Ordovician conodonts from the Bulltinden Formation, Motalafjella, central-western Spitsbergen

Abstract

Seven samplcs from the Limcstonc and Boulder Conglomerate Members of the Bulltinden Formation have yicldcd poorly prcscrvcd conodonts. On tentative identifications Periodon aculeatus Hadding and Prioniodus cf. P. alobatus Bergström at the basc of thc formation suggest an Ordovician lower Caradoc, or older agc. This confirms that the Vcstgötabrccn Formation unconformably beneath underwent highpressure metamorphism during the Taconic and/or Finmarkian phases of the Caledonian orogeny. The conodonts show affinity to the North Atlantic Province suggesting a deeper water marine depositional cnvironmcnt. Conodont colour alteration indiccs of five indicate that the Bulltinden Formation was heated to tcmpcraturcs in cxcess of 300°C, probably during thc middle-upper Silurian main Caledonian uplift cvcnt.