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

众所周知，冷水珊瑚丘或碳酸盐丘在豪猪海中广泛存在。挑战者丘重力覆盖沉积物岩心，特别是ICDP 307考察队钻探岩心显示了碳酸盐岩丘生长的周期性和突发性变化。在浮游和底栖有孔虫的生物成因测试中，以及在冷水珊瑚的骨骼中，地球化学信号将使我们了解这些变化的机制。底栖有孔虫（δ18O, δ13O）稳定同位素特征与源自地中海（地中海流出）的水体特征有明显的变化。从珊瑚骨架中提取的Sr/Ca古温度表明了这些生物群的最佳生长条件。我们推测，现今冷水珊瑚生长的环境海水的密度包络σ ω = 27.35 ~ 27.65 kg/m3的特征在过去也起了重要作用。为了重建和更好地理解土丘生长中“关闭”和“关闭”条件之间的变化，我们的目标是对lODP-Kem 1317C的更多样本进行日期测定，以弥补现有的信息差距。由于传统的U/Th方法仅限于岩芯的上部（约350 ka），我们还将采用精确的234U/238U （234U过量衰变）和87Sr/86Sr（海洋放射性成因Sr演化），以更好地约束生长模式并重建遇到的中断。地质年代学方面是去年的一个中心部分，重建与古环境、古气候和古地质条件有关的丘形机制。地球化学方面的工作将集中在有孔虫的同位素分析和珊瑚的元素含量分析上，以重建古温度和古盐度，两者结合可以提供海水的古密度数据。

, 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.