1:45 PM - 3:15 PM
[SCG52-P04] Alternation of the multiple corer and operational tests to collect long undisturbed sediment samples
Keywords:Multiple corer, Undisturbed
Multiple corers are capable of sampling near-bottom surface sediments and water above the seafloor, and their ability to obtain the undisturbed sediments makes them indispensable instruments for biology, geochemistry, and sedimentology (Ikehara, 1993). Furthermore, continuous core samples of historical ages are becoming increasingly important for understanding the environmental changes during the Anthropocene, which has recently been the focus of much attention. However, the length of core samples is limited because the conventional 60 cm-long tubes are basically designed to collect about 30 cm of sediments. This length is often insufficient to obtain a full core sample through the surface sediments to the piston core samples. Therefore, we modified the conventional multiple corer with the aim of making the core tube longer and tested its operation. We also report on the core samples taken using this sampler.
In this study, we attempted to collect samples using the sample tube extended by 40 cm by modifying the Japanese multiple corer (made by Rigo Co., Ltd. and operated at the Atmosphere and Ocean Research Institute of the University of Tokyo). The arm and its spring strength were modified to use the 100 cm long polycarbonate tubes (made by Rigo Co., Ltd.). The arm was lengthened to accommodate the 100 cm long tube. The number of springs was increased to prevent the sample from flowing out of the lower lid due to the weight of the collected sediment.
The operational tests of the modified long multiple corer were conducted twice during the KS-23-1 cruise. The sampling point was at a depth of 1039 m in Sagami Bay, where the multiple cores had previously sampled (core length of 32 cm on the KH-19-5 cruise), and both times were conducted at the same point. Although the multiple corer can be equipped with a maximum of eight tubes, only four long tubes were used for the test operation. A self-recording deep-sea camera was attached to the frame of the multiple corer to record the coring operation on the seafloor. The first test successfully operated the modified multiple corer and obtained the four core samples of ~50 cm. However, the initial assumption of collecting a 70 cm core sample was not reached. After checking the recorded movie, it was found that the sample tubes were not pushed into the sediments sufficiently. Then, the second operation test was conducted with two tubes. As a result, the corer was able to penetrate deeper than the four tube operation and collected the core samples of ~60 cm.
The obtained surface sediments were consisted of the silt with a thin sandy layer in the upper 30 cm and the alternating layers of sandy silt and sand in the lower part. It is possible that this sampling point did not reach the expected core length of 70 cm because of the sandy sediments in the lower part. To further extent the sample tube, the extension of the arm and the additional weight are currently being modified, and it will be possible to collect longer undisturbed samples in the future.
In this study, we attempted to collect samples using the sample tube extended by 40 cm by modifying the Japanese multiple corer (made by Rigo Co., Ltd. and operated at the Atmosphere and Ocean Research Institute of the University of Tokyo). The arm and its spring strength were modified to use the 100 cm long polycarbonate tubes (made by Rigo Co., Ltd.). The arm was lengthened to accommodate the 100 cm long tube. The number of springs was increased to prevent the sample from flowing out of the lower lid due to the weight of the collected sediment.
The operational tests of the modified long multiple corer were conducted twice during the KS-23-1 cruise. The sampling point was at a depth of 1039 m in Sagami Bay, where the multiple cores had previously sampled (core length of 32 cm on the KH-19-5 cruise), and both times were conducted at the same point. Although the multiple corer can be equipped with a maximum of eight tubes, only four long tubes were used for the test operation. A self-recording deep-sea camera was attached to the frame of the multiple corer to record the coring operation on the seafloor. The first test successfully operated the modified multiple corer and obtained the four core samples of ~50 cm. However, the initial assumption of collecting a 70 cm core sample was not reached. After checking the recorded movie, it was found that the sample tubes were not pushed into the sediments sufficiently. Then, the second operation test was conducted with two tubes. As a result, the corer was able to penetrate deeper than the four tube operation and collected the core samples of ~60 cm.
The obtained surface sediments were consisted of the silt with a thin sandy layer in the upper 30 cm and the alternating layers of sandy silt and sand in the lower part. It is possible that this sampling point did not reach the expected core length of 70 cm because of the sandy sediments in the lower part. To further extent the sample tube, the extension of the arm and the additional weight are currently being modified, and it will be possible to collect longer undisturbed samples in the future.