Downhole Logs as Paleoclimate Tools: A Case Study from Ocean Drilling Project Leg 128, Sea of Japan

该提案的主要目标是根据位于日本海Oki Ridge的ODP Site 798的井下测井和岩心数据重建连续的、定量的生物和陆源沉积记录。我们采用了一种创新而高效的研究策略，即使用从岩心获得的“地面真实”沉积物岩性信息校准连续的多变量测井数据。798地点是leg128的目标，为这个气候重要的地区建立一个完整的晚新近纪古海洋学“参考”部分；然而，零星的岩心恢复排除了仅基于岩心重建这些记录的可能性，这些记录低于约1myr。我们描述了单独的基于岩心和基于日志的研究线，其产品将被合并以重建过去3myr的沉积物成分百分比和通量记录。使用模拟测井分辨率的连续30厘米“通道”样品，分析离散岩心剖面的生物成因蛋白石、碳酸盐、有机碳和陆源百分比。灰层提供了精确的岩心-测井深度相关性，氧同位素数据用于定义冰川-间冰期地层学、沉积速率和相位关系。斯伦贝谢-多尔研究公司（Schlumberger-Doll Research）开发的新计算技术用于提高测井分辨率和灵敏度。这些和其他统计技术用于定量地将特定的电、化学和物理测井响应与测量的岩心岩性变化联系起来。本研究的连续百分比和通量记录为我们提供了一个独特的机会：1)评估井下测井方法在古气候研究中的实用性；2)在其他全球气候记录的背景下了解日本海古海洋学和古气候的上新世-更新世演化。

The primary goal of this proposal is to reconstruct continuous, quantitative biogenic and terrigenous deposition records from downhole logs and core data at ODP Site 798 on the Oki Ridge, Sea of Japan. We employ an innovative and efficient research strategy whereby continuous, multivariable log data are calibrated using "ground-truth" sediment lithological information obtained from cores. Site 798 was the Leg 128 target for a complete late Neogene paleoceanographic "reference" section for this climatically-important region; however, sporatic core recovery precludes a solely core-based reconstruction of these records below ca. 1 Myr. We describe separate core-based and log-based lines of research whose products will be merged to reconstruct sediment component percentage and flux records for the last 3 Myr. Discrete core sections are analyzed for biogenic opal, carbonate, organic carbon, and terrigenous percent using contiguous 30-cm "channel" samples which mimic log resolution. Ash layers provide accurate core-log depth correlations, and oxygen isotopic data are used to define glacial-interglacial stratigraphy, sedimentation rates, and phasing relationships. New computational techniques developed by Schlumberger-Doll Research are used to enhance the log resolution and sensitivity. These and other statistical techniques are used to quantitatively relate specific electrical, chemical, and physical log responses to the measured core lithological variations. The continuous percentage and flux records developed from this research provide us with an unique opportunity to: 1) Evaluate the utility of downhole logging methods to paleoclimate research, and 2) Understand the Pliocene-Pleistocene evolution of Japan Sea paleoceanography and paleoclimate within the context of other global climate records.