Abstract Amber is a complex, organic polymer that offers unparalleled utility as a preservation medium, providing insights into past organisms and environments. However, under specific circumstances, this information can be compromised through alteration of the amber structure. Understanding the degradation of amber in the geosphere could improve prospecting techniques and maximise the quality and validity of chemical information from altered samples. This study analysed 114 amber samples retrieved from two new Eocene Australian deposits at Strahan, Tasmania and Anglesea, Victoria using a combination of attenuated total reflectance Fourier transform infrared and solid-state 13C cross-polarised magic angle spinning nuclear magnetic resonance spectroscopy. Results identified both Class Ib polylabdanoid and Class II cadinene-based amber. The presence of Class II amber in Australia suggests one of two possibilities: (1) a local Dipterocarpaceae source, the primary producer of Class II resins, despite the absence of this family from the Australian Eocene fossil record; or (2) a local, unidentified botanical source of cadinene-based amber. A third alternative, that Class II amber was transported to Australia from Southeast Asia via ocean currents, is rejected. Taphonomic analysis revealed four mechanisms of alteration prevalent in amber across the two study regions, with evidence of oxidation and metal carboxylate formation. Both the nature and extent of these alterations were found to vary significantly between classes I and II, suggesting that amber class may play a defining role in determining the chemical pathways by which amber degrades. Of note was the high proportion of amber that exhibited no significant chemical changes despite extensive visible alteration features, suggesting the integrity of palaeobiological and palaeoenvironmental information in these samples may be preserved.

中文翻译：

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澳大利亚东南部始新世琥珀的埋藏学和化学分类学

摘要 琥珀是一种复杂的有机聚合物，作为保存介质具有无与伦比的效用，可让您深入了解过去的生物和环境。然而，在特定情况下，这些信息可能会因琥珀结构的改变而受到损害。了解地圈中琥珀的退化可以改进勘探技术，并最大限度地提高来自改变样本的化学信息的质量和有效性。本研究结合使用衰减全反射傅里叶变换红外光谱和固态 13C 交叉极化魔角旋转核磁共振波谱分析了从位于塔斯马尼亚州斯特拉恩和维多利亚州安格尔西的两个始新世澳大利亚新矿床中提取的 114 个琥珀样品。结果确定了 Ib 类聚劳丹脂和 II 类基于卡二烯的琥珀。澳大利亚 II 类琥珀的存在表明了以下两种可能性之一：(1) 当地龙脑香科来源，即 II 类树脂的主要生产者，尽管澳大利亚始新世化石记录中没有该科；或 (2) 当地未鉴定的基于卡地烯的琥珀植物来源。第三种选择，即 II 类琥珀是通过洋流从东南亚运到澳大利亚的，被拒绝。埋藏分析揭示了两个研究区域的琥珀中普遍存在的四种改变机制，以及氧化和金属羧酸盐形成的证据。发现这些改变的性质和程度在 I 类和 II 类之间存在显着差异，这表明琥珀类可能在确定琥珀降解的化学途径方面发挥决定性作用。