By Dave Tucker
Saturday, July 31, 2010
Grandson Alec Foote at the site Saturday 7/31/10. Click to enlarge any image.
Construction has nearly completely destroyed the glacially smoothed and striated slab on Samish Hill in Bellingham. The site was featured in a March posting. Now there is an 8-foot-deep pit blasted into coarse facies of the Chuckanut Formation; this will be the home of the new Temple Beth El synagogue. A few interesting sites remain to be seen: coal seams, curiously-textured very coarse-grained sandstone, some coalified fossil branches. If the big yellow tracked crusher is still there, that is worth a look-see. The erratics discussed in the previous story are still there, though getting overgrown by high field grass. TH SITE FEATURED ON THIS FIELD TRIP WILL LIKELY BE GONE WITHIN DAYS, SO DO NOT DELAY. It makes for a quick outing, an hour at most on a sunny day (well, it was sunny when I started this!) this weekend.
How to find the 'Samish Slab'. Click to enlarge
Getting there: These are new directions, as access through the construction entrance is less feasable now. Begin at a foot trail on City of Bellingham right of way at the south end of 47th Street. The trail, ‘paved’ with poorly sorted glacial drift, goes south through shaded and pleasantly cool second [third?] growth forest. Turn left at a T-junction after about 200 yards. The trail ascends slightly, and shortly comes to a nexus of several trails. The construction site is visible off to the left, but instead of crossing over the ‘no trespassing’ sign, continue straight on a trail with low bushes to the left between you and the construction site. You will see one or more faint tracks going left a few feet into the grassy construction clearing. Walk east (right) along the fence at the top of the pit. If there is no work going on, you’ll figure out how to get down into the pit.
The upper part of the drill hole is in competent, fine sandstone. When it entered the poorly cemented coarser sediment, the hole sheared.
Once in the pit, examine the SE corner to see the remnant of a blasting drill hole. At the top, it is smooth and half-round, but lower down, it enters a very friable coarse granule layer and becomes very distorted due to incompetence of the lower rock layer; the drill must have crushed its way through this layer before reentering solid sandstone beneath it. Just to the left are a couple of small coal seams. Walk along the south face of the pit wall and watch for some coalified wood. At the SW corner, a cross section reveals smooth glacial till overlying the ice-planed smooth surface of the slab- an unconformity representing around 50 million years of missing time. This smooth rock surface is about all that is left of the once very extensive striated surface of the Samish Slab.
Till overlies the glacially smoothed erosional surface of Chuckanut Formation sandstone. Alec's hand is on a 50 million-year unconformity
Fay, Alec's 1-foot-long pug, for scale at the coalified wood exposure.
I climbed up onto to the big, yellow, tracked, crusher beside the big pile of crushed rock. This heap is all that is left of the rock that filled the excavation. The climb up was not simple, but the big jaws are very impressive. If you have seen a rock crusher in a geology lab, you’ll be doubly impressed at the comparison.
The tracked crusher with Alec and Fay.
Filed under: Bellingham area, Chuckanut Formation, Geology field trips | Tagged: Bellingham, Chuckanut Formation, Geology field trips, Pleistocene deposits; Whidbey Island; geology | 2 Comments »