TAPHONOMIC ANALYSIS OF CAMBRIAN VERMIFORM FOSSILS OF UTAH AND NEVADA, AND IMPLICATIONS FOR THE CHEMISTRY OF BURGESS SHALE-TYPE PRESERVATION
TAPHONOMIC ANALYSIS OF CAMBRIAN VERMIFORM FOSSILS OF UTAH AND NEVADA, AND IMPLICATIONS FOR THE CHEMISTRY OF BURGESS SHALE-TYPE PRESERVATION
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DOI：
10.2110/palo.2017.011
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发表时间：
2017-09-01
期刊：
影响因子：
1.6
通讯作者：
Schiffbauer, James D.
中科院分区：
文献类型：
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作者：
Broce, Jesse S.;Schiffbauer, James D.
伯吉斯页岩型保存主要是通过干酪根化过程实现的古生代特殊化石化，通过该过程，有机组织转化为地质上更稳定的碳形式。它通常与另外两种矿化模式相关：（1）黄铁矿化，黄铁矿在腐烂的有机物上、附近或替代腐烂的有机物的沉淀的总称； (2)铝硅化，粘土矿物的结合，经常形成化石材料。此外，通过伯吉斯页岩型途径保存的一些生物体也表现出有限的磷酸化，即磷灰石对组织的复制，通常仅限于消化道/器官。在这里，使用基于扫描电子显微镜的方法对美国西部大盆地三个地层中通过伯吉斯页岩型保存保存的 16 块寒武纪蠕虫状化石进行了分析。这些化石表现出广泛的埋藏学特征，除了一些被认为是肠道的保存完好的内侧结构外，在与红岩、黄铁矿和铝硅酸盐相关的保存方面也存在视觉差异。微化学分析表明还有其他独特的矿物组合，包括重晶石和独居石，这些矿物组合可广泛归因于初始保存矿化的后期成岩蚀变。提出了矿化年代学和驱动因素的一致模型，并且可能对考虑其他地区的伯吉斯页岩型保存有用。
Burgess Shale-type preservation is a predominantly Paleozoic style of exceptional fossilization via the process of kerogenization, through which organic tissues arc converted to more geologically stable forms of carbon. It is often associated with two additional modes of mineralization: (1) pyritization, collectively the precipitation of pyrite on, near, or replacing decaying organic matter; and (2) aluminosilicification, the association of clay minerals, frequently templating the fossil material. Further, some organisms preserved through the Burgess Shale-type pathway also show limited phosphatization, the replication of tissues by apatite, which is usually restricted to digestive tracts/organs. Here, sixteen Cambrian vermiform (worm-like) fossils, preserved via Burgess Shale-type preservation in three formations of the Great Basin, western US, were analyzed using scanning electron microscopy-based methodologies. These fossils display a wide range of taphonomic character, with visual differences in kcrogcnous-, pyrite-, and aluminosilicate-associated preservation, in addition to some preserved medial structures presumed to be gut tracts. Microchemical analyses indicate additional unique mineral associations, including barite and monazite, which can be broadly attributed to later-stage diagenetic alteration of the initial preservational mineralization. A consistent model of the chronology and drivers of mineralization is presented, and may prove useful for considering Burgess Shale-type preservation at other localities.