Isotope Signature of calcareous Organisms from upper and Lower carbonate mound sediments 2

上部和下部碳酸盐丘沉积物中钙质生物的同位素特征 2

基本信息

批准号：
49066122
负责人：
Professor Dr. Wolf-Christian Dullo
金额：
--
依托单位：
GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
依托单位国家：
德国
项目类别：
Infrastructure Priority Programmes
财政年份：
2007
资助国家：
德国
起止时间：
2006-12-31 至 2011-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/49066122?language=en
关键词：
Isotope Signature calcareous Organisms upper

项目摘要

, Cold-water coral mounds or carbonate mounds are known to occur widespread within the Porcupine Seabight. Sediment cores from gravity corer and especially drill cores from ICDP Expedition 307 at Challenger Mound indicate the recurring and abrupt occurring changes of carbonate mound growth. Geochemical signals in biogenic tests of planctonic and benthic foraminifers, as well as in skeletons of cold-water corals will allow us to understand the mechanisms of these changes. Stable isotope signature of benthic foraminifera (δ18O, δ13O) from the mound initiation shows a significant change to values characteristic for the water masses derived from the Mediterranean Sea (Mediterranean Outflow). Paleotemperatures derived from Sr/Ca from coral skeletons indicate optimum conditions of growth fort these biota. We speculate that the density envelope of σө= 27.35 - 27.65 kg/m3 characteristic for the ambient seawater of present day cold water coral growth played also an important role in the past. To reconstruct and to better understand these changes between „shut on" and „shut off“ conditions in mound growth we aim to date more samples from lODP-Kem 1317C to close thc existing gap in information. Since conventional U/Th methods are limited to the upper portions of the core (about 350 ka), we shall also apply precise 234U/238U (234U excess decay) and 87Sr/86Sr (radiogenic Sr evolution in the ocean), to better constrain the growth modcl and to reconstmct the encountered hiatuses. The geochronological aspect is a central part for the last year, to reconstmct the mound shaping mechanisms in relation to paleoenvironmental, to paleoclimatotological and to palcoceanographical conditions. The geochemical work will focus on thc analysis of isotopes in foraminifera and element rations in corals to reconstruct paleotemperatures and paleosalinilies, which in combination may provide data on paleodensities of sea water.

众所周知，冷水珊瑚丘或碳酸盐丘广泛存在于豪猪湾的沉积物岩心中，特别是来自挑战者丘的 ICDP 探险队 307 的岩心钻探表明碳酸盐丘生长的反复出现和突然的变化。对浮游生物和底栖有孔虫以及冷水珊瑚骨骼的生物测试将使我们能够了解这些变化的机制。土丘起始阶段的底栖有孔虫（δ18O、δ13O）的稳定同位素特征显示，来自地中海的水团特征值发生了显着变化（地中海流出），来自珊瑚骨骼的 Sr/Ca 的古温度表明了最佳条件。我们推测这些生物群的密度包络线特征为 σο= 27.35 - 27.65 kg/m3。当今冷水珊瑚生长的环境海水在过去也发挥了重要作用，为了重建和更好地理解土丘生长中“关闭”和“关闭”条件之间的这些变化，我们的目标是从其中获取更多样本。 IODP-Kem 1317C 缩小了现有的信息差距由于传统的 U/Th 方法仅限于核心的上部（约 350 ka），因此我们还将应用精确的 234U/238U。（234U过量衰变）和87Sr/86Sr（海洋中放射性Sr演化），以更好地限制生长模式并重建所遇到的间断。地质年代学方面是去年的核心部分，以重建土丘形成机制。与古环境、古气候和古海洋学条件的关系地球化学工作将集中于同位素分析。在珊瑚中有孔虫和元素配给中重建古温度和古盐度，这两者结合起来可以提供有关海水古密度的数据。