Middle Cambrian Diplocraterion parallelum from North China: Ethologic significance and facies controls

The middle Cambrian Mantou Formation of the Mianchi section of western Henan Province, North China provides an opportunity to address infaunal colonization during the aftermath of the Cambrian explosion. The trace fossil Diplocraterion is common within intertidal very fine-grained sandstone of the Member II of the Mantou Formation (Stage 5). Diplocraterion consists of perpendicular to bedding plane, lined U-shaped burrows with well-developed marginal tubes, having distinctive, dark and light colored, laminae forming retrusive and protrusive spreiten reflecting the activity of a suspension feeder. No scratches are observed on the wall of the marginal tubes. SEM-EDS mapping detection shows that the dark laminae are dominated by Si, Al and Fe, whereas the light laminae are dominated by Ca and Si. Based on ichnological, stratigraphical and SEM-EDS features, it is suggested that the specimens of Diplocraterion studied here results from the equilibrium behavior and that the delayed appearance of this ichnotaxon in North China is due to lack of appropriate siliciclastic facies.