Data from: Diachronous increase in early Cambrian ichnofossil size and benthic faunal activity in different climatic regions

In order to clarify the pattern of diversification and processes of biological activity during the Cambrian radiation, ichnofossils were comparatively studied in the early Cambrian sections of Newfoundland, South China and western Mongolia. Special attention was paid to size distributions of the most common ichnogenus, Planolites, and the densities of all the observed ichnofossils that preserve animal activity as expressed by bedding plane bioturbation indices (BPBI). From the Fortune Head section in Newfoundland, a clear size increase in the ichnogenus Planolites is confirmed from the Treptichnus pedum Zone to the overlying Rusophycus avalonensis Zone. The BPBI also shows much stronger biological activity in the R. avalonensis Zone than in the T. pedum Zone. In Meishucun, South China and Gobi-Altai, Mongolia, however, a variety of Planolites sizes had already appeared in the T. pedum Zone, and the BPBI's on some bedding surfaces of the T. pedum Zone are already comparable to those in the R. avalonensis Zone in Newfoundland. In the earliest Cambrian, diversification and increase in the biological activity of the benthic fauna were diachronous in the wide geographic scale, starting earlier at lower latitudes (South China and western Mongolia) than at higher latitudes (Newfoundland), reflecting differences in the onset of Cambrian benthic animal activity under different climatic conditions.

为厘清寒武纪大爆发期间生物活动的演化模式与过程，研究团队对纽芬兰、华南及蒙古西部的寒武纪早期地层剖面中的遗迹化石（ichnofossils）开展了对比分析。本次研究重点关注两类指标：其一为最常见的遗迹属（ichnogenus）漫游迹（Planolites）的粒径分布，其二为以层面生物扰动指数（bedding plane bioturbation indices, BPBI）表征的、所有观测到的保留下动物活动痕迹的遗迹化石的丰度。在纽芬兰福特角（Fortune Head）剖面中，自佩德姆三叶形虫迹带（Treptichnus pedum Zone）至其上覆的阿瓦隆鲁斯菲克迹带（Rusophycus avalonensis Zone），漫游迹属的粒径呈现出明确的递增趋势；层面生物扰动指数同样显示，阿瓦隆鲁斯菲克迹带内的生物活动强度远高于佩德姆三叶形虫迹带。但在华南梅树村（Meishucun）与蒙古戈壁-阿尔泰（Gobi-Altai）地区，佩德姆三叶形虫迹带中已出现多种粒径的漫游迹，且该遗迹带部分层面的层面生物扰动指数已可与纽芬兰阿瓦隆鲁斯菲克迹带的水平相当。寒武纪最早期，底栖动物群的生物多样性与活动强度在广阔地理尺度上呈现穿时性特征：低纬度区域（华南与蒙古西部）的活动启动时间早于高纬度区域（纽芬兰），这反映了不同气候条件下寒武纪底栖动物活动起始过程的差异。