气候变化领域集成服务门户

Rates of northern Alaska Range thrust system deformation are poorly constrained. Shortening at the system's west end is focused on the Kantishna Hills anticline. Where the McKinley River cuts across the anticline, the landscape records both Late Pleistocene deformation and climatic change. New optically stimulated luminescence and cosmogenic Be-10 depth profile dates of three McKinley River terrace levels (similar to 22, similar to 18, and similar to 14-9 ka) match independently determined ages of local glacial maxima, consistent with climate-driven terrace formation. Terrace ages quantify rates of differential bedrock incision, uplift, and shortening based on fault depth inferred from microseismicity. Differential rock uplift and incision (1.4 m/kyr) drive significant channel width narrowing in response to ongoing folding at a shortening rate of similar to 1.2 m/kyr. Our results constrain northern Alaska Range thrust system deformation rates, and elucidate superimposed landscape responses to Late Pleistocene climate change and active folding with broad geomorphic implications.

Plain Language Summary Where plate tectonics deforms Earth's surface, river landscapes hold information about the distribution and rate of earthquake-related deformation over thousands of years. The processes that form these landscapes remain uncertain. Here we study the landscape where the McKinley River cuts across the Kantishna Hills anticline to quantify previously unknown rates of earthquake-related tectonic deformation in intracontinental Alaska, and investigate the mechanisms by which this landscape evolved. We date McKinley River terraces that were the river channel similar to 22, similar to 18, and similar to 14-9 ka; the ages match independent ages of regional glacial advances and hence indicate climatic control on river terrace formation. Digital topography analysis shows that the terraces have been folded and uplifted above the channel at rates up to similar to 1.4 m/kyr associated with shortening at similar to 1.2 m/kyr. The McKinley River channel narrows and slightly steepens across the fold where uplift rates are highest, indicating that the river adjusts to uplift primarily by reducing channel width and not by steepening as common incision models assume. Kantishna Hills anticline shortening accounts for similar to 10% of the total similar to 13-mm/year plate strain rate; similar to 6mm/year remains unaccounted for at this latitude and is likely distributed across structures south of the Denali Fault.