Vibracoring: a new method for coring deep lakes

A major limitation facing lacustrine researchers is an inability to take long (6 to 18 m), continuous sediment cores in water depths greater than several metres at a low cost. These problems have limited the advancement of palaeolimnology and Quaternary stratigraphy. Working from a frozen lake surface, new developments make it possible to take 18 m long vibracores in water depths of at least 55 m. High-frequency low-amplitude vibrations are transferred down a series of 6 m long, 7.6 cm diameter core tubes (3 inch aluminum irrigation pipe) rigidly coupled end-to-end. Vibrations liquify sediment adjacent to the core tube walls, thus allowing penetration of the sediment. A core catcher prevents sediment from extruding out of the tube end during extraction. This cost-effective and labour efficient (two persons) coring system has been achieved by developing rigid core tube couplers, a hand-powered drum cable hoist and a set of operation procedures. The hoist cable end is attached to a clamp 1 m above the core catcher and at each coupler along the pipe string at 6 m intervals. Lifting or lowering using a drum cable hoist allows for quick coupling and decoupling of core tubes. Although vibracoring is an improvement over other systems, it still has portability limitations because of the bulk and weight of the equipment and large amount of pipe required for deep coring. Three sleds are required to transport equipment from the nearest vehicle access to the coring sites.