A Day in Suntrana

One of my favorite places to get out to is the Suntrana Creek region, near Healy, Alaska. This place has a lot of historical, geologic and aesthetic beauty. Currently, I’m using this site as a place to practice my droning. I’m also using this as a project site to document the constant changes to the Suntrana Creek alluvial fan with 2D orthoimagery.

Geology of Suntrana Region:

Geologically, this area represents a great change in the flow of water in the interior of Alaska from a time when water flowed all the way to the Gulf to it being forced 180-degrees into the current Yukon River drainage as the Alaska Mountain Range formed.

The stratigraphy of the area, shows rocks and sediments classified as being part of the Usibelli Group, consisting of the Healy Creek Formation, Sanctuary Formation, Lower, middle and upper Suntrana formations and the Lignite and Grubstake Formations. These are all capped by the Nenana Gravels. The Usibelli Group, in general, consist of interbedded sands, silts, muds and coals in the tens of meters thick, with an overall thickness approximately 550 meters, while the overlaying Nenana gravels consist primarily of sand and gravel conglomerates that are about 800-meters thick. Isotope dating of the Usibelli group place their deposition at 23 Ma on the lower formations up to 5 Ma on the upper formations.

What the drainage reconstruction of this area tends to indicate is that up to about 18 Ma, the flow of water for these historic rivers was South through what is now the Alaska Range and sometime around 18 Ma the formation of the Alaska Range had progresses to such a degree as to cause the Nenana River to reverse course and flow North into the Yukon River drainage.

History of the Suntrana Region:

Historically, this area represents the major development of the Nenana area coal fields. While coal exploration has been occurring in Alaska since the late 1700’s, the first commercial development of coal didn’t occur until 1855 on the Kenai Peninsula.

With the increase in development of resources in the state, more coal was required to help fuel ships and trains that made their way to the fishing grounds and mining fields. Even as rich as the Nenana coal fields are, the Alaska Railroad did not reach them until 1919 and it was not until 1922 for the railroad to connect up Nenana with Seward and install a 4 ½ mile spur rail up Healy Creek that enabled the establishment of the Suntrana Mine.

By 1928, the Suntrana Mine was producing half of the total coal mined in the State and became the largest producer of coal in 1940. Coal mining at Suntrana continued up until the mine was shut down due to serious fires in the coal seams. Today, coal mining is still a visible activity in the near by valleys by the Usibelli Mining Company.

Observations at Suntrana Creek:

In the time that I’ve spent out in the Suntrana Creek area, I’ve noticed a lot of changes that have occurred. Most recently, the alluvial fan of Suntrana Creek has pushed out into Healy Creek, forcing it to the other side of the valley. This has since changed with Healy Creek incising into the Suntrana Creek alluvial fan and removing several acres of land.

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References:

Historic Photos: Alaska Digital Archives at: https://vilda.alaska.edu/

Geologic Images: Benowitz, Jeff; Davis, Kailyn; Roeske, Sarah; A river runs through it both ways across time, Geologic Society of America Geosphere, Volume 15, Number 3