LOW-IMPACT CORE TUBE DESIGN FOR VARVED CLAYS

We present an alternative method to retrieving varved clays from the subsurface in the field. Previous methods of retrieval involve a cumbersome driving mechanism fashioned out of metal plumbing pipes. The PVC core tube is then hammered into the ground, and surrounding sediment must be dug away, removing up to 1 m³ of extra sediment per meter of sample. While providing researchers a comprehensive outcrop to reference in the field, this process is relatively destructive and may not be favorable in areas where low-impact sampling is preferred, like park grounds or private land.

We have conceptualized and tested a new method, which is substantially lighter, requires less manpower and time to retrieve core, and is less invasive to the surrounding landscape. Further, our method does not require an outcrop and can be used for short cores in low-relief areas where clays are near the surface. Metal rods are used to perforate the sediment multiple times to release suction around the tube. A test plug gasket is used to maintain inner suction and a bolt mounted through the tube provides a point to secure a rope or strap, allowing workers to hoist the core up with the straight grip of a sledgehammer or pickax. The resulting damage includes only the removed sediment. We include a schematic, list of hardware, and assembly instructions for a coring tube.