelity of the epoxy-impregnation method was demonstrated for finely laminated artificial flume sediment. Our affordable AGC is attractive not only for work in developing countries, but lends itself broadly for coring in remote regions where challenging logistics prevent the use of heavy coring equipment. The improved epoxy-impregnation technique saves effort and costly chemical reagents, while at the same time preserving the texture of the sediment.
Highlights
Fine-grained lacustrine and marine laminated sediments contain valuable high-resolution archives ofenvironmental conditions, especially when laminations are annual.The high-resolution structural and compositional information in unconsolidated sediment requires utmost care in sediment coring and preservation of cores
This study introduces a modular Autonomous Gravity Corer (AGC)
Repeated field work in Biển Hồ Lake in 2016, 2017 and 2018 offered opportunities to improve the design of the AGC and to optimize the balance between rock ballast and styrofoam according to specific coring objectives, namely to either gently recover the topmost sediment layers, or to maximize the speed of impact for deeper core recovery
Summary
Fine-grained lacustrine and marine laminated sediments contain valuable high-resolution archives of (paleo)environmental conditions, especially when laminations are annual (i.e., varves [1,2]). The high-resolution structural and compositional information in unconsolidated sediment requires utmost care in sediment coring and preservation of cores. The recovery of modern undisturbed sediment with an intact sediment/water interface is commonly performed via freeze coring, box coring, or multi-coring, yet such coring methods are frequently impractical or unaffordable in remote areas and in developing countries. This study introduces a modular Autonomous Gravity Corer (AGC). The AGC with adjustable sinking speed proved its utility for recovery of undisturbed laminated sediment from Biển Hồ maar lake in central Vietnam. Maar/crater lakes and dry maars in Vietnam and neighboring countries offer long-time paleoclimatic archives [3,4]
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