Wednesday, February 11, 2015

Notes from Grandy Creek, Skagit County

I was up the Skagit River valley and then up Grandy Creek Road to assess a slope. Grandy Creek Road is the access route to Baker Lake a hydro electric reservoir east of Mount Bake on the Baker River, a major tributary of the Skagit.  
I put my foot up on this cut bank slope for scale.
The sand and gravel is poorly sorted glacial outwash
The unit was compacted suggesting that it had been overridden by glacial ice

On the way back from my work ventures I stopped by Grandy Lake. A Skagit County Park is located along the shores of the lake.

The lake adjacent to the shore clearly has some history as indicated by the pilings 

The pilings supported buildings and an old power pole suggests indicates the old site had electric power. I am not clear on the history of the lake and valley, but suspect the lake was used as a log pond and the pilings supported a mill. Settlement had penetrated this area by the early 1900s and included power plants and extensive trails and rail lines are indicated to have been extended part way up Grandy Creek in 1915 and I suspect rail came further up as logging spurs of short duration. Further up the valley a swampy was converted to a log pond and in the 1960s was dredged and dammed to create a recreational center, Lake Tyee.  
The local geology is a bit complex. Jon Rediel (2007) has made a good go at working out the mix of continental and alpine glaciation that has impacted this area. he proposed a large set glaciers coming off of Mount Baker and the other high peaks to the north blocked the Skagit Valley prior to the arrival of the Continental ice. The compact units I observed above combined with LiDAR suggests that the unit was overridden by Ice from the north and continental ice.
The valley Grandy Lake is located is a bit over sized valley for the stream now occupying the valley. A late glacial age former water route carved into the terraces on the north side of the Skagit Valley as water from up the valley drained to the west around and possibly under that blocked the valley.    

On the lower end of Grandy Creek I took in the view of a high cut bank above the creek. The creek has cut through the glacial-age terrace providing a nice cross sectional view. The units grade coarser up section suggesting this set of sediments is a prograding deposit as an ice lobe from the Puget Lobe advanced up the valley.

Massive sand and silty sand overlain by very poorly sorted gravel and cobbles to boulders.

Silts at the base of the slope consistent with lake sediments in a lake that would have formed from the lower Skagit being blocked by ice to the west.

I wrapped up the afternoon by indulging in my support of the local rural economy at the Grandy Creek Grocery.

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