Low Cost, Lightweight Gravity Coring and Improved Epoxy Impregnation Applied to Laminated Maar Sediment in Vietnam

Abstract

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.

Archivos de tefroestratigrafía en Patagonia como herramienta de conservación, divulgación y concientización de riesgos volcánicos

“…Douillet et al (2018) han realizado una revisión bibliográfica a la que se puede recurrir para obtener una síntesis del desarrollo histórico del método y de las publicaciones que relacionan sus aplicaciones en diversos campos disciplinarios, desde la sedimentología costera hasta la arqueología, la paleontología o la botánica, pasando por aspectos técnicos como los tipos de resinas utilizados. De ello, otros trabajos han propuesto mejoras metodológicas específicamente sobre sedimentología lacustre (Dhavamani et al, 2020;Schimmelmann et al, 2018). Douillet et al (2018) también señalan que los depósitos piroclásticos responden muy bien al método de impregnación, mencionando en particular los trabajos de De Rosa et al (1992) en Italia y Klapper et al (2010) en las Azores, señalando que secciones epóxicas piroclásticas están expuestas en varios museos volcánicos del mundo.…”

Paleoenvironmental potential of lacustrine sediments in the Central Highlands of Vietnam: a review on the state of research

“…For shallow coring down to ca. 0.8 m, we built an affordable and lightweight Autonomous Gravity Corer (AGC) with a pneumatic core catcher, which we successfully employed for the recovery of undisturbed short sediment cores from Biển Hồ Lake at water depths up to 21 m (Schimmelmann et al, 2018). In Ia Bang, Ea Tyn, Lak, and Ea Sno lakes with water depth shallower than Biển Hồ, we used a Wildco ® hand core sediment sampler to obtain surface cores for initial analyses quickly.…”

Coring of Antarctic Subglacial Sediments

“…Thus, the corer 'free-falls' and pushes the core barrel to penetrate through the sediments by its gravitational potential energy [37]. The penetration depth of a gravity corer depends on the net weight of the coring assembly, the diameter of the core catcher and core liner, the hydrodynamic properties of the coring assembly (e.g., water drag resistance), and the physical properties of the sediment [38]. above the sediment surface [35].…”

“…Thus, the corer 'free-falls' and pushes the core barrel to penetrate through the sediments by its gravitational potential energy [37]. The penetration depth of a gravity corer depends on the net weight of the coring assembly, the diameter of the core catcher and core liner, the hydrodynamic properties of the coring assembly (e.g., water drag resistance), and the physical properties of the sediment [38]. Published data shows that there are mainly two gravity corer types depending on sampling aims, including (1) long tube sequence gravity corers, which will obtain sediment cores 1-6 m long, and (2) light corers, which will obtain undisturbed surface water-sediment interface core samples.…”