Manganese cycles in Quaternary sediments of the Arctic Ocean - Climatic signals or diagenesis?

该项目的重点是对在北冰洋中部罗蒙诺索夫海岭（Lomonosov Ridge）进行的IODP远征302（北极取芯远征ACEX）中回收的上古/更新世矿床中存在的锰（Mn）循环进行高分辨率地球化学研究。在这个项目中，将探讨沉积Mn含量的旋回峰是否记录了a)主要的气候诱导信号，b)受成岩Mn再分配的影响，或者c)由两者的结合形成。在北极沉积物中，Mn峰记录了通过北极河流增强的流体输入，已被认为是一种适合的化学地层学工具，用于在冰期-间冰期时间尺度上进行全流域气候事件的相关性。然而，Mn在缺氧条件下很容易在沉积物中被动员。因此，海洋沉积物中的多个Mn峰也可能由于沉积物中氧/亚氧氧化斜的波动而形成或改变。北极锰循环的这两种相互竞争的解释只能通过详细的生物地球化学研究来解开。除了ACEX记录外，我们还将包括2008年R/V极地探险ARK XXIII/3号期间恢复的两个较短的岩心，这些岩心也显示出明显的Mn旋回。我们在R/V Polarstern上进行了高分辨率孔隙水项目。这将有助于我们构建北冰洋锰生物地球化学的概念模型，适用于现有和未来的IODP记录。核心问题是：1)固相和溶解态锰在沉积物和孔隙水中是如何分布的，它们与其他沉积参数有何关系？2)哪些沉积层目前受到锰成岩作用的影响，元素再分配对原始沉积物组成的改变程度如何？3)某些氧化还原敏感/硫化物形成元素（如Cd， Ce, Co, Cu, Fe, Mo, Ni， S， V）是否与Mn峰存在关系，微量金属模式是否可以作为单个循环主要起源的诊断工具？4)沉积物中主要的Mn相（如（氧合）氧化物、碳酸盐）是什么，它们的比例是否随埋深而变化？

The focus of the proposed project is a high-resolution geochemical study of manganese (Mn) cycles present in the uppermost Plio-/Pleistocene deposits recovered during IODP Expedition 302 (Arctic Coring Expedition ACEX) on Lomonosov Ridge, Central Arctic Ocean. During this project it will be explored whether cyclic peaks in sedimentary Mn content document a) primary climate-induced signals, b) are affected by diagenetic Mn redistribution, or c) are formed by a combination of both. In Arctic sediments Mn peaks, which document enhanced fluviatile input through Arctic rivers, have been suggested as a suitable chemostratigraphic tool for basin-wide correlation of climatic events on glacial- interglacial time scales. However, Mn is easilly mobilized in sediments under oxygen- depleted conditions. Therefore, multiple Mn peaks in marine sediments may also form or are altered by fluctuations of the oxic/suboxic redoxcline in the sediments. These two competitive interpretations of Arctic Mn cycles can only be unraveled by a detailed biogeochemical study. Apart from the ACEX record, we will include in our study two shorter cores recovered during R/V Polarstern Expedition ARK XXIII/3 in 2008, which show pronounced Mn cycles as well. We conducted a high-resolution pore water program onboard R/V Polarstern. This will help us to construct a conceptual model of Mn biogeochemistry in the Arctic Ocean, applicable to existing and future IODP records. Central questions are: 1) How are solid phase and dissolved Mn distributed in sediments and pore waters, and how do they relate to other sedimentary parameters?2) Which sediment layers are presently affected by Mn diagenesis, and to what degree is the primary sediment composition altered by element redistribution?3) Do relations of certain redox-sensitive/ sulfide-forming elements (e.g. Cd, Ce, Co, Cu, Fe, Mo, Ni, S, V) exist with Mn peaks and are trace metal patterns a diagnostic tool for or against a primary origin of individual cycles?4) What are the dominant Mn phases in the sediments (e.g. (oxyhydr)oxides, carbonates), and does their proportion vary with burial depth?