An acid-free method of microfossil extraction from clay-rich lithologies using the surfactant Rewoquat
An acid-free method of microfossil extraction from clay-rich lithologies using the surfactant Rewoquat
复制标题
使用表面活性剂 Rewoquat 从富含粘土的岩性中提取微化石的无酸方法
DOI：
10.26879/382
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发表时间：
2013
影响因子：
2
通讯作者：
A. Munnecke
中科院分区：
文献类型：
--
作者：
E. Jarochowska;A. Munnecke
海相岩石粘土含量高，为化石的保存提供了良好的条件，特别是对网状石笔石和几丁质动物等有机壁微化石。然而，构成粘土成分的层状硅酸盐矿物使微化石的提取变得困难。这个问题是由于层状硅酸盐倾向于在低pH值下形成聚集体，因为微化石提取的标准方法使用酸来消化岩石。因此，对富含粘土的岩石使用酸通常是低效和耗时的。我们提出了一种用表面活性剂Rewoquat分解岩石的方法，并将其与两种常用的方法进行了比较：缓冲醋酸消解和盐酸-氢氟酸消解。以哥特兰志留纪的Mulde砖粘土段和布拉格盆地泥盆纪的Daleje页岩为例，我们观察到Rewoquat的分解（天）比酸消化（月）快，并且除了有机壁化石外，还可以回收钙质化石。除牙形刺在使用盐酸-氟化物后蚀刻强烈外，产率和保存性均较好。使用Rewoquat回收的网状石笔石以3D形式保存，显示出较低的破碎程度。由于粘土团聚体的分散，Rewoquat获得的残渣中化石含量较高。为了观察脆弱的化石，我们建议在样品上涂上表面活性剂。Rewoquat的应用可以揭示最微妙的形态和生长阶段，从而更好地了解一些化石群的个体发生、构造和体型分布。
Marine rocks characterized by high clay content provide excellent conditions for fossil preservation, particularly for organic-walled microfossils such as retiolitid graptolites and chitinozoans. Nevertheless, the phyllosilicate minerals, which constitute the clay component, make microfossil extractions difficult. The problem results from the tendency of phyllosilicates to form aggregates in low pH values, as standard methods of microfossil extraction employ acids for rock digestion. Consequently, the use of acids for clay-rich rocks is often inefficient and time-consuming. We propose a method of rock disintegration using the surfactant Rewoquat and compare it with two commonly applied approaches: digestion in buffered acetic acid and in HCl-HF. Using examples from the Mulde Brick-clay Member from the Silurian of Gotland and the Daleje Shale from the Devonian of the Prague Basin we observed that disintegration in Rewoquat was faster (days) than digestion in acid (months), and allowed to recover calcareous in addition to organic-walled fossils. The yield and preservation was comparably good, except for conodonts, which were strongly etched after using HCl-HF. Retiolitid graptolites recovered using Rewoquat were preserved in 3D and showed a lower degree of fragmentation. The fossil content of the residue obtained using Rewoquat was higher due to dispersion of clay aggregates. For observation of delicate fossils we recommend to coat the sample with the surfactant. Application of Rewoquat can reveal the most delicate forms and growth stages, and thus provide a better insight into the ontogeny, autecology, and body size distributions of a number of fossil groups.