Susan Siltstone is feeling much better now, after she resolved her dispute with Jimmy Shale. Nobody wants a grumpy neighbor. Since then, many questions came into her mind about her origin. “How did I get so lucky to have all the shales around me, but the limestones up on Mount Tyrwhitt did not?” She tries to remember the times in the Late Jurassic–Early Cretaceous when she formed. Everything was under water. The many small grains composing her siltstone layer all came from the mountainous land in the West.
“I remember the sea was pretty deep, and it was dark at the seabed.” Thinking about this place now, Susan remembers that it was not her first choice––to settle that deep in the sea. That seems like something Jimmy Shale would do. They like to hide in the dark.
“It’s not the dark or deep we like, it is the calm water that made us settle.” Jimmy explains. “We don’t like rushing. We much rather take time to find a quiet place to settle down.” Such calm waters are hard to find, except where the sea is very deep.
“They are so sensitive” Susan mumbles. “Only settling where it is really boring. What’s wrong with rushing?” Now Susan remembers that her silty grains first deposited somewhere else––in shallower waters, right at the edge to the deep sea. Shortly after the grains thought they found their place to settle, they all got stirred up again and flushed rapidly down the slope. Like a large avalanche of grains––driven by gravity. This turbiditic rush caused the grains to form a big underwater cloud of grains that quickly deposited on top of the shale––forming Susan’s rock layer. Over time, more shale settled on top of her marking, but occasionally, a big silty cloud rushed down the slope to form another silt layer. Layer by layer building up meters and meters of sediments in the Alberta foreland basin. “The limestones look so different, they must have a different story” Susan wonders looking at the many limestone peaks around Highwood Pass.