The Neotectonic framework of the Talkeetna Mountains, southcentral Alaska


Demi Mixon

When it comes to studying plate tectonics, Alaska is one of the best locations in the world. With more than 1,000 earthquakes a month, Alaska accounts for more than 11 percent of the world's earthquakes. Because of Alaska's predilection for tremors, it's no surprise that the state is home to unusual formations. Case in point: the Talkeetna Mountains. (click on photo for more of the story)

“Alaska is geologically complex and not everything is entirely understood yet,” said Demi Mixon, a masters student studying geology at UAF. Mixon has spent the past two years studying the Talkeetna Mountains in south-central Alaska, focusing on neotectonics, geomorphology and structure.

Mixon's research has been on the positioning of the Talkeetna Mountains, what has tectonically influenced their uplift and deformation, and if the range is tectonically active. Her project will help researchers understand the consequences of both flat-slab subduction and transpression. Subduction occurs when one tectonic plate moves under another, while transpression occurs when plates slide against each other.

A better understanding of the Talkeetna Mountains tectonic activity is important due to its housing several towns, a major transportation corridor, and a proposed hydroelectric dam site along the Susitna River.
During summer 2014, Mixon spent time in the Northwest Talkeetna Mountains doing field work. “I had an amazing time doing field work and collecting samples,” she said. Despite being rained-out for the majority of her time in the mountains, she noted that “it was still a great experience.”

While Mixon intends for her project to contribute to understanding plate tectonics, she also recognizes her research adds to scientist's knowledge of the range themselves. “The Talkeetna Mountains haven’t had too many detailed studies conducted [on them] and haven’t been explicitly explored in this context so I will be introducing new ideas,” Mixon said.

“Conducting research can be fun and interesting as much as it can [be] frustrating,” she said. “It’s important to keep looking at things from different perspectives to help keep your eyes fresh and to work through those problems.”

The Talkeetna Mountains are an anomalous topographic high in south central Alaska located in the center of a long-lived forearc basin. Observing such a topographic high between a forearc basin raises some speculation about its origin. Why are the Talkeetna Mountains a topographic high when they are along the trend of this basin, and do active tectonic structures contribute to its uplift? A relevant tectonic feature that might have influenced the creation of this topographic high is the northward flat-slab subducting Yakutat microplate beneath the North American margin. The boundary of flat-slab subduction of the buoyant Yakutat microplate is taking place beneath the mountains (Finzel, 2011). I hypothesize that the Talkeetna Mountains have been uplifted primarily as a result of buoyancy and/or flexure associated with flat-slab subduction, but local relief may reflect fold and fault structures resulting from westward rotation of the southern Alaska block south of the Denali fault.


Name: Demi Mixon, Graduate Student

Institution: University of Alaska Fairbanks

Mentor: Wesley Wallace,

Award: Research Grant

Funding Period: 2014