Paleozoic and Triassic conodonts from the Northwind Ridge of the Arctic Ocean

Abstract

Conodonts are present in the basal part of six Arctic Ocean sediment cores recovered from the Northwind Ridge in the Chukchi Borderland area of the western Arctic Ocean. The conodonts include species typical of the Upper Cambrian, Lower and Middle Ordovician, Middle to Upper Pennsylvanian, probable Lower, middle and Upper Permian, and Lower Triassic. Most of the conodont elements, including a few of the Cambro-Ordovician and all of the Upper Permian species, were recovered from the sand fraction of the Northwind Breccia in the basal 1.5 m of core 92-P34. Other Ordovician and younger Paleozoic conodont specimens occur in carbonate clasts incorporated in the Northwind Breccia. The talus breccia occurs in the lower part of the Early Pliocene/Miocene unit A (undifferentiated) and is overlain unconformably by Pleistocene age sediment. A few Paleozoic and Triassic conodonts also occur in clasts recovered from the basal parts of five other Northwind Ridge cores. Upper Permian specimens are the most numerous of the conodont elements and occur together with an abundant ichthyolith assemblage. In addition, the sand fraction of the Northwind Breccia contains poorly preserved foraminifera, holothurians, and sponges spicules that are common in all Arctic Ocean Plio-Pleistocene sediment. Occurrence of conodonts in what is interpreted to be talus derived from bedrock indicates that the enigmatic Northwind Ridge is a true continental fragment that includes marine strata of at least Paleozoic and Triassic age. The nature of the conodonts and other fossils recovered from the breccia suggests that the Northwind Ridge originated as part of the Canadian Arctic Islands.