Application of elemental and isotopic ratios of bulk sediment and detrital carbonate to identify and source Heinrich events in IODP Exp 303/306 sites.

海因里希事件（英语：Heinrich events），以哈特穆特·海因里希（英语：Hartmut Heinrich）命名，他在1988年首次描述了它们，是在北大西洋沉积物岩心中发现的冰筏碎片（IRD）层，可以追溯到末次冰期。它们被认为是在加拿大北方的哈德逊海峡附近的劳伦泰德冰盖涌动时，由冰山的大量排放形成的。这些事件产生的冰山在北纬40至55度之间穿越整个北大西洋，融化并将沉积物抛到海底（称为“冰筏碎片”）。Heinrich事件的特征是它们含有来自加拿大北方和格陵兰西北部大型下古生代盆地的碎屑碳酸盐（石灰岩和白云岩）。冰山融化产生的融水降低了北大西洋表层沃茨的盐度，增加了表层水的分层和水柱的稳定性。反过来，这增加了海冰的形成，减少了深水生产率，导致格陵兰岛和欧洲的温度大幅下降。已经提出了几种机制来解释这些引人注目的事件，但没有一个得到普遍接受。虽然海因里希事件已被研究的最后一个冰期周期，很少有人知道他们在更新世的前几个冰期的发生。由于北大西洋IRD带沉积速率高的长的连续岩心的可用性，这类研究受到阻碍。为了解决这一缺陷，综合大洋钻探计划（IODP）第303远征队从北大西洋多个地点回收了沉积速率高（5至20厘米/千年）的长岩心。为了研究这些长记录，我们面临着必须在多个地点进行数万次测量以识别Heinrich和其他类型的IRD事件的前景。这样的努力将是不切实际的时间和费用方面的数百米的部分收集在IODP Exp。303/306.相反，我们的方法一直是利用自动化，非破坏性的核心测井和扫描技术，以确定在以前的冰川期类似海因里希事件。例如，我们已经发现，一些海因里希事件的标志是由核心扫描X射线荧光（XRF），一种分析技术，测量半定量元素数据沿着在高空间分辨率的核心表面测量的Ca/Sr比的峰值。在这里，我们建议测试和校准的XRF元素比，并开发新的技术（散装沉积物的氧同位素），用于识别海因里希事件在北大西洋沉积物中使用IODP Exp恢复的核心。303/306.这些方法在北大西洋~40 ~ 55 N的IRD带追踪Heinrich事件中具有广泛的应用价值。除了识别海因里希和其他IRD事件外，还需要确定IRD的来源，以表征特定冰盖的推进，激增或崩溃的动力学。通过对海洋沉积物岩芯中的IRD进行地球化学分析，通常可以对冰盖移动过的基岩进行指纹识别。以往的研究主要集中在Heinrich事件中IRD的硅酸盐组分来确定物源，而Heinrich（H）事件所依据的碎屑碳酸盐颗粒则较少受到关注。在这里，我们建议测试新的方法（使用氧，锶，铅同位素），以确定在北大西洋沉积物中的IRD层所含的碎屑碳酸盐矿物颗粒的来源。然后，这些方法将被应用于识别和源碎屑碳酸盐层（海因里希事件）在旧的冰川期的更新世，以帮助限制这些显着的事件在北大西洋的起源和原因。

Heinrich events, named after Hartmut Heinrich who first described them in 1988, are layers of ice rafted debris (IRD) found in North Atlantic sediment cores dating to the last glaciation. They are believed to have formed by massive discharges of ice bergs during surging of the Laurentide Ice Sheet in the region off Hudson Strait in northern Canada. The ice bergs produced by these events traveled across the entire North Atlantic between ~40 and 55 oN, melted, and dropped sediment onto the seafloor (known as 'ice rafted debris'). The diagnostic feature of Heinrich events is they contain detrital carbonate (limestone and dolomite) derived from large lower Paleozoic basins in northern Canada and northwest Greenland. The melting icebergs produced meltwater that decreased the salinity of North Atlantic surface waters and increased surface water stratification and water column stability. In turn, this increased sea ice formation and diminished rates of deep-water production, resulting in large decreases in temperatures over Greenland and Europe. Several mechanisms have been proposed to explain these remarkable events, but none have met with universal acceptance. Although Heinrich events have been studied for the last glacial cycle, little is known about their occurrence in previous glacial periods of the Pleistocene. Such studies have been hampered by the availability of long continuous cores with high sedimentation rates from the North Atlantic IRD belt. To address this shortcoming, Integrated Ocean Drilling Program (IODP) Expedition 303 recovered long cores from multiple locations in the North Atlantic with high sedimentation rates (5 to 20 cm/kyr). To study these long records, we are faced with the prospect of having to make tens of thousands of measurements at multiple sites to identify Heinrich and other types of IRD events. Such an effort would be impractical in terms of both time and expense for the hundreds of meters of section collected during IODP Exp. 303/306. Instead, our approach has been to utilize automated, non-destructive core logging and scanning techniques to identify Heinrich-like events in previous glacial periods. For example, we have found that some Heinrich events are marked by peaks in Ca/Sr ratio measured by core scanning x-ray fluorescence (XRF), an analytical techniques that measures semi-quantitive elemental data along the surface of the core at high spatial resolution. Here we propose to test and calibrate the XRF elemental ratios and develop new techniques (oxygen isotopes of bulk sediment) for recognizing Heinrich events in North Atlantic sediments using cores recovered by IODP Exp. 303/306. These methods should have widespread application for tracing Heinrich events throughout the North Atlantic IRD belt between ~40 and 55 N. In addition to identifying Heinrich and other IRD events, it is necessary to determine the source of the IRD to characterize the dynamics of the specific ice sheets that have advanced, surged, or collapsed. It is often possible to fingerprint the bedrock over which an ice sheet has moved by analyzing geochemically the IRD in marine sediment cores. Most studies have focused on the silicate fraction of IRD in Heinrich events to determine provenance, but the detrital carbonate grains on which Heinrich (H) events are defined have received less attention. Here we propose to test new methods (using oxygen, strontium, and lead isotopes) to identify the source of detrital carbonate mineral grains contained in IRD layers in North Atlantic sediments. These methods will then be applied to identify and source detrital carbonate layers (Heinrich-like events) in older glacial periods of the Pleistocene to help constrain the origin and cause of these remarkable events in the North Atlantic.