POSSIBLE TRACE FOSSILS FROM THE EARLY EDIACARAN (620 MA) OF NORTH CAROLINA, OR TECTONIC PSUEDOFOSSILS?

Tectonic forces have long been considered the cause of the 1.1-meter-long and 0.5-2 cm wide tectographic pseudofossils referred to as Vermiforma antiqua. However, our reexamination of these specimens lead us to consider them as possible trace fossils. The specimens were found in the 1970s along the South Fork of the Little River, Durham County, North Carolina and have resided in the Smithsonian Museum Support Center (SMSC) since the 1980s. The structures are preserved in laminated, greenish, volcaniclastic, metasedimentary rocks; Pb-U dates derived from zircons indicate ages of 620 ±20 Ma, during the Late Cryogenian and Early Ediacaran Periods. Those dates place these sediments after Marinoan glaciation, but before the brief Gaskiers glaciation, which is a poorly represented interval in studies of Ediacaran organisms. The specimens are linear to looping “trails,” some with negative relief and others with apparent internal structures resembling meniscae. Closer examination of the specimens reveals that parallelism along their long axes is limited, arguing against a tectonic influence. Furthermore, directions of “movement,” as shown by menisci-like structures, differ among different “trails” and in some examples are opposite one another. The structures also seemingly cut across large, discontinuous fossilized microbial mats or microbially induced sedimentary structures, which is more consistent with burrows or surface trails made by mobile metazoans. Tentative identification of these and other possible trace fossils on the slab are “Helminthoidichnites” and “Planolites.” Nevertheless, their ichnotaxonomy remains uncertain until verification of their trace fossil origin, and we acknowledge that these structures also may be undiagnosed tool marks or body fossils. These new data combined with previous structural research thus suggest the possibility of ichnologic data related to the Early Ediacaran, which would provide rare insights on the early evolution of metazoans during that time.