陕西迹(Shaanxilithes)见证了埃迪卡拉纪–寒武纪之交生物演化及生态环境的变化, 是埃迪卡拉纪末期标志性的疑难化石, 具有全球对比意义。本文首次报道了云南曲靖会泽县大海乡朱家箐剖面灯影组旧城段泥质灰岩中新发现的宁强陕西迹(Shaanxilithes ningqiangensis Xing, Yue and Zhang, 1984)。所采集的标本整体形态上呈条带状, 边缘呈锯齿状参差不齐, 可见环状体分布。通过镜下观察, 可发现散落圆盘状单元。将大海乡朱家箐剖面与晋宁六街镇王家湾剖面渔户村组旧城段所产出的Shaanxilithes化石对比后发现, 朱家箐剖面的标本宽度更窄, 长度更长, 碎片化更加明显。通过微区X射线荧光光谱仪(μ-XRF)将朱家箐剖面和王家湾剖面的标本进行对比分析后可知, 前者形态在Si、Al、K的元素分布图中显示清晰, 而后者的形态主要体现在Fe元素的分布图上; 前者化石和围岩中Ca元素的含量远远高于后者; S元素仅在前者存在微量的分布, 在后者中未有信号显示。新的化石证据表明Shaanxilithes并非只产出自碎屑岩中, 还可以在灰岩中保存。化石μ-XRF的面扫描和半定量分析表明可能为伊利石矿物交代, 并且说明在不同岩相背景下, 风化作用程度的强弱造成两个产地化石的差异性保存。随着研究区域不断扩大,Shaanxilithes相继在华南板块滇东地区、印度西北缘、纳米比亚、华北板块西南缘等地区晚埃迪卡拉世地层中被发现。此次在滇东会泽地区发现的Shaanxilithes, 进一步表明该化石分布的广泛性, 可作为全球晚埃迪卡拉世地层对比的标准化石。本文结合形态学分析和微区X射线荧光光谱分析, 讨论了Shaanxilithes的埋藏学信息与亲缘关系, 为探索埃迪卡拉纪–寒武纪过渡时期的生物和生态特征提供了更多视角。
Emerging in the late Ediacaran Period, Shaanxilithes witnessed the biological evolution and ecological environment changes during the Ediacaran-Cambrian transitional interval, which has a significant role in stratigraphic correlation. This paper pre-sents the first report of the Shaanxilithes ningqiangensis Xing, Yue and Zhang, 1984 preserved in argillaceous limestone in Jiucheng Member of Zhujiaqing Section in Huize, Yunnan. The specimens show ribbons with jagged edges and annulations, as well as the distribution of discoidal components. When compared to the material of Shaanxilithes from Wangjiawan Sec-tion in Jinning, the newly discovered specimens from Zhujiaqing type Section are relatively thinner, longer and more frag-mented. According to the results of Micro X-ray Fluorescence Spectrometer (μ-XRF), the new carbonate-hosted specimens show a high concentration of silicon, aluminum and potassium, while the morphology of the material from Wangjiawan Sec-tion are prominent in iron mapping; the concentration of calcium in the fossil and matrix is much higher in the new material; sulphur only shows a little concentration in the new material, by contrast no signal indicated in the latter. These new evidence indicates that the problematic Shaanxilithes can be preserved not only in clastic settings, but also in an argillaceous limestone environment. In addition, it may suggest that the materials of Shaanxilithes were fossilized by illite, and the degree of weath-ering in different lithofacies results in different preservation of fossils recovered from two sections. Shaanxilithes has been reported in the late Ediacaran in East Yunnan, northwest margin of India, Namibia and southwest margin of North China Platform. The new discovery of Shaanxilithes in the Huize region of Eastern Yunnan further demonstrates the worldwide distribution of this taxon, which could be used as an index fossil in the upper Ediacaran successions for global stratigraphic correlation. Based on the morphological observations and the results of elemental mappings and semi-quantitative elemental analyses, this paper discussed their morphological and taphonomic information and phylogenetic affinities, which provided new perspectives on exploring the biological and ecological evolution of metazoans during the Ediacaran-Cambrian transi-tional interval.