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The AAPG/Datapages Combined Publications Database

Alaska Geological Society


Alaska Geological Society 2003 Geology Symposium, 2003
Page 25

Implications for the active tectonics of the north-central Alaska Range foothills from bedrock structure and river terraces - Abstract

Sean P. Bemis1

Thermochronometry and the stratigraphic record suggest that the central Alaska Range has risen over the last ~6 Ma. In the northern foothills of the Alaska Range, the Nenana Gravel, composed of coarse-grained alluvial sediments, represents the first ~3 Ma of this uplift. Subsequently, this unit has been uplifted and deformed into a series of east-trending folds, but the origin and evolution of these structures has not been studied. Mapping the distribution and elevations of Quaternary river terraces shows a relationship between the structures in the Nenana Gravel and deformation of the terraces. Differential GPS surveys of terrace treads show small-scale terrace deformation, while profiles derived from digital elevation models show broader-scale folding. Profiles of the base of the Nenana Gravel illustrate the amount of deformation since its deposition, and this folding corresponds with the folding of the terraces.

The northward-convex arcuate fold pattern, northward decrease in relief, and adjacent basin to the north of the foothills suggest that a fold-and-thrust belt has built outward from the Alaska Range orogen. Young, deformed geomorphic features along the Nenana River suggest that this belt is active and prograding northwards into the Tanana basin. Understanding the active tectonics of this region is important to assess the seismic hazard of the associated faults, as well as the evolution of the central Alaska Range.

Acknowledgments and Associated Footnotes

1 Sean P. Bemis: Department of Geology & Geophysics, University of Alaska, Fairbanks, AK;

Copyright © 2014 by the Alaska Geological Society