Cryophilic polychaetes at the subtropical Laurentian margin of the Iapetus Ocean: Evidence for cold-water ocean circulation and upwelling

Abstract

Through the Phanerozoic eon, the trace fossil Macaronichnus—made by sediment-burrowing polychaetes—appears to be restricted to intermediate- and high-latitude shallow-marine habitats with cold to temperate waters or coastal areas closer to the equator with cold-water upwelling. We present records of such trace fossils in Ordovician (Darriwilian–Sandbian?) shallow- and deep-water marine deposits in the Central Norwegian Caledonides, pointing toward previously undocumented deep-ocean circulation and upwelling of cold water along the subtropical eastern Laurentian margin and adjacent volcanic arcs and microcontinents in the early Paleozoic Iapetus Ocean. Possible implications for Middle Ordovician ocean circulation patterns are discussed in relation to paleogeographic reconstructions and paleoclimatic models.