Regional significance of the Blow Me Down Brook Formation, western Newfoundland: New fossil evidence for an Early Cambrian age

Abstract

Allochthonous sandstone-shale sequences cropping out directly beneath the ophiolite massifs of the Bay of Islands region of western Newfoundland have been designated the Blow Me Down Brook Formation. The unit has previously been described as an easterly derived flysch sequence deposited in front of the advancing Humber Arm allochthon at the time of its emplacement during the Middle Ordovician Taconic orogeny. On the basis of presumed stratigraphic relations, the Blow Me Down Brook Formation has been interpreted as the youngest formation within the allochthonous Curling Group, although fossil evidence has not been previously reported from the type locality. Recent questions have arisen regarding the provenance and age of the Blow Me Down Brook Formation as the result of recent sandstone petrography studies. We report 20 new localities in the Bay of Islands region where we have found Oldhamia antiqua , Oldhamia smithi , Oldhamia occidens , and Oldhamia flabellata trace fossils that indicate an Early Cambrian age for the Blow Me Down Brook Formation. These sites confirm that the Blow Me Down Brook Formation and correlative units within the Humber Arm allochthon do not represent easterly derived Middle Ordovician flysch deposits, but westerly derived turbiditic sandstone-shale sequences deposited along the eastern North American rifted margin during latest Precambrian to Early Cambrian time. Intact easterly derived flysch units within the allochthon appear to be scarce. These units were apparently prone to severe disruption and incorporation into meelange zones and areas of broken formation.