贵州寒武纪杷榔组古蠕虫类埋藏特征及意义*

贵州剑河寒武纪杷榔组辣子寨剖面含有丰度较高的古蠕虫类化石。化石鉴定为Wronascolex geyiensis, 主要保存在三个层位。在对三个层位的岩石、沉积特征、化石成因及埋藏特征探讨分析后, 证实W. geyiensis化石保存于快速的沉积事件导致的浊流沉积层内, 而化石埋藏的完美程度受到成岩过程中埋藏位置、沉积物中矿物结晶和充填方式的影响, 这些后期的成岩、成矿作用对先期形成的化石精细结构产生了直接和间接的破坏作用。本文通过对W. geyiensis化石体上黏土矿物、草莓状黄铁矿、自形–半自形黄铁矿的成因分析后, 获得最适合保存软躯体化石的环境应该为缺氧且生物体与孔隙水中的硫酸盐无接触的原地和近原地埋藏条件。

Taphonomic characteristics and significance of the Palaeoscolecids from the Cambrian Balang Formation in Jianhe County, Guizhou Province

Abundant Cambrian palaeoscolecidan fossils, collected mainly from three beds of the Lazizhai Section of the Balang Formation in Jianhe County, Guizhou Province, are identified as Wronascolex geyiensis. By analyzing the characteristics of rocks, sedimentation, fossil preservation and taphonomic characteristics of the three beds, we discover that fossils of Wronascolex geyiensis were preserved inside the turbidite sediments which were formed at a rapid deposition rate. However, whether the fossils were perfectly preserved or not depends on the burial sites during the diagenetic processes, mineral crystallizations in the depositions, as well as the modes of infilling, all of which had made direct or indirect damages to the microstructures of the fossils formed previously. After analyzing the origins of the clay minerals, framboidal pyrite, idiomorphic or hypidiomorphic pyrite adhered to the Wronascolex geyiensis fossils, we propose that the most appropriate environment for preserving the microstructures of soft-bodied fossils is the oxygen-deficient environment with no contact between the organisms and sulphates in the pore water under autochthonous and nearly autochthonous burial conditions.