腕足动物是寒武纪海洋底栖生态系统中的关键成员, 通过高效滤食和附着固着功能稳定底栖环境, 其密集层在寒武纪大爆发中对生态分层和群落结构的构建起到了重要作用。在中国贵州息烽地区的寒武系第四阶金顶山组剖面中部, 发现了大量腕足动物密集层, 并主要表现出两种埋藏特征: (1)以保存为黑色壳体的Westonia sp.单一物种为主的密集层; (2)以保存为灰白色壳体的Westonia sp.为主, 并与少量马龙始圆货贝(Eoobolus malongensis)、三叶虫、开腔骨类及软舌螺类共存的密集层。密集层中的化石几乎平行于层面, 壳体大小不一, 缺乏明显的定向性; 岩石光面和薄片也仅显示出微弱的水平层理, 未见其他强水动力的沉积构造或生物扰动痕迹。表明该区域的腕足动物群落在相对稳定的水体环境中被原地掩埋, 未经历显著的流体侵蚀或搬运作用。能谱分析(EDS)显示, 该区腕足动物化石壳体中富含铁铝硅酸盐, 表明埋藏过程中经历了矿物交代作用, 早期成岩阶段黄铁矿化转化后, 富铁铝硅酸盐作为次生矿物沉积, 在成岩过程中发挥了重要作用。

Brachiopods are key components of the Cambrian marine benthic ecosystems. Through the efficient filter-feeding and attachment functions, they contributed to the stabilization of the benthic environments. Brachiopod shell concentrations played a significant role in shaping the ecological tiering and community structures during the Cambrian explosion. Numerous brachiopod shell concentrations have been discovered from the middle part of the Jindingshan Formation (Cambrian Stage 4) in Xifeng, Guizhou Province, China. Comprehensive investigations reveal that these brachiopod shell concentrations predominantly exhibit two distinct burial types: (1) The concentrations are mainly composed of a single species, Westonia sp., with shells preserved in black; and (2) The concentrations are dominated by Westonia sp., but with grayish-white shells, co-occurring with a few specimens of Eoobolus malongensis, trilobites, chancelloriids, and hyoliths. The shells in both types of concentrations are oriented nearly parallel to the bedding plane. The shell sizes vary considerably, and no obvious preferred orientation is observed. Examination of polished, longitudinal surfaces of rock slabs and thin sections reveals only faint horizontal bedding, with no evidence of strong hydrodynamic forces or traces of bioturbation. These observations suggest that the brachiopod communities were buried in situ in a relatively stable environment, without significant disturbance from currents or transportation Energy-dispersive spectroscopy (EDS) analyses show that the brachiopod shells from this area are enriched in iron-aluminum silicates. During burial, mineral replacement occurred: Pyrite in the shell resulted from early diagensis was altered, and iron-aluminum-rich silicates were subsequently deposited as secondary minerals, playing an important role in diagenesis. These findings not only provide new insights into the brachiopod assemblages of the Jindingshan Formation but also offer crucial evidence for reconstructing the paleoenvironmental conditions and sedimentary events during the Cambrian explosion.

国家自然科学基金项目(42262003, 42330209)和贵州省科技计划项目(黔科合基础-ZK[2005]重点100, 黔科合平台ZSYS [2024]002)联合资助