Dissolved carbon(dissolved organic carbon and dissolved inorganic carbon)is the major component of the ocean carbon cycle,representing one of the largest carbon pools on Earth.Cold seeps and hydrothermal systems serve as the two main windows for the material and energy recycling exchange between the lithosphere and outer spheres(biosphere,hydrosphere and atmosphere).However,recent studies have found that the dynamic activities of fluids in these two extreme systems are a crucial source of‘new'carbon in the deep ocean.These carbon sources may become vital contributors to carbon and energy in marine ecosystems,which affect the global deep-sea carbon budget,and the marine ecosystems as well.In this review,we summarize the sources and formation mechanisms of dissolved carbon in the seep fluids from the cold seeps and hydrothermal vents,the contribution of methane oxidation to dissolved carbon,and the characteristics of the carbon isotope composition in the fluid.Furthermore,we analyze and discuss the influence of carbon discharged from seabed on the seawater carbon cycle by comparing and contrasting these two extreme environments.The research may assist in promoting a deeper understanding of the carbon cycle and material interaction in the ocean,particularly further carbon cycle research in the back-arc basin where cold seeps and hydrothermal vents commonly prevail.
An organic geochemical,petrographical,and palynological evaluation was conducted on 30 claystone outcrop samples of the Toraja Formation,along with a geochemical analysis of an oil seep in the Enrekang Sub-basin.The aim of the study was to determine the correlation between oil and source rock in terms of age,depositional environment,organic material sources,and maturity level.The total organic carbon content of the claystone samples varies from 0.03 to 4.52 wt%,which are classified as poor to excellent.The claystones are immature to post-mature with a mixture of TypeⅡandⅢkerogen.Their vitrinite reflectance values range from 0.47 to 4.52%Ro.The samples of Toraja Formation rock and the oil seep source rock might have a similar depositional environment,a deltaic marine depositional setting with high oxidizing conditions.Organic material sources for rock and oil samples are dominated by terrestrial input.The oil is inferred to have originated from the Paleogene source rocks,which correlates in age with the Toraja Formation.The recovered palynomorphs from the studied rock samples suggest a late Eocene to Oligocene age with a strong terrestrial influence of shallow marine depositional setting.The biomarker analysis shows that the rock samples have a more substantial contribution from the terrigenous higher plants,while the oil sample indicates a higher degree of marine influence.The maturity levels are also different between the oil(peak mature)and the analyzed rock samples(immature).It is inferred that the oil seep source rock is equivalent to the analyzed rock sample but more mature,having been deposited under more marine conditions.The oil seep source rock is not exposed and is located in the deeper part of the basin.A deeper marine facies(i.e.distal delta front and prodelta facies)in front of the distributary mouth bar within a delta is interpreted as the source rock of the oil seep sample.
Agus Ardianto BudimanKomang AnggayanaAgus Haris WidayatDwiwahju SasongkoRakhmat Fakhruddin
