But the clincher for me was a menagerie of glacial erratics, found embedded throughout these clay deposits, from surface to bedrock. For example: sandstones both gray and blonde, sedimentary metamorphic 'mudstones' of several types, white and pink quartzite, fine-grained 'black granite' dacite or andesite (very tough to break w/ hammer), and two 'fire opal' specimens, one orange the other red. Almost all of these specimens exhibit glacial fracturing; many appear to have once been oval and stream-worn, while exhibiting unmistakable evidence of recent stressful trauma (meaning before I got to 'em with a hammer!).
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The nearest well-known for fire agates is Francois Lake, British Columbia, where the University of Nebraska's Agate Lexicon Database reports this 1966 entry: "Omineca Agate, British Columbia, red, crimson, and pink amygdaloidal agates from the vicinity of Francois Lake near Omineca and the Omineca Mountains". Francois Lake and the Omineca Mountains are right in the feeder zone to the Rocky Mountain Trench system, so this is a significant find in building a circumstantial case for Missoula Floods deposits.
This entire area seems to be an Ice Raft Graveyard, and here's a my initial 'engineering conjecture' explaining why it may be so:
- Flood flows here at times were over 185 meters, which is more than 50 meters above the crest of the Chehalis Saddle resulting in a spillway more than 15km wide. Another geologist once asked me 'If this happened as you say, where's the spillway?" Answer: We built Interstate 5, and the towns of Chehalis and Centralia in it!
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| Fig. 2: Chehalis Spillway |
- Lake Allison in the Willamette Valley was a 'bathtub', with no outlet and perhaps 1000km of shoreline. Ice rafts entering there had plenty of space in which to scatter. Ice rafts entering what I call the 'Cowlitz Slough' on the other hand would be funneled and drawn along by the current to the outlet spillway near this site. The processional flotilla of ice rafts were melting at this point, dropping debris (sand, gravel, cobbles and larger) into the muck on the bottom as they passed.
- Then the level of Lake Allison began to fall almost as quickly as it had risen, and the suspended clays here were dewatered and decelerated to a stop, forming nodules where conditions were favorable. And a squadron of in-transit ice rafts became stranded in the icky gooey brown slime. Where they quietly melted away, depositing their tell-tale cargo in several eventful layers throughout the recent Ice Age.
- Then about a month ago, somebody finally noticed! While it is rewarding to be the first to figure something like this out, I'll be the first to admit I stand on the shoulders of some real giants...Harlen Bretz, Ira Allison -- without their groundbreaking efforts, there simply would be no framework upon which to build an explanation for these observations.
- And also a big 'thanks' is owed by everyone with an interest in the history of the Missoula Floods and the geology of Washington State to Alan Good of Napavine WA and his industrious enterprise; without Goods Quarries opening windows into the past, this mystery likely would remain unsolved yet today.
In something like 50 years of diligent searching, Ira Allison and his OSU colleagues managed to find just over 400 glacial erratics in the Willamette Valley. Here on the Chehalis Saddle, I'm certain that an organized effort could find hundreds of glacial erratics in a single day at any one of several promising sites in these extensive Missoula Floods clay deposits I have discovered and named the 'Goods Formation'.
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