Tectonic Contacts of Miogeoclinal Strata in East-Central Alaska

David L. Jones, Susan Boundy-Sanders, Richard W. Murray, David G. Howell, Thomas J. Wiley

The well-known and remarkably complete Precambrian to upper Mesozoic sequence exposed north of Eagle in the Yukon River drainage basin has generally been considered to be an in-situ part of the Cordilleran miogeocline. Recent field studies in Alaska and adjoining Canada, however, show that significant stratigraphic differences and sedimentologic anomalies exist across faults that separate the Yukon River section from autochthonous strata of the miogeocline; therefore, continuity between these two regions can no longer be assumed to exist. Three separate fault-bounded stratigraphic sequences are now recognized along the international border north of the Yukon River, as follows: the classic deep-water section best exposed along the Yukon, Tatonduk, and Nation rivers; the do inantly shallow-water carbonate sequence exposed in a small area to the east on Jones Ridge; and the main miogeoclinal section of Canada that terminates against a fault that trends nearly north-south and appears to connect the east-west-trending Dawson thrust with the more northerly trending Yukon thrust. Sense of movement along this fault is uncertain but may be left lateral. Movements along the Yukon-Dawson fault systems appear to involve both strike-slip and thrust displacements, resulting in juxtaposition of unlike stratigraphic assemblages whose original paleogeographic relations remain to be determined.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.