Trace metal content in Pliocene to Pleistocene sediments of ODP Leg 127 holes

Quaternary sedimentation within the Japan Sea was controlled by the configuration of peripheral sills, seasonal and long-term climatic variability, and the resultant fluctuations in sea level (Tamaki, 1988). Prior to drilling in the area, piston cores recovered from its basins contained Pleistocene sediments having distinctive color and fabric variation. Sedimentological and geochemical studies conducted on those facies indicated that the variability in fabric was the result of fluctuating marine and/or terrigenous influx to the deep-water basins of the Japan Sea (see, for example, Chough, 1984; Matoba, 1984).
The sequences recovered during Leg 127 at Sites 794, 795, and 797 contain long, virtually undisturbed sequences (92.3, 123, and 119.9 mbsf [Hole 797B], respectively) of upper Miocene, upper Pliocene, and Pleistocene/Holocene sediments. The majority of these sequences consists of dark-colored (dark brown, green, and black) silty-clays, many of which are enriched in biogenic components (majority silicious, some carbonate) and/or organic matter, some containing pyrite and/or ash. These facies alternate with light-colored
silty-clays, some containing ash and some showing signs of bioturbation (for example, Tamaki, Pisciotto, Allan, et al., 1990, p. 425-433). The dark-to-light sequences are present throughout the section, although they are especially dominant throughout the Pleistocene (for a more detailed lithology of Quaternary sequences recovered at Sites 794, 795, and 797, see Follmi et al. 1992 and Tada et al., 1992).
This data report provides trace metal information on Pliocene-Pleistocene-Holocene samples at Sites 794,795, and 797. These data can be used (1) to provide information related to the depositional environments of the Japan Sea during the Quaternary period, (2) to permit comparisons between the dark organic-rich sediments recovered from this semi-enclosed basin and those reported for other silled basins (for example, the Mediterranean and Black seas), and (3) to permit comparisons between these sediments and contemporary equivalents found, for instance, beneath areas of high biogenic productivity.
By providing such data, one should be able (1) to determine more precisely the processes governing the deposition of sediments with various levels of organic matter within enclosed basins, (2) to compare individual basin-wide processes, (3) to look for and compare the signatures present as a result of climatic fluctuation, and (4) to attempt to identify the presence and/or absence of cyclicity within such sequences.

日本海第四纪沉积（Quaternary sedimentation）受周边海槛（peripheral sills）、季节性与长期气候变率（seasonal and long-term climatic variability），以及由此引发的海平面波动（sea level fluctuations）控制（Tamaki, 1988）。在该区域开展钻探之前，从其盆地中获取的活塞岩心（piston cores）已采获具有独特颜色与组构变化（fabric variation）的更新世（Pleistocene）沉积物。针对这些岩相（facies）开展的沉积学（sedimentological）与地球化学（geochemical）研究表明，组构变化是日本海深水盆地（deep-water basins）中海洋与/或陆源输入（terrigenous influx）波动的结果（例如参见Chough, 1984; Matoba, 1984）。
大洋钻探第127航次（Leg 127）在794、795、797站位（Sites 794, 795, and 797）采获的地层序列，包含长距离、近乎未受扰动的上中新世（upper Miocene）、上新世晚期（upper Pliocene）以及更新世/全新世（Pleistocene/Holocene）沉积物序列（对应797B孔分别为92.3、123及119.9米深海底（meters below seafloor, mbsf））。其中绝大多数序列由深色（暗棕色、绿色及黑色）粉砂质黏土（silty-clays）组成，多数粉砂质黏土富含有生物成因组分（biogenic components，以硅质（silicious）为主，部分含碳酸盐（carbonate））和/或有机质（organic matter），部分样品含有黄铁矿（pyrite）和/或火山灰（ash）。这些岩相与浅色粉砂质黏土（light-colored silty-clays）交替出现，部分浅色粉砂质黏土含有火山灰，且部分显示出生物扰动（bioturbation）迹象（例如参见Tamaki, Pisciotto, Allan et al., 1990, 第425-433页）。尽管深色-浅色序列在整个剖面中均有分布，但在更新统中尤为发育（关于794、795、797站位第四纪序列的更详细岩性信息，请参见Follmi et al., 1992及Tada et al., 1992）。
本数据报告提供了794、795、797站位上新世-更新世-全新世样品的痕量金属（trace metal）信息。这些数据可用于：(1) 揭示第四纪时期日本海的沉积环境（depositional environments）相关信息；(2) 对比从该半封闭盆地（semi-enclosed basin）采获的富有机质深色沉积物与其他海槛盆地（例如地中海与黑海（Mediterranean and Black seas））已报道的同类沉积物；(3) 对比这些沉积物与例如高生物生产力区（high biogenic productivity）下方发现的现代对应沉积物（contemporary equivalents）。
通过提供此类数据，有望实现以下目标：(1) 更精准地确定控制半封闭盆地中不同有机质含量沉积物沉积的过程；(2) 对比不同的全盆地尺度沉积过程；(3) 探寻并对比由气候波动产生的沉积标识；(4) 尝试识别此类地层序列中旋回性的存在与否。