Exotic new erratic discovery in Seattle

The erratic lies beside a newly built trail. Darryl Howe photo.

An interesting fossiliferous erratic has been found following some new trail work in the upper part of Leschi Park in Seattle. Location is along a new section of trail just west of Lake Washington Blvd and south of Yesler Way. The rock is not huge, but one of the more intriguing ones I’ve heard of since sending out the ‘cool erratic call out’ to website visitors. The erratic, according to reader Darryl Howe, is chock full of bivalve, perhaps brachiopod, fossils. I don’t know what marine formation this might be from other than the Nooksack rocks near Mount Baker. I can’t tell from the photos if that is a good guess. There are other marine units from further north in BC, but I don’t know them well.

The rock appears to be chock full o' fossils. Darryl Howe photo. Click to enlarge.

I’ll go visit this erratic someday, but in the meantime, the more website readers that go look at it, the more likely someone will recognize the source formation, or at least be able to tell us all more about the rock.

Leschi Park is in Seattle, east of downtown near the shore of Lake Washington on Lake Washington Blvd. Darryl says the best access to the new trail is from the parking lot at the tennis courts.

Bivalve fossil in the Leschi Erratic. Darryl Howe photo.

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3 Responses

  1. Dave,
    Hey that’s exciting. I will try and check it out, if I can survive our massive snow storm!
    All the best,
    David

    • Yes, David, when you have dug out from winter’s last gasp, have a look see at that erratic. See if it looks like the Nooksack Fm rocks- generally a very dense, black, shiny argillite with marine fossils.

  2. I briefly visited this erratic on March 6. It is clearly visible directly west and uphill in the woods (recently cleared of most undergrowth by trail crews) from the small parking lot by the tennis courts. I took pictures but they don’t show anything that Darryl’s don’t show. It is indeed “chock full” of bivalve fossils. I am not enough of a paleontologist to know them, nor could I recognize the formation from which the erratic came. It looks similar to Nooksack Group rocks I have seen in the Mt. Baker area….it is fine-grained (very fine sand or silt) and appears to be well sorted and not particularly well stratified. The rock is weathered, as one would expect from sitting in the woods in a humid climate for about 13 or 14,000 years since being dumped by ice. Curious folks have hammered at a few chunks that are lying nearby. This is a fascinating find, the likes of which I haven’t see among several thousand erratics personally observed from the Fraser Glaciation. It is worth further investigation by paleontologists (George, are you reading?) and sedimentary petrologists. I wonder if anyone from UW has seen and described it.

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