Palm reading: a pilot study to discriminate phytoliths of four Arecaceae (Palmae) taxa

A pilot study of an opal phytolith morphotype series diagnostic for palms (Arecaceae), using modern specimens of four economically important palm species (Areca catechu L., Calamus aruensis Becc., Cocos nucifera L., and Metroxylon sagu Rottb.), was undertaken to identify distinctive features of leaf phytoliths from each taxon. Our univariate and multivariate analyses documented that although it was not possible to identify individual palm phytoliths unambiguously to taxon, interspecific differences in phytolith morphology significantly outweighed intraspecific variation, revealing the potential value of further research in this area and the possible utility of assemblage-level analysis to palm phytoliths in archæological assemblages. The methods are applied to archæological phytoliths from Watom Island, East New Britain, Papua New Guinea, and directions for further research outlined.     

Stability of phytoliths in the archaeological record: a dissolution study of modern and fossil phytoliths

Opaline phytoliths are important microfossils used in archaeological and ecological research. Relatively little is known about the stability of phytoliths after burial. Under alkaline pH conditions they can dissolve, and mechanical disturbances can cause a loss of their more delicate appendages. Here we present an experimental study of phytolith stability (combination of solubility and abrasion). Modern and fossil phytoliths were extracted from wheat using new methods to minimize dissolution, and by burning in an oven. These assemblages were placed in a solution buffered to pH 10 and maintained under constant temperature and shaking conditions. The silicon concentrations in the solution were monitored once a week for 5 weeks. The phytolith morphologies in each assemblage were determined at the outset of the experiment and after 5 weeks. The results show that there are differences in stability between various assemblages. Modern inflorescence wheat phytolith assemblages are more unstable than those from leaves/stems. Burnt assemblages are less stable than unburnt assemblages, and a fossil phytolith assemblage about 3000 years old is more stable than the modern wheat assemblages. The results also show that individual phytolith morphotypes have different stabilities, and as a result of dissolution and abrasion, some morphotypes may resemble others. This study further shows that archaeological and/or paleo-environmental interpretation of phytolith assemblages may change with the assemblage’s state of preservation.     

海昏侯墓出土马蹄金、麟趾金内嵌物的分析研究

南昌西汉海昏侯墓发掘出土了数量较多的马蹄金,为汉代黄金货币的研究工作提供了宝贵资料,出土马蹄金内均存在镶嵌物,大部分腐蚀严重。结合偏光显微分析、背散射扫描电镜\能谱、红外光谱、X射线衍射光谱对海昏侯墓主棺头箱出土的部分马蹄金内嵌物进行分析研究,依据分析结果将马蹄金内嵌物分为透闪石软玉、蛋白石、铅钡玻璃和疑似高铅玻璃4种类型。其中,铅钡玻璃基本保留玻璃态,腐蚀产物随着埋藏环境的变化存在二次结晶现象,腐蚀的最终产物是碳酸铅;疑似高铅玻璃表现出完全不同的腐蚀状态,外层硅质成分较高形成较为致密的壳状结构,内部碳酸铅以葡萄状填充在少量的硅质成分中。研究结果可为后续的保护处理与马蹄金、麟趾金的复制工作提供理论支持。