Sediment analyses of three sediment cores from Galway Mound, NE-Atlantik

During the past decade, knowledge about the ecology and the environment of giant carbonate mounds has been growing continuously. However, still little is known about their growth dynamics. Three gravity cores from Galway Mound, Belgica Mound Province in the Porcupine Seabight off Ireland, were investigated for their sedimentological, geophysical and geochemical properties to get insight into the long-term development of this cold-water coral covered carbonate mound. These data were supplemented by radiometric age determinations on planktonic foraminifera and coral skeletons. The records from three different settings on Galway Mound reveal a coherent growth history that in general is similar to what is known from other carbonate mounds at the Irish margin. However, whereas other cores are often disturbed by numerous and not correlateable hiatuses, Galway Mound, in contrast, appears to be characterised by only one major hiatus representing a time gap of ~ 250 kyr. Several mechanisms are discussed in this study as possible causes for the observed stratigraphic record at Galway Mound. The most likely explanation is that the hiatus has its origin in a major mass wasting event on an instable, possibly glacial, unit that could have acted as a slip plane. The overall Late Quaternary growth history of Galway Mound fits well into existing cyclical mound development models, pointing to Galway Mound being an 'actively growing' mound ("coral bank stage") at present.

近数十年来，学界对大型碳酸盐岩丘（giant carbonate mounds）的生态与环境认知持续深化，但对其生长动力学机制的了解仍十分有限。本次研究对爱尔兰外海豪猪海盆（Porcupine Seabight）内贝尔吉卡海丘省（Belgica Mound Province）戈尔韦海丘（Galway Mound）的3个重力岩心（gravity cores）展开沉积学、地球物理与地球化学特征分析，以揭示这套被冷水珊瑚覆盖的碳酸盐岩丘的长期发育过程。研究辅以浮游有孔虫（planktonic foraminifera）与珊瑚骨骼的放射同位素定年数据。来自戈尔韦海丘3种不同沉积环境的岩心记录显示出一致的生长历史，整体与爱尔兰陆缘其他碳酸盐岩丘的已知发育特征相似。不过，多数其他岩心常受大量无法对比的沉积间断干扰，而戈尔韦海丘仅存在一处主要沉积间断，对应约25万年的时间缺失。本研究探讨了多种可能解释戈尔韦海丘地层记录的机制，其中最合理的假说为：该沉积间断源于不稳定（可能为冰期成因）地层单元发生的大规模块体搬运事件，该单元曾充当滑动面（slip plane）。戈尔韦海丘的晚第四纪（Late Quaternary）整体发育历史与现有海丘周期性发育模型高度契合，表明其目前仍处于“活跃生长”状态，即“珊瑚丘发育期”（coral bank stage）。