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Local Geology!
The soils being exposed by our excavation are part of the Troutdale formation. They were laid down by the ancestral Columbia river during the late Miocene and the Pliocene epochs – think 4 million years ago. It is interesting to note in this and the following picture the wavy interface between the lowest layers, with their distinctive orange coloration and the next higher layer, with its dark grey colors. The Troutdale formation is a complicated accumulation of fluvial materials - sediments transported by rivers or streams. Clearly there was a major event that occurred millions of years ago that produced the striking contrast in the walls of our excavation. Interesting too to note that the upper, grey layer, is perhaps 3 feet thick, with the grey color transitioning back to the more orange hue. How many tens of thousands of years does this layer represent?
