Towards the Development of Magnetic Provenance Tracers in Antarctic Glacial Marine Sediments: A Pilot Study in the Antarctic Peninsula Region.

该奖项由极地方案办公室南极地质学和地球物理学方案提供，为一项试点研究提供资金，该研究旨在测试利用岩石磁性作为南极冰川海洋沉积物来源示踪剂的潜力。一种追踪沉积物来源的手段将能够对沉积物芯中记录的迁移和沉积过程作出更有意义的解释。人们可以想象，大陆冰盖的哪些部分正在前进并提供冰碛，或者正在分解以形成充满碎片的冰山。可以想象，人们可以追踪携带IRD负载冰山的古水流，或者识别携带风成物质的风模式。岩石磁性方法的优点是使用能够处理少量材料的高灵敏度仪器进行廉价、快速和非破坏性的分析，选定的试验区域是南极半岛（AP）区域。鉴于最近的变暖趋势、冰架的解体以及目前正在发生的快速生态和物理变化，AP地区是古气候-全球变化界非常感兴趣的主题。AP地区的构造背景和岩石学已被广泛研究，该地区是正在进行的海洋地质和LTER研究的地点。伯德极地研究中心保存了数千个来自主要岩石类型的现有样品（以及支持已发表的岩石学和化学数据），可供研究。岩石磁性方法提供了一种快速、灵敏、廉价的方法来识别岩石和沉积物中的含铁矿物。该项目将系统地调查南极半岛沿着暴露的主要基岩地层的材料性质和磁性，并收集选定的地表和历史沉积物样品。开发可靠的磁性物源示踪剂的步骤是：o通过沉积物的物质特性，如精确的化学成分、氧化参数、晶格参数和颗粒形态，将沉积物与其源物质可靠地联系起来确定是否可以使用独特的磁性特征来识别这些物质特性o测试沉积物中的磁性特征是否可以识别，从而提供一种岩石磁性方法，将沉积物追溯到其源岩o通过使用现有的岩石学和化学数据，证明磁性方法的成功格雷厄姆地的火成岩和沉积物含有磁铁矿、钛磁铁矿和赤铁矿。初步研究表明，AP岩石中的磁铁矿和钛磁铁矿颗粒受到不同程度的氧化和杂质含量的影响，这产生了可重复的，可测量的磁性特征。所有的磁铁矿都不一样。即使是金属-氧化学计量的微小偏差和阳离子分布的偏差也会对金属氧化物的物理和磁性产生很大的影响。这是提出磁性方法可能是有效示踪剂的基础。没有一个单一的磁性参数足以唯一地表征一个样品或作为沉积物和源岩之间的联系。因此，通过遵循上述步骤，希望可以建立基于可量化材料特性的联系，然后可以确定这些特性的磁特征。这项工作将测试的概念，磁参数的组合可以用来识别材料的性能。如果可以证明沉积物中独特的磁性特征是物质状态的指示，并且这些状态可以与其母体物质相匹配，那么岩石磁学可能提供一种快速，廉价的方法来追踪沉积物的来源。

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, provides funds for a pilot study designed to test the potential of using rock magnetic properties as sediment provenance tracers for Antarctic glacial marine sediment. A means of tracing sediment provenance would enable more meaningful interpretation of transport and depositional processes recorded in sediment cores. One could conceivably determine which parts of the continental ice sheet were advancing and supplying till, or disintegrating to create debris-laden icebergs. One could conceivably trace the paleocurrents that carried IRD-laden bergs, or identify wind patterns that carried the eolian material. Rock magnetic methods have the advantage of being inexpensive, rapid, non-destructive analyses using highly sensitive instrumentation capable of working with small amounts of material.The chosen test area is the Antarctic Peninsula (AP) region. The AP region is the subject of intense interest to the paleoclimate-global change community in light of the recent warming trend, disintegration of ice shelves, and rapid ecological and physical changes presently taking place. The tectonic setting and petrology of the AP region have been studied extensively, and this region is site of on-going marine geology and LTER research. Thousands of pre-existing samples from the major rock types (and supporting published petrologic and chemical data) are housed at the Byrd Polar Research Center and are available for study.Rock magnetic methods provide a rapid, sensitive, inexpensive means of identifying iron-bearing minerals in rocks and sediment. This project will systematically investigate the material properties and magnetic properties of the major bedrock formations exposed on the Antarctic Peninsula along with selected surface and historic sediment samples. The steps in developing reliable magnetic provenance tracers are:o Confidently linking sediments with their source materials via their materials properties such as precise chemical composition, oxidation parameter, lattice parameter, and grain morphologyo Determining if a unique magnetic signature can be used to identify those material propertieso Testing if the magnetic signature is recognizable in the sediment, thus providing a rock magnetic means of tracing sediments back to their source rockso Verifying the success of the magnetic method by using existing petrologic and chemical dataIgneous rocks and sediment from Graham Land contain magnetite, titanomagnetite, and hematite. Initial studies indicate that the magnetite and titanomagnetite grains in the AP rocks are affected by varying degrees of oxidation and impurity content, which generates a reproducible, measurable magnetic signature. All magnetite is not the same. Even small deviations from metal-oxygen stoichiometry and deviations in cation distributions can have large effects on the physical and magnetic properties of metal oxides. This is the basis for suggesting that magnetic methods may be effective tracers. No single magnetic parameter is sufficient to uniquely characterize a sample or to serve as a link between sediment and source rock. Therefore, by following the steps outlined above it is hoped that a link based on quantifiable material properties can be established, and then magnetic signature of those properties can be determined. This work will test the concept that combinations of magnetic parameters can be used to identify material properties. If it can be demonstrated that distinctive magnetic properties in sediments are indicative of material states, and these states can be matched with their parent material, then rock magnetism may provide a rapid, inexpensive means of tracing sediment provenance.