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

这项提议的主要目标是根据日本海冲之岭798号ODP站的井下测井和岩心数据重建连续、定量的生物和陆源沉积记录。我们采用了一种创新和高效的研究策略，利用从岩心获得的“地面真实”沉积物岩性信息来校准连续的多变量测井数据。798站是新近纪晚期古海洋学“参考”区段的128个目标，该地区具有重要的气候意义；然而，孢子状岩心的恢复排除了这些记录在约1Myr以下的完全基于岩心的重建。我们描述了基于岩心和基于测井的不同研究路线，它们的产品将被合并，以重建过去3个月的沉积物组分百分比和通量记录。利用连续的30厘米长的模拟测井分辨率的“通道”样品，对离散的岩心剖面进行生物蛋白石、碳酸盐、有机碳和陆源百分比的分析。火山灰层提供了准确的岩心-测井深度对比，氧同位素数据被用来定义冰川-间冰期地层、沉积速率和阶段关系。斯伦贝谢-多尔研究所开发的新计算技术被用来提高测井分辨率和灵敏度。这些和其他统计技术被用来定量地将特定的电性、化学和物理测井响应与测量的岩心岩性变化相关联。这项研究产生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作用；2)在其他全球气候记录的背景下，了解上新世-更新世日本海古海洋学和古气候的演化。

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.