341 research outputs found

    DATA REPORT

    Get PDF
    INTRODUCTION Ocean Drilling Program (ODP) Leg 116 cored the distal part of the Bengal Fan at three closely spaced sites (717-719). The recovered sediments consisted dominantly of turbidites that varied in thickness between a few centimeters and 2 m or more. A number of different facies have been identified in the sequence and are described by Stow et al. (this volume). Representative examples of these facies types were selected and sampled for grain-size analysis. The results of these analyses are tabulated in this data report. METHODS Sediment samples of approximately 2-g dry weight were placed in 50-cm 3 beakers and disaggregated in a solution of 10% Calgon. To assist in complete disaggregation of the sediment, an ultrasonic probe was used for approximately 2 min. on each sample. Suspended sample concentrations were of the order of 20 g/L. The prepared suspensions were stored in 150-cm 3 plastic bottles. The grain-size analyses were performed by laser diffraction using Malvern particle sizers, models 35OOD and 2600C. The principles of particle-size analysis by laser diffraction are described by The Malvern laser-sizers consist of a laser source, beam expander, sample chamber, focusing lens, ring detector, and a microcomputer. In this study each analysis used a 100-mm focal length focusing lens yielding data consisting of 15 size classes between 1.9 and 188 µm. A percentage of sample outside of this range above and below these limits is also given. The grain-size distribution was computed using the model-independent program option. The sample suspension is introduced into a small ultrasonic tank from which the suspension is continuously pumped through the sample chamber in the path of the laser. The main attraction of laser diffraction analysis for this study was the relatively small sample size required for analysis. Only 2-5 cm 3 of the prepared suspensions are required for each analysis. Several repeat analyses can therefore be performed even on very small original samples. An additional advantage is the speed with which analyses can be performed, generally about 10 min per sample. For many of the samples, duplicate or triplicate analyses were performed to test the reproducibility of the results. 1 Cochran, J. R., Stow, D.A.V., et al., 1990. Proc. ODP, Sci. Results, 116: College Station, TX (Ocean Drilling Program)

    Contourite porosity, grain size and reservoir characteristics

    Get PDF
    Acknowledgements Many people are to thank for the collection and release of the data used in this study. In particular, we thank the captain, officers and crew, and the scientific and technical shipboard parties of the different IODP expeditions utilised. We each thank our respective institutes for their ongoing support. Xiaohang Yu acknowledges financial support from the National Natural Science Foundation of China (No. 41976067).Peer reviewedPostprin

    A reference time scale for Site U1385 (Shackleton Site) on the SW Iberian Margin

    Get PDF
    Variations in sediment color contain very strong precession signals at Site U1385, and the amplitude modulation of these cycles provides a powerful tool for developing an orbitally-tuned age model. We tuned the U1385 record by correlating peaks in L* to the local summer insolation maxima at 37°N. The benthic δ18O record of Site U1385, when placed on the tuned age model, generally agrees with other time scales within their respective chronologic uncertainties. The age model is transferred to down-core data to produce a continuous time series of log(Ca/Ti) that reflect relative changes of biogenic carbonate and detrital sediment. Biogenic carbonate increases during interglacial and interstadial climate states and decreases during glacial and stadial periods. Much of the variance in the log(Ca/Ti) is explained by a linear combination of orbital frequencies (precession, tilt and eccentricity), whereas the residual signal reflects suborbital climate variability. The strong correlation between suborbital log(Ca/Ti) variability and Greenland temperature over the last glacial cycle at Site U1385 suggests that this signal can be used as a proxy for millennial-scale climate variability over the past 1.5 Ma. Millennial climate variability, as expressed by log(Ca/Ti) at Site U1385, was a persistent feature of glacial climates over the past 1.5 Ma, including glacial periods of the early Pleistocene (‘41-kyr world’) when boundary conditions differed significantly from those of the late Pleistocene (‘100-kyr world’). Suborbital variability was suppressed during interglacial stages and enhanced during glacial periods, especially when benthic δ18O surpassed ~ 3.3–3.5‰. Each glacial inception was marked by appearance of strong millennial variability and each deglaciation was preceded by a terminal stadial event. Suborbital variability may be a symptomatic feature of glacial climate or, alternatively, may play a more active role in the inception and/or termination of glacial cycles

    Fine-grained sediments in deep water:An overview of processes and facies models

    No full text

    Fine-grained sediments: Terminology

    No full text

    Geological aid to developing countries

    No full text
    corecore