新生代深海冷水碳酸盐泥丘成因及IODP 307航次初步研究结果

记述了新生代深海冷水碳酸盐泥丘近期的9个重要研究事件;总结了冷水泥丘具有全球海洋(大陆斜坡为主)分布、形态各异、冷水枝状珊瑚构筑泥丘的特点;介绍了冷水泥丘形成的(地质流体渗流和微生物作用)内因及(海底牵引底流作用)外因两种主要观点.对2005年IODP 307航次实施的北大西洋Porcupine Seabight冷水泥丘大洋钻探工作初步成果进行了编译,公布了中国科学家在碳氧同位素方面的初步实验结果.实验结果显示上新世中期以来的2 Ma里冷水碳酸盐泥丘启动和发育过程中存在2次碳氧同位素偏移事件(Ⅰ和Ⅱ),碳氧同位素偏移事件Ⅰ与泥丘的启动相呼应,暗示北大西洋古海洋气候发生巨大变化,可能与北极冰盖极盛有关.

A Review of Cenozoic Deep Sea Cold-water Carbonate Mounds and Prileminary Results of Cabon and Oxygen Isotopes from IODP 307

Some research events, chacteristics and causes of deep sea cold water carbonate mounds are reviewed, and prelimary results of cabon and oxygen isotope values are reported from the IODP 307 hole 1317E in this paper. There are at least nine social events in cold water coral and carbonate mound development that have taken place for the recent years, which stimulates the research of the deep sea cold water organism. Cold water carbonate mounds are of concentration on continenatal slopes in ocean, with variable shapes and sizes, and they are mainly constructed by cold water tree corals. In general, cold water carbonate mounds could be triggered by either geofluid, or mcrio biota, or submarine current, but few evidences on geofluid or mcrio biota have been found in the IODP 307 sites, Porcupine Seabight, west off the Ireland shelf. According to primary results from the IODP 307 hole 1317E, two excursion events (I & II) of carbon and oxygen isotope values are recognized in the Middle Pleiocene Lower Pleistocene intervals of the tree coral mound. Both extremely negative excursion of carbon isotope values and strongly positive excursion of oxygen isotope values (Event I) happened at the base of the mound, which indicates a linkage to the initiation of the mound. An extremely postive excursion of carbon isotope values (Event II) can be recognized from the sample 1317E-3-6w-50-52. The isotope excursion events, especially Event I imply that the paleoceanographic climate has greatly changed since the initial carbonate mound, which is to some extent related to the extremely properous Arctic ice sheet.