Highway 397 Road Cut West of Nine Mile Canyon, Part I

 

Highway 397 is a spur highway off of Interstate 84 south of Kennewick that accesses the Finley area to the east of Kennewick. The route by-passes Kennewick, angling across the northern slopes of the Horse Heaven Hills south of Kennewick. A road cut just west of South Nine Canyon Road (46.07'47", 119.04'38") got my attention with a variety of geology units. This post is Part I and is focused on the west end of the cut slope where a sedimentary unit is exposed between Columbia River Basalt Group lava flows.

West end of the cut slope

Lake sediments from between lava flows. The sediment appears tuffaceous.

A mix of basalt rubble and sediment

Basalt rubble within sediment with some very 'cooked' sediment

Sediment at base of lava flow

Closer view of sediment at base of lava flow

Reidel and Fecht (1994) geology map covers this area at a 1:100,000 scale. The scale precludes some detail and the sediment interbeds are not shown. Furthermore the road cut post dates the geology mapping of the area. They note that these interbeds of sediment are generally best exposed in road cuts. Where the interbeds are mapped they are referred to as continental sedimentary deposits. In places where gravel is present, the gravel appears to be sourced from ancestral Columbia River or Salmon/Clearwater River flow paths as the grvael contains rocks with a continental affinity.

The map does indicate that the lower basalt below the sediment is the Umatilla Member and the upper basalt is the Pamona Member. Both of these members are part of the Saddle Mountains Formation of the Columbia River Basalt Group. 

The delineation of these basalt flows was accomplished via a combination of geochemistry, magnetic polarity and isotopic ages.  

The lava flows in the chart above between the Umatilla and Pamona are generally more localized lava flows or smaller flows restricted to ancestral river valleys. The lack of flows between the Umatilla and Pamona as well as the thinness of Continental deposits at this site suggests this site was elevated relative to the broader Columbia Basin similar to today.

 

My Forest Enemy: Ilex aquifofium

While doing field work I come across what I have decided is a personal enemy on regular basis.

Eglish Holly (Ilex aquifolium)

I was able to pull this one out by the roots.

I at times visuzlize the Pacific Northwest forests in 10,000 years being a forest of holly. The holly shown above was in an old growth forest. I have come across holly in old forest areas ranging in elevation from the inland coastal areas to as much as 3500 feet in the Cascade Range. I have been digging it out of my own forest stand on regular basis, and when I can, I yank it out of the ground and stick it into a spot above the ground while traversing through the forest during a field ventures.  .

KUOW covered recent efforts to get this plant listed as a noxiuos weed (kuow.org/have-a-holly-noxious-christmas). The issue strikes me as a state government and ethics failure.  

Windfall and Dog Hair

I plotted out a route to a steep slope at the headwaters of a creek in the Northwest Cascades. While approaching the site I noted windfall trees on the edge of a clearcut.

While walking the road and a section of trail took about 2 hours to cover 6 miles with a fair bit of elevation gain and hiking out took about 1.5 hours as it was downhill, the last quarter mile to the steep slopes I wanted to reach took nearly an hour each way. 

Windfall trees and dog hair young trees

Dog hair western hemlock obscuring downed trees

It is a slow process navigating over fallen logs and brancheds that tend to break. It did not help that portions of the area were also steep. 

I did reach my goal of getting to the steep headwater slope - that presented its own challenge as there were cliffs in the forest.

Very steep forested slope

Made for a bit of a long day and light got a bit dim before getting back to my starting point, but I did get some nice views as the clouds broke up. 

Whitechuck and Glacier Peak

Whitehorse and Three Fingers