Biogeographical significance of Cambrian trilobites from the Carolina slate belt

Abstract

Abundant middle Middle Cambrian trilobites of the Ptychagnostus atavus Interval-zone are described from the upper Asbill Pond formation (informal name) near Batesburg, South Carolina. The fauna, containing at least nine species, has strong affinities with cool-water faunas of both Armorica and Baltica, but little affinity with warm-water, shelf faunas of Laurentia. This is compatible with previous conclusions that the Carolina slate belt is an exotic terrane that was accreted to North America during the early or middle Paleozoic. Further evaluation, however, introduces an alternative possibility that the fauna could have lived in deep, cool-water environments along the periphery of Laurentia, and subsequent displacement need not necessarily have been great. Combined faunal and stratigraphic components of the Carolina slate belt do not precisely match those of any known region, but may be closest to those of Bohemia. Although a southpolar location in proximity to Armorica, Baltica, and Gondwana seems likely, a definitive placement in a reconstruction of the Cambrian world is not yet possible. Included in the trilobite fauna are the agnostoids Hypagnostus mammillatus , H. parvifrons , Peronopsis fallax , Ptychagnostus sp.,and Tomagnostus fissus . The polymeroids include Agraulos sp., Paradoxides cf. polonicus , Paradoxides sp., and Skreiaspis ? sp.