Abstract Drilling, coring, and geophysical logging were performed with the MARUM-MeBo200 seafloor drilling rig to investigate gas hydrate occurrences of the Danube deep sea fan, off Romania, Black Sea. Three sites within a channel-levee complex were investigated. Geophysical log data of P-wave velocity, electrical resistivity, and spectral gamma ray are combined with core-derived physical properties of porosity, magnetic susceptibility, and bulk density. Core- and log physical property data are used to define a time-depth conversion by synthetic seismogram modeling, which is then used to interpret the seismic data. Individual polarity reversed reflectors within the stratigraphic column drilled are linked to reduction in P-wave velocity and bulk density. Those reflectors (and associated reflection packages) are accompanied by distinct and systematic changes in sediment porosity, magnetic susceptibility, and electrical resistivity. Overall, the sediments at drill site GeoB22605 (MeBo-17) represent the younger (upper) levee sequence of the channel, that has been eroded at drill site GeoB22603 (MeBo-16). Splicing seismic data across the channel from the East (MeBo-16) to the West (MeBo-17) demonstrates the continuation of reflectors underneath the channel. The upper ~50 m below seafloor (mbsf) at site MeBo-16 do not stratigraphically belong to the same sequence of the (deeper) levee-deposits. Above the marked erosional unconformity, sediments at Site MeBo-16 are likely derived by a mixture of repeated slump-events (identified as seismically transparent units) interbedded with hemi-pelagic sedimentation. Similarly, sediments within the upper ~20 mbsf at Site MeBo-17 are not stratigraphically the same levee-deposits, but are derived by a mixture of slump-events (also seen in the marked seafloor amphitheatre architecture of a large failure complex extending further upslope) and hemi-pelagic sedimentation. All observations combined show that the seismically observed stratigraphic pattern represents a reflectivity sequence mostly driven by variations in density (porosity) and correspondingly by changes in P-wave velocity and electrical resistivity. Observations from the geophysical log- and core, as well as geochemical data, show no evidence for the presence of any significant gas hydrates within the drilled/cored sequences.

中文翻译：

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黑海多瑙河深海扇钻井的物理特性和岩心-测井地震整合

摘要 使用 MARUM-MeBo200 海底钻机进行钻探、取心和地球物理测井，以调查罗马尼亚黑海附近多瑙河深海扇的天然气水合物产状。调查了河道堤坝内的三个地点。P 波速度、电阻率和光谱伽马射线的地球物理测井数据与岩心衍生的孔隙度、磁化率和体积密度等物理特性相结合。岩心和测井物理特性数据用于通过合成地震图建模定义时深转换，然后用于解释地震数据。钻探的地层柱内的单个极性反向反射器与 P 波速度和体积密度的降低有关。这些反射器（和相关的反射包）伴随着沉积物孔隙度、磁化率和电阻率的明显和系统变化。总体而言，钻探地点 GeoB22605 (MeBo-17) 的沉积物代表了通道的较年轻（上部）堤防序列，在钻探地点 GeoB22603 (MeBo-16) 已被侵蚀。从东部 (MeBo-16) 到西部 (MeBo-17) 的通道上拼接地震数据表明通道下方反射体的延续。位于 MeBo-16 站点的海底 (mbsf) 下方约 50 m 在地层上不属于（更深的）堤坝沉积物的相同序列。在明显的侵蚀不整合面之上，站点 MeBo-16 的沉积物很可能是由重复的坍塌事件（被确定为地震透明单元）与半远洋沉积层混合而成。类似地，站点 MeBo-17 上层约 20 mbsf 内的沉积物在地层上不是相同的堤坝沉积物，而是由坍塌事件的混合产生的（也见于一个大型破坏复合体的标志性海底圆形剧场结构，该结构进一步向上延伸) 和半远洋沉积。综合所有观察结果表明，地震观测到的地层模式代表了一个反射率序列，主要由密度（孔隙度）的变化驱动，相应地由 P 波速度和电阻率的变化驱动。来自地球物理测井和岩心的观测，以及地球化学数据，