PALEOENVIRONMENTAL AND PALEOBIOGEOGRAPHIC IMPLICATIONS OF A SWARTPUNTIID FROM THE EDIACARAN PERIOD, CAROLINA TERRANE, STANLY COUNTY, NORTH CAROLINA

The Carolina Terrane has previously been considered the southern extension of the Avalon Terrane. A new partial swartpuntiid (assigned to Swartpuntia sp. (NCSM 9581)), recovered from Ediacaran age rocks of the mudstone member of the Cid Formation, Albemarle Group, Carolina Terrane in Stanly County, North Carolina adds additional evidence that the Carolina Terrane is distinct from the Avalon Terrane. The specimen shows two collapsed petaloids, straight petaloidal segments abruptly curving at their distal ends to form a candle-flame shaped termination, extremely high angles between the petaloids, possible remains of a central stalk, and implied 4-5 vanes.

Recent studies divide Ediacaran organisms into Avalon, White Sea and Nama Assemblage types. While Pteridinium, previously described from the stratigraphically higher Floyd Church Formation in North Carolina, is considered a cosmopolitan genus, Swartpuntia is considered characteristic or indicative of the Nama assemblage type. With the discovery of Swartpuntia sp., a case can be made that the Ediacaran biota from the Carolina and Avalon Terranes are representative of different paleobiogeographic provinces.

Age and taphonomy of the Ediacarans from the two terranes are notably different. Previously reported isotopic ages bracket the age of the Cid Formation mudstone member as terminal Proterozoic to Early Cambrian, 539.4-556 Ma (Ingle et al., 2003), significantly younger than ages reported for Avalonian biotas. In taphonomic terms, the Swartpuntia reported here shows Nama-style preservation, while specimens from Avalonian assemblages are generally preserved in a Fermeuse-style preservation. Combining assemblage types, age and taphonomy, the discovery of Swartpuntia indicates that the Carolina Terrane may have been separate from the Avalon Terrane in the terminal Proterozoic complex of peri-Gondwanan terranes.