Deep Sea Carbonates: Acoustic, Physical, and Stratigraphic Properties
Deep Sea Carbonates: Acoustic, Physical, and Stratigraphic Properties
复制标题
深海碳酸盐：声学、物理和地层特性
DOI：
--
复制
发表时间：
1979
期刊：
影响因子：
--
通讯作者：
L. Mayer
中科院分区：
文献类型：
--
作者：
L. Mayer
摘要 对赤道东部太平洋深海碳酸盐的声学、地层和物理性质之间关系的研究表明，声阻抗的变化几乎完全由饱和体积密度（或其倒数，孔隙率）的变化控制。速度变化非常小。饱和堆积密度的变化与碳酸钙百分比的变化高度相关。高碳酸盐样品以高密度板状碳酸盐物质为主，低碳酸盐物质以低密度多刺硅质微化石为主。地层控制是通过以下方式实现的：(1) 将岩心下碳酸盐百分比的变化与定年岩心（例如 RC11-209）的碳酸盐曲线进行比较，(2) Pulleniatin 卷绕方向的地层学，(3) 放射虫分带，(4) P. lacunosa 的灭绝，以及 (5) discoasters 的最后出现。研究发现，过去 70 万年的沉积速率为每百万年 6.17 米，在此之前为每百万年 4.15 米。氧同位素记录提供了将声学特性与古海洋记录联系起来的最终证据。导致声阻抗变化的饱和堆积密度（或其倒数，孔隙率）的变化最终是由气候变化引起的。温暖时期是溶解增强的时期，导致碳酸盐百分比低和饱和堆积密度（因此阻抗低）值低。寒冷时期则相反。这些气候循环可以与过去一百万年的冰川期和间冰期相匹配，但也发生在更新世冰川作用出现之前。因此，赤道碳酸盐岩的声学记录包含强烈的古海洋信号。
ABSTRACT An examination of the relationship between acoustic, stratigraphic and physical properties of deep-sea carbonates from the eastern equatorial Pacific revealed that variations in acoustic impedance are almost entirely controlled by changes in saturated bulk density (or its inverse, porosity). Velocity changes are very small. Saturated bulk density changes are highly correlated with variations in percent calcium carbonate. High carbonate samples are dominated by high density platy carbonate material while low carbonate material is dominated by low density spiny siliceous microfossils. Stratigraphic control was achieved through: (1) comparison of the downcore variations in percent carbonate with the carbonate curves of well-dated cores (e.g., RC11-209), (2) stratigraphy of Pulleniatin coiling directions, (3) radiolarian zonation, (4) the extinction of P. lacunosa, and (5) last appearance of discoasters. Sedimentation rates in the area studied are found as 6.17 meters per million years for the last 700,000 years and 4.15 meters per million years before that time. The oxygen isotope record provided the final evidence linking the acoustic properties to the paleo-oceanographic record. Variations in saturated bulk density (or its inverse, porosity) that account for the changes in acoustic impedance are ultimately caused by climatic changes. Warm periods were times of enhanced dissolution which caused low percent carbonate and low saturated bulk density (and therefore low impedance) values. The opposite is true for cold periods. These climatic cycles can be matc ed with glacials and interglacials for the past one million years, but have also occurred before the advent of Pleistocene glaciation. Thus the acoustic record of equatorial carbonates contains a strong paleo-oceanographic signal.