We address two key issues relevant to using downhole logs to obtain quantitative paleoclimate data: Tool resolution and the origin of log responses. The vertical resolution of a given logging device sets an upper limit on its temporal resolution, so we present theoretical estimates for the minimum sedimentation rates required to resolve bedding cycles at the primary orbital periodicities using the standard suite of Schlumberger logging tools. We also investigate the sedimentologic origin of the 5-to 6-m bedding cycles within the logging data collected at Hole 798B on the Oki Ridge. Contiguous 30-cm channel samples were taken from Cores 128-798B-13H, -14H, and -15H to mimic tool resolution, and these were analyzed for biogenic opal, carbonate, terrigenous percent, and bulk mineralogy by X-ray diffraction.The 5-to 6-m cycles apparent within the log data are equivalent to -40 k.y. based on the average sedimentation rate (-13 cm/k.y.) of the 1.0-to 2.8-Ma sequence. The core data demonstrate that the log variations reflect periodic changes in opal and terrigenous sedimentation. Much of the log variance is concentrated at the 41-k.y. obliquity band, and there is a close correspondence of the log data with the Pliocene-Pleistocene marine δ 18 θ record. Quartz is highly correlated with terrigenous fraction variations, and the bulk mineralogical assemblage is similar to that of Chinese loess, a probable upwind source of eolian dust. The Chinese loess deposits indicate a linkage between glacial climate and Asian aridity, so the periodic increases in terrigenous concentration may reflect the downwind propagation of this signal. Alternatively, the logs could be reflecting variations in biogenic opal production resulting from glacial-interglacial changes in surface productivity.

Core-log comparisons are often not considered routinely enough within the exploration environment. This may be for a number of reasons, such as problems with depth-matching the core and log datasets, the environment of acquisition of both datasets, the lack of understanding of log and core acquisition or a lack of confidence in laboratory or log measurements. These problems are discussed as a preliminary step to the development of a strategy aimed at improving core-log integration.Using recent technological advances in the side-by-side presentation of core and high resolution image data from logging tools, a strategy is presented with the aim of making core-log integration more rigid and routine. Features in both core and images are correlated interactively--thus ensuring the best possible integration. This is a two stage process involving core-to-image matching, and then image-to-log matching. This strategy has the potential to make core-log integration more accurate and as a result enable the interpreter to realize the most from sub-surface data.Borehole logging provides quasi-continuous (typically every 150mm), in situ measurements

We address two key issues relevant to using downhole logs to obtain quantitative paleoclimate data: Tool resolution and the origin of log responses. The vertical resolution of a given logging device sets an upper limit on its temporal resolution, so we present theoretical estimates for the minimum sedimentation rates required to resolve bedding cycles at the primary orbital periodicities using the standard suite of Schlumberger logging tools. We also investigate the sedimentologic origin of the 5-to 6-m bedding cycles within the logging data collected at Hole 798B on the Oki Ridge. Contiguous 30-cm channel samples were taken from Cores 128-798B-13H, -14H, and -15H to mimic tool resolution, and these were analyzed for biogenic opal, carbonate, terrigenous percent, and bulk mineralogy by X-ray diffraction.The 5-to 6-m cycles apparent within the log data are equivalent to -40 k.y. based on the average sedimentation rate (-13 cm/k.y.) of the 1.0-to 2.8-Ma sequence. The core data demonstrate that the log variations reflect periodic changes in opal and terrigenous sedimentation. Much of the log variance is concentrated at the 41-k.y. obliquity band, and there is a close correspondence of the log data with the Pliocene-Pleistocene marine δ 18 θ record. Quartz is highly correlated with terrigenous fraction variations, and the bulk mineralogical assemblage is similar to that of Chinese loess, a probable upwind source of eolian dust. The Chinese loess deposits indicate a linkage between glacial climate and Asian aridity, so the periodic increases in terrigenous concentration may reflect the downwind propagation of this signal. Alternatively, the logs could be reflecting variations in biogenic opal production resulting from glacial-interglacial changes in surface productivity.

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