科研之友
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摘要
<jats:title>Abstract</jats:title><jats:p>To better understand the present and past carbon cycling and transformation processes in methane‐influenced fjord and shelf areas of northern Norway, we compared two sediment cores from the Hola trough and from Ullsfjorden. We investigated (1) the organic matter composition and sedimentological characteristics to study the sources of organic carbon (C<jats:sub>org</jats:sub>) and the factors influencing C<jats:sub>org</jats:sub> burial, (2) pore water geochemistry to determine the contribution of organoclastic sulfate reduction and methanogenesis to total organic carbon turnover, and (3) the carbon isotopic signature of hydrocarbons to identify the carbon transformation processes and gas sources. High sedimentation and C<jats:sub>org</jats:sub> accumulation rates in Ullsfjorden support the notion that fjords are important C<jats:sub>org</jats:sub> sinks. The depth of the sulfate‐methane‐transition (SMT) in the fjord is controlled by the supply of predominantly marine organic matter to the sediment. Organoclastic sulfate reduction accounts for 60% of the total depth‐integrated sulfate reduction in the fjord. In spite of the presence of ethane, propane, and butane, we suggest a purely microbial origin of light hydrocarbons in the sediments based on their low δ<jats:sup>13</jats:sup>C values. In the Hola trough, sedimentation and C<jats:sub>org</jats:sub> accumulation rates changed during the deglacial‐to‐post‐glacial transition from approximately 80 cm ka<jats:sup>−1</jats:sup> to erosion at present. Thus, C<jats:sub>org</jats:sub> burial in this part of the shelf is presently absent. Low organic matter content in the sediment and low rates of organoclastic sulfate reduction (only 3% of total depth‐integrated sulfate reduction) entail that the shallow depth of the SMT is controlled mostly by ascending thermogenic methane from deeper sources.</jats:p>
- 出版日期2016-10
