...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Marine Chemistry >Late Quaternary sporadic development of Desmophyllum dianthus deep-coral populations in the southern Labrador Sea with specific attention to their ~(14)C-and ~(230)Th-dating
【24h】

Late Quaternary sporadic development of Desmophyllum dianthus deep-coral populations in the southern Labrador Sea with specific attention to their ~(14)C-and ~(230)Th-dating

机译：Desmophyllum Den-Leanthus of Desmophyllum Den-Lead-Coral群体的晚期四态偶发性，具有特别关注他们的〜（14）C-and〜（230）Th约会

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

About 70 fossil and live-collected specimens of Desmophyllum dianthus were collected from steep rocky surfaces and time-averaged assemblages at their base ("coral graveyards") in the southern Labrador Sea at depths ranging from similar to 1700 m (Orphan Knoll) to similar to 2200 m (Flemish Cap). Aside from stable isotope and mineralogical analysis, U-series and C-14 age determinations were performed on the samples. Fossil corals from the coral graveyards display two principal age clusters corresponding respectively to the Holocene and Marine Isotope Stage (MIS) 5c intervals. Three samples lay outside these clusters, at similar to 13.5 ka (Bolling-Allerod), similar to 64 ka (MIS 3) and at similar to 181 ka (MIS 7a). The clusters are thought to record intervals with both i) high food availability, either through pelagic primary production in the overlying water column or more effectively in relation with particulate and dissolved organic carbon transport via an active Western Boundary Undercurrent (WBUC), and ii) high carbonate micrite advection by this current from more open North Atlantic coccolithophorid production areas, maintaining an aragonite saturation horizon (now at 2300 m) slightly deeper than the coral habitat (similar to 2200 m). Attempts at estimating ventilation ages from Th-230 vs C-14 age offsets in Holocene samples failed. This is due to uncertainties about the initial C-14-apparentage of coral skeletons and to their high initial excesses in Th-230. This initial excess relates mostly to the scavenging of Th-230 produced by the dissolved marine U by the coral-feeding organic matter carried along the WBUC trajectory. In addition, discrete diagenetic U-fluxes can be documented in fossil samples. They are well illustrated in specimens from MIS 5c age, which depict variable excesses in U-234 VS U-238, but similar Th-230/U-238 activity ratios, pointing to a recent but fractionating redistribution of uranium in the samples. These are also documented by the development of Fe-Mn coatings of specimens exposed at the sea floor, due to the winnowing of embedding slope sediments, with the mid- to late Holocene intensified WBUC. Such diagenetic processes are to be notably taken into consideration for the dating of pre-Holocene samples. Thus, both the initial isotopic properties of corals from this WBUC-influenced, mid-continental slope, and subsequent diagenetic effects impact their calculated ages, and blur estimates of "ventilation ages" based on their C-14 vs Th-230-ages offsets.
机译：从陡峭的岩石表面和时间平均集会中收集了大约70个化石和活收集的Desmophyllum Dianthus标本，在南塔拉多群岛的南部拉布拉多海中的南部拉布拉多海洋中的深度范围从类似于1700米（孤儿的Knoll）到相似到2200米（佛兰芒）。除了稳定的同位素和矿物学分析，对样品进行U系列和C-14年龄测定。来自珊瑚墓地的化石珊瑚展示了分别对应于全茂和海洋同位素阶段（MIS）5C间隔对应的两个主要年龄簇。三个样品置于这些簇外，类似于13.5ka（Bolling-Allerod），类似于64ka（MIS 3），类似于181ka（MIS 7a）。群集被认为是通过覆盖水柱中的覆盆子初级生产或者通过活性西方边界暗流（WBUC）和II）通过覆盖水柱中的覆盆子初级生产来记录高食物可用性的间隔。或者更有效地通过颗粒状和溶解的有机碳转运。高碳酸盐酸微型技术从更多开放的北大西洋碳水化合物的生产领域，维护一个基石饱和度视野（现在在2300米处）略深于珊瑚栖息地（类似于2200米）。在全新世时代的估算来自TH-230 VS C-14年龄抵消的通风年龄的尝试失败。这是由于珊瑚骨架最初的C-14 - 表观的不确定性以及其在TH-230中的高初始过量。该初始过量主要涉及溶解海洋U通过沿WBUC轨迹携带的珊瑚喂养有机物产生的Th-230的清除。此外，可以在化石样品中记录离散的成岩U-助熔剂。它们在MIS 5C年龄的标本中被良好地说明，其描绘了U-234 VS U-238中的可变过量，而是相似的TH-230 / U-238活性比，指向近期但分馏样品中的铀的再分分布。由于嵌入坡沉积物的次数，因此还通过在海底上暴露的标本的开发，其中包括嵌入坡度沉积物，中期至晚期全新世。尤其考虑到预全烯样品的约会考虑到这种成岩过程。因此，来自这种WBUC受影响的，中大陆坡和随后的成岩作用的初始同位素特性，以及随后的成岩作用影响其计算的年龄，并根据其C-14 VS TH-230-AGES抵消抵消的“通风年龄”的模糊估计。

著录项

相似文献

  • 外文文献
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号