[MIS29-05] TOC and stable carbon isotope in surface deposit at Tanegashima mud volcanoes
Keywords:Mud volcano, stable carbon isotope, Total organic carbon, geochemistry
The TOC of the sediments at both MV#2 and MV#3 shows range from 0.47 to 0.76%, TN shows from 0.09 to 0.12%. The relatively low TOC may reflect the influence of underground mud erupt from mud volcanoes. Both TOC and TN tend to decrease as it gets deeper. Both TOC and TN at MV#3 slightly higher than those of MV#2. The difference of TOC and TN between MV#2 and MV#3 may be caused by a colony of Calyptogene observed at MV#3 or other differences such as a timing or a scale of an eruption each mud volcanoes.
The values of δ13Corg in the sediments of MV#2 and MV#3 show relatively low, from -25 to -23‰, and there is no difference between MV#2 and MV#3. The relatively low δ13Corg values are considered the influence of thermogenic methane included in the deep mud erupted from mud volcanoes. The δ13Corg also tend to decrease as it gets deeper at both MV#2 and MV#3, especially around 10cm depth. The sharp decrease of the δ13Corg under to 10cm may be caused by hemipelagic sediment or organic matter originated methane oxidation.