Environmental Impacts of Caribbean Plateau Volcanism: Timing and Composition of Magmatic Activity Related to Ocean Anoxic Event 2

智慧价值大洋高原是异常厚的洋壳，被认为是由地幔增强的部分熔融迅速形成的。如此大规模的海底火山活动的自然后果是在地质上很短的时间内向海洋释放大量的热量和富含金属的流体，这很可能导致海洋化学的变化，导致海洋缺氧事件(OAEs)和海洋生物的选择性灭绝。白垩纪是一个极端气候条件的时期，伴随着海洋-大气生物地球化学循环的重大扰动。最耐人寻味的特征之一是，在缺氧条件下沉积的富含有机物质的沉积物零星地中断了正常海洋中上层沉积物的沉积。目前关于这些事件突然开始和结束的模型涉及在与大洋高原建设有关的大规模火山活动期间向表层海洋输送生物限制痕量金属(营养物)，这增加了浮游植物的生产，并导致深海最终耗尽氧气和沉积富含有机物质的沉积物。认为微量金属以脱气岩浆流体和以水/岩交换为主的热液流出物的形式释放。这项研究将具体评估与加勒比高原建造有关的金属释放与塞诺马尼亚-图罗尼亚(C/T)边界(约93.5 Ma)OAE2之间的拟议联系。为此，将采取以下方式：(1)利用暴露在完好的中部高原(海地和库拉索/阿鲁巴)北部和南部边缘的厚地壳段，建立加勒比高原岩浆活动初始、体积和数量占主导地位的较坚定的时间段；(2)通过分析橄榄石和辉石中的熔体包裹体，确定海底熔岩母岩浆中某些微量金属的丰度，以便与相同岩石的玻璃枕状边缘的元素丰度进行比较。在记录了OAE2的近场和远场海洋沉积剖面中，已经发现了痕量金属丰度异常以及Pb、Os和Nd的同位素漂移。这些发现与加勒比海高原熔岩的释放是一致的。布罗德影响我们将支持和指导一名研究生，包括现场采样、放射性测年和微量分析方法方面的培训。本科生将从我们与大学荣誉学院的合作项目中招聘，该项目要求毕业http://oregonstate.edu/dept/honors/research/coasreu).提交一份高级论文该计划也是由COAS和地球科学(EarthSystem5)联合提供的一项新的5年地球系统科学学士+硕士荣誉的支线。对这些学生的资助将通过大学研究室对本科生研究的支持来平衡。我们还参与了NSF资助的COAS暑期网站REU，以及分析设施有限的面向本科生的大学(雷德兰兹和波莫纳)。邓肯和肯特将在俄亥俄州立大学指导学生的研究方法和高级论文/项目报告的撰写。调查结果将通过正在进行的外联活动向更广泛的受众传达，例如史密森学会？S海洋厅，邓肯？S在嘴唇上的工作被列入视频？采访？，并在诸如海洋学等流行期刊上发表[Coffin等人，2007年]。

Intellectual MeritOceanic plateaus are anomalously thick oceanic crust, believed to have formed rapidly by enhanced partial melting of the mantle. A natural consequence of such massive submarine volcanism is the release of extraordinary amounts of heat and metal-rich fluids to the ocean over geologically brief intervals, which are likely to have produced changes in ocean chemistry that lead to ocean anoxic events (OAEs) and selective extinctions of marine organisms. The Cretaceous was a period of extreme climatic conditions accompanied by major perturbations in ocean-atmosphere biogeochemical cycles. One of the most intriguing features is the sporadic interruption of normal marine pelagic sediment deposition by organic-rich sediments deposited during oxygen-deficient conditions (OAEs). A current model for the abrupt onset and conclusion of these events relates delivery of biolimiting trace metals (nutrients) to the surface ocean during massive volcanic activity associated with ocean plateau construction, that increased phytoplankton production and lead to the eventual depletion of oxygen in the deep ocean and deposition of organic-rich sediments. It is proposed that the trace metals were releasedin degassed magmatic fluids plus hydrothermal effluents dominated by water/rock exchange. This study will specifically evaluate the proposed link between metal release associated with the construction of the Caribbean plateau and OAE2 at the Cenomanian-Turonian (C/T) boundary (~93.5 Ma). This will be done by (1) establishing a firmer time scale for the initial,volumetrically dominant phase of Caribbean plateau magmatic activity from thick crustal sections exposed on the northern and southern margins of the intact central plateau (in Haiti and Curaçao/Aruba), and by (2) determining the abundances of select trace metals in parental magmas for submarine lavas through analysis of melt inclusions in olivines and pyroxenes, for comparison with elemental abundances in glassy pillow margins of the same rocks. Trace metal abundance anomalies, as well as isotopic excursions in Pb, Os and Nd, have already been identified in near-field and far-field marine sedimentary sections that record OAE2. These findings are consistent with release from Caribbean plateau lavas.Broader ImpactsWe will support and mentor a graduate student, including training in field sampling, in radiometric dating and micro-analytical methods. Undergraduate students will be recruited from our cooperative program with the University Honors College that requires a senior thesis for graduation http://oregonstate.edu/dept/honors/research/coasreu). This program is also a feeder for a new 5-yr honors B.S. + M.S. in Earth System science, offered jointly by COAS and Geosciences (EarthSystem5). Funding for these students will be leveraged through University research office support for undergraduate research. We also participate in an NSF-funded COAS summer site REU, and with undergraduate-oriented colleges with limited analytical facilities (Redlands and Pomona). Duncan and Kent will supervise students in research methods andwriting of senior theses/project reports at OSU. Findings will be conveyed to broader audiences through ongoing outreach activities, such as the Smithsonian Institution?s Ocean Hall, where Duncan?s work on LIPs is included as a video ?interview?, and in popular journals such as Oceanography [Coffin et al., 2007].