BURROWS OF THE POLYCHAETE PERINEREIS AIBUHIUTENSIS ON A TIDAL FLAT OF THE YELLOW RIVER DELTA IN CHINA: IMPLICATIONS FOR THE ICHNOFOSSILS POLYKLADICHNUS AND ARCHAEONASSA

Abundant biogenic sedimentary structures produced by Perinereis aibuhitensis (formerly Nereis) occur in tidal flats of the Yellow River Delta in China. The burrows of Perinereis are visible as vertical tubes and irregular strings in slabbed cores. The cores were studied by X-ray radiography, computed tomography and VGStudio MAX to obtain three-dimensional images of the burrows and their inner structure. The burrows are vertical to steeply oblique, Y-shaped tubes with multiple branches. They are considered as analogues of the trace fossil Polykladichnus. Some gutter-like surface traces are similar to the trace fossil Archaeonassa. Perinereis burrows and trails occur mainly in the mixed flat, less frequently in the mud flat or sand flats. Potentially abundant occurrences of some analogous fossil burrows and trails (Polykladichnus, Archaeonassa) could mark position of the intertidal zone.