Magnetic fabric and archaeomagnetic analyses of anthropogenic ash horizons in a cave sediment succession (Crvena Stijena site, Montenegro)
Magnetic fabric and archaeomagnetic analyses of anthropogenic ash horizons in a cave sediment succession (Crvena Stijena site, Montenegro)
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DOI：
10.1093/gji/ggaa461
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发表时间：
2021-02-01
影响因子：
2.8
通讯作者：
Borovinic, Nikola
中科院分区：
文献类型：
--
作者：
Bradak, Balazs;Carrancho, Angel;Borovinic, Nikola
在黑山Crvena斯蒂耶纳（“红岩”）岩石掩蔽部的旧石器时代中期沉积层XXIV中，对7个人为灰层进行了考古磁性、岩石磁性和磁性组构研究。这项研究有多个目标，包括识别燃烧过程中形成的含铁矿物，评估这些燃烧特征是否适合记录地球磁场方向，揭示磁组构及其在洞穴（岩石掩体）燃烧相表征中的意义，以及识别燃烧后的蚀变过程。磁铁矿已被确定为灰的主要铁磁性成分。灰层表现出高的热磁可逆性，在对比的不可逆行为，其subjectious烧黑层，这是有关不同的温度达到。七个平均考古地磁方向获得了可接受的统计值，表明这些功能记录的字段方向在燃烧的时候。然而，他们中的一些弧的长期变化的预期范围内的中纬度地区，建议燃烧后的变化。火山灰的磁组构的特点是各向异性的低场磁化率测量。统计分析（盒须图）的基本各向异性参数，如叶理，线理，各向异性程度和形状参数，沿着与立体图上的主要的非均质性的对齐，揭示了灰单位之间的变化。不同的，扁长形，线状或强烈的叶理，准水平和垂直方向的面料的单位可能表明不同的斜坡过程，如重力，solifliteration，径流水，准垂直迁移的地下水和燃烧后/沉积后的岩石崩落影响的结构改变的方向。总之，灰层的磁性特征表明，发生了以前在现场没有发现的不同的燃烧后蚀变过程。史前燃烧特征中的蚀变过程通常从宏观观察中确定，但我们的研究表明，多个过程可以影响它们，并且通常不被注意，因为它们发生在微观尺度上。它们的识别对于正确地对遗址进行年代和文化解释至关重要（例如，收集样品用于测年，遗骸的地层位移），特别是如果涉及重大变更。因此，磁方法是一个强大的，但未充分利用的工具，在旧石器时代的研究，确定和评价的埋藏过程影响史前火灾。
An archaeomagnetic, rock magnetic and magnetic fabric study has been carried out on seven anthropogenic ash horizons in the Middle Palaeolithic sedimentary level XXIV at the rock shelter of Crvena Stijena ('Red Rock'), Montenegro. The study has multiple goals, including the identification of iron bearing minerals formed during combustion, assessment of the suitability of these combustion features for recording the Earth's magnetic field direction, revelation of the magnetic fabric and its significance in the characterization of cave (rock shelter) burnt facies, and identification of post-burning alteration processes. Magnetite has been identified as the main ferromagnetic component of the ash. The ash layers exhibit a high thermomagnetic reversibility in contrast to the irreversible behaviour of their subjacent burnt black layers which is related to the different temperatures attained. Seven mean archaeomagnetic directions were obtained with acceptable statistical values indicating that these features recorded the field direction at the time of burning. However, some of them arc out of the expected range of secular variation for mid-latitude regions suggesting post-burning alterations. The magnetic fabric of the ash was characterized by anisotropy of low field magnetic susceptibility measurements. Statistical analysis (box and whisker plot) of the basic anisotropy parameters, such as foliation, lineation, degree of anisotropy and the shape parameter, along with the alignment of the principal susceptibilities on stereoplots, revealed variation among the ash units. The diverse, oblate to prolate, lineated or strongly foliated, quasi-horizontally and vertically oriented fabrics of the units may indicate different slope processes, such as orientation by gravity, solifluction, run-off water, quasi-vertical migration of groundwater and post-burning/post-depositional alteration of the fabric by rockfall impact. In sum, the magnetic characterization of the ash layers has shown the occurrence of different post-burning alteration processes previously not identified at the site. Alteration processes in prehistoric combustion features are often identified from macroscopic observations but our study demonstrates that multiple processes can affect them and are usually unnoted because they take place on a microscopic scale. Their identification is critical for a correct chronological and cultural interpretation of a site (e.g. collection of samples for dating, stratigraphic displacement of remains), especially if significant alterations are involved. Magnetic methods are therefore a powerful but underutilized tool in palaeolithic research for the identification and evaluation of taphonomic processes affecting prehistoric fires.