Collaborative Research: Paleomagnetic Analysis of Speleothems and High Precision Dating of Geomagnetic Records

对过去地磁场行为的记录为了解地球对流外核的行为提供了一个窗口，并有助于更好地理解产生地球磁场的地球动力学过程。该项目旨在开发一个相对未开发的古磁学和岩石磁学信息储层，即洞穴主题（如石笋和流石）。洞穴在存档高质量、高分辨率地磁记录方面具有巨大的潜力，并且可以使用辐射测量技术以极高的精度确定年代。本研究利用岩石磁学和显微成像技术研究了洞穴中自然剩余物获取的基本过程，并建立了过去130 ka特定时期地磁场行为的时间限制。本研究项目的总体目标是利用洞穴中保存的氧化铁矿物组合构建高分辨率的地磁场行为和古气候条件记录。我们将讨论洞穴中氧化铁矿物的机械运输和化学沉淀，以便更好地了解洞穴如何以及何时获得地球磁场的记录。最近的仪器进展提供了所需的灵敏度和样品处理能力，以前所未有的空间分辨率从洞穴中收集丰富多样的磁测量。在亚毫米尺度上对洞穴层磁化的研究将促进对洞穴层磁性过程的理解，从变化的滴水条件到可用于产生区域古水文记录的偶发洪水。精确确定年代、高保真度的古地磁记录将有助于更好地约束随时间变化的全球地磁场模型。拥有详细、高精度的古地磁变化年表的另一个好处是，年表信息可以转移到具有相关古地磁记录的现有沉积物中，但年龄模型约束较少（例如，考古遗址和/或沉积物岩心）。从岩心中恢复的高分辨率地磁波动将为关注小尺度岩心流动动力学的地球动力学模型提供有价值的信息。洞穴的环境磁记录将弥补传统洞穴测量（如氧同位素）的气候和环境解释与其他沉积环境的环境磁记录之间存在的差距。

Records of past geomagnetic field behavior offer a window into the behavior of the Earth's convecting outer core, and lead to a better understanding of geodynamo processes that generate Earth's magnetic field. This project aims to develop a relatively untapped reservoir of paleomagnetic and rock magnetic information, speleothems (e.g., stalagmites, and flowstone). Speleothems have immense potential for archiving high quality, high resolution geomagnetic records, and can be dated with supreme precision using radiometric techniques. This research investigates the fundamental processes involved in natural remanence acquisition in speleothems using rock magnetic and microscopic imaging techniques, and establishes chronological constraints for geomagnetic field behavior during specific periods in the last 130 ka.The overarching goal of this research project is to construct high-resolution records of geomagnetic field behavior and paleoclimate conditions using the iron oxide mineral assemblages preserved within speleothems. We will address both the mechanical transport and chemical precipitation of iron oxide minerals in speleothems in order to better understand how and when speleothems acquire a recording of the Earth's magnetic field. Recent instrumental progress provides the sensitivity and sample handling capabilities needed to collect a rich variety of magnetic measurements from speleothems, at an unprecedented spatial resolution. The investigation of speleothem magnetization on a sub-millimeter scale will advance the understanding of magnetic processes in speleothems, ranging from changing dripwater conditions to episodic flooding that can be used to produce regional paleohydrology records. Precisely dated, high fidelity paleomagnetic records from speleothems will help better constrain time-dependent, global geomagnetic field models. An additional benefit of having detailed, high-precision chronologies of paleomagnetic variations is that the chronological information can be transferred to existing deposits with correlatable paleomagnetic records, but with less constrained age models (e.g., archaeological sites, and/or sediment cores). High resolution geomagnetic fluctuations recovered from speleothems will contribute valuable information to geodynamo models that focus on small-scale core flow dynamics. The environmental magnetic records of speleothems will bridge the gap that exists between climatic and environmental interpretations from traditional speleothem measurements such as oxygen isotopes, and the environmental magnetic records of other depositional environments.