The oceanographic community routinely uses anisotropy of magnetic susceptibility to identify deformation associated with sediment core collection and sampling, as well as to reconstruct primary and post-depositional conditions. These measurements are also applicable to lacustrine settings. Using anisotropy of magnetic susceptibility, in combination with geochemical and physical analyses of lake sediments, permits differentiation of primary depositional conditions from sediment disturbance associated with post-depositional processes and core collection. Detailed analysis of piston cores from Seneca Lake and Owasco Lake, New York (USA) revealed evidence for relatively weak anisotropies that resulted from normal lacustrine sedimentation since ~ 16.8–16.6 cal ka BP. A middle to late Holocene lowstand and associated erosional unconformity was inferred in both lakes using the magnitude of the anisotropy, changes in lithofacies, and increase in % sand. Anomalous magnetic fabrics were also preserved in post-glacial sediment that resulted from core collection and subaqueous slides. Stratigraphic disruptions (“flow-ins”) that formed during coring were recognized by vertically oriented laminae or soupy sediment near the base and top of cores, respectively, and confirmed the rationale for using magnetic fabric measurements. Mid-core “flow-ins” throughout the uppermost 1–2 m of three of the four cores in this study could only be identified by a gradual shift in the dominant shape of the magnetic fabric. Imperfect piston coring likely resulted in vertical strain that produced overthickened sections without destroying the stratigraphic integrity of these sediments. Subaqueous slides were recognized in Owasco Lake by abrupt changes in lithofacies and magnetic fabric. Anisotropy of magnetic susceptibility proved to be a powerful tool to assess lacustrine core integrity in massive and laminated sediment prior to paleoenvironmental reconstruction.

中文翻译：

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两个纽约手指湖（美国）的冰川后沉积物保存的磁性织物揭示了取芯过程中变形和侵蚀不整合的证据

海洋学界通常使用磁化率的各向异性来识别与沉积物岩心收集和采样相关的变形，以及重建初级和沉积后条件。这些测量也适用于湖泊环境。使用磁化率的各向异性，结合湖泊沉积物的地球化学和物理分析，可以将原始沉积条件与与沉积后过程和岩心收集相关的沉积物扰动区分开来。对来自纽约（美国）塞内卡湖和奥瓦斯科湖的活塞岩心的详细分析揭示了自约 16.8-16.6 cal ka BP 以来正常湖泊沉积导致的各向异性相对较弱的证据。使用各向异性的大小、岩相的变化和沙子百分比的增加，在两个湖泊中推断出中晚期全新世低水位和相关的侵蚀不整合面。异常磁性织物也保存在由岩心收集和水下滑动产生的冰后沉积物中。取芯过程中形成的地层破坏（“流入”）分别被岩心底部和顶部附近垂直取向的薄层或泥状沉积物识别，并证实了使用磁性织物测量的基本原理。在本研究中，四个磁芯中三个磁芯的最上面 1-2 m 处的中间磁芯“流入”只能通过磁性结构的主要形状的逐渐变化来识别。不完美的活塞取芯可能会导致垂直应变，从而在不破坏这些沉积物的地层完整性的情况下产生过厚的截面。通过岩相和磁性结构的突然变化，在 Owasco 湖中识别出水下滑坡。磁化率各向异性被证明是在古环境重建之前评估块状和层状沉积物中湖心完整性的有力工具。