COMPARING VIBRACORE AND LIVINGSTONE CORING TECHNIQUES

There are many ways to obtain sediment cores from lakes. This study compares the results of coring with a vibracorer and a Livingstone corer. Livingstone cores were taken by hand and by hydraulic assist. Sand Lake, a small kettle lake in the Irish Hills of Michigan, was chosen because of the relative simplicity of sediment available. The stratigraphy consists of a 6 m thick basal unit of rhythmically laminated sand-silt-clay overlain by a 0.75 m thick massive silt unit, and capped by a 5 m thick sapropel. Cores were collected from lake ice within a few meters of each other. Each Livingston core has an adjacent overlap core. These cores were aligned using visual, and obvious sedimentologic characteristics such as thick sand units, contacts between organic matter and silt-rich material, and differences in banding color within the sapropel. Once the cores were aligned, measurements were taken to determine how much sediment was lost between each core. There was no notable compaction in the vibracore when comparing unit thicknesses with the Livingstone cores. For each Livingstone core with overlap, hydraulic and hand collected, average core loss was 9%, 15%, 4%, and 9%, respectively. The hydraulic assist core penetrated 2 m further into the lake sediment before refusal, but more material was lost between cores,and false sand units were collected from sand falling into the hole. Each method worked equally well for recovery of the different sediment types. The hydraulic assisted Livingstone core was longer, cores taken in one meter increments are easier to handle, and the sediment is viewable during the coring procedure.The benefits of the vibracore are a larger diameter (7.4 cm), an overlap core is not needed, and that it is more continuous than Livingstone cores, except where cut into pieces for transport.