Variation in the Deterioration of Fossil Resins and Implications for the Conservation of Fossils in Amber
Variation in the Deterioration of Fossil Resins and Implications for the Conservation of Fossils in Amber
复制标题
化石树脂劣化的变化及其对琥珀化石保护的启示
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
D. Grimaldi
中科院分区：
文献类型：
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作者：
C. Bisulca;Paul c. Nascimbene;Lisa Elkin;D. Grimaldi
摘要通过比较一年的加速老化--特别是单独和混合暴露在光、热和变化的湿度下--对几个天然树脂沉积物样品的影响，研究了化石树脂的劣化(龟裂、破裂和变暗)。其中包括两个白垩纪琥珀(来自缅甸和新泽西州中部)，两个第三纪琥珀(来自波罗的海和多米尼加共和国)，以及来自桑给巴尔的全新世科帕尔。选择这五种树脂是因为它们的年龄和植物学来源(因此化学和物理特性)不同，以及它们的古生物学意义。在所有情况下，基于表面银纹和紫外线区域(360-400 nm)光吸光度的下降，在光和波动的湿度的联合暴露下发生了显著的恶化。虽然在黑暗条件下湿度波动或单独紫外线照射的情况下没有明显的银纹发生，但分光光度证据表明确实发生了一些恶化。除缅甸琥珀外，所有被测试的样品都在高温下变黄。所有四个真正的琥珀在受热后都表现出紫外线吸收的减少(而COPAL实际上显示出增加)。这五个矿藏的样本代表了化石树脂的三个化学亚类，每种树脂对不同老化条件的反应不同，新泽西州的琥珀特别不稳定。根据这些结果，琥珀收藏品应该储存在湿度稳定、热量相对较低、光照最少的环境中。缺氧密封和储存，特别是将琥珀样品嵌入高级环氧树脂中，可能是有益的，并指出进一步的研究。
ABSTRACT The deterioration of fossil resins (crazing, cracking, and darkening) was investigated by comparing the effects of one year of accelerated aging—specifically intensive exposure to light, heat, and fluctuating humidity, both individually and in combination—on samples from several natural resin deposits. These included two Cretaceous ambers (from Myanmar [Burma] and central New Jersey), two Tertiary ambers (from the Baltic and the Dominican Republic), and Holocene copal from Zanzibar. The five resins were chosen for their disparate ages and botanical origins (and thus chemical and physical properties), as well as their paleontological significance. In all cases, pronounced deterioration occurred under combined exposure to light and fluctuating humidity, based on surface crazing and a decrease in absorbance of light in the UV region (360–400 nm). While crazing did not visibly occur in cases of fluctuating humidity in dark conditions, or UV exposure alone, spectrophotometric evidence indicates that some deterioration did take place. Yellowing after exposure to elevated temperatures occurred in all samples tested, with the exception of Burmese amber. All four true ambers exhibited a decrease in UV absorbance after exposure to heat (while copal actually showed an increase). The samples from the five deposits represent three chemical subclasses of fossil resins, and each of the resins reacted differently to the various aging conditions, with New Jersey amber particularly unstable. Based on these results, amber collections should be stored in an environment with stable humidity, relatively low heat, and minimal exposure to light. Anoxic sealing and storage, and particularly embedding amber samples in a high-grade epoxy, may be beneficial, and further investigation is indicated.