Devonian and Older Tectonic Plate Sequences of Arctic Alaska: Siberian Connection

By

J.G. Clough (Alaska Division of Geological & Geophysical Surveys) and R.B. Blodgett (Oregon State University)

Devonian and older strata beneath the regional sub-Mississippian angular unconformity developed across northern Alaska were previously and inappropriately assigned to the “Franklinian megasequence” of northern Canada. Based on new sedimentologic and paleobiogeographic evidence for Precambrian through Lower Devonian strata of the Sadlerochit and Shublik Mountains region, we propose three new unconformity-bounded megasequences; Nularvikian, Katakturukian , and Nanookian for Arctic Alaska. Each megasequence records a unique depositional and tectonic episode in the Proterozoic through Early Paleozoic history of the Arctic Alaska plate.

The Nularvikian sequence (Precambrian), composed of polydeformed slate, quartzite and dolomite, represents a Late Precambrian precursor basin. The overlying Katakturukian sequence (Neoproterozoic) includes mafic volcanics, and slope to ramp carbonates deposited in a rift to drift phase of the Arctic Alaska plate. Following tectonic uplift, carbonates represented by the Nanookian sequence were deposited in a new passive margin setting.

Strong biogeographic affinities of Late Ordovician (Ashgillian) faunas in the Nanookian megasequence indicate that this terrane was more closely associated with Siberia (particularly Kolyma and Taimyr) than North America. Rather than a rotational model for the opening of the Canada Basin, we prefer a translational model that involves rifting of the Arctic Alaska plate from Siberia in Triassic (Norian) time along a sinistral transform system adjacent to the Canadian Arctic Islands. Cambrian, Ordovician and Devonian volcanics indicate the Arctic Alaska plate was involved in multiple rifting and failed rift events, but carbonate sedimentation dominated at least its southern margin from Neoproterozoic through Early Devonian (Emsian) time.

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.