Chronicles of vadose zone diagenesis: cone‐shaped iron oxide concretions,Triassic Trujillo Formation,Palo Duro Canyon,Texas

Unusual cone‐shaped iron oxide concretions occur in the Late Triassic, lower fluvial sandstone member of the Trujillo Formation at Palo Duro Canyon in the Texas panhandle. In situ concretions are significant because they record both historical information about past processes that occurred within the geologic unit and present‐day information about the ability of the unit to conduct fluids. The dominant orientation of the concretions is cone‐apex up, body radiating down and out, with long axis perpendicular to bedding. Concretion morphologies are associated with the sedimentary texture and primary bedding structure of the host rock and the corresponding hydrologic regime (i.e. advection versus dispersion for iron‐transport behavior). Three lithofacies in the lower Trujillo member exhibit different cone forms. Field observations of cone orientation and morphology suggest vadose conditions for diagenetic precipitation of iron oxide cements, with timing potentially represented by the major pre‐Miocene unconformity.     

海底打捞铁质文物的腐蚀机理及其脱氯方法

综述了铁质文物在海水中及打捞出水后的腐蚀机理,如电化学循环机理、氧浓差电池腐蚀机理等,同时简述了从海水中打捞出来的铁质文物的各种脱氯方法,包括碱性溶液浸泡法、碱性亚硫酸盐还原法,电解还原法及高温还原法等.     

Galvanic removal of metallic wrought iron from marine encrustations

Historic shipwrecks frequently contain a large proportion of wrought-iron tools, fasteners, and other types of artefacts. Encrustations readily form around such objects in many marine environments. Depending on many factors, the iron objects inside these encrustations may be well preserved, completely disintegrated, or poorly preserved but still present. The latter type of encrustation is every conservator's nightmare because removing the encrustation yields merely a poorly preserved artefact still in need of extensive additional conservation. Neatly separating the artefact from its encrustation in order to obtain a natural mould for casting is generally impossible. Having encountered this problem many times, the authors began to experiment with the extraction of metallic iron from poorly preserved encrusted artefacts using galvanic dissolution. Data on rates of dissolution were gathered for three experimental configurations. The results of a test conducted on an encrusted artefact were promising, but inconclusive.     

Bleached mudstone,iron concretions,and calcite veins: a natural analogue for the effects of reducing CO2‐bearing fluids on migration and mineralization of iron,sealing properties,and composition of mudstone cap rocks

This study investigates the Wangfu Depression of the Songliao Basin, China, as a natural analogue site for Fe migration (bleaching) and mineralization (formation of iron concretions) caused by reducing CO₂‐bearing fluids that leak along fractures after carbon capture, utilization, and storage. We also examined the origin of fracture‐filling calcite veins, the properties of self‐sealing fluids, the influence of fluids on the compositions of mudstone and established a bleaching model for the study area. Our results show that iron concretions are the oxidative products of precursor minerals (pyrite and siderite) during uplift and are linked to H₂S and CO₂ present in early stage fluids. The precipitation of calcite veins is the result of CO₂ degassing and is related to CO₂, CH₄, and minor heavy hydrocarbons in the main bleaching fluids. In our model, fluids preferentially enter high‐permeability fracture systems and result in the bleaching of surrounding rocks and precipitation of calcite veins. The infilling of calcite veins significantly decreases the permeability of fractures and forces the fluids to slowly enter and bleach the mudstone rocks. The Fe²⁺ released during bleaching migrates to elsewhere with the solutions or is reprecipitated in the calcite veins and iron concretions. The formation of calcite veins reduces the fracture space and effectively prevents fluid flow. The fluids have an insignificant effect on minerals within the mudstone. In terms of the chemistry of the mudstone, only the contents of Fe₂O₃, U, and Mo change significantly, with the content of U increasing in the mudstone and the contents of Fe₂O₃ and Mo decreasing during bleaching.     

宁波“小白礁I号”清代木质沉船中硫铁化合物脱除技术研究

近年来的分析与研究表明,海洋出水沉船的木材中普遍存在大量的以Fe S2和Fe S为代表的硫铁化合物难溶盐,它们在空气中和一定湿度条件下,会氧化生成硫酸,使木材纤维素发生快速降解,从而对木船造成毁灭性的破坏。目前,硫铁化合物的脱除仍然是世界性难题,很多国家发现的木质沉船都面临这方面的困扰。为此,本研究以宁波象山"小白礁I号"清代沉船遗址出水的船体木材构件为研究对象,研发了金属络合剂与氧化剂复配材料EDTAHO,开展了海洋出水木材中沉积的二硫化亚铁的去除技术初步研究,取得了良好的保护效果。本研究结果可为后续脱水定型和加固修复打下良好的基础,有利于海洋出水木质船体的长期保存。     

Sulfur and iron analyses of marine archaeological wood in shipwrecks from the Baltic Sea and Scandinavian waters

Analyses of marine archaeological wood from shipwrecks in the Baltic Sea area, Kronan, Riksnyckeln, Tattran, the Puck Bay Boat and the Ghost wreck, and at the Scandinavian West coast, the Göta wreck, Stora Sofia and the Viking shipwrecks of Skuldelev, show accumulation of sulfur compounds. The penetration profiles of sulfur and iron into the wood and the speciation of characteristic sulfur groups were evaluated by combining X-ray spectroscopic analyses, in particular S K-edge XANES (X-ray absorption near edge structure) and X-ray fluorescence, with ESCA and elemental analyses. The combined analyses support the hypothesis that hydrogen sulfide produced by sulfate-reducing bacteria reacts and accumulates at low iron concentration mainly as organically bound sulfur, which as in previous studies was found by X-ray spectro-microscopy to accumulate in lignin-rich parts of the wood cell walls. The presence of iron(II) ions from corroding iron promotes formation of pyrite and other iron(II) sulfides, which easily oxidise in aerobic conditions with high humidity. No significant differences in sulfur and iron accumulation were found in wood from shipwrecks in the east coast brackish water and the west coast seawater. Sediments from three wreck sites, the Göta wreck, Stora Sofia and Kronan, were analyzed to a depth of a few decimeters and showed especially at the Stora Sofia high sulfur concentrations, exceeding 3 mass%. S K-edge XANES analyses of the sediments showed mainly reduced forms of sulfur, in particular pyrite and iron(II) sulfides together with elemental sulfur.     

Archaeology on both sides of the iron bars

La conmemoración anual de la llegada de Colón a América como se experimenta en Argentina proporciona un foco para la definición de preguntas acerca de la comprensión de la arqueología como conocimiento. Para los grupos Indígenas es el aniversario del último día de la independencia de las poblaciones aborígenes. Los arqueólogos deben cuestionarse su posición cuando estudian el mundo y los objetos indígenas. Las interpretaciones de los “pioneros” arqueólogos argentinos son discutidas junto con el concepto de “la ruptura metafísica” sobre la que la arqueología construye su objeto, esa ruptura entre el mundo indígena subjetive y el mundo del conocimiento arqueológico. En el siglo XXI quedan preguntas pendientes acerca de la arqueología que, si es vista como una práctica descolonizadora, debe implicar su propio proceso de descolonización. Proporciona la Arqueología de Un Mundo el contexto para continuar esta tarea descolonizadora?

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Résumé La commémoration annuelle de l'arrivé de Christophe Colomb en Amérique, comme c'est le cas en Argentine, donne l'occasion de se concentrer sur des questions de définition concernant la compréhension de l'archéologie comme source de connaissance. Pour les groupes autochtones, cette journée est la dernière de leur indépendance. Les archéologues devraient se demander comment ils se positionnent quand ils étudient le monde et les objets autochtones. Les interprétations des “pionniers” argentins de l'archéologie sont discutées en lien avec le concept de “d'écart métaphysique” sur lequel l'archéologie construit son objet: cet espace entre la réalité du monde des autochtones et des archéologues qui revendiquent la connaissance à travers la méthode scientifique. Au 21ième siècle, il y a encore des questions à demander concernant l'archéologie, qui même si elle est per?ue comme une pratique décolonisatrice, doit inclure le processus de décolonisation d'elle-même. One World Archaeology procure une contexte pour continuer cette tache de décolonisation?

     

The coral Cothonion from the lower Cambrian of North Greenland

Originally described from the Coonigan Formation of New South Wales, Australia, a second occurrence of the operculate coral Cothonion sympomatum is here described from the Paralledal Formation of North Greenland. Both finds are of late early Cambrian age, Series 2, Stage 4 in the emerging fourfold classification of the Cambrian. The new find supports widespread distribution patterns seen in early Cambrian Small Shelly Fossils, although associated trilobites belong to traditional redlichiid (Australia) and olenellid (Greenland) realms, respectively.     

Thorium-230 coral chronology of a late prehistoric Hawaiian chiefdom

Documenting the history of settlement in Hawaii during the last few centuries before European contact, is crucial to charting the evolution of the most complex chiefdom in Polynesia. It is precisely this period that Hawaii, and many Polynesian societies, underwent their most rapid changes in political, economic and social organisation. The last ∼500 to 300 years in the ¹⁴C calibration curve is problematic with wide fluctuations often rendering large age spans that do not precisely date single events, especially troubling with a culture-historical record of ∼1000 years duration. Here we present an extremely high precision ²³⁰Th chronology for archaeologically constrained coral samples from a range of occupancy sites. Our high precision dates allow the time of site use to be clearly demonstrated. They also provide the first dates for habitation sites in Hawaii that clearly show contemporaneous occupation—the major problem in settlement pattern archaeology. We demonstrate that two sites were occupied within the same year. Our refined chronology, provides new and exciting opportunities for tracking sociopolitical and economic developments during the last few centuries—the crucial period in the evolution and transformation of Polynesian societies.     

A preliminary study on the role and implication of plate-type iron artifacts in the ancient iron technology of Korea

Special iron objects in the form of a narrow plate with a fan-shaped blade on one or both ends, but with a substantial variation in shape and size, have continually been excavated from ancient historical sites located in the southern part of the Korean peninsula. The frequency and abundance of their excavation imply that they must have played a crucial role in the initial shaping of the Korean iron industry. Little is known, however, of their intended purposes or the exact engineering processes applied in their production. Speculation suggests that they might have been used as currencies or intermediate materials for the making of finished products. This study examined the microstructures of three such iron objects from the Korean Three Kingdoms Period (ca. 300–600 AD). It was determined that they were made of low carbon iron generally containing a number of non-metallic inclusions, with hints of surface carburization particularly at the ends of the plates. These results reveal the likely presence of an iron technology based primarily on the bloomery technique as opposed to the Chinese style of iron-making based on cast iron technology, which was also in use in ancient Korea.     

论钱穆文化民族主义史学思想的形成

在20世纪的中国史学中,钱穆的史学独树一帜,是文化民族主义史学的代表人物。钱穆的文化民族主义思想,发轫于30年代中期,形成于30年代末,以《国史大纲》的完成为其标志。以考据起家的钱穆最终转向对考据学风的批评,是因为他认识到一味埋首考据,不利于民族精神的张扬,所以他站在民族文化的立场上对新考据派作不遗余力的批评,这是他文化民族主义思想产生的内在动因;基于民族危机的刺激而产生的救亡意识是他文化民族主义思想产生的现实动因。自《国史大纲》完成后,钱穆学问研究的重心发生了转变,由历史研究转向文化研究,为中国文化招魂、续命遂成为他一生的志业所在。     

区域旅游竞争力的形成机理研究

区域旅游竞争力是目前学术研究的一个热点问题。本文在梳理国内外对区域旅游竞争力研究成果的基础上,构建了区域旅游竞争力的要素模型,对区域旅游竞争力的形成机理进行了分析,并对影响区域旅游竞争力提升的因素进行了尝试性研究。